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，如今就对学习过程做下简介。帮助大家实现这样的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非常复杂啊，常常依赖于GestureDetectors和onInterceptTouchEvent，各种手势操作，感觉非常萌逼啊。

可是看了Paul Burke写的ItemTouchHelper之后，感觉豁然开朗。在RecyclerView上加入拖动特性有一个非常easy的方法。这种方法仅仅须要ItemTouchHelper一个类，而且它也是Android 兼容包的一部分。它处理好了关于在RecyclerView上加入拖动排序与滑动删除的全部事情，听了是不是非常激动，感觉就跟保姆似的。

话不多说。献上效果图

是不是非常激动，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

首先加入依赖

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

因为v7包包括RecylerView。所以这么加入依赖也能够

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

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>

这没啥好讲的。就是加入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" />

就显示一个textview，显示就不弄那么复杂。大家越easy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;
    }

}

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。非常easy吧

所以要创建构造方法

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

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);
    }

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);
        }

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);
        }
    }
}

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

英文比較的好的同志们能够更具体的了解一下。

源代码下载 https://pan.baidu.com/s/1nuZ4rqh