Android-Swife可以在背景上使用动画来删除RecyclerView

Question

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？

Answer 1

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。