Android学习之ItemTouchHelper实现RecylerView的拖拽以及滑动删除功能

今天在群里见大神们提到控件的拖动以及滑动删除的效果实现，就在网上找了资料ItemTouchHelper学习，并实现其功能。不胜窃喜之至，忍不住跟大家分享一下，现在就对学习过程做下简单介绍，帮助大家实现这种拖动以及滑动删除效果。

之前了解到要实现以上效果有View.OnDragListener，SwipeToDismiss两种方法，看了下简介之后感觉很复杂啊，经常依赖于GestureDetectors和onInterceptTouchEvent，各种手势操作，感觉很萌逼啊。

但是看了Paul Burke写的ItemTouchHelper之后，感觉豁然开朗，在RecyclerView上添加拖动特性有一个非常简单的方法。这个方法只需要ItemTouchHelper一个类，并且它也是Android 兼容包的一部分，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，听了是不是很激动，感觉就跟保姆似的。

话不多说，献上效果图



是不是很激动，先看我的代码是怎么实现的吧

代码结构图



这里主要是helper包，然后就是recylerview以及其adapter

首先添加依赖

compile 'com.android.support:appcompat-v7:23.2.1'
compile 'com.android.support:design:23.1.1'

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由于v7包包含RecylerView，所以这么添加依赖也可以

compile 'com.android.support:recyclerview-v7:23.1.1'

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为了保险起见也贴上recyclerview的依赖

然后看布局

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="up72.com.testtouchhelper.MainActivity">

<android.support.v7.widget.RecyclerView
android:id="@+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</RelativeLayout>

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这没啥好讲的，就是添加RecyclerView

RecyclerView item的布局

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

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就显示一个textview，显示就不弄那么复杂，大家越容易看懂越好

package up72.com.testtouchhelper;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.helper.ItemTouchHelper;

import java.util.ArrayList;

import up72.com.testtouchhelper.helper.OnStartDragListener;
import up72.com.testtouchhelper.helper.SimpleItemTouchHelperCallback;

public class MainActivity extends AppCompatActivity implements OnStartDragListener{

private RecyclerView recyclerView;
private RecyclerViewAdapter adapter;
private ItemTouchHelper mItemTouchHelper;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false));
recyclerView.setAdapter(adapter = new RecyclerViewAdapter(this));
ItemTouchHelper.Callback callback = new SimpleItemTouchHelperCallback(adapter);
mItemTouchHelper = new ItemTouchHelper(callback);
mItemTouchHelper.attachToRecyclerView(recyclerView);
adapter.replaceAll(getDatas());

}

@Override
public void onStartDrag(RecyclerView.ViewHolder viewHolder) {
mItemTouchHelper.startDrag(viewHolder);
}

private ArrayList<String> getDatas() {
ArrayList<String> list = new ArrayList<>();
for (int i = 0; i < 10; i++) {
String text = "item" + i;
list.add(text);
}
return list;
}

}

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这里主要填充数据，实现OnStartDragListener接口， mItemTouchHelper.attachToRecyclerView(recyclerView)绑定recyclerView，适配器传递的不是activity的引用，而是OnStartDragListener的，很简单吧

所以要创建构造方法

private OnStartDragListener mDragStartListener;
public RecyclerViewAdapter(OnStartDragListener mDragStartListener) {
this.mDragStartListener = mDragStartListener;
}

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剩下的看看适配器吧，适配器实现implements ItemTouchHelperAdapter方法，重写了onItemMove，onItemDismiss两个方法，分别处理拖动，滑动删除

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

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

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ViewHolder实现ItemTouchHelperViewHolder接口，实现onItemSelected，onItemClear两个方法

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

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

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完整的适配器设置

package up72.com.testtouchhelper;

import android.graphics.Color;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.Collections;

import up72.com.testtouchhelper.helper.ItemTouchHelperAdapter;
import up72.com.testtouchhelper.helper.ItemTouchHelperViewHolder;
import up72.com.testtouchhelper.helper.OnStartDragListener;

/**
* Created by wangchang on 2016/3/25.
*/
public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.BaseViewHolder> implements ItemTouchHelperAdapter {
private ArrayList<String> dataList = new ArrayList<>();
private OnStartDragListener mDragStartListener;

public RecyclerViewAdapter(OnStartDragListener mDragStartListener) {
this.mDragStartListener = mDragStartListener;
}
public void replaceAll(ArrayList<String> list) {
dataList.clear();
if (list != null) {
dataList.addAll(list);
}
notifyDataSetChanged();
}
@Override
public RecyclerViewAdapter.BaseViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
return new DemoViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.item_main, parent, false));
}

@Override
public void onBindViewHolder(RecyclerViewAdapter.BaseViewHolder holder, int position) {
holder.setData(dataList.get(position));
}

@Override
public int getItemCount() {
return dataList!=null?dataList.size():0;
}

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

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

public class BaseViewHolder extends RecyclerView.ViewHolder {
public BaseViewHolder(View itemView) {
super(itemView);
}
void setData(String data){

}
}

private class DemoViewHolder extends BaseViewHolder implements
ItemTouchHelperViewHolder {
private TextView tv;
public DemoViewHolder(View view) {
super(view);
tv= (TextView) view.findViewById(R.id.text);
}

@Override
void setData(String  data) {
super.setData(data);

tv.setText(data);

}

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

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

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就这样效果就实现了，最后贴上Paul Burke大神的原文地址。

Drag and Swipe with RecyclerView

英文比较的好的同志们可以更详细的了解一下。

源码下载 https://pan.baidu.com/s/1nuZ4rqh