ItemTouchHelper实现拖拽和侧滑删除

1. 编写item布局文件:

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/item"
android:layout_width="match_parent"
android:layout_height="?listPreferredItemHeight"
android:clickable="true"
android:focusable="true"
android:foreground="?selectableItemBackground">

<TextView
android:id="@+id/text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_vertical"
android:layout_marginLeft="16dp"
android:textAppearance="?android:attr/textAppearanceMedium" />

<ImageView
android:id="@+id/handle"
android:layout_width="?listPreferredItemHeight"
android:layout_height="match_parent"
android:layout_gravity="center_vertical|right"
android:scaleType="center"
android:src="@drawable/ic_reorder_grey_500_24dp" />
</FrameLayout>

2.编写一个触发滑动的监听

/**
* Listener for manual initiation of a drag.
*/
public interface OnStartDragListener {

/**
* Called when a view is requesting a start of a drag.
*
* @param viewHolder The holder of the view to drag.
*/
/*自定义滑动或拖拽事件的开启回调方法*/
void onStartDrag(RecyclerView.ViewHolder viewHolder);

}

3.编写通知Callback监听器item处于激活状态的监听

/**
* Interface to notify an item ViewHolder of relevant callbacks from {@link
* ItemTouchHelper.Callback}.
*/
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.
*/
/*当item被拖拽或者滑动的时候, item背景变为激活状态*/
void onItemSelected();

/**
* Called when the {@link ItemTouchHelper} has completed the move or swipe, and the active item
* state should be cleared.
*/
/*当滑动或拖拽完成后,激活的item的背景应恢复为原来状态*/
void onItemClear();
}

4. 监听item滑动或者拖拽:

/**
* Interface to listen for a move or dismissal event from a {@link ItemTouchHelper.Callback}.
*/
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()
*/
/*item被拖拽时调用*/
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()
*/
/*item滑动删除时调用*/
void onItemDismiss(int position);
}

5. 编写RecyclerView.Adapter实现类:

/**
* Simple RecyclerView.Adapter that implements {@link ItemTouchHelperAdapter} to respond to move and
* dismiss events from a {@link android.support.v7.widget.helper.ItemTouchHelper}.
*/
public class RecyclerListAdapter extends RecyclerView.Adapter<RecyclerListAdapter.ItemViewHolder>
implements ItemTouchHelperAdapter {

private final List<String> mItems = new ArrayList<>();

private final OnStartDragListener mDragStartListener;

public RecyclerListAdapter(Context context, OnStartDragListener dragStartListener) {
mDragStartListener = dragStartListener;
mItems.addAll(Arrays.asList(context.getResources().getStringArray(R.array.dummy_items)));
}

@Override
public ItemViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_main, parent, false);
ItemViewHolder itemViewHolder = new ItemViewHolder(view);
return itemViewHolder;
}

@Override
public void onBindViewHolder(final ItemViewHolder holder, int position) {
holder.textView.setText(mItems.get(position));

// Start a drag whenever the handle view it touched
holder.handleView.setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
if (MotionEventCompat.getActionMasked(event) == MotionEvent.ACTION_DOWN) {
mDragStartListener.onStartDrag(holder);
}
return false;
}
});
}

@Override
public void onItemDismiss(int position) {
mItems.remove(position);
notifyItemRemoved(position);
}

@Override
public boolean onItemMove(int fromPosition, int toPosition) {
Collections.swap(mItems, fromPosition, toPosition);
notifyItemMoved(fromPosition, toPosition);
return true;
}

@Override
public int getItemCount() {
return mItems.size();
}

/**
* Simple example of a view holder that implements {@link ItemTouchHelperViewHolder} and has a
* "handle" view that initiates a drag event when touched.
*/
public static class ItemViewHolder extends RecyclerView.ViewHolder implements
ItemTouchHelperViewHolder {

public final TextView textView;
public final ImageView handleView;

public ItemViewHolder(View itemView) {
super(itemView);
textView = (TextView) itemView.findViewById(R.id.text);
handleView = (ImageView) itemView.findViewById(R.id.handle);
}

@Override
public void onItemSelected() {
itemView.setBackgroundColor(Color.LTGRAY);
}

@Override
public void onItemClear() {
itemView.setBackgroundColor(0);
}
}
}

6. 编写Activity

public class RecylerViewListActivity  extends AppCompatActivity implements OnStartDragListener{
private RecyclerView mRecyclerView;
private ItemTouchHelper mItemTouchHelper;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_swipe_recycler);
mRecyclerView= (RecyclerView) findViewById(R.id.recycler);

RecyclerListAdapter adapter = new RecyclerListAdapter(this, this);

mRecyclerView.setHasFixedSize(true);
mRecyclerView.setAdapter(adapter);
mRecyclerView.setItemAnimator(new DefaultItemAnimator());
mRecyclerView.addItemDecoration(new DividerItemDecoration(this,DividerItemDecoration.VERTICAL_LIST));
mRecyclerView.setLayoutManager(new LinearLayoutManager(this));

ItemTouchHelper.Callback callback = new SimpleItemTouchHelperCallback(adapter);
mItemTouchHelper = new ItemTouchHelper(callback);
mItemTouchHelper.attachToRecyclerView(mRecyclerView);

}

@Override
public void onStartDrag(RecyclerView.ViewHolder viewHolder) {

//开启滑动或者拖拽
mItemTouchHelper.startDrag(viewHolder);
}
}