Java tutorial
/* * Copyright (C) 2013 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 com.hayukleung.app.view.refresh; import android.content.Context; import android.content.res.TypedArray; import android.support.v4.view.MotionEventCompat; import android.support.v4.view.ViewCompat; import android.support.v7.widget.LinearLayoutManager; import android.support.v7.widget.RecyclerView; import android.support.v7.widget.StaggeredGridLayoutManager; import android.util.AttributeSet; import android.util.DisplayMetrics; import android.util.Log; import android.view.MotionEvent; import android.view.View; import android.view.ViewConfiguration; import android.view.ViewGroup; import android.view.animation.AccelerateInterpolator; import android.view.animation.Animation; import android.view.animation.Animation.AnimationListener; import android.view.animation.DecelerateInterpolator; import android.view.animation.Transformation; import android.widget.AbsListView; import com.hayukleung.app.view.util.ReflectUtils; /** * The SwipeRefreshLayout should be used whenever the user can refresh the * contents of a view via a vertical swipe gesture. The activity that * instantiates this view should add an OnRefreshListener to be notified * whenever the swipe to refresh gesture is completed. The SwipeRefreshLayout * will notify the listener each and every time the gesture is completed again; * the listener is responsible for correctly determining when to actually * initiate a refresh of its content. If the listener determines there should * not be a refresh, it must call setRefreshing(false) to cancel any visual * indication of a refresh. If an activity wishes to show just the progress * animation, it should call setRefreshing(true). To disable the gesture and progress * animation, call setEnabled(false) on the view. * <p> * <p> This layout should be made the parent of the view that will be refreshed as a * result of the gesture and can only support one direct child. This view will * also be made the target of the gesture and will be forced to match both the * width and the height supplied in this layout. The SwipeRefreshLayout does not * provide accessibility events; instead, a menu item must be provided to allow * refresh of the content wherever this gesture is used.</p> */ public class SwipeRefreshLayout extends ViewGroup { protected static final float MAX_SWIPE_DISTANCE_FACTOR = .6f; protected static final int REFRESH_TRIGGER_DISTANCE = 120; private static final String LOG_TAG = SwipeRefreshLayout.class.getSimpleName(); private static final long RETURN_TO_ORIGINAL_POSITION_TIMEOUT = 300; private static final float ACCELERATE_INTERPOLATION_FACTOR = 1.5f; private static final float DECELERATE_INTERPOLATION_FACTOR = 2f; private static final float PROGRESS_BAR_HEIGHT = 4; private static final int INVALID_POINTER = -1; private static final int[] LAYOUT_ATTRS = new int[] { android.R.attr.enabled }; private final DecelerateInterpolator mDecelerateInterpolator; private final AccelerateInterpolator mAccelerateInterpolator; // private SwipeProgressBar mProgressBar; //the thing that shows progress is going protected View mTarget; //the content that gets pulled down protected int mOriginalOffsetTop; protected float mDistanceToTriggerSync = -1; private OnRefreshListener mListener; private int mFrom; private final Animation mAnimateToStartPosition = new Animation() { @Override public void applyTransformation(float interpolatedTime, Transformation t) { int targetTop = 0; if (mFrom != mOriginalOffsetTop) { targetTop = (mFrom + (int) ((mOriginalOffsetTop - mFrom) * interpolatedTime)); } int offset = targetTop - mTarget.getTop(); final int currentTop = mTarget.getTop(); if (offset + currentTop < 0) { offset = 0 - currentTop; } setTargetOffsetTopAndBottom(offset); } }; private boolean mRefreshing = false; private int mTouchSlop; private int mMediumAnimationDuration; private float mFromPercentage = 0; private float mCurrPercentage = 0; private final AnimationListener mShrinkAnimationListener = new BaseAnimationListener() { @Override public void onAnimationEnd(Animation animation) { mCurrPercentage = 0; } }; private int mCurrentTargetOffsetTop; private final AnimationListener mReturnToStartPositionListener = new BaseAnimationListener() { @Override public void onAnimationEnd(Animation animation) { // Once the target content has returned to its start position, reset // the target offset to 0 mCurrentTargetOffsetTop = 0; } }; private float mInitialMotionY; private float mLastMotionY; private boolean mIsBeingDragged; private boolean mIsRefreshable; private int mActivePointerId = INVALID_POINTER; // Target is returning to its start offset because it was cancelled or a // refresh was triggered. private boolean mReturningToStart; private final Runnable mReturnToStartPosition = new Runnable() { @Override public void run() { mReturningToStart = true; animateOffsetToStartPosition(mCurrentTargetOffsetTop + getPaddingTop(), mReturnToStartPositionListener); } }; private Animation mShrinkTrigger = new Animation() { @Override public void applyTransformation(float interpolatedTime, Transformation t) { float percent = mFromPercentage + ((0 - mFromPercentage) * interpolatedTime); mListener.onProgress(mCurrPercentage); } }; // Cancel the refresh gesture and animate everything back to its original state. private final Runnable mCancel = new Runnable() { @Override public void run() { mReturningToStart = true; // Timeout fired since the user last moved their finger; animate the // trigger to 0 and put the target back at its original position mFromPercentage = mCurrPercentage; mShrinkTrigger.setDuration(mMediumAnimationDuration); mShrinkTrigger.setAnimationListener(mShrinkAnimationListener); mShrinkTrigger.reset(); mShrinkTrigger.setInterpolator(mDecelerateInterpolator); startAnimation(mShrinkTrigger); animateOffsetToStartPosition(mCurrentTargetOffsetTop + getPaddingTop(), mReturnToStartPositionListener); } }; private boolean mTimeoutable; /** * Simple constructor to use when creating a SwipeRefreshLayout from code. * * @param context */ public SwipeRefreshLayout(Context context) { this(context, null); } /** * Constructor that is called when inflating SwipeRefreshLayout from XML. * * @param context * @param attrs */ public SwipeRefreshLayout(Context context, AttributeSet attrs) { super(context, attrs); mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop(); mMediumAnimationDuration = getResources().getInteger(android.R.integer.config_mediumAnimTime); setWillNotDraw(false); mDecelerateInterpolator = new DecelerateInterpolator(DECELERATE_INTERPOLATION_FACTOR); mAccelerateInterpolator = new AccelerateInterpolator(ACCELERATE_INTERPOLATION_FACTOR); final TypedArray a = context.obtainStyledAttributes(attrs, LAYOUT_ATTRS); setEnabled(a.getBoolean(0, true)); a.recycle(); } @Override public void onAttachedToWindow() { super.onAttachedToWindow(); removeCallbacks(mCancel); removeCallbacks(mReturnToStartPosition); } @Override public void onDetachedFromWindow() { super.onDetachedFromWindow(); removeCallbacks(mReturnToStartPosition); removeCallbacks(mCancel); } private void animateOffsetToStartPosition(int from, AnimationListener listener) { mFrom = from; mAnimateToStartPosition.reset(); mAnimateToStartPosition.setDuration(mMediumAnimationDuration); mAnimateToStartPosition.setAnimationListener(listener); mAnimateToStartPosition.setInterpolator(mDecelerateInterpolator); mTarget.startAnimation(mAnimateToStartPosition); } /** * Set the listener to be notified when a refresh is triggered via the swipe * gesture. */ public void setOnRefreshListener(OnRefreshListener listener) { mListener = listener; } private void setTriggerPercentage(float percent) { if (percent == 0f) { // No-op. A null trigger means it's uninitialized, and setting it to zero-percent // means we're trying to reset state, so there's nothing to reset in this case. mCurrPercentage = 0; return; } mCurrPercentage = percent; mListener.onProgress(mCurrPercentage); } /** * @return Whether the SwipeRefreshWidget is actively showing refresh * progress. */ public boolean isRefreshing() { return mRefreshing; } /** * Notify the widget that refresh state has changed. Do not call this when * refresh is triggered by a swipe gesture. * * @param refreshing Whether or not the view should show refresh progress. */ public void setRefreshing(boolean refreshing) { if (mRefreshing != refreshing) { ensureTarget(); mCurrPercentage = 0; mRefreshing = refreshing; } } protected void ensureTarget() { // Don't bother getting the parent height if the parent hasn't been laid out yet. if (mTarget == null) { if (getChildCount() > 1 && !isInEditMode()) { throw new IllegalStateException("SwipeRefreshLayout can host only one direct child"); } mTarget = getChildAt(0); mOriginalOffsetTop = mTarget.getTop() + getPaddingTop(); } if (mDistanceToTriggerSync == -1) { if (getParent() != null && ((View) getParent()).getHeight() > 0) { final DisplayMetrics metrics = getResources().getDisplayMetrics(); mDistanceToTriggerSync = (int) Math.min( ((View) getParent()).getHeight() * MAX_SWIPE_DISTANCE_FACTOR, REFRESH_TRIGGER_DISTANCE * metrics.density); } } } @Override protected void onLayout(boolean changed, int left, int top, int right, int bottom) { final int width = getMeasuredWidth(); final int height = getMeasuredHeight(); if (getChildCount() == 0) { return; } final View child = getChildAt(0); final int childLeft = getPaddingLeft(); final int childTop = mCurrentTargetOffsetTop + getPaddingTop(); final int childWidth = width - getPaddingLeft() - getPaddingRight(); final int childHeight = height - getPaddingTop() - getPaddingBottom(); child.layout(childLeft, childTop, childLeft + childWidth, childTop + childHeight); } @Override public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); if (getChildCount() > 1 && !isInEditMode()) { throw new IllegalStateException("SwipeRefreshLayout can host only one direct child"); } if (getChildCount() > 0) { getChildAt(0).measure( MeasureSpec.makeMeasureSpec(getMeasuredWidth() - getPaddingLeft() - getPaddingRight(), MeasureSpec.EXACTLY), MeasureSpec.makeMeasureSpec(getMeasuredHeight() - getPaddingTop() - getPaddingBottom(), MeasureSpec.EXACTLY)); } } /** * @return Whether it is possible for the child view of this layout to * scroll up. Override this if the child view is a custom view. */ public boolean canChildScrollUp() { if (android.os.Build.VERSION.SDK_INT < 14) { if (mTarget instanceof AbsListView) { final AbsListView absListView = (AbsListView) mTarget; return absListView.getChildCount() > 0 && (absListView.getFirstVisiblePosition() > 0 || absListView.getChildAt(0).getTop() < absListView.getPaddingTop()); } else if (mTarget instanceof RecyclerView) { final RecyclerView recyclerView = (RecyclerView) mTarget; RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager(); if (layoutManager instanceof LinearLayoutManager) { int position = ((LinearLayoutManager) layoutManager).findFirstCompletelyVisibleItemPosition(); return position != 0; } else if (layoutManager instanceof StaggeredGridLayoutManager) { int[] positions = ((StaggeredGridLayoutManager) layoutManager) .findFirstCompletelyVisibleItemPositions(null); for (int i = 0; i < positions.length; i++) { if (positions[i] == 0) { return false; } } } return true; } else { return mTarget.getScrollY() > 0; } } else { return ViewCompat.canScrollVertically(mTarget, -1); } } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { ensureTarget(); final int action = MotionEventCompat.getActionMasked(ev); if (mReturningToStart && action == MotionEvent.ACTION_DOWN) { mReturningToStart = false; } if (!isEnabled() || mReturningToStart || canChildScrollUp() || isDisallowInterceptTouchEvent()) { // Fail fast if we're not in a state where a swipe is possible return false; } switch (action) { case MotionEvent.ACTION_DOWN: mLastMotionY = mInitialMotionY = ev.getY(); mActivePointerId = MotionEventCompat.getPointerId(ev, 0); mIsBeingDragged = false; mCurrPercentage = 0; break; case MotionEvent.ACTION_MOVE: if (mActivePointerId == INVALID_POINTER) { Log.e(LOG_TAG, "Got ACTION_MOVE event but don't have an active pointer id."); return false; } final int pointerIndex = MotionEventCompat.findPointerIndex(ev, mActivePointerId); if (pointerIndex < 0) { Log.e(LOG_TAG, "Got ACTION_MOVE event but have an invalid active pointer id."); return false; } if (mRefreshing) { return false; } final float y = MotionEventCompat.getY(ev, pointerIndex); final float yDiff = y - mInitialMotionY; if (yDiff > mTouchSlop) { mLastMotionY = y; mIsBeingDragged = true; } break; case MotionEventCompat.ACTION_POINTER_UP: onSecondaryPointerUp(ev); break; case MotionEvent.ACTION_UP: case MotionEvent.ACTION_CANCEL: mIsBeingDragged = false; mCurrPercentage = 0; mActivePointerId = INVALID_POINTER; break; } return mIsBeingDragged; } private boolean isDisallowInterceptTouchEvent() { if (mTarget == null) { return false; } try { Integer groupFlags = ReflectUtils.getFieldValue(mTarget, ViewGroup.class, "mGroupFlags"); Integer FLAG_DISALLOW_INTERCEPT = ReflectUtils.getFieldValue(mTarget, ViewGroup.class, "FLAG_DISALLOW_INTERCEPT"); return (groupFlags & FLAG_DISALLOW_INTERCEPT) != 0; } catch (NoSuchFieldException ignored) { } catch (IllegalAccessException ignored) { } return false; } @Override public void requestDisallowInterceptTouchEvent(boolean b) { // Nope. } @Override public boolean onTouchEvent(MotionEvent ev) { final int action = MotionEventCompat.getActionMasked(ev); if (mReturningToStart && action == MotionEvent.ACTION_DOWN) { mReturningToStart = false; } if (!isEnabled() || mReturningToStart || canChildScrollUp()) { // Fail fast if we're not in a state where a swipe is possible return false; } switch (action) { case MotionEvent.ACTION_DOWN: mLastMotionY = mInitialMotionY = ev.getY(); mActivePointerId = MotionEventCompat.getPointerId(ev, 0); mIsBeingDragged = false; mCurrPercentage = 0; break; case MotionEvent.ACTION_MOVE: final int pointerIndex = MotionEventCompat.findPointerIndex(ev, mActivePointerId); if (pointerIndex < 0) { Log.e(LOG_TAG, "Got ACTION_MOVE event but have an invalid active pointer id."); return false; } final float y = MotionEventCompat.getY(ev, pointerIndex); final float yDiff = y - mInitialMotionY; if (!mIsBeingDragged && yDiff > mTouchSlop) { mIsBeingDragged = true; } if (mIsBeingDragged) { // User velocity passed min velocity; trigger a refresh if (yDiff > mDistanceToTriggerSync) { // User movement passed distance; trigger a refresh mIsRefreshable = true; } else { // Just track the user's movement mIsRefreshable = false; if (mLastMotionY > y && mTarget.getTop() == getPaddingTop()) { // If the user puts the view back at the top, we // don't need to. This shouldn't be considered // cancelling the gesture as the user can restart from the top. removeCallbacks(mCancel); } else { updatePositionTimeout(); } } float diff = Math.min(yDiff, mDistanceToTriggerSync); setTriggerPercentage(mAccelerateInterpolator.getInterpolation(diff / mDistanceToTriggerSync)); updateContentOffsetTop((int) (yDiff)); mLastMotionY = y; } break; case MotionEventCompat.ACTION_POINTER_DOWN: { final int index = MotionEventCompat.getActionIndex(ev); mLastMotionY = MotionEventCompat.getY(ev, index); mActivePointerId = MotionEventCompat.getPointerId(ev, index); break; } case MotionEventCompat.ACTION_POINTER_UP: onSecondaryPointerUp(ev); break; case MotionEvent.ACTION_UP: case MotionEvent.ACTION_CANCEL: if (mIsRefreshable) { startRefresh(); } mIsRefreshable = false; mIsBeingDragged = false; mCurrPercentage = 0; mActivePointerId = INVALID_POINTER; mCancel.run(); return false; } return true; } private void startRefresh() { removeCallbacks(mCancel); mReturnToStartPosition.run(); setRefreshing(true); mListener.onRefresh(); } private void updateContentOffsetTop(int targetTop) { final int currentTop = mTarget.getTop(); if (targetTop > mDistanceToTriggerSync) { targetTop = (int) mDistanceToTriggerSync; } else if (targetTop < 0) { targetTop = 0; } setTargetOffsetTopAndBottom(targetTop - currentTop); } private void setTargetOffsetTopAndBottom(int offset) { mTarget.offsetTopAndBottom(offset); if (android.os.Build.VERSION.SDK_INT < android.os.Build.VERSION_CODES.ICE_CREAM_SANDWICH) { mTarget.invalidate(); } mCurrentTargetOffsetTop = mTarget.getTop(); } public boolean isTimeoutable() { return mTimeoutable; } public void setTimeoutable(boolean timeoutable) { this.mTimeoutable = timeoutable; } private void updatePositionTimeout() { if (mTimeoutable) { removeCallbacks(mCancel); postDelayed(mCancel, RETURN_TO_ORIGINAL_POSITION_TIMEOUT); } } private void onSecondaryPointerUp(MotionEvent ev) { final int pointerIndex = MotionEventCompat.getActionIndex(ev); final int pointerId = MotionEventCompat.getPointerId(ev, pointerIndex); if (pointerId == mActivePointerId) { // This was our active pointer going up. Choose a new // active pointer and adjust accordingly. final int newPointerIndex = pointerIndex == 0 ? 1 : 0; mLastMotionY = MotionEventCompat.getY(ev, newPointerIndex); mActivePointerId = MotionEventCompat.getPointerId(ev, newPointerIndex); } } /** * Classes that wish to be notified when the swipe gesture correctly * triggers a refresh should implement this interface. */ public interface OnRefreshListener { public void onRefresh(); public void onProgress(float progress); } /** * Simple AnimationListener to avoid having to implement unneeded methods in * AnimationListeners. */ private class BaseAnimationListener implements AnimationListener { @Override public void onAnimationStart(Animation animation) { } @Override public void onAnimationEnd(Animation animation) { } @Override public void onAnimationRepeat(Animation animation) { } } }