[Android]RecyclerView的简单示例

去年google的IO上就展示了一个新的ListView，它就是RecyclerView。

以下是官方的说明，我英语能力有限，不过我大概这么理解：RecyclerView会比ListView更具有拓展性，使用更有效率，而且更灵活了，具体怎么样，时隔一年，我们也发现了它越来越强大，所以有必要去认识一下这个小伙伴了。

The RecyclerView widget is a more advanced and flexible version of ListView. This widget is a container for displaying large data sets that can be scrolled very efficiently by maintaining a limited number of views. Use the RecyclerViewwidget when you have data collections whose elements change at runtime based on user action or network events.

The RecyclerView class simplifies the display and handling of large data sets by providing:

Layout managers for positioning items
Default animations for common item operations, such as removal or addition of items

You also have the flexibility to define custom layout managers and animations for RecyclerView widgets.

我们可以在最新版本的support-v7上找到这个玩意儿，本文在v21上找到这个jar的：sdk\extras\android\m2repository\com\android\support\recyclerview-v7\21.0.0，在目录下将recyclerview-v7-21.0.0.aar解压，取出classes.jar,你可以更名为：android-support-v7-recyclerview.jar，至少我是这么干的。

好了，进入这次demo的主题

1.demo结构

2.示例效果图

3.让我们边看代码边了解一下，这个控件吧，首先在界面布局文件中引入这个组件：

activity_main.xml

<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="${relativePackage}.${activityClass}" >

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:orientation="vertical" >

        <RadioGroup
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:checkedButton="@+id/linearlayout_rb"
            android:gravity="center_horizontal"
            android:orientation="horizontal" >

            <RadioButton
                android:id="@+id/linearlayout_rb"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@string/linearlayout" />

            <RadioButton
                android:id="@+id/gridlayout_rb"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@string/gridlayout" />
        </RadioGroup>
<span style="white-space:pre">	</span>
        <android.support.v7.widget.RecyclerView
            android:id="@+id/recyclerView"
            android:scrollbars="vertical"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    </LinearLayout>

</RelativeLayout>

4.下面就是怎么使用它，这边就是简单的使用方法,在代码上我已经加上了注释，简单理解一下吧。

MainActivity.java

package org.jan.components.demo;

import java.util.ArrayList;

import org.jan.components.demo.CustomAdapter.OnItemPressedListener;

import android.app.Activity;
import android.os.Bundle;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.RecyclerView.RecyclerListener;
import android.support.v7.widget.RecyclerView.ViewHolder;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.RadioButton;
import android.widget.Toast;
/**
 * android recyclerView的简单实例代码
 * @author jan
 */
public class MainActivity extends Activity {
	private static final String TAG = "MainActivity";
	private static final String KEY_LAYOUT_MANAGER = "layoutManager";
	private enum LayoutManagerType {
		GRID_LAYOUT_MANAGER, LINEAR_LAYOUT_MANAGER
	}

	private RadioButton mLinearlayoutButton;
	private RadioButton mGridLayoutButton;

	private RecyclerView mRecyclerView;
	private CustomAdapter mAdapter;
	private RecyclerView.LayoutManager mLayoutManager;
	private LayoutManagerType mCurrentLayoutManagerType;
	//建立的模拟数据
	private ArrayList<String> mDataList;
	//网格布局中的设置列数
	private static int SpanCount=3;
	//模拟数据的个数
	private static int DataSize = 100;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		initDatas();
		initViews(savedInstanceState);
	}

	private void initViews(Bundle savedInstanceState) {
		mLinearlayoutButton = (RadioButton) findViewById(R.id.linearlayout_rb);
		mLinearlayoutButton.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View v) {
				setRecyclerViewManagerType(LayoutManagerType.LINEAR_LAYOUT_MANAGER);
			}
		});
		mGridLayoutButton = (RadioButton) findViewById(R.id.gridlayout_rb);
		mGridLayoutButton.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View v) {
				setRecyclerViewManagerType(LayoutManagerType.GRID_LAYOUT_MANAGER);
			}
		});
		mCurrentLayoutManagerType = LayoutManagerType.LINEAR_LAYOUT_MANAGER;
		if(savedInstanceState!=null){
			 mCurrentLayoutManagerType = (LayoutManagerType) savedInstanceState
	                    .getSerializable(KEY_LAYOUT_MANAGER);
			 Log.i(TAG, "mCurrentLayoutManagerType="+mCurrentLayoutManagerType);
		}
		
		mRecyclerView = (RecyclerView) findViewById(R.id.recyclerView);
		setRecyclerViewManagerType(mCurrentLayoutManagerType);
		mAdapter = new CustomAdapter(mDataList);
		mRecyclerView.setAdapter(mAdapter);
		//设置recycler拥有固定的大小，提高展示效率
		mRecyclerView.setHasFixedSize(true);
		//设置默认的动画，在移除和添加的效果下展现，现在github上可以找到许多拓展，有兴趣的可以找找
		mRecyclerView.setItemAnimator(new DefaultItemAnimator());
		//实现我们给Adapter监听的方法，因为recyclerview没有Listview的OnClick和OnlongClick相似的方法
		mAdapter.setOnItemPressedListener(new OnItemPressedListener() {
			@Override
			public void onItemClick(int position) {
				Toast.makeText(MainActivity.this, "你点击了 item-"+mDataList.get(position), Toast.LENGTH_SHORT).show();
			}
			
			@Override
			public boolean OnItemLongClick(int position) {
				//这里模拟了删除的功能
				removeItemByPosition(position);
//				insertItemByPosition(position);
				Toast.makeText(MainActivity.this, "你长按了 item-"+mDataList.get(position), Toast.LENGTH_SHORT).show();
				return true;
			}
		});
		mRecyclerView.setRecyclerListener(new RecyclerListener() {
			//资源回收后被调用
			@Override
			public void onViewRecycled(ViewHolder viewHolder) {
				CustomAdapter.ViewHolder vh = (org.jan.components.demo.CustomAdapter.ViewHolder) viewHolder;
				Log.d(TAG, "onViewRecycled->"+vh.getItemText().getText());
			}
		});
	}
	
	//创建模拟的数据
	private void initDatas() {
		mDataList = new ArrayList<String>();
		for (int i = 0; i < DataSize; i++) {
			mDataList.add(String.format(getString(R.string.iamstudent), i));
		}
	}
	/**
	 * 可以改变recycler的布局显示方式
	 * @param type
	 */
	protected void setRecyclerViewManagerType(LayoutManagerType type) {
		int scrollPosition = 0;
		if (mRecyclerView.getLayoutManager() != null) {
			scrollPosition = ((LinearLayoutManager) mRecyclerView
					.getLayoutManager())
					.findFirstCompletelyVisibleItemPosition();
		}
		switch (type) {
		//网状
		case GRID_LAYOUT_MANAGER:
			mLayoutManager = new GridLayoutManager(this, SpanCount);
			mCurrentLayoutManagerType = LayoutManagerType.GRID_LAYOUT_MANAGER;
			break;
		//线性，如list
		case LINEAR_LAYOUT_MANAGER:
			mLayoutManager = new LinearLayoutManager(this);
			mLayoutManager.canScrollHorizontally();
			mCurrentLayoutManagerType = LayoutManagerType.LINEAR_LAYOUT_MANAGER;
			break;
		default:
			mLayoutManager = new LinearLayoutManager(this);
			mCurrentLayoutManagerType = LayoutManagerType.LINEAR_LAYOUT_MANAGER;
			break;
		}
		mRecyclerView.setLayoutManager(mLayoutManager);
		mRecyclerView.scrollToPosition(scrollPosition);
	}
	
	/**
	 * 通过RecyclerView的adapter来移除指定位置的数据
	 * @param position
	 */
	protected void removeItemByPosition(int position) {
		if(mAdapter!=null&&position>0){			
			mAdapter.notifyItemRemoved(position);
			mDataList.remove(position);
			mAdapter.notifyItemRangeChanged(position, mAdapter.getItemCount());
			//你如果用了这个 ，就没有动画效果了。
//			mAdapter.notifyDataSetChanged();
		}
	}
	//对应这是可以新增指定索引的
	protected void insertItemByPosition(int position) {
		if(mAdapter!=null&&position>0){			
			mAdapter.notifyItemInserted(position);
			mDataList.add(position, String.format(getString(R.string.iamstudent), position));
			mAdapter.notifyItemRangeChanged(position, mAdapter.getItemCount());
		}
	}
	
	@Override
	protected void onSaveInstanceState(Bundle outState) {
		outState.putSerializable(KEY_LAYOUT_MANAGER, mCurrentLayoutManagerType);
		super.onSaveInstanceState(outState);
	}

	@Override
	protected void onRestoreInstanceState(Bundle savedInstanceState) {
		super.onRestoreInstanceState(savedInstanceState);
	}

}

5.这个customAdapter是实现了RecyclerView.Adapter，其中的ViewHolder貌似是给我们自己定义的，我没看过源码，但我的直觉告诉我他一定是优化了ListView对viewholder的重复利用。

package org.jan.components.demo;

import java.util.List;

import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnLongClickListener;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

public class CustomAdapter extends
		RecyclerView.Adapter<CustomAdapter.ViewHolder> {

	private List<String> dataList;
	
	private OnItemPressedListener onItemPressedListener;

	public CustomAdapter(List<String> data) {
		this.dataList = data;
	}

	@Override
	public int getItemCount() {
		return dataList.size();
	}
	//替换视图内的内容
	@Override
	public void onBindViewHolder(ViewHolder viewHolder, int position) {
		viewHolder.getDrawableId().setBackgroundResource(R.drawable.school_student);
		viewHolder.getItemText().setText(dataList.get(position));
	}
	//由RecyclerView的Layout manager来生成一个新的ViewHolder
	@Override
	public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {
		View v = LayoutInflater.from(viewGroup.getContext()).inflate(
				R.layout.layout_row_item, viewGroup, false);
		return new ViewHolder(v);
	}
	/**
	 * 继承RecyclerView的ViewHolder来自定义一个视图内的ViewHolder
	 */
	public class ViewHolder extends RecyclerView.ViewHolder {
		
		private ImageView drawableId;
		private TextView itemText;
		
		public ViewHolder(View itemView) {
			super(itemView);
			if(itemView!=null){
				//这里我为这个View添加了点击和长按事件的监听绑定，为了使本demo更像一个listView
				itemView.setOnClickListener(new OnClickListener() {
					@Override
					public void onClick(View v) {
						if(onItemPressedListener!=null){
							onItemPressedListener.onItemClick(getPosition());
						}
					}
				});
				itemView.setOnLongClickListener(new OnLongClickListener() {
					@Override
					public boolean onLongClick(View v) {
						if(onItemPressedListener!=null){
							return onItemPressedListener.OnItemLongClick(getPosition());
						}
						return false;
					}
				});
				drawableId = (ImageView) itemView.findViewById(R.id.item_image);
				itemText = (TextView) itemView.findViewById(R.id.item_text);
			}
		}

		public ImageView getDrawableId() {
			return drawableId;
		}
		
		public TextView getItemText() {
			return itemText;
		}
	}

	public void setOnItemPressedListener(
			OnItemPressedListener onItemPressedListener) {
		this.onItemPressedListener = onItemPressedListener;
	}

	protected static interface OnItemPressedListener{
		void onItemClick(int position);
		boolean OnItemLongClick(int position);
	}
}

好，代码都讲的很清楚简洁，主要是为了增加对RecyclerView的认识，现在很多新的app，都已经加入了这组件，很多大牛也写了对他的强大的拓展。

我在这里也添加一个有进阶性的博文，可供你我有时间学习

Android RecyclerView 使用完全解析体验艺术般的控件

[Android]使用RecyclerView替代ListView（二）

[Android]RecyclerView的简单示例

[Android初級]自定義SeekBar樣式（簡單說明）

[Android]RecyclerView的簡單示例

學習是自我規範的過程

[Android異常]java.lang.IllegalStateException:ViewHolder views must not be attached when created.

[Android]關於換膚功能的遐想篇

https://yachay.unat.edu.pe/blog/index.php?comment_area=format_blog&comment_component=blog&comment_co

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