据我所知，为RecolyerView实现一个在被刷项下方有背景的Swipe-to-Dississ的一种可能性（就像在许多google应用程序中一样）是为ItemTouchHelper实现一个简单的回调，并在onChildDraw方法中绘制背景。
这是我的实现：
ItemTouchHelper.SimpleCallback simpleItemTouchCallback = new ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.RIGHT) {
// create objects once and avoid allocating them in the onChildDraw method
Drawable background;
Drawable icon;
int iconMargin;
boolean initialized;
private void init() {
background = new ColorDrawable(Color.RED);
icon = ContextCompat.getDrawable(mAppContext, R.drawable.ic_delete_white_24dp);
iconMargin = (int) mAppContext.getResources().getDimension(R.dimen.fab_margin);
initialized = true;
}
@Override
public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
return false;
}
@Override
public void onSwiped(RecyclerView.ViewHolder viewHolder, int swipeDir) {
// remove swiped item from the list and notify the adapter
int position = viewHolder.getAdapterPosition();
mItemList.remove(position);
mRecyclerViewAdapter.notifyDataSetChanged();
}
@Override
public void onChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
if (actionState == ItemTouchHelper.ACTION_STATE_SWIPE) {
if (dX > 0) {
View itemView = viewHolder.itemView;
// if viewHolder has been swiped away, don't do anything
if (viewHolder.getAdapterPosition() == -1) {
return;
}
if (!initialized) {
init();
}
// draw background
int dXSwipe = (int) (dX * 1.05); // increase slightly dX to avoid view flickering, compensating loss of precision due to int conversion
background.setBounds(itemView.getLeft(), itemView.getTop(),
itemView.getLeft() + dXSwipe, itemView.getBottom());
background.draw(c);
// draw icon
int top = (itemView.getTop() + itemView.getBottom() - icon.getIntrinsicHeight()) / 2;
int left = itemView.getLeft() + iconMargin;
icon.setBounds(left, top, left + icon.getIntrinsicWidth(), top + icon.getIntrinsicHeight());
icon.draw(c);
}
}
super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
}
};
ItemTouchHelper itemTouchHelper = new ItemTouchHelper(simpleItemTouchCallback);
itemTouchHelper.attachToRecyclerView(mRecyclerView);
现在，问题是如何在下面的背景中动画视图。这个动画的一个例子可以从google Calendar中获得：当事件或提醒被滑动时，左边的图标会相应地按水平位移的量缩放。
有没有人知道如何做到这一点？是否需要一种不同的方法，也许在ViewWholder中有两个视图，一个在另一个上，就像这里建议的RecolyerView滑动，下面有一个视图？
我知道怎么做了。
对于那些有兴趣的人来说，解决方案是使用两个视图（前景和背景），并随着滑动的进行对背景进行动画化。
布局：
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/item_delete_background">
<ImageView
android:id="@+id/item_delete_icon"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_vertical"
android:layout_marginLeft="@dimen/fab_margin"
android:layout_marginStart="@dimen/fab_margin"
app:srcCompat="@drawable/ic_delete_white_24dp" />
<android.support.constraint.ConstraintLayout
android:id="@+id/item_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/gray_bg">
<!--recyclerview item layout-->
</android.support.constraint.ConstraintLayout>
</FrameLayout>
视图持有者：
class MyViewHolder extends RecyclerView.ViewHolder {
private ConstraintLayout mItemLayout;
private ImageView mItemDeleteIcon;
MyViewHolder(View v) {
super(v);
mItemLayout = (ConstraintLayout) v.findViewById(R.id.item_layout);
mEventDeleteIcon = (ImageView) v.findViewById(R.id.item_delete_icon);
}
View getViewToSwipe() {
return mItemLayout;
}
View getViewToAnimate() {
return mItemDeleteIcon;
}
}
和ItemTouchHelper回调：
ItemTouchHelper.SimpleCallback mItemTouchCallback = new ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.RIGHT) {
// override methods
public void onChildDrawOver(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder,
float dX, float dY,
int actionState, boolean isCurrentlyActive) {
// get the view which is currently swiped
ConstraintLayout itemLayout = (ConstraintLayout) ((MyViewHolder) viewHolder).getViewToSwipe();
// calculate relative horizontal displacement
// with proportion dXRelative : 1 = dX : (layoutWidth / 3)
float dXRelative = dX / itemLayout.getWidth() * 3;
// check size boundaries
if (dXRelative > 1) {
dXRelative = 1;
}
if (dXRelative < 0) {
dXRelative = 0;
}
// animate the icon with scaling on both dimensions
((MyViewHolder) viewHolder).getViewToAnimate().animate().scaleX(dXRelative).scaleY(dXRelative).setDuration(0).start();
// call draw over
getDefaultUIUtil().onDrawOver(c, recyclerView, ((MyViewHolder) viewHolder).getViewToSwipe(), dX, dY, actionState, isCurrentlyActive);
}
};
基本行为（视图保持器中的前景/背景）的实现是在下面的文章中完成的：使用ItemTouchHelper进行Swipe-to-Dississ，并在swiped Out后面显示另一个视图。
希望这对某人有用。
