我需要在一个ListView中实现像Gmail应用中的“滑动删除”功能，并带有撤消功能。
我知道已经有一些问题询问如何进行滑动删除，例如：
和
但是它们都没有解释如何在删除后管理撤消，并在撤消时将已删除的视图动画化返回！
我发现这里还有一个没有回答的问题
How to implement gmail like Achieve or Undo action in a list item
所以这是我的问题。
如何在Android中创建一个具有滑动删除功能的ListView，然后在已删除的空间中显示UNDO，并在按下撤消时将相同的视图动画化返回，同时在滚动或其他项目点击或滑动时删除撤消选项？
你聪明的人有什么想法吗？
| ----------- ITEM 1-----------|
| ----------- ITEM 2-----------|
| --Deleted-------<[UNDO]>|
| ----------- ITEM 4-----------|
| ----------- ITEM 5-----------|
注：抱歉，由于我的声望不高，我无法添加图片！
根据您的问题，似乎您困惑于如何管理撤销操作。如果是这种情况，我建议您研究名为“命令设计模式”的设计模式。您可以将“命令”（例如删除）排队，然后在撤销计时器或其他实现方式完成后才执行它们。
这是一个库，可以使 ListView 或 RecyclerView 中的项目可被滑动删除，并提供撤销功能。您可以使用自己的视图来实现此功能，就像 Android 上的 Gmail 应用程序一样。
https://github.com/hudomju/android-swipe-to-dismiss-undo
以下是代码片段，以防页面更改或链接失效：
ListViewActivity：
public class ListViewActivity extends Activity {
private static final int TIME_TO_AUTOMATICALLY_DISMISS_ITEM = 3000;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.list_view_activity);
init((ListView) findViewById(R.id.list_view));
}
private void init(ListView listView) {
final MyBaseAdapter adapter = new MyBaseAdapter();
listView.setAdapter(adapter);
final SwipeToDismissTouchListener<ListViewAdapter> touchListener =
new SwipeToDismissTouchListener<>(
new ListViewAdapter(listView),
new SwipeToDismissTouchListener.DismissCallbacks<ListViewAdapter>() {
@Override
public boolean canDismiss(int position) {
return true;
}
@Override
public void onPendingDismiss(ListViewAdapter recyclerView, int position) {
}
@Override
public void onDismiss(ListViewAdapter view, int position) {
adapter.remove(position);
}
});
touchListener.setDismissDelay(TIME_TO_AUTOMATICALLY_DISMISS_ITEM);
listView.setOnTouchListener(touchListener);
// Setting this scroll listener is required to ensure that during ListView scrolling,
// we don't look for swipes.
listView.setOnScrollListener((AbsListView.OnScrollListener) touchListener.makeScrollListener());
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
if (touchListener.existPendingDismisses()) {
touchListener.undoPendingDismiss();
} else {
Toast.makeText(ListViewActivity.this, "Position " + position, LENGTH_SHORT).show();
}
}
});
}
static class MyBaseAdapter extends BaseAdapter {
private static final int SIZE = 100;
private final List<String> mDataSet = new ArrayList<>();
MyBaseAdapter() {
for (int i = 0; i < SIZE; i++)
mDataSet.add(i, "This is row number " + i);
}
@Override
public int getCount() {
return mDataSet.size();
}
@Override
public String getItem(int position) {
return mDataSet.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
public void remove(int position) {
mDataSet.remove(position);
notifyDataSetChanged();
}
static class ViewHolder {
TextView dataTextView;
ViewHolder(View view) {
dataTextView = (TextView) view.findViewById(R.id.txt_data);
view.setTag(this);
}
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder viewHolder = convertView == null
? new ViewHolder(convertView = LayoutInflater.from(parent.getContext())
.inflate(R.layout.list_item, parent, false))
: (ViewHolder) convertView.getTag();
viewHolder.dataTextView.setText(mDataSet.get(position));
return convertView;
}
}
}
SwipeToDismissTouchListener：
public class SwipeToDismissTouchListener<SomeCollectionView extends ViewAdapter> implements
View.OnTouchListener {
// Cached ViewConfiguration and system-wide constant values
private final int mSlop;
private final int mMinFlingVelocity;
private final int mMaxFlingVelocity;
private final long mAnimationTime;
// Fixed properties
private final SomeCollectionView mRecyclerView;
private final DismissCallbacks<SomeCollectionView> mCallbacks;
private int mViewWidth = 1; // 1 and not 0 to prevent dividing by zero
// Transient properties
private PendingDismissData mPendingDismiss;
private float mDownX;
private float mDownY;
private boolean mSwiping;
private int mSwipingSlop;
private VelocityTracker mVelocityTracker;
private int mDownPosition;
private RowContainer mRowContainer;
private boolean mPaused;
// Handler to dismiss pending items after a delay
private final Handler mHandler;
private final Runnable mDismissRunnable = new Runnable() {
@Override
public void run() {
processPendingDismisses();
}
};
private long mDismissDelayMillis = -1; // negative to disable automatic dismissing
public class RowContainer {
final View container;
final View dataContainer;
final View undoContainer;
boolean dataContainerHasBeenDismissed;
public RowContainer(ViewGroup container) {
this.container = container;
dataContainer = container.getChildAt(0);
undoContainer = container.getChildAt(1);
dataContainerHasBeenDismissed = false;
}
View getCurrentSwipingView() {
return dataContainerHasBeenDismissed ? undoContainer: dataContainer;
}
}
/**
* The callback interface used by {@link SwipeToDismissTouchListener} to inform its client
* about a successful dismissal of one or more list item positions.
*/
public interface DismissCallbacks<SomeCollectionView extends ViewAdapter> {
/**
* Called to determine whether the given position can be dismissed.
*/
boolean canDismiss(int position);
/**
* Called when an item is swiped away by the user and the undo layout is completely visible.
* Do NOT remove the list item yet, that should be done in {@link #onDismiss(com.hudomju.swipe.adapter.ViewAdapter, int)}
* This may also be called immediately before and item is completely dismissed.
*
* @param recyclerView The originating {@link android.support.v7.widget.RecyclerView}.
* @param position The position of the dismissed item.
*/
void onPendingDismiss(SomeCollectionView recyclerView, int position);
/**
* Called when the item is completely dismissed and removed from the list, after the undo layout is hidden.
*
* @param recyclerView The originating {@link android.support.v7.widget.RecyclerView}.
* @param position The position of the dismissed item.
*/
void onDismiss(SomeCollectionView recyclerView, int position);
}
/**
* Constructs a new swipe-to-dismiss touch listener for the given list view.
*
* @param recyclerView 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 SwipeToDismissTouchListener(SomeCollectionView recyclerView,
DismissCallbacks<SomeCollectionView> callbacks) {
ViewConfiguration vc = ViewConfiguration.get(recyclerView.getContext());
mSlop = vc.getScaledTouchSlop();
mMinFlingVelocity = vc.getScaledMinimumFlingVelocity() * 16;
mMaxFlingVelocity = vc.getScaledMaximumFlingVelocity();
mAnimationTime = recyclerView.getContext().getResources().getInteger(
android.R.integer.config_shortAnimTime);
mRecyclerView = recyclerView;
mCallbacks = callbacks;
mHandler = new Handler();
}
/**
* 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;
}
/**
* Set the delay after which the pending items will be dismissed when there was no user action.
* Set to a negative value to disable automatic dismissing items.
* @param dismissDelayMillis The delay between onPendingDismiss and onDismiss calls, in milliseconds.
*/
public void setDismissDelay(long dismissDelayMillis) {
this.mDismissDelayMillis = dismissDelayMillis;
}
/**
* Returns an {@link android.widget.AbsListView.OnScrollListener} to be added to the {@link
* android.widget.ListView} using {@link android.widget.ListView#setOnScrollListener(android.widget.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 SwipeToDismissTouchListener} is
* paused during list view scrolling.</p>
*
* @see SwipeToDismissTouchListener
*/
public Object makeScrollListener() {
return mRecyclerView.makeScrollListener(new AbsListView.OnScrollListener() {
@Override
public void onScrollStateChanged(AbsListView absListView, int scrollState) {
processPendingDismisses();
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 = mRecyclerView.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 = mRecyclerView.getChildCount();
int[] listViewCoords = new int[2];
mRecyclerView.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 = mRecyclerView.getChildAt(i);
child.getHitRect(rect);
if (rect.contains(x, y)) {
assert child instanceof ViewGroup &&
((ViewGroup) child).getChildCount() == 2 :
"Each child needs to extend from ViewGroup and have two children";
boolean dataContainerHasBeenDismissed = mPendingDismiss != null &&
mPendingDismiss.position == mRecyclerView.getChildPosition(child) &&
mPendingDismiss.rowContainer.dataContainerHasBeenDismissed;
mRowContainer = new RowContainer((ViewGroup) child);
mRowContainer.dataContainerHasBeenDismissed = dataContainerHasBeenDismissed;
break;
}
}
if (mRowContainer != null) {
mDownX = motionEvent.getRawX();
mDownY = motionEvent.getRawY();
mDownPosition = mRecyclerView.getChildPosition(mRowContainer.container);
if (mCallbacks.canDismiss(mDownPosition)) {
mVelocityTracker = VelocityTracker.obtain();
mVelocityTracker.addMovement(motionEvent);
} else {
mRowContainer = null;
}
}
return false;
}
case MotionEvent.ACTION_CANCEL: {
if (mVelocityTracker == null) {
break;
}
if (mRowContainer != null && mSwiping) {
// cancel
mRowContainer.getCurrentSwipingView()
.animate()
.translationX(0)
.alpha(1)
.setDuration(mAnimationTime)
.setListener(null);
}
mVelocityTracker.recycle();
mVelocityTracker = null;
mDownX = 0;
mDownY = 0;
mRowContainer = 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 RowContainer downView = mRowContainer; // mDownView gets null'd before animation ends
final int downPosition = mDownPosition;
mRowContainer.getCurrentSwipingView()
.animate()
.translationX(dismissRight ? mViewWidth : -mViewWidth)
.alpha(0)
.setDuration(mAnimationTime)
.setListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
performDismiss(downView, downPosition);
}
});
} else {
// cancel
mRowContainer.getCurrentSwipingView()
.animate()
.translationX(0)
.alpha(1)
.setDuration(mAnimationTime)
.setListener(null);
}
mVelocityTracker.recycle();
mVelocityTracker = null;
mDownX = 0;
mDownY = 0;
mRowContainer = 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;
mRecyclerView.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));
mRecyclerView.onTouchEvent(cancelEvent);
cancelEvent.recycle();
}
if (mSwiping) {
mRowContainer.getCurrentSwipingView().setTranslationX(deltaX - mSwipingSlop);
mRowContainer.getCurrentSwipingView().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 RowContainer rowContainer;
public PendingDismissData(int position, RowContainer rowContainer) {
this.position = position;
this.rowContainer= rowContainer;
}
@Override
public int compareTo(@NonNull PendingDismissData other) {
// Sort by descending position
return other.position - position;
}
}
private void performDismiss(RowContainer dismissView, 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.
if (mPendingDismiss != null) {
boolean dismissingDifferentRow = mPendingDismiss.position != dismissPosition;
int newPosition = mPendingDismiss.position < dismissPosition ? dismissPosition-1 : dismissPosition;
processPendingDismisses();
if (dismissingDifferentRow) {
addPendingDismiss(dismissView, newPosition);
}
} else {
addPendingDismiss(dismissView, dismissPosition);
}
}
private void addPendingDismiss(RowContainer dismissView, int dismissPosition) {
dismissView.dataContainerHasBeenDismissed = true;
dismissView.undoContainer.setVisibility(View.VISIBLE);
mPendingDismiss = new PendingDismissData(dismissPosition, dismissView);
// Notify the callbacks
mCallbacks.onPendingDismiss(mRecyclerView, dismissPosition);
// Automatically dismiss the item after a certain delay
if(mDismissDelayMillis >= 0)
mHandler.removeCallbacks(mDismissRunnable);
mHandler.postDelayed(mDismissRunnable, mDismissDelayMillis);
}
/**
* If a view was dismissed and the undo container is showing it will proceed with the final
* dismiss of the item.
* @return whether there were any pending rows to be dismissed.
*/
public boolean processPendingDismisses() {
boolean existPendingDismisses = existPendingDismisses();
if (existPendingDismisses) processPendingDismisses(mPendingDismiss);
return existPendingDismisses;
}
/**
* Whether a row has been dismissed and is waiting for confirmation
* @return whether there are any pending rows to be dismissed.
*/
public boolean existPendingDismisses() {
return mPendingDismiss != null && mPendingDismiss.rowContainer.dataContainerHasBeenDismissed;
}
/**
* If a view was dismissed and the undo container is showing it will undo and make the data
* container reappear.
* @return whether there were any pending rows to be dismissed.
*/
public boolean undoPendingDismiss() {
boolean existPendingDismisses = existPendingDismisses();
if (existPendingDismisses) {
mPendingDismiss.rowContainer.undoContainer.setVisibility(View.GONE);
mPendingDismiss.rowContainer.dataContainer
.animate()
.translationX(0)
.alpha(1)
.setDuration(mAnimationTime)
.setListener(null);
mPendingDismiss = null;
}
return existPendingDismisses;
}
private void processPendingDismisses(final PendingDismissData pendingDismissData) {
mPendingDismiss = null;
final ViewGroup.LayoutParams lp = pendingDismissData.rowContainer.container.getLayoutParams();
final int originalHeight = pendingDismissData.rowContainer.container.getHeight();
ValueAnimator animator = ValueAnimator.ofInt(originalHeight, 1).setDuration(mAnimationTime);
animator.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
if (mCallbacks.canDismiss(pendingDismissData.position))
mCallbacks.onDismiss(mRecyclerView, pendingDismissData.position);
pendingDismissData.rowContainer.dataContainer.post(new Runnable() {
@Override
public void run() {
pendingDismissData.rowContainer.dataContainer.setTranslationX(0);
pendingDismissData.rowContainer.dataContainer.setAlpha(1);
pendingDismissData.rowContainer.undoContainer.setVisibility(View.GONE);
pendingDismissData.rowContainer.undoContainer.setTranslationX(0);
pendingDismissData.rowContainer.undoContainer.setAlpha(1);
lp.height = originalHeight;
pendingDismissData.rowContainer.container.setLayoutParams(lp);
}
});
}
});
animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator valueAnimator) {
lp.height = (Integer) valueAnimator.getAnimatedValue();
pendingDismissData.rowContainer.container.setLayoutParams(lp);
}
});
animator.start();
}
}