Java tutorial
/* * Copyright (C) 2006 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package android.widget; import android.annotation.NonNull; import android.annotation.UnsupportedAppUsage; import android.content.Context; import android.content.res.Configuration; import android.content.res.TypedArray; import android.graphics.Canvas; import android.graphics.Rect; import android.os.Build; import android.os.Build.VERSION_CODES; import android.os.Bundle; import android.os.Parcel; import android.os.Parcelable; import android.os.StrictMode; import android.util.AttributeSet; import android.util.Log; import android.view.FocusFinder; import android.view.InputDevice; import android.view.KeyEvent; import android.view.MotionEvent; import android.view.VelocityTracker; import android.view.View; import android.view.ViewConfiguration; import android.view.ViewDebug; import android.view.ViewGroup; import android.view.ViewHierarchyEncoder; import android.view.ViewParent; import android.view.accessibility.AccessibilityEvent; import android.view.accessibility.AccessibilityNodeInfo; import android.view.animation.AnimationUtils; import com.android.internal.R; import java.util.List; /** * A view group that allows the view hierarchy placed within it to be scrolled. * Scroll view may have only one direct child placed within it. * To add multiple views within the scroll view, make * the direct child you add a view group, for example {@link LinearLayout}, and * place additional views within that LinearLayout. * * <p>Scroll view supports vertical scrolling only. For horizontal scrolling, * use {@link HorizontalScrollView} instead.</p> * * <p>Never add a {@link android.support.v7.widget.RecyclerView} or {@link ListView} to * a scroll view. Doing so results in poor user interface performance and a poor user * experience.</p> * * <p class="note"> * For vertical scrolling, consider {@link android.support.v4.widget.NestedScrollView} * instead of scroll view which offers greater user interface flexibility and * support for the material design scrolling patterns.</p> * * <p>To learn more about material design patterns for handling scrolling, see * <a href="https://material.io/guidelines/patterns/scrolling-techniques.html#"> * Scrolling techniques</a>.</p> * * @attr ref android.R.styleable#ScrollView_fillViewport */ public class ScrollView extends FrameLayout { static final int ANIMATED_SCROLL_GAP = 250; static final float MAX_SCROLL_FACTOR = 0.5f; private static final String TAG = "ScrollView"; @UnsupportedAppUsage private long mLastScroll; private final Rect mTempRect = new Rect(); @UnsupportedAppUsage private OverScroller mScroller; @UnsupportedAppUsage private EdgeEffect mEdgeGlowTop; @UnsupportedAppUsage private EdgeEffect mEdgeGlowBottom; /** * Position of the last motion event. */ @UnsupportedAppUsage private int mLastMotionY; /** * True when the layout has changed but the traversal has not come through yet. * Ideally the view hierarchy would keep track of this for us. */ private boolean mIsLayoutDirty = true; /** * The child to give focus to in the event that a child has requested focus while the * layout is dirty. This prevents the scroll from being wrong if the child has not been * laid out before requesting focus. */ @UnsupportedAppUsage private View mChildToScrollTo = null; /** * True if the user is currently dragging this ScrollView around. This is * not the same as 'is being flinged', which can be checked by * mScroller.isFinished() (flinging begins when the user lifts his finger). */ @UnsupportedAppUsage private boolean mIsBeingDragged = false; /** * Determines speed during touch scrolling */ @UnsupportedAppUsage private VelocityTracker mVelocityTracker; /** * When set to true, the scroll view measure its child to make it fill the currently * visible area. */ @ViewDebug.ExportedProperty(category = "layout") private boolean mFillViewport; /** * Whether arrow scrolling is animated. */ private boolean mSmoothScrollingEnabled = true; private int mTouchSlop; @UnsupportedAppUsage private int mMinimumVelocity; private int mMaximumVelocity; @UnsupportedAppUsage private int mOverscrollDistance; @UnsupportedAppUsage private int mOverflingDistance; private float mVerticalScrollFactor; /** * ID of the active pointer. This is used to retain consistency during * drags/flings if multiple pointers are used. */ private int mActivePointerId = INVALID_POINTER; /** * Used during scrolling to retrieve the new offset within the window. */ private final int[] mScrollOffset = new int[2]; private final int[] mScrollConsumed = new int[2]; private int mNestedYOffset; /** * The StrictMode "critical time span" objects to catch animation * stutters. Non-null when a time-sensitive animation is * in-flight. Must call finish() on them when done animating. * These are no-ops on user builds. */ private StrictMode.Span mScrollStrictSpan = null; // aka "drag" @UnsupportedAppUsage private StrictMode.Span mFlingStrictSpan = null; /** * Sentinel value for no current active pointer. * Used by {@link #mActivePointerId}. */ private static final int INVALID_POINTER = -1; private SavedState mSavedState; public ScrollView(Context context) { this(context, null); } public ScrollView(Context context, AttributeSet attrs) { this(context, attrs, com.android.internal.R.attr.scrollViewStyle); } public ScrollView(Context context, AttributeSet attrs, int defStyleAttr) { this(context, attrs, defStyleAttr, 0); } public ScrollView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) { super(context, attrs, defStyleAttr, defStyleRes); initScrollView(); final TypedArray a = context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.ScrollView, defStyleAttr, defStyleRes); setFillViewport(a.getBoolean(R.styleable.ScrollView_fillViewport, false)); a.recycle(); if (context.getResources().getConfiguration().uiMode == Configuration.UI_MODE_TYPE_WATCH) { setRevealOnFocusHint(false); } } @Override public boolean shouldDelayChildPressedState() { return true; } @Override protected float getTopFadingEdgeStrength() { if (getChildCount() == 0) { return 0.0f; } final int length = getVerticalFadingEdgeLength(); if (mScrollY < length) { return mScrollY / (float) length; } return 1.0f; } @Override protected float getBottomFadingEdgeStrength() { if (getChildCount() == 0) { return 0.0f; } final int length = getVerticalFadingEdgeLength(); final int bottomEdge = getHeight() - mPaddingBottom; final int span = getChildAt(0).getBottom() - mScrollY - bottomEdge; if (span < length) { return span / (float) length; } return 1.0f; } /** * @return The maximum amount this scroll view will scroll in response to * an arrow event. */ public int getMaxScrollAmount() { return (int) (MAX_SCROLL_FACTOR * (mBottom - mTop)); } private void initScrollView() { mScroller = new OverScroller(getContext()); setFocusable(true); setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); setWillNotDraw(false); final ViewConfiguration configuration = ViewConfiguration.get(mContext); mTouchSlop = configuration.getScaledTouchSlop(); mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); mOverscrollDistance = configuration.getScaledOverscrollDistance(); mOverflingDistance = configuration.getScaledOverflingDistance(); mVerticalScrollFactor = configuration.getScaledVerticalScrollFactor(); } @Override public void addView(View child) { if (getChildCount() > 0) { throw new IllegalStateException("ScrollView can host only one direct child"); } super.addView(child); } @Override public void addView(View child, int index) { if (getChildCount() > 0) { throw new IllegalStateException("ScrollView can host only one direct child"); } super.addView(child, index); } @Override public void addView(View child, ViewGroup.LayoutParams params) { if (getChildCount() > 0) { throw new IllegalStateException("ScrollView can host only one direct child"); } super.addView(child, params); } @Override public void addView(View child, int index, ViewGroup.LayoutParams params) { if (getChildCount() > 0) { throw new IllegalStateException("ScrollView can host only one direct child"); } super.addView(child, index, params); } /** * @return Returns true this ScrollView can be scrolled */ @UnsupportedAppUsage private boolean canScroll() { View child = getChildAt(0); if (child != null) { int childHeight = child.getHeight(); return getHeight() < childHeight + mPaddingTop + mPaddingBottom; } return false; } /** * Indicates whether this ScrollView's content is stretched to fill the viewport. * * @return True if the content fills the viewport, false otherwise. * * @attr ref android.R.styleable#ScrollView_fillViewport */ public boolean isFillViewport() { return mFillViewport; } /** * Indicates this ScrollView whether it should stretch its content height to fill * the viewport or not. * * @param fillViewport True to stretch the content's height to the viewport's * boundaries, false otherwise. * * @attr ref android.R.styleable#ScrollView_fillViewport */ public void setFillViewport(boolean fillViewport) { if (fillViewport != mFillViewport) { mFillViewport = fillViewport; requestLayout(); } } /** * @return Whether arrow scrolling will animate its transition. */ public boolean isSmoothScrollingEnabled() { return mSmoothScrollingEnabled; } /** * Set whether arrow scrolling will animate its transition. * @param smoothScrollingEnabled whether arrow scrolling will animate its transition */ public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { mSmoothScrollingEnabled = smoothScrollingEnabled; } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); if (!mFillViewport) { return; } final int heightMode = MeasureSpec.getMode(heightMeasureSpec); if (heightMode == MeasureSpec.UNSPECIFIED) { return; } if (getChildCount() > 0) { final View child = getChildAt(0); final int widthPadding; final int heightPadding; final int targetSdkVersion = getContext().getApplicationInfo().targetSdkVersion; final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); if (targetSdkVersion >= VERSION_CODES.M) { widthPadding = mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin; heightPadding = mPaddingTop + mPaddingBottom + lp.topMargin + lp.bottomMargin; } else { widthPadding = mPaddingLeft + mPaddingRight; heightPadding = mPaddingTop + mPaddingBottom; } final int desiredHeight = getMeasuredHeight() - heightPadding; if (child.getMeasuredHeight() < desiredHeight) { final int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec, widthPadding, lp.width); final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(desiredHeight, MeasureSpec.EXACTLY); child.measure(childWidthMeasureSpec, childHeightMeasureSpec); } } } @Override public boolean dispatchKeyEvent(KeyEvent event) { // Let the focused view and/or our descendants get the key first return super.dispatchKeyEvent(event) || executeKeyEvent(event); } /** * You can call this function yourself to have the scroll view perform * scrolling from a key event, just as if the event had been dispatched to * it by the view hierarchy. * * @param event The key event to execute. * @return Return true if the event was handled, else false. */ public boolean executeKeyEvent(KeyEvent event) { mTempRect.setEmpty(); if (!canScroll()) { if (isFocused() && event.getKeyCode() != KeyEvent.KEYCODE_BACK) { View currentFocused = findFocus(); if (currentFocused == this) currentFocused = null; View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, View.FOCUS_DOWN); return nextFocused != null && nextFocused != this && nextFocused.requestFocus(View.FOCUS_DOWN); } return false; } boolean handled = false; if (event.getAction() == KeyEvent.ACTION_DOWN) { switch (event.getKeyCode()) { case KeyEvent.KEYCODE_DPAD_UP: if (!event.isAltPressed()) { handled = arrowScroll(View.FOCUS_UP); } else { handled = fullScroll(View.FOCUS_UP); } break; case KeyEvent.KEYCODE_DPAD_DOWN: if (!event.isAltPressed()) { handled = arrowScroll(View.FOCUS_DOWN); } else { handled = fullScroll(View.FOCUS_DOWN); } break; case KeyEvent.KEYCODE_SPACE: pageScroll(event.isShiftPressed() ? View.FOCUS_UP : View.FOCUS_DOWN); break; } } return handled; } private boolean inChild(int x, int y) { if (getChildCount() > 0) { final int scrollY = mScrollY; final View child = getChildAt(0); return !(y < child.getTop() - scrollY || y >= child.getBottom() - scrollY || x < child.getLeft() || x >= child.getRight()); } return false; } private void initOrResetVelocityTracker() { if (mVelocityTracker == null) { mVelocityTracker = VelocityTracker.obtain(); } else { mVelocityTracker.clear(); } } private void initVelocityTrackerIfNotExists() { if (mVelocityTracker == null) { mVelocityTracker = VelocityTracker.obtain(); } } private void recycleVelocityTracker() { if (mVelocityTracker != null) { mVelocityTracker.recycle(); mVelocityTracker = null; } } @Override public void requestDisallowInterceptTouchEvent(boolean disallowIntercept) { if (disallowIntercept) { recycleVelocityTracker(); } super.requestDisallowInterceptTouchEvent(disallowIntercept); } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { /* * This method JUST determines whether we want to intercept the motion. * If we return true, onMotionEvent will be called and we do the actual * scrolling there. */ /* * Shortcut the most recurring case: the user is in the dragging * state and he is moving his finger. We want to intercept this * motion. */ final int action = ev.getAction(); if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { return true; } if (super.onInterceptTouchEvent(ev)) { return true; } /* * Don't try to intercept touch if we can't scroll anyway. */ if (getScrollY() == 0 && !canScrollVertically(1)) { return false; } switch (action & MotionEvent.ACTION_MASK) { case MotionEvent.ACTION_MOVE: { /* * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check * whether the user has moved far enough from his original down touch. */ /* * Locally do absolute value. mLastMotionY is set to the y value * of the down event. */ final int activePointerId = mActivePointerId; if (activePointerId == INVALID_POINTER) { // If we don't have a valid id, the touch down wasn't on content. break; } final int pointerIndex = ev.findPointerIndex(activePointerId); if (pointerIndex == -1) { Log.e(TAG, "Invalid pointerId=" + activePointerId + " in onInterceptTouchEvent"); break; } final int y = (int) ev.getY(pointerIndex); final int yDiff = Math.abs(y - mLastMotionY); if (yDiff > mTouchSlop && (getNestedScrollAxes() & SCROLL_AXIS_VERTICAL) == 0) { mIsBeingDragged = true; mLastMotionY = y; initVelocityTrackerIfNotExists(); mVelocityTracker.addMovement(ev); mNestedYOffset = 0; if (mScrollStrictSpan == null) { mScrollStrictSpan = StrictMode.enterCriticalSpan("ScrollView-scroll"); } final ViewParent parent = getParent(); if (parent != null) { parent.requestDisallowInterceptTouchEvent(true); } } break; } case MotionEvent.ACTION_DOWN: { final int y = (int) ev.getY(); if (!inChild((int) ev.getX(), (int) y)) { mIsBeingDragged = false; recycleVelocityTracker(); break; } /* * Remember location of down touch. * ACTION_DOWN always refers to pointer index 0. */ mLastMotionY = y; mActivePointerId = ev.getPointerId(0); initOrResetVelocityTracker(); mVelocityTracker.addMovement(ev); /* * If being flinged and user touches the screen, initiate drag; * otherwise don't. mScroller.isFinished should be false when * being flinged. We need to call computeScrollOffset() first so that * isFinished() is correct. */ mScroller.computeScrollOffset(); mIsBeingDragged = !mScroller.isFinished(); if (mIsBeingDragged && mScrollStrictSpan == null) { mScrollStrictSpan = StrictMode.enterCriticalSpan("ScrollView-scroll"); } startNestedScroll(SCROLL_AXIS_VERTICAL); break; } case MotionEvent.ACTION_CANCEL: case MotionEvent.ACTION_UP: /* Release the drag */ mIsBeingDragged = false; mActivePointerId = INVALID_POINTER; recycleVelocityTracker(); if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) { postInvalidateOnAnimation(); } stopNestedScroll(); break; case MotionEvent.ACTION_POINTER_UP: onSecondaryPointerUp(ev); break; } /* * The only time we want to intercept motion events is if we are in the * drag mode. */ return mIsBeingDragged; } @Override public boolean onTouchEvent(MotionEvent ev) { initVelocityTrackerIfNotExists(); MotionEvent vtev = MotionEvent.obtain(ev); final int actionMasked = ev.getActionMasked(); if (actionMasked == MotionEvent.ACTION_DOWN) { mNestedYOffset = 0; } vtev.offsetLocation(0, mNestedYOffset); switch (actionMasked) { case MotionEvent.ACTION_DOWN: { if (getChildCount() == 0) { return false; } if ((mIsBeingDragged = !mScroller.isFinished())) { final ViewParent parent = getParent(); if (parent != null) { parent.requestDisallowInterceptTouchEvent(true); } } /* * If being flinged and user touches, stop the fling. isFinished * will be false if being flinged. */ if (!mScroller.isFinished()) { mScroller.abortAnimation(); if (mFlingStrictSpan != null) { mFlingStrictSpan.finish(); mFlingStrictSpan = null; } } // Remember where the motion event started mLastMotionY = (int) ev.getY(); mActivePointerId = ev.getPointerId(0); startNestedScroll(SCROLL_AXIS_VERTICAL); break; } case MotionEvent.ACTION_MOVE: final int activePointerIndex = ev.findPointerIndex(mActivePointerId); if (activePointerIndex == -1) { Log.e(TAG, "Invalid pointerId=" + mActivePointerId + " in onTouchEvent"); break; } final int y = (int) ev.getY(activePointerIndex); int deltaY = mLastMotionY - y; if (dispatchNestedPreScroll(0, deltaY, mScrollConsumed, mScrollOffset)) { deltaY -= mScrollConsumed[1]; vtev.offsetLocation(0, mScrollOffset[1]); mNestedYOffset += mScrollOffset[1]; } if (!mIsBeingDragged && Math.abs(deltaY) > mTouchSlop) { final ViewParent parent = getParent(); if (parent != null) { parent.requestDisallowInterceptTouchEvent(true); } mIsBeingDragged = true; if (deltaY > 0) { deltaY -= mTouchSlop; } else { deltaY += mTouchSlop; } } if (mIsBeingDragged) { // Scroll to follow the motion event mLastMotionY = y - mScrollOffset[1]; final int oldY = mScrollY; final int range = getScrollRange(); final int overscrollMode = getOverScrollMode(); boolean canOverscroll = overscrollMode == OVER_SCROLL_ALWAYS || (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0); // Calling overScrollBy will call onOverScrolled, which // calls onScrollChanged if applicable. if (overScrollBy(0, deltaY, 0, mScrollY, 0, range, 0, mOverscrollDistance, true) && !hasNestedScrollingParent()) { // Break our velocity if we hit a scroll barrier. mVelocityTracker.clear(); } final int scrolledDeltaY = mScrollY - oldY; final int unconsumedY = deltaY - scrolledDeltaY; if (dispatchNestedScroll(0, scrolledDeltaY, 0, unconsumedY, mScrollOffset)) { mLastMotionY -= mScrollOffset[1]; vtev.offsetLocation(0, mScrollOffset[1]); mNestedYOffset += mScrollOffset[1]; } else if (canOverscroll) { final int pulledToY = oldY + deltaY; if (pulledToY < 0) { mEdgeGlowTop.onPull((float) deltaY / getHeight(), ev.getX(activePointerIndex) / getWidth()); if (!mEdgeGlowBottom.isFinished()) { mEdgeGlowBottom.onRelease(); } } else if (pulledToY > range) { mEdgeGlowBottom.onPull((float) deltaY / getHeight(), 1.f - ev.getX(activePointerIndex) / getWidth()); if (!mEdgeGlowTop.isFinished()) { mEdgeGlowTop.onRelease(); } } if (mEdgeGlowTop != null && (!mEdgeGlowTop.isFinished() || !mEdgeGlowBottom.isFinished())) { postInvalidateOnAnimation(); } } } break; case MotionEvent.ACTION_UP: if (mIsBeingDragged) { final VelocityTracker velocityTracker = mVelocityTracker; velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId); if ((Math.abs(initialVelocity) > mMinimumVelocity)) { flingWithNestedDispatch(-initialVelocity); } else if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) { postInvalidateOnAnimation(); } mActivePointerId = INVALID_POINTER; endDrag(); } break; case MotionEvent.ACTION_CANCEL: if (mIsBeingDragged && getChildCount() > 0) { if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) { postInvalidateOnAnimation(); } mActivePointerId = INVALID_POINTER; endDrag(); } break; case MotionEvent.ACTION_POINTER_DOWN: { final int index = ev.getActionIndex(); mLastMotionY = (int) ev.getY(index); mActivePointerId = ev.getPointerId(index); break; } case MotionEvent.ACTION_POINTER_UP: onSecondaryPointerUp(ev); mLastMotionY = (int) ev.getY(ev.findPointerIndex(mActivePointerId)); break; } if (mVelocityTracker != null) { mVelocityTracker.addMovement(vtev); } vtev.recycle(); return true; } private void onSecondaryPointerUp(MotionEvent ev) { final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent.ACTION_POINTER_INDEX_SHIFT; final int pointerId = ev.getPointerId(pointerIndex); if (pointerId == mActivePointerId) { // This was our active pointer going up. Choose a new // active pointer and adjust accordingly. // TODO: Make this decision more intelligent. final int newPointerIndex = pointerIndex == 0 ? 1 : 0; mLastMotionY = (int) ev.getY(newPointerIndex); mActivePointerId = ev.getPointerId(newPointerIndex); if (mVelocityTracker != null) { mVelocityTracker.clear(); } } } @Override public boolean onGenericMotionEvent(MotionEvent event) { switch (event.getAction()) { case MotionEvent.ACTION_SCROLL: final float axisValue; if (event.isFromSource(InputDevice.SOURCE_CLASS_POINTER)) { axisValue = event.getAxisValue(MotionEvent.AXIS_VSCROLL); } else if (event.isFromSource(InputDevice.SOURCE_ROTARY_ENCODER)) { axisValue = event.getAxisValue(MotionEvent.AXIS_SCROLL); } else { axisValue = 0; } final int delta = Math.round(axisValue * mVerticalScrollFactor); if (delta != 0) { final int range = getScrollRange(); int oldScrollY = mScrollY; int newScrollY = oldScrollY - delta; if (newScrollY < 0) { newScrollY = 0; } else if (newScrollY > range) { newScrollY = range; } if (newScrollY != oldScrollY) { super.scrollTo(mScrollX, newScrollY); return true; } } break; } return super.onGenericMotionEvent(event); } @Override protected void onOverScrolled(int scrollX, int scrollY, boolean clampedX, boolean clampedY) { // Treat animating scrolls differently; see #computeScroll() for why. if (!mScroller.isFinished()) { final int oldX = mScrollX; final int oldY = mScrollY; mScrollX = scrollX; mScrollY = scrollY; invalidateParentIfNeeded(); onScrollChanged(mScrollX, mScrollY, oldX, oldY); if (clampedY) { mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange()); } } else { super.scrollTo(scrollX, scrollY); } awakenScrollBars(); } /** @hide */ @Override public boolean performAccessibilityActionInternal(int action, Bundle arguments) { if (super.performAccessibilityActionInternal(action, arguments)) { return true; } if (!isEnabled()) { return false; } switch (action) { case AccessibilityNodeInfo.ACTION_SCROLL_FORWARD: case R.id.accessibilityActionScrollDown: { final int viewportHeight = getHeight() - mPaddingBottom - mPaddingTop; final int targetScrollY = Math.min(mScrollY + viewportHeight, getScrollRange()); if (targetScrollY != mScrollY) { smoothScrollTo(0, targetScrollY); return true; } } return false; case AccessibilityNodeInfo.ACTION_SCROLL_BACKWARD: case R.id.accessibilityActionScrollUp: { final int viewportHeight = getHeight() - mPaddingBottom - mPaddingTop; final int targetScrollY = Math.max(mScrollY - viewportHeight, 0); if (targetScrollY != mScrollY) { smoothScrollTo(0, targetScrollY); return true; } } return false; } return false; } @Override public CharSequence getAccessibilityClassName() { return ScrollView.class.getName(); } /** @hide */ @Override public void onInitializeAccessibilityNodeInfoInternal(AccessibilityNodeInfo info) { super.onInitializeAccessibilityNodeInfoInternal(info); if (isEnabled()) { final int scrollRange = getScrollRange(); if (scrollRange > 0) { info.setScrollable(true); if (mScrollY > 0) { info.addAction(AccessibilityNodeInfo.AccessibilityAction.ACTION_SCROLL_BACKWARD); info.addAction(AccessibilityNodeInfo.AccessibilityAction.ACTION_SCROLL_UP); } if (mScrollY < scrollRange) { info.addAction(AccessibilityNodeInfo.AccessibilityAction.ACTION_SCROLL_FORWARD); info.addAction(AccessibilityNodeInfo.AccessibilityAction.ACTION_SCROLL_DOWN); } } } } /** @hide */ @Override public void onInitializeAccessibilityEventInternal(AccessibilityEvent event) { super.onInitializeAccessibilityEventInternal(event); final boolean scrollable = getScrollRange() > 0; event.setScrollable(scrollable); event.setScrollX(mScrollX); event.setScrollY(mScrollY); event.setMaxScrollX(mScrollX); event.setMaxScrollY(getScrollRange()); } private int getScrollRange() { int scrollRange = 0; if (getChildCount() > 0) { View child = getChildAt(0); scrollRange = Math.max(0, child.getHeight() - (getHeight() - mPaddingBottom - mPaddingTop)); } return scrollRange; } /** * <p> * Finds the next focusable component that fits in the specified bounds. * </p> * * @param topFocus look for a candidate is the one at the top of the bounds * if topFocus is true, or at the bottom of the bounds if topFocus is * false * @param top the top offset of the bounds in which a focusable must be * found * @param bottom the bottom offset of the bounds in which a focusable must * be found * @return the next focusable component in the bounds or null if none can * be found */ private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { List<View> focusables = getFocusables(View.FOCUS_FORWARD); View focusCandidate = null; /* * A fully contained focusable is one where its top is below the bound's * top, and its bottom is above the bound's bottom. A partially * contained focusable is one where some part of it is within the * bounds, but it also has some part that is not within bounds. A fully contained * focusable is preferred to a partially contained focusable. */ boolean foundFullyContainedFocusable = false; int count = focusables.size(); for (int i = 0; i < count; i++) { View view = focusables.get(i); int viewTop = view.getTop(); int viewBottom = view.getBottom(); if (top < viewBottom && viewTop < bottom) { /* * the focusable is in the target area, it is a candidate for * focusing */ final boolean viewIsFullyContained = (top < viewTop) && (viewBottom < bottom); if (focusCandidate == null) { /* No candidate, take this one */ focusCandidate = view; foundFullyContainedFocusable = viewIsFullyContained; } else { final boolean viewIsCloserToBoundary = (topFocus && viewTop < focusCandidate.getTop()) || (!topFocus && viewBottom > focusCandidate.getBottom()); if (foundFullyContainedFocusable) { if (viewIsFullyContained && viewIsCloserToBoundary) { /* * We're dealing with only fully contained views, so * it has to be closer to the boundary to beat our * candidate */ focusCandidate = view; } } else { if (viewIsFullyContained) { /* Any fully contained view beats a partially contained view */ focusCandidate = view; foundFullyContainedFocusable = true; } else if (viewIsCloserToBoundary) { /* * Partially contained view beats another partially * contained view if it's closer */ focusCandidate = view; } } } } } return focusCandidate; } /** * <p>Handles scrolling in response to a "page up/down" shortcut press. This * method will scroll the view by one page up or down and give the focus * to the topmost/bottommost component in the new visible area. If no * component is a good candidate for focus, this scrollview reclaims the * focus.</p> * * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} * to go one page up or * {@link android.view.View#FOCUS_DOWN} to go one page down * @return true if the key event is consumed by this method, false otherwise */ public boolean pageScroll(int direction) { boolean down = direction == View.FOCUS_DOWN; int height = getHeight(); if (down) { mTempRect.top = getScrollY() + height; int count = getChildCount(); if (count > 0) { View view = getChildAt(count - 1); if (mTempRect.top + height > view.getBottom()) { mTempRect.top = view.getBottom() - height; } } } else { mTempRect.top = getScrollY() - height; if (mTempRect.top < 0) { mTempRect.top = 0; } } mTempRect.bottom = mTempRect.top + height; return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); } /** * <p>Handles scrolling in response to a "home/end" shortcut press. This * method will scroll the view to the top or bottom and give the focus * to the topmost/bottommost component in the new visible area. If no * component is a good candidate for focus, this scrollview reclaims the * focus.</p> * * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} * to go the top of the view or * {@link android.view.View#FOCUS_DOWN} to go the bottom * @return true if the key event is consumed by this method, false otherwise */ public boolean fullScroll(int direction) { boolean down = direction == View.FOCUS_DOWN; int height = getHeight(); mTempRect.top = 0; mTempRect.bottom = height; if (down) { int count = getChildCount(); if (count > 0) { View view = getChildAt(count - 1); mTempRect.bottom = view.getBottom() + mPaddingBottom; mTempRect.top = mTempRect.bottom - height; } } return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); } /** * <p>Scrolls the view to make the area defined by <code>top</code> and * <code>bottom</code> visible. This method attempts to give the focus * to a component visible in this area. If no component can be focused in * the new visible area, the focus is reclaimed by this ScrollView.</p> * * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} * to go upward, {@link android.view.View#FOCUS_DOWN} to downward * @param top the top offset of the new area to be made visible * @param bottom the bottom offset of the new area to be made visible * @return true if the key event is consumed by this method, false otherwise */ private boolean scrollAndFocus(int direction, int top, int bottom) { boolean handled = true; int height = getHeight(); int containerTop = getScrollY(); int containerBottom = containerTop + height; boolean up = direction == View.FOCUS_UP; View newFocused = findFocusableViewInBounds(up, top, bottom); if (newFocused == null) { newFocused = this; } if (top >= containerTop && bottom <= containerBottom) { handled = false; } else { int delta = up ? (top - containerTop) : (bottom - containerBottom); doScrollY(delta); } if (newFocused != findFocus()) newFocused.requestFocus(direction); return handled; } /** * Handle scrolling in response to an up or down arrow click. * * @param direction The direction corresponding to the arrow key that was * pressed * @return True if we consumed the event, false otherwise */ public boolean arrowScroll(int direction) { View currentFocused = findFocus(); if (currentFocused == this) currentFocused = null; View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); final int maxJump = getMaxScrollAmount(); if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump, getHeight())) { nextFocused.getDrawingRect(mTempRect); offsetDescendantRectToMyCoords(nextFocused, mTempRect); int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); doScrollY(scrollDelta); nextFocused.requestFocus(direction); } else { // no new focus int scrollDelta = maxJump; if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { scrollDelta = getScrollY(); } else if (direction == View.FOCUS_DOWN) { if (getChildCount() > 0) { int daBottom = getChildAt(0).getBottom(); int screenBottom = getScrollY() + getHeight() - mPaddingBottom; if (daBottom - screenBottom < maxJump) { scrollDelta = daBottom - screenBottom; } } } if (scrollDelta == 0) { return false; } doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); } if (currentFocused != null && currentFocused.isFocused() && isOffScreen(currentFocused)) { // previously focused item still has focus and is off screen, give // it up (take it back to ourselves) // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are // sure to // get it) final int descendantFocusability = getDescendantFocusability(); // save setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); requestFocus(); setDescendantFocusability(descendantFocusability); // restore } return true; } /** * @return whether the descendant of this scroll view is scrolled off * screen. */ private boolean isOffScreen(View descendant) { return !isWithinDeltaOfScreen(descendant, 0, getHeight()); } /** * @return whether the descendant of this scroll view is within delta * pixels of being on the screen. */ private boolean isWithinDeltaOfScreen(View descendant, int delta, int height) { descendant.getDrawingRect(mTempRect); offsetDescendantRectToMyCoords(descendant, mTempRect); return (mTempRect.bottom + delta) >= getScrollY() && (mTempRect.top - delta) <= (getScrollY() + height); } /** * Smooth scroll by a Y delta * * @param delta the number of pixels to scroll by on the Y axis */ private void doScrollY(int delta) { if (delta != 0) { if (mSmoothScrollingEnabled) { smoothScrollBy(0, delta); } else { scrollBy(0, delta); } } } /** * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. * * @param dx the number of pixels to scroll by on the X axis * @param dy the number of pixels to scroll by on the Y axis */ public final void smoothScrollBy(int dx, int dy) { if (getChildCount() == 0) { // Nothing to do. return; } long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; if (duration > ANIMATED_SCROLL_GAP) { final int height = getHeight() - mPaddingBottom - mPaddingTop; final int bottom = getChildAt(0).getHeight(); final int maxY = Math.max(0, bottom - height); final int scrollY = mScrollY; dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY; mScroller.startScroll(mScrollX, scrollY, 0, dy); postInvalidateOnAnimation(); } else { if (!mScroller.isFinished()) { mScroller.abortAnimation(); if (mFlingStrictSpan != null) { mFlingStrictSpan.finish(); mFlingStrictSpan = null; } } scrollBy(dx, dy); } mLastScroll = AnimationUtils.currentAnimationTimeMillis(); } /** * Like {@link #scrollTo}, but scroll smoothly instead of immediately. * * @param x the position where to scroll on the X axis * @param y the position where to scroll on the Y axis */ public final void smoothScrollTo(int x, int y) { smoothScrollBy(x - mScrollX, y - mScrollY); } /** * <p>The scroll range of a scroll view is the overall height of all of its * children.</p> */ @Override protected int computeVerticalScrollRange() { final int count = getChildCount(); final int contentHeight = getHeight() - mPaddingBottom - mPaddingTop; if (count == 0) { return contentHeight; } int scrollRange = getChildAt(0).getBottom(); final int scrollY = mScrollY; final int overscrollBottom = Math.max(0, scrollRange - contentHeight); if (scrollY < 0) { scrollRange -= scrollY; } else if (scrollY > overscrollBottom) { scrollRange += scrollY - overscrollBottom; } return scrollRange; } @Override protected int computeVerticalScrollOffset() { return Math.max(0, super.computeVerticalScrollOffset()); } @Override protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { ViewGroup.LayoutParams lp = child.getLayoutParams(); int childWidthMeasureSpec; int childHeightMeasureSpec; childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft + mPaddingRight, lp.width); final int verticalPadding = mPaddingTop + mPaddingBottom; childHeightMeasureSpec = MeasureSpec.makeSafeMeasureSpec( Math.max(0, MeasureSpec.getSize(parentHeightMeasureSpec) - verticalPadding), MeasureSpec.UNSPECIFIED); child.measure(childWidthMeasureSpec, childHeightMeasureSpec); } @Override protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, int parentHeightMeasureSpec, int heightUsed) { final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin + widthUsed, lp.width); final int usedTotal = mPaddingTop + mPaddingBottom + lp.topMargin + lp.bottomMargin + heightUsed; final int childHeightMeasureSpec = MeasureSpec.makeSafeMeasureSpec( Math.max(0, MeasureSpec.getSize(parentHeightMeasureSpec) - usedTotal), MeasureSpec.UNSPECIFIED); child.measure(childWidthMeasureSpec, childHeightMeasureSpec); } @Override public void computeScroll() { if (mScroller.computeScrollOffset()) { // This is called at drawing time by ViewGroup. We don't want to // re-show the scrollbars at this point, which scrollTo will do, // so we replicate most of scrollTo here. // // It's a little odd to call onScrollChanged from inside the drawing. // // It is, except when you remember that computeScroll() is used to // animate scrolling. So unless we want to defer the onScrollChanged() // until the end of the animated scrolling, we don't really have a // choice here. // // I agree. The alternative, which I think would be worse, is to post // something and tell the subclasses later. This is bad because there // will be a window where mScrollX/Y is different from what the app // thinks it is. // int oldX = mScrollX; int oldY = mScrollY; int x = mScroller.getCurrX(); int y = mScroller.getCurrY(); if (oldX != x || oldY != y) { final int range = getScrollRange(); final int overscrollMode = getOverScrollMode(); final boolean canOverscroll = overscrollMode == OVER_SCROLL_ALWAYS || (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0); overScrollBy(x - oldX, y - oldY, oldX, oldY, 0, range, 0, mOverflingDistance, false); onScrollChanged(mScrollX, mScrollY, oldX, oldY); if (canOverscroll) { if (y < 0 && oldY >= 0) { mEdgeGlowTop.onAbsorb((int) mScroller.getCurrVelocity()); } else if (y > range && oldY <= range) { mEdgeGlowBottom.onAbsorb((int) mScroller.getCurrVelocity()); } } } if (!awakenScrollBars()) { // Keep on drawing until the animation has finished. postInvalidateOnAnimation(); } } else { if (mFlingStrictSpan != null) { mFlingStrictSpan.finish(); mFlingStrictSpan = null; } } } /** * Scrolls the view to the given child. * * @param child the View to scroll to */ private void scrollToChild(View child) { child.getDrawingRect(mTempRect); /* Offset from child's local coordinates to ScrollView coordinates */ offsetDescendantRectToMyCoords(child, mTempRect); int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); if (scrollDelta != 0) { scrollBy(0, scrollDelta); } } /** * If rect is off screen, scroll just enough to get it (or at least the * first screen size chunk of it) on screen. * * @param rect The rectangle. * @param immediate True to scroll immediately without animation * @return true if scrolling was performed */ private boolean scrollToChildRect(Rect rect, boolean immediate) { final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); final boolean scroll = delta != 0; if (scroll) { if (immediate) { scrollBy(0, delta); } else { smoothScrollBy(0, delta); } } return scroll; } /** * Compute the amount to scroll in the Y direction in order to get * a rectangle completely on the screen (or, if taller than the screen, * at least the first screen size chunk of it). * * @param rect The rect. * @return The scroll delta. */ protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { if (getChildCount() == 0) return 0; int height = getHeight(); int screenTop = getScrollY(); int screenBottom = screenTop + height; int fadingEdge = getVerticalFadingEdgeLength(); // leave room for top fading edge as long as rect isn't at very top if (rect.top > 0) { screenTop += fadingEdge; } // leave room for bottom fading edge as long as rect isn't at very bottom if (rect.bottom < getChildAt(0).getHeight()) { screenBottom -= fadingEdge; } int scrollYDelta = 0; if (rect.bottom > screenBottom && rect.top > screenTop) { // need to move down to get it in view: move down just enough so // that the entire rectangle is in view (or at least the first // screen size chunk). if (rect.height() > height) { // just enough to get screen size chunk on scrollYDelta += (rect.top - screenTop); } else { // get entire rect at bottom of screen scrollYDelta += (rect.bottom - screenBottom); } // make sure we aren't scrolling beyond the end of our content int bottom = getChildAt(0).getBottom(); int distanceToBottom = bottom - screenBottom; scrollYDelta = Math.min(scrollYDelta, distanceToBottom); } else if (rect.top < screenTop && rect.bottom < screenBottom) { // need to move up to get it in view: move up just enough so that // entire rectangle is in view (or at least the first screen // size chunk of it). if (rect.height() > height) { // screen size chunk scrollYDelta -= (screenBottom - rect.bottom); } else { // entire rect at top scrollYDelta -= (screenTop - rect.top); } // make sure we aren't scrolling any further than the top our content scrollYDelta = Math.max(scrollYDelta, -getScrollY()); } return scrollYDelta; } @Override public void requestChildFocus(View child, View focused) { if (focused != null && focused.getRevealOnFocusHint()) { if (!mIsLayoutDirty) { scrollToChild(focused); } else { // The child may not be laid out yet, we can't compute the scroll yet mChildToScrollTo = focused; } } super.requestChildFocus(child, focused); } /** * When looking for focus in children of a scroll view, need to be a little * more careful not to give focus to something that is scrolled off screen. * * This is more expensive than the default {@link android.view.ViewGroup} * implementation, otherwise this behavior might have been made the default. */ @Override protected boolean onRequestFocusInDescendants(int direction, Rect previouslyFocusedRect) { // convert from forward / backward notation to up / down / left / right // (ugh). if (direction == View.FOCUS_FORWARD) { direction = View.FOCUS_DOWN; } else if (direction == View.FOCUS_BACKWARD) { direction = View.FOCUS_UP; } final View nextFocus = previouslyFocusedRect == null ? FocusFinder.getInstance().findNextFocus(this, null, direction) : FocusFinder.getInstance().findNextFocusFromRect(this, previouslyFocusedRect, direction); if (nextFocus == null) { return false; } if (isOffScreen(nextFocus)) { return false; } return nextFocus.requestFocus(direction, previouslyFocusedRect); } @Override public boolean requestChildRectangleOnScreen(View child, Rect rectangle, boolean immediate) { // offset into coordinate space of this scroll view rectangle.offset(child.getLeft() - child.getScrollX(), child.getTop() - child.getScrollY()); return scrollToChildRect(rectangle, immediate); } @Override public void requestLayout() { mIsLayoutDirty = true; super.requestLayout(); } @Override protected void onDetachedFromWindow() { super.onDetachedFromWindow(); if (mScrollStrictSpan != null) { mScrollStrictSpan.finish(); mScrollStrictSpan = null; } if (mFlingStrictSpan != null) { mFlingStrictSpan.finish(); mFlingStrictSpan = null; } } @Override protected void onLayout(boolean changed, int l, int t, int r, int b) { super.onLayout(changed, l, t, r, b); mIsLayoutDirty = false; // Give a child focus if it needs it if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { scrollToChild(mChildToScrollTo); } mChildToScrollTo = null; if (!isLaidOut()) { if (mSavedState != null) { mScrollY = mSavedState.scrollPosition; mSavedState = null; } // mScrollY default value is "0" final int childHeight = (getChildCount() > 0) ? getChildAt(0).getMeasuredHeight() : 0; final int scrollRange = Math.max(0, childHeight - (b - t - mPaddingBottom - mPaddingTop)); // Don't forget to clamp if (mScrollY > scrollRange) { mScrollY = scrollRange; } else if (mScrollY < 0) { mScrollY = 0; } } // Calling this with the present values causes it to re-claim them scrollTo(mScrollX, mScrollY); } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); View currentFocused = findFocus(); if (null == currentFocused || this == currentFocused) return; // If the currently-focused view was visible on the screen when the // screen was at the old height, then scroll the screen to make that // view visible with the new screen height. if (isWithinDeltaOfScreen(currentFocused, 0, oldh)) { currentFocused.getDrawingRect(mTempRect); offsetDescendantRectToMyCoords(currentFocused, mTempRect); int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); doScrollY(scrollDelta); } } /** * Return true if child is a descendant of parent, (or equal to the parent). */ private static boolean isViewDescendantOf(View child, View parent) { if (child == parent) { return true; } final ViewParent theParent = child.getParent(); return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); } /** * Fling the scroll view * * @param velocityY The initial velocity in the Y direction. Positive * numbers mean that the finger/cursor is moving down the screen, * which means we want to scroll towards the top. */ public void fling(int velocityY) { if (getChildCount() > 0) { int height = getHeight() - mPaddingBottom - mPaddingTop; int bottom = getChildAt(0).getHeight(); mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, Math.max(0, bottom - height), 0, height / 2); if (mFlingStrictSpan == null) { mFlingStrictSpan = StrictMode.enterCriticalSpan("ScrollView-fling"); } postInvalidateOnAnimation(); } } private void flingWithNestedDispatch(int velocityY) { final boolean canFling = (mScrollY > 0 || velocityY > 0) && (mScrollY < getScrollRange() || velocityY < 0); if (!dispatchNestedPreFling(0, velocityY)) { dispatchNestedFling(0, velocityY, canFling); if (canFling) { fling(velocityY); } } } @UnsupportedAppUsage private void endDrag() { mIsBeingDragged = false; recycleVelocityTracker(); if (mEdgeGlowTop != null) { mEdgeGlowTop.onRelease(); mEdgeGlowBottom.onRelease(); } if (mScrollStrictSpan != null) { mScrollStrictSpan.finish(); mScrollStrictSpan = null; } } /** * {@inheritDoc} * * <p>This version also clamps the scrolling to the bounds of our child. */ @Override public void scrollTo(int x, int y) { // we rely on the fact the View.scrollBy calls scrollTo. if (getChildCount() > 0) { View child = getChildAt(0); x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); if (x != mScrollX || y != mScrollY) { super.scrollTo(x, y); } } } @Override public void setOverScrollMode(int mode) { if (mode != OVER_SCROLL_NEVER) { if (mEdgeGlowTop == null) { Context context = getContext(); mEdgeGlowTop = new EdgeEffect(context); mEdgeGlowBottom = new EdgeEffect(context); } } else { mEdgeGlowTop = null; mEdgeGlowBottom = null; } super.setOverScrollMode(mode); } @Override public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) { return (nestedScrollAxes & SCROLL_AXIS_VERTICAL) != 0; } @Override public void onNestedScrollAccepted(View child, View target, int axes) { super.onNestedScrollAccepted(child, target, axes); startNestedScroll(SCROLL_AXIS_VERTICAL); } /** * @inheritDoc */ @Override public void onStopNestedScroll(View target) { super.onStopNestedScroll(target); } @Override public void onNestedScroll(View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) { final int oldScrollY = mScrollY; scrollBy(0, dyUnconsumed); final int myConsumed = mScrollY - oldScrollY; final int myUnconsumed = dyUnconsumed - myConsumed; dispatchNestedScroll(0, myConsumed, 0, myUnconsumed, null); } /** * @inheritDoc */ @Override public boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed) { if (!consumed) { flingWithNestedDispatch((int) velocityY); return true; } return false; } @Override public void draw(Canvas canvas) { super.draw(canvas); if (mEdgeGlowTop != null) { final int scrollY = mScrollY; final boolean clipToPadding = getClipToPadding(); if (!mEdgeGlowTop.isFinished()) { final int restoreCount = canvas.save(); final int width; final int height; final float translateX; final float translateY; if (clipToPadding) { width = getWidth() - mPaddingLeft - mPaddingRight; height = getHeight() - mPaddingTop - mPaddingBottom; translateX = mPaddingLeft; translateY = mPaddingTop; } else { width = getWidth(); height = getHeight(); translateX = 0; translateY = 0; } canvas.translate(translateX, Math.min(0, scrollY) + translateY); mEdgeGlowTop.setSize(width, height); if (mEdgeGlowTop.draw(canvas)) { postInvalidateOnAnimation(); } canvas.restoreToCount(restoreCount); } if (!mEdgeGlowBottom.isFinished()) { final int restoreCount = canvas.save(); final int width; final int height; final float translateX; final float translateY; if (clipToPadding) { width = getWidth() - mPaddingLeft - mPaddingRight; height = getHeight() - mPaddingTop - mPaddingBottom; translateX = mPaddingLeft; translateY = mPaddingTop; } else { width = getWidth(); height = getHeight(); translateX = 0; translateY = 0; } canvas.translate(-width + translateX, Math.max(getScrollRange(), scrollY) + height + translateY); canvas.rotate(180, width, 0); mEdgeGlowBottom.setSize(width, height); if (mEdgeGlowBottom.draw(canvas)) { postInvalidateOnAnimation(); } canvas.restoreToCount(restoreCount); } } } private static int clamp(int n, int my, int child) { if (my >= child || n < 0) { /* my >= child is this case: * |--------------- me ---------------| * |------ child ------| * or * |--------------- me ---------------| * |------ child ------| * or * |--------------- me ---------------| * |------ child ------| * * n < 0 is this case: * |------ me ------| * |-------- child --------| * |-- mScrollX --| */ return 0; } if ((my + n) > child) { /* this case: * |------ me ------| * |------ child ------| * |-- mScrollX --| */ return child - my; } return n; } @Override protected void onRestoreInstanceState(Parcelable state) { if (mContext.getApplicationInfo().targetSdkVersion <= Build.VERSION_CODES.JELLY_BEAN_MR2) { // Some old apps reused IDs in ways they shouldn't have. // Don't break them, but they don't get scroll state restoration. super.onRestoreInstanceState(state); return; } SavedState ss = (SavedState) state; super.onRestoreInstanceState(ss.getSuperState()); mSavedState = ss; requestLayout(); } @Override protected Parcelable onSaveInstanceState() { if (mContext.getApplicationInfo().targetSdkVersion <= Build.VERSION_CODES.JELLY_BEAN_MR2) { // Some old apps reused IDs in ways they shouldn't have. // Don't break them, but they don't get scroll state restoration. return super.onSaveInstanceState(); } Parcelable superState = super.onSaveInstanceState(); SavedState ss = new SavedState(superState); ss.scrollPosition = mScrollY; return ss; } /** @hide */ @Override protected void encodeProperties(@NonNull ViewHierarchyEncoder encoder) { super.encodeProperties(encoder); encoder.addProperty("fillViewport", mFillViewport); } static class SavedState extends BaseSavedState { public int scrollPosition; SavedState(Parcelable superState) { super(superState); } public SavedState(Parcel source) { super(source); scrollPosition = source.readInt(); } @Override public void writeToParcel(Parcel dest, int flags) { super.writeToParcel(dest, flags); dest.writeInt(scrollPosition); } @Override public String toString() { return "ScrollView.SavedState{" + Integer.toHexString(System.identityHashCode(this)) + " scrollPosition=" + scrollPosition + "}"; } public static final Parcelable.Creator<SavedState> CREATOR = new Parcelable.Creator<SavedState>() { public SavedState createFromParcel(Parcel in) { return new SavedState(in); } public SavedState[] newArray(int size) { return new SavedState[size]; } }; } }