Android SwipeToDismiss（左滑/右滑删除ListView条目Item） _ListView

博观而约取，厚积而薄发。这篇文章主要讲述Android SwipeToDismiss：左滑/右滑删除ListView条目Item相关的知识，希望能为你提供帮助。
??《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：https://github.com/romannurik/Android-SwipeToDismiss ）。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 https://github.com/romannurik/Android-SwipeToDismiss 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< String> adapter = null; private ArrayList< String> 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: * * * < 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> * * * 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< 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 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 ?【Android SwipeToDismiss（左滑/右滑删除ListView条目Item）】
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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