Java tutorial
/* * Copyright 2013 Google Inc. * * 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 org.notlocalhost.superlistview; import android.graphics.Rect; import android.os.SystemClock; import android.support.v4.view.MotionEventCompat; import android.view.*; import android.widget.AbsListView; import android.widget.ListView; import com.nineoldandroids.animation.Animator; import com.nineoldandroids.animation.AnimatorListenerAdapter; import com.nineoldandroids.animation.ValueAnimator; import com.nineoldandroids.view.animation.AnimatorProxy; import java.util.ArrayList; import java.util.Collections; import java.util.List; import static com.nineoldandroids.view.ViewPropertyAnimator.animate; /** * A {@link View.OnTouchListener} that makes the list items in a {@link ListView} * dismissable. {@link ListView} is given special treatment because by default it handles touches * for its list items... i.e. it's in charge of drawing the pressed state (the list selector), * handling list item clicks, etc. * * <p>After creating the listener, the caller should also call * {@link ListView#setOnScrollListener(AbsListView.OnScrollListener)}, passing * in the scroll listener returned by {@link #makeScrollListener()}. If a scroll listener is * already assigned, the caller should still pass scroll changes through to this listener. This will * ensure that this {@link SwipeDismissListViewTouchListener} is paused during list view * scrolling.</p> * * <p>Example usage:</p> * * <pre> * SwipeDismissListViewTouchListener touchListener = * new SwipeDismissListViewTouchListener( * listView, * new SwipeDismissListViewTouchListener.OnDismissCallback() { * public void onDismiss(ListView listView, int[] reverseSortedPositions) { * for (int position : reverseSortedPositions) { * adapter.remove(adapter.getItem(position)); * } * adapter.notifyDataSetChanged(); * } * }); * listView.setOnTouchListener(touchListener); * listView.setOnScrollListener(touchListener.makeScrollListener()); * </pre> * * <p>This class Requires API level 12 or later due to use of {@link * ViewPropertyAnimator}.</p> * * <p>For a generalized {@link View.OnTouchListener} that makes any view dismissable, * see {@link SwipeDismissTouchListener}.</p> * * @see SwipeDismissTouchListener */ public class SwipeDismissListViewTouchListener implements View.OnTouchListener { // Cached ViewConfiguration and system-wide constant values private int mSlop; private int mMinFlingVelocity; private int mMaxFlingVelocity; private long mAnimationTime; // Fixed properties private ListView mListView; private DismissCallbacks mCallbacks; private int mViewWidth = 1; // 1 and not 0 to prevent dividing by zero // Transient properties private List<PendingDismissData> mPendingDismisses = new ArrayList<PendingDismissData>(); private int mDismissAnimationRefCount = 0; private float mDownX; private float mDownY; private boolean mSwiping; private int mSwipingSlop; private VelocityTracker mVelocityTracker; private int mDownPosition; private View mDownView; private AnimatorProxy mDownViewProxy; private boolean mPaused; /** * The callback interface used by {@link SwipeDismissListViewTouchListener} to inform its client * about a successful dismissal of one or more list item positions. */ public interface DismissCallbacks { /** * Called to determine whether the given position can be dismissed. */ boolean canDismiss(int position); /** * Called when the user has indicated they she would like to dismiss one or more list item * positions. * * @param listView The originating {@link ListView}. * @param reverseSortedPositions An array of positions to dismiss, sorted in descending * order for convenience. */ void onDismiss(ListView listView, int[] reverseSortedPositions); } /** * Constructs a new swipe-to-dismiss touch listener for the given list view. * * @param listView The list view whose items should be dismissable. * @param callbacks The callback to trigger when the user has indicated that she would like to * dismiss one or more list items. */ public SwipeDismissListViewTouchListener(ListView listView, DismissCallbacks callbacks) { ViewConfiguration vc = ViewConfiguration.get(listView.getContext()); mSlop = vc.getScaledTouchSlop(); mMinFlingVelocity = vc.getScaledMinimumFlingVelocity() * 16; mMaxFlingVelocity = vc.getScaledMaximumFlingVelocity(); mAnimationTime = listView.getContext().getResources().getInteger(android.R.integer.config_shortAnimTime); mListView = listView; mCallbacks = callbacks; } /** * Enables or disables (pauses or resumes) watching for swipe-to-dismiss gestures. * * @param enabled Whether or not to watch for gestures. */ public void setEnabled(boolean enabled) { mPaused = !enabled; } /** * Returns an {@link AbsListView.OnScrollListener} to be added to the {@link * ListView} using {@link ListView#setOnScrollListener(AbsListView.OnScrollListener)}. * If a scroll listener is already assigned, the caller should still pass scroll changes through * to this listener. This will ensure that this {@link SwipeDismissListViewTouchListener} is * paused during list view scrolling.</p> * * @see SwipeDismissListViewTouchListener */ public AbsListView.OnScrollListener makeScrollListener() { return new AbsListView.OnScrollListener() { @Override public void onScrollStateChanged(AbsListView absListView, int scrollState) { setEnabled(scrollState != AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL); } @Override public void onScroll(AbsListView absListView, int i, int i1, int i2) { } }; } @Override public boolean onTouch(View view, MotionEvent motionEvent) { if (mViewWidth < 2) { mViewWidth = mListView.getWidth(); } switch (MotionEventCompat.getActionMasked(motionEvent)) { case MotionEvent.ACTION_DOWN: { if (mPaused) { return false; } // TODO: ensure this is a finger, and set a flag // Find the child view that was touched (perform a hit test) Rect rect = new Rect(); int childCount = mListView.getChildCount(); int[] listViewCoords = new int[2]; mListView.getLocationOnScreen(listViewCoords); int x = (int) motionEvent.getRawX() - listViewCoords[0]; int y = (int) motionEvent.getRawY() - listViewCoords[1]; View child; for (int i = 0; i < childCount; i++) { child = mListView.getChildAt(i); child.getHitRect(rect); if (rect.contains(x, y)) { mDownView = child; mDownViewProxy = AnimatorProxy.wrap(child); break; } } if (mDownView != null) { mDownX = motionEvent.getRawX(); mDownY = motionEvent.getRawY(); mDownPosition = mListView.getPositionForView(mDownView); if (mCallbacks.canDismiss(mDownPosition)) { mVelocityTracker = VelocityTracker.obtain(); mVelocityTracker.addMovement(motionEvent); } else { mDownView = null; mDownViewProxy = null; } } return false; } case MotionEvent.ACTION_CANCEL: { if (mVelocityTracker == null) { break; } if (mDownView != null && mSwiping) { // cancel animate(mDownView).translationX(0).alpha(1).setDuration(mAnimationTime).setListener(null); } mVelocityTracker.recycle(); mVelocityTracker = null; mDownX = 0; mDownY = 0; mDownView = null; mDownViewProxy = null; mDownPosition = ListView.INVALID_POSITION; mSwiping = false; break; } case MotionEvent.ACTION_UP: { if (mVelocityTracker == null) { break; } float deltaX = motionEvent.getRawX() - mDownX; mVelocityTracker.addMovement(motionEvent); mVelocityTracker.computeCurrentVelocity(1000); float velocityX = mVelocityTracker.getXVelocity(); float absVelocityX = Math.abs(velocityX); float absVelocityY = Math.abs(mVelocityTracker.getYVelocity()); boolean dismiss = false; boolean dismissRight = false; if (Math.abs(deltaX) > mViewWidth / 2 && mSwiping) { dismiss = true; dismissRight = deltaX > 0; } else if (mMinFlingVelocity <= absVelocityX && absVelocityX <= mMaxFlingVelocity && absVelocityY < absVelocityX && mSwiping) { // dismiss only if flinging in the same direction as dragging dismiss = (velocityX < 0) == (deltaX < 0); dismissRight = mVelocityTracker.getXVelocity() > 0; } if (dismiss && mDownPosition != ListView.INVALID_POSITION) { // dismiss final View downView = mDownView; // mDownView gets null'd before animation ends final int downPosition = mDownPosition; ++mDismissAnimationRefCount; animate(mDownView).translationX(dismissRight ? mViewWidth : -mViewWidth).alpha(0) .setDuration(mAnimationTime).setListener(new AnimatorListenerAdapter() { @Override public void onAnimationEnd(Animator animation) { performDismiss(downView, downPosition); } }); } else { animate(mDownView).translationX(0).alpha(1).setDuration(mAnimationTime).setListener(null); } mVelocityTracker.recycle(); mVelocityTracker = null; mDownX = 0; mDownY = 0; mDownView = null; mDownViewProxy = null; mDownPosition = ListView.INVALID_POSITION; mSwiping = false; break; } case MotionEvent.ACTION_MOVE: { if (mVelocityTracker == null || mPaused) { break; } mVelocityTracker.addMovement(motionEvent); float deltaX = motionEvent.getRawX() - mDownX; float deltaY = motionEvent.getRawY() - mDownY; if (Math.abs(deltaX) > mSlop && Math.abs(deltaY) < Math.abs(deltaX) / 2) { mSwiping = true; mSwipingSlop = (deltaX > 0 ? mSlop : -mSlop); mListView.requestDisallowInterceptTouchEvent(true); // Cancel ListView's touch (un-highlighting the item) MotionEvent cancelEvent = MotionEvent.obtain(motionEvent); cancelEvent.setAction(MotionEvent.ACTION_CANCEL | (MotionEventCompat .getActionIndex(motionEvent) << MotionEventCompat.ACTION_POINTER_INDEX_SHIFT)); mListView.onTouchEvent(cancelEvent); cancelEvent.recycle(); } if (mSwiping) { mDownViewProxy.setTranslationX(deltaX - mSwipingSlop); mDownViewProxy.setAlpha(Math.max(0f, Math.min(1f, 1f - 2f * Math.abs(deltaX) / mViewWidth))); return true; } break; } } return false; } class PendingDismissData implements Comparable<PendingDismissData> { public int position; public View view; public PendingDismissData(int position, View view) { this.position = position; this.view = view; } @Override public int compareTo(PendingDismissData other) { // Sort by descending position return other.position - position; } } private void performDismiss(final View dismissView, final int dismissPosition) { // Animate the dismissed list item to zero-height and fire the dismiss callback when // all dismissed list item animations have completed. This triggers layout on each animation // frame; in the future we may want to do something smarter and more performant. final ViewGroup.LayoutParams lp = dismissView.getLayoutParams(); final int originalHeight = dismissView.getHeight(); ValueAnimator animator = ValueAnimator.ofInt(originalHeight, 1).setDuration(mAnimationTime); animator.addListener(new AnimatorListenerAdapter() { @Override public void onAnimationEnd(Animator animation) { --mDismissAnimationRefCount; if (mDismissAnimationRefCount == 0) { // No active animations, process all pending dismisses. // Sort by descending position Collections.sort(mPendingDismisses); int[] dismissPositions = new int[mPendingDismisses.size()]; for (int i = mPendingDismisses.size() - 1; i >= 0; i--) { dismissPositions[i] = mPendingDismisses.get(i).position; } mCallbacks.onDismiss(mListView, dismissPositions); // Reset mDownPosition to avoid MotionEvent.ACTION_UP trying to start a dismiss // animation with a stale position mDownPosition = ListView.INVALID_POSITION; ViewGroup.LayoutParams lp; for (PendingDismissData pendingDismiss : mPendingDismisses) { // Reset view presentation AnimatorProxy.wrap(pendingDismiss.view).setAlpha(1f); AnimatorProxy.wrap(pendingDismiss.view).setTranslationX(0); lp = pendingDismiss.view.getLayoutParams(); lp.height = originalHeight; pendingDismiss.view.setLayoutParams(lp); } // Send a cancel event long time = SystemClock.uptimeMillis(); MotionEvent cancelEvent = MotionEvent.obtain(time, time, MotionEvent.ACTION_CANCEL, 0, 0, 0); mListView.dispatchTouchEvent(cancelEvent); mPendingDismisses.clear(); } } }); animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() { @Override public void onAnimationUpdate(ValueAnimator valueAnimator) { lp.height = (Integer) valueAnimator.getAnimatedValue(); dismissView.setLayoutParams(lp); } }); mPendingDismisses.add(new PendingDismissData(dismissPosition, dismissView)); animator.start(); } }