Android Design ItemTouchHelper实现酷炫列表的移行和滑动删除效果

        ItemTouchHelper主要是作用在RecyclerView上。本文仍在android 5.0新特性 RecyclerView使用初级基础上。可以看到实现的列表右边的ImageView的样式是一般常见的编辑图片 即提示用户可以进行 列表的移行操作。不知道各位看官是否看个我的这篇文章：自定义View（三） switch开关按钮 ViewDragHelper的使用初级 。其实ViewDragHelper很容易实现表格的滑动删除功能。但其更加普遍适用于所有View。而ItemTouchHelper是Android Design 库中专门针对RecyclerView的移动和滑动操作。好了。看看本文的具体实现。由于布局文件与android 5.0新特性 RecyclerView使用初级本文不在给出。

       实现上述功能主要依赖一下辅助类ItemTouchHelperViewHolder、ItemTouchHelperAdapter、OnStartDragListener。(本文主要参考github上开源项目点击打开链接)

1.ItemTouchHelperViewHolder  提供选中和（移行、滑动）手势完成后回调

public interface ItemTouchHelperViewHolder {    /**     * Called when the {@link ItemTouchHelper} first registers an item as being moved or swiped.     * Implementations should update the item view to indicate it's active state.     */    void onItemSelected();    /**     * Called when the {@link ItemTouchHelper} has completed the move or swipe, and the active item     * state should be cleared.     */    void onItemClear();}

2 ItemTouchHelperAdapter.java 提供move和dimiss删除接口

public interface ItemTouchHelperAdapter {    /**     * Called when an item has been dragged far enough to trigger a move. This is called every time     * an item is shifted, and <strong>not</strong> at the end of a "drop" event.<br/>     * <br/>     * Implementations should call {@link RecyclerView.Adapter#notifyItemMoved(int, int)} after     * adjusting the underlying data to reflect this move.     *     * @param fromPosition The start position of the moved item.     * @param toPosition   Then resolved position of the moved item.     * @return True if the item was moved to the new adapter position.     *     * @see RecyclerView#getAdapterPositionFor(RecyclerView.ViewHolder)     * @see RecyclerView.ViewHolder#getAdapterPosition()     */    boolean onItemMove(int fromPosition, int toPosition);    /**     * Called when an item has been dismissed by a swipe.<br/>     * <br/>     * Implementations should call {@link RecyclerView.Adapter#notifyItemRemoved(int)} after     * adjusting the underlying data to reflect this removal.     *     * @param position The position of the item dismissed.     *     * @see RecyclerView#getAdapterPositionFor(RecyclerView.ViewHolder)     * @see RecyclerView.ViewHolder#getAdapterPosition()     */    void onItemDismiss(int position);}

3 初始化Drag回调 OnStartDragListener

public interface OnStartDragListener {    /**     * Called when a view is requesting a start of a drag.     *     * @param viewHolder The holder of the view to drag.     */    void onStartDrag(RecyclerView.ViewHolder viewHolder);}

4 具体的ItemTouchHelper(callback)初始化需要传递一个callback参数。

/* * Copyright (C) 2015 Paul Burke * * 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 com.example.gzlanhengwu.touchhelperdemo;import android.annotation.TargetApi;import android.graphics.Canvas;import android.os.Build;import android.support.v7.widget.GridLayoutManager;import android.support.v7.widget.RecyclerView;import android.support.v7.widget.helper.ItemTouchHelper;/** * An implementation of {@link ItemTouchHelper.Callback} that enables basic drag & drop and * swipe-to-dismiss. Drag events are automatically started by an item long-press.<br/> * </br/> * Expects the <code>RecyclerView.Adapter</code> to listen for {@link * ItemTouchHelperAdapter} callbacks and the <code>RecyclerView.ViewHolder</code> to implement * {@link ItemTouchHelperViewHolder}. * * @author Paul Burke (ipaulpro) */public class SimpleItemTouchHelperCallback extends ItemTouchHelper.Callback {    public static final float ALPHA_FULL = 1.0f;    private final ItemTouchHelperAdapter mAdapter;    public SimpleItemTouchHelperCallback(ItemTouchHelperAdapter adapter) {        mAdapter = adapter;    }    //support longpress and swipe gesture    @Override    public boolean isLongPressDragEnabled() {        return true;    }    @Override    public boolean isItemViewSwipeEnabled() {        return true;    }    //    @Override    public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {        // Set movement flags based on the layout manager        if (recyclerView.getLayoutManager() instanceof GridLayoutManager) {            final int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN | ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT;            final int swipeFlags = 0;            return makeMovementFlags(dragFlags, swipeFlags);        } else {            final int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN;            final int swipeFlags = ItemTouchHelper.START | ItemTouchHelper.END;            return makeMovementFlags(dragFlags, swipeFlags);        }    }    @Override    public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder source, RecyclerView.ViewHolder target) {        if (source.getItemViewType() != target.getItemViewType()) {            return false;        }        // Notify the adapter of the move        mAdapter.onItemMove(source.getAdapterPosition(), target.getAdapterPosition());        return true;    }    @Override    public void onSwiped(RecyclerView.ViewHolder viewHolder, int i) {        // Notify the adapter of the dismissal        mAdapter.onItemDismiss(viewHolder.getAdapterPosition());    }    @TargetApi(Build.VERSION_CODES.HONEYCOMB)    @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) {            // Fade out the view as it is swiped out of the parent's bounds            final float alpha = ALPHA_FULL - Math.abs(dX) / (float) viewHolder.itemView.getWidth();            viewHolder.itemView.setAlpha(alpha);            viewHolder.itemView.setTranslationX(dX);        } else {            super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);        }    }    @Override    public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) {        // We only want the active item to change        if (actionState != ItemTouchHelper.ACTION_STATE_IDLE) {            if (viewHolder instanceof ItemTouchHelperViewHolder) {                // Let the view holder know that this item is being moved or dragged                ItemTouchHelperViewHolder itemViewHolder = (ItemTouchHelperViewHolder) viewHolder;                itemViewHolder.onItemSelected();            }        }        super.onSelectedChanged(viewHolder, actionState);    }    @TargetApi(Build.VERSION_CODES.HONEYCOMB)    @Override    public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {        super.clearView(recyclerView, viewHolder);        viewHolder.itemView.setAlpha(ALPHA_FULL);        if (viewHolder instanceof ItemTouchHelperViewHolder) {            // Tell the view holder it's time to restore the idle state            ItemTouchHelperViewHolder itemViewHolder = (ItemTouchHelperViewHolder) viewHolder;            itemViewHolder.onItemClear();        }    }}

主要的复写的方法有：

（1）支持手势的（长按和swipe）

 public boolean isLongPressDragEnabled()

 public boolean isItemViewSwipeEnabled()

（2）public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder)  由于本文采用列表  LinearLayoutManager
返回的是：

 final int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN;
            final int swipeFlags = ItemTouchHelper.START | ItemTouchHelper.END;
            return makeMovementFlags(dragFlags, swipeFlags);

即支持  上下drag移动和左右swipe

 （3）public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder source, RecyclerView.ViewHolder target) 对移行操作响应。具体丢给回调处理在RecyclerView.Adapter实现类中处理。

（4）public void onSwiped(RecyclerView.ViewHolder viewHolder, int i)  滑动操作处理 同上。

以下函数省略。注：这里的动画为属性动画 需要在 3.0以上才支持。可以使用nineoldandroids兼容较低版本。

5 又见MyRecycleViewAdapter类

public class MyRecycleViewAdapter extends RecyclerView.Adapter<MyRecycleViewAdapter.MyViewHolder>implements ItemTouchHelperAdapter {    private List<String>mData;    private Context mContext;    private final OnStartDragListener mDragStartListener;    public MyRecycleViewAdapter(List<String> mData, Context context, OnStartDragListener mDragStartListener) {        this.mData = mData;        mContext=context;        this.mDragStartListener = mDragStartListener;    }    @Override    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {        View itemView= LayoutInflater.from(mContext).inflate(R.layout.item_main,parent,false);        return new MyViewHolder(itemView);    }    @Override    public void onBindViewHolder(final MyViewHolder holder, int position) {        holder.text.setText(mData.get(position));        holder.image.setOnTouchListener(new View.OnTouchListener() {            @Override            public boolean onTouch(View v, MotionEvent event) {                if (MotionEventCompat.getActionMasked(event) == MotionEvent.ACTION_DOWN) {                    mDragStartListener.onStartDrag(holder);                }                return false;            }        });       // holder.itemView.setTag(mData.get(position));    }    @Override    public int getItemCount() {        return mData.size();    }    @Override    public boolean onItemMove(int fromPosition, int toPosition) {        Collections.swap(mData, fromPosition, toPosition);        notifyItemMoved(fromPosition, toPosition);        return true;    }    @Override    public void onItemDismiss(int position) {        mData.remove(position);        notifyItemRemoved(position);    }    public static class MyViewHolder extends RecyclerView.ViewHolder implements            ItemTouchHelperViewHolder{        public ImageView image;        public TextView text;        public MyViewHolder(View itemView) {            super(itemView);            image= (ImageView) itemView.findViewById(R.id.handle);            text= (TextView) itemView.findViewById(R.id.text);        }        @Override        public void onItemSelected() {            itemView.setBackgroundColor(Color.LTGRAY);        }        @Override        public void onItemClear() {            itemView.setBackgroundColor(0);        }    }}

本类中实现了ViewHolder事件绑定。

public boolean onItemMove(int fromPosition, int toPosition)

 public void onItemDismiss(int position)

具体实现了移行和删行功能。

6  使用 MainActivity类中

public class MainActivity extends ActionBarActivity implements OnStartDragListener{    private RecyclerView mRecyclerView;    private RecyclerView.Adapter mAdapter;    private RecyclerView.LayoutManager mLayoutManager;    private List<String> mData;    private ItemTouchHelper mItemTouchHelper;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        mRecyclerView = (RecyclerView) findViewById(R.id.my_recycler_view);        // setlayoutManager        mLayoutManager = new LinearLayoutManager(this);        mRecyclerView.setLayoutManager(mLayoutManager);        //setAdapter        mData = new ArrayList<>();        for (int i = 0; i < 100; i++) {            mData.add("this is position:" + i);        }        mAdapter = new MyRecycleViewAdapter(mData, this, this);        mRecyclerView.setAdapter(mAdapter);        ItemTouchHelper.Callback callback = new SimpleItemTouchHelperCallback((ItemTouchHelperAdapter) mAdapter);        mItemTouchHelper = new ItemTouchHelper(callback);        mItemTouchHelper.attachToRecyclerView(mRecyclerView);    }    @Override    public void onStartDrag(RecyclerView.ViewHolder viewHolder) {        mItemTouchHelper.startDrag(viewHolder);    }}

参考：https://medium.com/@ipaulpro/drag-and-swipe-with-recyclerview-6a6f0c422efd