ItemTouchHelper是一个强大的工具,它处理好了关于在RecyclerView上添加拖动排序与滑动删除的所有事情。它是RecyclerView.ItemDecoration的子类。
基本使用
1继承 ItemTouchHelper.Callback
主要方法
方法名 | 作用 |
---|---|
getMovementFlags | 在此方法里面我们需要构建两个flag,一个是dragFlags,表示拖动效果支持的方向,另一个是swipeFlags,表示侧滑效果支持的方向。在我们的Demo中,拖动执行上下两个方向,侧滑执行左右两个方向,这些操作我们都可以在此方法里面定义。 |
onMove | 当拖动效果已经产生了,会回调此方法。在此方法里面,我们通常会更新数据源,就比如说,一个ItemView 从0拖到了1位置,那么对应的数据源也需要更改位置。 |
onSwiped | 当侧滑效果以上产生了,会回调此方法。在此方法里面,我们也会更新数据源。与onMove 方法不同到的是,我们在这个方法里面从数据源里面移除相应的数据,然后调用notifyXXX 方法就行了。 |
也可能复写一下方法
onChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) |
我们可以在这个方法内实现我们自定义的交互规则或者自定义的动画效果。。 |
clearView(RecyclerView recyclerView, ViewHolder viewHolder) | 当用户操作完毕某个item并且其动画也结束后会调用该方法,一般我们在该方法内恢复ItemView的初始状态,防止由于复用而产生的显示错乱问题。 |
onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) | 从静止状态变为拖拽或者滑动的时候会回调该方法,参数actionState表示当前的状态。 |
isLongPressDragEnabled | ItemTouchHelper可以用于没有滑动的拖动操作(或者反过来),你必须指明你到底要支持哪一种。要支持长按RecyclerView item进入拖动操作,你必须在isLongPressDragEnabled()方法中返回true。或者,也可以调用ItemTouchHelper.startDrag(RecyclerView.ViewHolder) 方法来开始一个拖动。这会在后面讲到。 |
isItemViewSwipeEnabled | 而要在view任意位置触摸事件发生时启用滑动操作,则直接在sItemViewSwipeEnabled()中返回true就可以了。或者,你也主动调用ItemTouchHelper.startSwipe(RecyclerView.ViewHolder) 来开始滑动操作。 |
2 attachToRecyclerView
ItemTouchHelper.Callback callback = new SimpleItemTouchHelperCallback(adapter);
mItemTouchHelper = new ItemTouchHelper(callback);
mItemTouchHelper.attachToRecyclerView(recyclerView);
以下是Demo源码部分 基于开源https://github.com/iPaulPro/Android-ItemTouchHelper-Demo 简单修改加了侧滑划出项
修改部分
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);
if (Math.abs(dX) <= getSlideLimitation(viewHolder)){
viewHolder.itemView.scrollTo(-(int) dX,0);
}
} else {
super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
}
}
运行效果
/*
* 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 co.paulburke.android.itemtouchhelperdemo.helper;
import android.graphics.Canvas;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.helper.ItemTouchHelper;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import co.paulburke.android.itemtouchhelperdemo.R;
/**
* 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;
}
@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());
}
@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);
if (Math.abs(dX) <= getSlideLimitation(viewHolder)){
viewHolder.itemView.scrollTo(-(int) dX,0);
}
} else {
super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
}
}
/**
* 获取删除方块的宽度
*/
public int getSlideLimitation(RecyclerView.ViewHolder viewHolder){
ViewGroup viewGroup = (ViewGroup) viewHolder.itemView;
return viewGroup.getChildAt(1).getLayoutParams().width;
}
@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);
}
@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();
}
}
}