《Android SwipeToDismiss：左右滑动删除ListView条目Item》

Android的SwipeToDismiss是github上一个第三方开源框架（github上的项目链接地址： ）。该开源项目旨在：使得一个ListView的item在用户的手指在屏幕上左滑或者右滑时候，删除当前的这个ListView Item。

 此种特效在新版的Android中应用不少。比方在Android 5.0及以上版本号中，通知栏下拉菜单中的条目。就是这样的操作效果，用户把通知栏下拉出来。手指轻触某一项。左滑或者右滑。删除（清除）此项。

 在   上下载到到库文件有两个（此说是基于截止2015年7月27日的版本号，兴许版本号或许会有所不同）：SwipeDismissListViewTouchListener.java 和 SwipeDismissTouchListener.java 。假设仅仅是打算简单的仅仅是支持一个ListView列表中item左滑/右滑删除，那么仅仅仅仅导入SwipeDismissListViewTouchListener.java这一个库文件就可以。

如今就给出一个简单样例，说明怎样改造一个标准ListView。使其支持左右滑动某个item然后删除之。

測试用的MainActivity.java :

package zhangphil.listview;import java.util.ArrayList;import android.app.ListActivity;import android.os.Bundle;import android.util.Log;import android.widget.ArrayAdapter;import android.widget.ListView;public class MainActivity extends ListActivity {	private ArrayAdapter
     
       adapter = null;	private ArrayList
      
        items = null;	@Override	protected void onCreate(Bundle savedInstanceState) {		super.onCreate(savedInstanceState);		ListView listView = this.getListView();		// 測试数据集。
      
     

items = new ArrayList<String>(); for (int i = 0; i < 50; i++) { items.add("数据:" + i); } adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, items); listView.setAdapter(adapter); // 将ListView传递过来。

SwipeDismissListViewTouchListener touchListener = new SwipeDismissListViewTouchListener( listView, new SwipeDismissListViewTouchListener.DismissCallbacks() { @Override public boolean canDismiss(int position) { return true; } // 此处将运行删除。记得要notifyDataSetChanged()。 @Override public void onDismiss(ListView listView, int[] reverseSortedPositions) { for (int pos : reverseSortedPositions) { items.remove(pos); Log.i(this.getClass().getName(), "删除:" + pos); } adapter.notifyDataSetChanged(); } }); listView.setOnTouchListener(touchListener); } }

须要的库文件 SwipeDismissListViewTouchListener.java ：

/* * 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 zhangphil.listview;import android.animation.Animator;import android.animation.AnimatorListenerAdapter;import android.animation.ValueAnimator;import android.graphics.Rect;import android.os.SystemClock;import android.view.MotionEvent;import android.view.VelocityTracker;import android.view.View;import android.view.ViewConfiguration;import android.view.ViewGroup;import android.view.ViewPropertyAnimator;import android.widget.AbsListView;import android.widget.ListView;import java.util.ArrayList;import java.util.Collections;import java.util.List;/** * 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. * * 
 * 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. * 
 * * 
 * Example usage: * 
 * * 
 * 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()); * 
 * * 
 * This class Requires API level 12 or later due to use of * {@link ViewPropertyAnimator}. * 
 * * 
 * For a generalized {@link View.OnTouchListener} that makes any view * dismissable, see {@link SwipeDismissTouchListener}. * 
 * * @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
     
       mPendingDismisses = new ArrayList
      
       ();	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 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.
       
	 *	 * @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 (motionEvent.getActionMasked()) {		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;					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;				}			}			return false;		}		case MotionEvent.ACTION_CANCEL: {			if (mVelocityTracker == null) {				break;			}			if (mDownView != null && mSwiping) {				// cancel				mDownView.animate().translationX(0).alpha(1)						.setDuration(mAnimationTime).setListener(null);			}			mVelocityTracker.recycle();			mVelocityTracker = null;			mDownX = 0;			mDownY = 0;			mDownView = 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;				mDownView.animate()						.translationX(dismissRight ?
      
     

mViewWidth : -mViewWidth) .alpha(0).setDuration(mAnimationTime) .setListener(new AnimatorListenerAdapter() { @Override public void onAnimationEnd(Animator animation) { performDismiss(downView, downPosition); } }); } else { // cancel mDownView.animate().translationX(0).alpha(1) .setDuration(mAnimationTime).setListener(null); } mVelocityTracker.recycle(); mVelocityTracker = null; mDownX = 0; mDownY = 0; mDownView = 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 | (motionEvent.getActionIndex() << MotionEvent.ACTION_POINTER_INDEX_SHIFT)); mListView.onTouchEvent(cancelEvent); cancelEvent.recycle(); } if (mSwiping) { mDownView.setTranslationX(deltaX - mSwipingSlop); mDownView.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 pendingDismiss.view.setAlpha(1f); 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(); } }

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