Java tutorial
/* * Copyright (C) 2015 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.support.designox.widget; import android.content.Context; import android.content.res.TypedArray; import android.os.Parcel; import android.os.Parcelable; import android.support.annotationox.IntDef; import android.support.annotationox.NonNull; import android.support.v4ox.view.MotionEventCompat; import android.support.v4ox.view.NestedScrollingChild; import android.support.v4ox.view.VelocityTrackerCompat; import android.support.v4ox.view.ViewCompat; import android.support.v4ox.widget.ViewDragHelper; import android.util.AttributeSet; import android.view.MotionEvent; import android.view.VelocityTracker; import android.view.View; import android.view.ViewConfiguration; import android.view.ViewGroup; import com.gigigo.permissions.R; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.ref.WeakReference; /** * An interaction behavior plugin for a child view of {@link CoordinatorLayout} to make it work as * a bottom sheet. */ public class BottomSheetBehavior<V extends View> extends CoordinatorLayout.Behavior<V> { /** * Callback for monitoring events about bottom sheets. */ public abstract static class BottomSheetCallback { /** * Called when the bottom sheet changes its state. * * @param bottomSheet The bottom sheet view. * @param newState The new state. This will be one of {@link #STATE_DRAGGING}, * {@link #STATE_SETTLING}, {@link #STATE_EXPANDED}, * {@link #STATE_COLLAPSED}, or {@link #STATE_HIDDEN}. */ public abstract void onStateChanged(@NonNull View bottomSheet, @State int newState); /** * Called when the bottom sheet is being dragged. * * @param bottomSheet The bottom sheet view. * @param slideOffset The new offset of this bottom sheet within its range, from 0 to 1 * when it is moving upward, and from 0 to -1 when it moving downward. */ public abstract void onSlide(@NonNull View bottomSheet, float slideOffset); } /** * The bottom sheet is dragging. */ public static final int STATE_DRAGGING = 1; /** * The bottom sheet is settling. */ public static final int STATE_SETTLING = 2; /** * The bottom sheet is expanded. */ public static final int STATE_EXPANDED = 3; /** * The bottom sheet is collapsed. */ public static final int STATE_COLLAPSED = 4; /** * The bottom sheet is hidden. */ public static final int STATE_HIDDEN = 5; /** @hide */ @IntDef({ STATE_EXPANDED, STATE_COLLAPSED, STATE_DRAGGING, STATE_SETTLING, STATE_HIDDEN }) @Retention(RetentionPolicy.SOURCE) public @interface State { } private static final float HIDE_THRESHOLD = 0.5f; private static final float HIDE_FRICTION = 0.1f; private float mMaximumVelocity; private int mPeekHeight; private int mMinOffset; private int mMaxOffset; private boolean mHideable; @State private int mState = STATE_COLLAPSED; private ViewDragHelper mViewDragHelper; private boolean mIgnoreEvents; private int mLastNestedScrollDy; private boolean mNestedScrolled; private int mParentHeight; private WeakReference<V> mViewRef; private WeakReference<View> mNestedScrollingChildRef; private BottomSheetCallback mCallback; private VelocityTracker mVelocityTracker; private int mActivePointerId; private int mInitialY; private boolean mTouchingScrollingChild; /** * Default constructor for instantiating BottomSheetBehaviors. */ public BottomSheetBehavior() { } /** * Default constructor for inflating BottomSheetBehaviors from layout. * * @param context The {@link Context}. * @param attrs The {@link AttributeSet}. */ public BottomSheetBehavior(Context context, AttributeSet attrs) { super(context, attrs); TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.BottomSheetBehavior_Params); setPeekHeight(a.getDimensionPixelSize(R.styleable.BottomSheetBehavior_Params_behavior_peekHeight_ox, 0)); setHideable(a.getBoolean(R.styleable.BottomSheetBehavior_Params_behavior_hideable_ox, false)); a.recycle(); ViewConfiguration configuration = ViewConfiguration.get(context); mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); } @Override public Parcelable onSaveInstanceState(CoordinatorLayout parent, V child) { return new SavedState(super.onSaveInstanceState(parent, child), mState); } @Override public void onRestoreInstanceState(CoordinatorLayout parent, V child, Parcelable state) { SavedState ss = (SavedState) state; super.onRestoreInstanceState(parent, child, ss.getSuperState()); // Intermediate states are restored as collapsed state if (ss.state == STATE_DRAGGING || ss.state == STATE_SETTLING) { mState = STATE_COLLAPSED; } else { mState = ss.state; } } @Override public boolean onLayoutChild(CoordinatorLayout parent, V child, int layoutDirection) { // First let the parent lay it out if (mState != STATE_DRAGGING && mState != STATE_SETTLING) { parent.onLayoutChild(child, layoutDirection); } // Offset the bottom sheet mParentHeight = parent.getHeight(); mMinOffset = Math.max(0, mParentHeight - child.getHeight()); mMaxOffset = Math.max(mParentHeight - mPeekHeight, mMinOffset); if (mState == STATE_EXPANDED) { ViewCompat.offsetTopAndBottom(child, mMinOffset); } else if (mHideable && mState == STATE_HIDDEN) { ViewCompat.offsetTopAndBottom(child, mParentHeight); } else if (mState == STATE_COLLAPSED) { ViewCompat.offsetTopAndBottom(child, mMaxOffset); } if (mViewDragHelper == null) { mViewDragHelper = ViewDragHelper.create(parent, mDragCallback); } mViewRef = new WeakReference<>(child); mNestedScrollingChildRef = new WeakReference<>(findScrollingChild(child)); return true; } @Override public boolean onInterceptTouchEvent(CoordinatorLayout parent, V child, MotionEvent event) { if (!child.isShown()) { return false; } int action = MotionEventCompat.getActionMasked(event); // Record the velocity if (action == MotionEvent.ACTION_DOWN) { reset(); } if (mVelocityTracker == null) { mVelocityTracker = VelocityTracker.obtain(); } mVelocityTracker.addMovement(event); switch (action) { case MotionEvent.ACTION_UP: case MotionEvent.ACTION_CANCEL: mTouchingScrollingChild = false; mActivePointerId = MotionEvent.INVALID_POINTER_ID; // Reset the ignore flag if (mIgnoreEvents) { mIgnoreEvents = false; return false; } break; case MotionEvent.ACTION_DOWN: int initialX = (int) event.getX(); mInitialY = (int) event.getY(); View scroll = mNestedScrollingChildRef.get(); if (scroll != null && parent.isPointInChildBounds(scroll, initialX, mInitialY)) { mActivePointerId = event.getPointerId(event.getActionIndex()); mTouchingScrollingChild = true; } mIgnoreEvents = mActivePointerId == MotionEvent.INVALID_POINTER_ID && !parent.isPointInChildBounds(child, initialX, mInitialY); break; } if (!mIgnoreEvents && mViewDragHelper.shouldInterceptTouchEvent(event)) { return true; } // We have to handle cases that the ViewDragHelper does not capture the bottom sheet because // it is not the top most view of its parent. This is not necessary when the touch event is // happening over the scrolling content as nested scrolling logic handles that case. View scroll = mNestedScrollingChildRef.get(); return action == MotionEvent.ACTION_MOVE && scroll != null && !mIgnoreEvents && mState != STATE_DRAGGING && !parent.isPointInChildBounds(scroll, (int) event.getX(), (int) event.getY()) && Math.abs(mInitialY - event.getY()) > mViewDragHelper.getTouchSlop(); } @Override public boolean onTouchEvent(CoordinatorLayout parent, V child, MotionEvent event) { if (!child.isShown()) { return false; } int action = MotionEventCompat.getActionMasked(event); if (mState == STATE_DRAGGING && action == MotionEvent.ACTION_DOWN) { return true; } mViewDragHelper.processTouchEvent(event); // Record the velocity if (action == MotionEvent.ACTION_DOWN) { reset(); } if (mVelocityTracker == null) { mVelocityTracker = VelocityTracker.obtain(); } mVelocityTracker.addMovement(event); // The ViewDragHelper tries to capture only the top-most View. We have to explicitly tell it // to capture the bottom sheet in case it is not captured and the touch slop is passed. if (action == MotionEvent.ACTION_MOVE) { if (Math.abs(mInitialY - event.getY()) > mViewDragHelper.getTouchSlop()) { mViewDragHelper.captureChildView(child, event.getPointerId(event.getActionIndex())); } } return true; } @Override public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout, V child, View directTargetChild, View target, int nestedScrollAxes) { mLastNestedScrollDy = 0; mNestedScrolled = false; return (nestedScrollAxes & ViewCompat.SCROLL_AXIS_VERTICAL) != 0; } @Override public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, V child, View target, int dx, int dy, int[] consumed) { View scrollingChild = mNestedScrollingChildRef.get(); if (target != scrollingChild) { return; } int currentTop = child.getTop(); int newTop = currentTop - dy; if (dy > 0) { // Upward if (newTop < mMinOffset) { consumed[1] = currentTop - mMinOffset; ViewCompat.offsetTopAndBottom(child, -consumed[1]); setStateInternal(STATE_EXPANDED); } else { consumed[1] = dy; ViewCompat.offsetTopAndBottom(child, -dy); setStateInternal(STATE_DRAGGING); } } else if (dy < 0) { // Downward if (!ViewCompat.canScrollVertically(target, -1)) { if (newTop <= mMaxOffset || mHideable) { consumed[1] = dy; ViewCompat.offsetTopAndBottom(child, -dy); setStateInternal(STATE_DRAGGING); } else { consumed[1] = currentTop - mMaxOffset; ViewCompat.offsetTopAndBottom(child, -consumed[1]); setStateInternal(STATE_COLLAPSED); } } } dispatchOnSlide(child.getTop()); mLastNestedScrollDy = dy; mNestedScrolled = true; } @Override public void onStopNestedScroll(CoordinatorLayout coordinatorLayout, V child, View target) { if (child.getTop() == mMinOffset) { setStateInternal(STATE_EXPANDED); return; } if (target != mNestedScrollingChildRef.get() || !mNestedScrolled) { return; } int top; int targetState; if (mLastNestedScrollDy > 0) { top = mMinOffset; targetState = STATE_EXPANDED; } else if (mHideable && shouldHide(child, getYVelocity())) { top = mParentHeight; targetState = STATE_HIDDEN; } else if (mLastNestedScrollDy == 0) { int currentTop = child.getTop(); if (Math.abs(currentTop - mMinOffset) < Math.abs(currentTop - mMaxOffset)) { top = mMinOffset; targetState = STATE_EXPANDED; } else { top = mMaxOffset; targetState = STATE_COLLAPSED; } } else { top = mMaxOffset; targetState = STATE_COLLAPSED; } if (mViewDragHelper.smoothSlideViewTo(child, child.getLeft(), top)) { setStateInternal(STATE_SETTLING); ViewCompat.postOnAnimation(child, new SettleRunnable(child, targetState)); } else { setStateInternal(targetState); } mNestedScrolled = false; } @Override public boolean onNestedPreFling(CoordinatorLayout coordinatorLayout, V child, View target, float velocityX, float velocityY) { return target == mNestedScrollingChildRef.get() && (mState != STATE_EXPANDED || super.onNestedPreFling(coordinatorLayout, child, target, velocityX, velocityY)); } /** * Sets the height of the bottom sheet when it is collapsed. * * @param peekHeight The height of the collapsed bottom sheet in pixels. * @attr ref android.support.designox.R.styleable#BottomSheetBehavior_Params_behavior_peekHeight */ public final void setPeekHeight(int peekHeight) { mPeekHeight = Math.max(0, peekHeight); mMaxOffset = mParentHeight - peekHeight; } /** * Gets the height of the bottom sheet when it is collapsed. * * @return The height of the collapsed bottom sheet. * @attr ref android.support.designox.R.styleable#BottomSheetBehavior_Params_behavior_peekHeight */ public final int getPeekHeight() { return mPeekHeight; } /** * Sets whether this bottom sheet can hide when it is swiped down. * * @param hideable {@code true} to make this bottom sheet hideable. * @attr ref android.support.designox.R.styleable#BottomSheetBehavior_Params_behavior_hideable */ public void setHideable(boolean hideable) { mHideable = hideable; } /** * Gets whether this bottom sheet can hide when it is swiped down. * * @return {@code true} if this bottom sheet can hide. * @attr ref android.support.designox.R.styleable#BottomSheetBehavior_Params_behavior_hideable */ public boolean isHideable() { return mHideable; } /** * Sets a callback to be notified of bottom sheet events. * * @param callback The callback to notify when bottom sheet events occur. */ public void setBottomSheetCallback(BottomSheetCallback callback) { mCallback = callback; } /** * Sets the state of the bottom sheet. The bottom sheet will transition to that state with * animation. * * @param state One of {@link #STATE_COLLAPSED}, {@link #STATE_EXPANDED}, or * {@link #STATE_HIDDEN}. */ public final void setState(@State int state) { V child = mViewRef.get(); if (child == null) { return; } int top; if (state == STATE_COLLAPSED) { top = mMaxOffset; } else if (state == STATE_EXPANDED) { top = mMinOffset; } else if (mHideable && state == STATE_HIDDEN) { top = mParentHeight; } else { throw new IllegalArgumentException("Illegal state argument: " + state); } setStateInternal(STATE_SETTLING); if (mViewDragHelper.smoothSlideViewTo(child, child.getLeft(), top)) { ViewCompat.postOnAnimation(child, new SettleRunnable(child, state)); } } /** * Gets the current state of the bottom sheet. * * @return One of {@link #STATE_EXPANDED}, {@link #STATE_COLLAPSED}, {@link #STATE_DRAGGING}, * and {@link #STATE_SETTLING}. */ @State public final int getState() { return mState; } private void setStateInternal(@State int state) { if (mState == state) { return; } mState = state; View bottomSheet = mViewRef.get(); if (bottomSheet != null && mCallback != null) { mCallback.onStateChanged(bottomSheet, state); } } private void reset() { mActivePointerId = ViewDragHelper.INVALID_POINTER; if (mVelocityTracker != null) { mVelocityTracker.recycle(); mVelocityTracker = null; } } private boolean shouldHide(View child, float yvel) { if (child.getTop() < mMaxOffset) { // It should not hide, but collapse. return false; } final float newTop = child.getTop() + yvel * HIDE_FRICTION; return Math.abs(newTop - mMaxOffset) / (float) mPeekHeight > HIDE_THRESHOLD; } private View findScrollingChild(View view) { if (view instanceof NestedScrollingChild) { return view; } if (view instanceof ViewGroup) { ViewGroup group = (ViewGroup) view; for (int i = 0, count = group.getChildCount(); i < count; i++) { View scrollingChild = findScrollingChild(group.getChildAt(i)); if (scrollingChild != null) { return scrollingChild; } } } return null; } private float getYVelocity() { mVelocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); return VelocityTrackerCompat.getYVelocity(mVelocityTracker, mActivePointerId); } private final ViewDragHelper.Callback mDragCallback = new ViewDragHelper.Callback() { @Override public boolean tryCaptureView(View child, int pointerId) { if (mState == STATE_DRAGGING) { return false; } if (mTouchingScrollingChild) { return false; } if (mState == STATE_EXPANDED && mActivePointerId == pointerId) { View scroll = mNestedScrollingChildRef.get(); if (scroll != null && ViewCompat.canScrollVertically(scroll, -1)) { // Let the content scroll up return false; } } return mViewRef != null && mViewRef.get() == child; } @Override public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) { dispatchOnSlide(top); } @Override public void onViewDragStateChanged(int state) { if (state == ViewDragHelper.STATE_DRAGGING) { setStateInternal(STATE_DRAGGING); } } @Override public void onViewReleased(View releasedChild, float xvel, float yvel) { int top; @State int targetState; if (yvel < 0) { // Moving up top = mMinOffset; targetState = STATE_EXPANDED; } else if (mHideable && shouldHide(releasedChild, yvel)) { top = mParentHeight; targetState = STATE_HIDDEN; } else if (yvel == 0.f) { int currentTop = releasedChild.getTop(); if (Math.abs(currentTop - mMinOffset) < Math.abs(currentTop - mMaxOffset)) { top = mMinOffset; targetState = STATE_EXPANDED; } else { top = mMaxOffset; targetState = STATE_COLLAPSED; } } else { top = mMaxOffset; targetState = STATE_COLLAPSED; } if (mViewDragHelper.settleCapturedViewAt(releasedChild.getLeft(), top)) { setStateInternal(STATE_SETTLING); ViewCompat.postOnAnimation(releasedChild, new SettleRunnable(releasedChild, targetState)); } else { setStateInternal(targetState); } } @Override public int clampViewPositionVertical(View child, int top, int dy) { return MathUtils.constrain(top, mMinOffset, mHideable ? mParentHeight : mMaxOffset); } @Override public int clampViewPositionHorizontal(View child, int left, int dx) { return child.getLeft(); } @Override public int getViewVerticalDragRange(View child) { if (mHideable) { return mParentHeight - mMinOffset; } else { return mMaxOffset - mMinOffset; } } }; private void dispatchOnSlide(int top) { View bottomSheet = mViewRef.get(); if (bottomSheet != null && mCallback != null) { if (top > mMaxOffset) { mCallback.onSlide(bottomSheet, (float) (mMaxOffset - top) / mPeekHeight); } else { mCallback.onSlide(bottomSheet, (float) (mMaxOffset - top) / ((mMaxOffset - mMinOffset))); } } } private class SettleRunnable implements Runnable { private final View mView; @State private final int mTargetState; SettleRunnable(View view, @State int targetState) { mView = view; mTargetState = targetState; } @Override public void run() { if (mViewDragHelper != null && mViewDragHelper.continueSettling(true)) { ViewCompat.postOnAnimation(mView, this); } else { setStateInternal(mTargetState); } } } protected static class SavedState extends View.BaseSavedState { @State final int state; public SavedState(Parcel source) { super(source); //noinspection ResourceType state = source.readInt(); } public SavedState(Parcelable superState, @State int state) { super(superState); this.state = state; } @Override public void writeToParcel(Parcel out, int flags) { super.writeToParcel(out, flags); out.writeInt(state); } public static final Parcelable.Creator<SavedState> CREATOR = new Parcelable.Creator<SavedState>() { @Override public SavedState createFromParcel(Parcel source) { return new SavedState(source); } @Override public SavedState[] newArray(int size) { return new SavedState[size]; } }; } /** * A utility function to get the {@link BottomSheetBehavior} associated with the {@code view}. * * @param view The {@link View} with {@link BottomSheetBehavior}. * @return The {@link BottomSheetBehavior} associated with the {@code view}. */ @SuppressWarnings("unchecked") public static <V extends View> BottomSheetBehavior<V> from(V view) { ViewGroup.LayoutParams params = view.getLayoutParams(); if (!(params instanceof CoordinatorLayout.LayoutParams)) { throw new IllegalArgumentException("The view is not a child of CoordinatorLayout"); } CoordinatorLayout.Behavior behavior = ((CoordinatorLayout.LayoutParams) params).getBehavior(); if (!(behavior instanceof BottomSheetBehavior)) { throw new IllegalArgumentException("The view is not associated with BottomSheetBehavior"); } return (BottomSheetBehavior<V>) behavior; } }