ListView和RecyclerView的使用和性能优化总结

1.ListView介绍

  在手机中，使用列表显示是一种常见的显示格式，那么ListView就是一种常见的方式。例如：今日头条，网易新闻都是使用ListView或者是最近流行的RecyclerView进行首页的布局，最后一节将会对它进行介绍。

2.ListView常用方法和实现逻辑介绍

2.1使用ListView

Android提供了ListView和ExpandableListView用来实现ListView这个功能。

2.2 Adapter适配器

当你需要创建一个ListView时，需要绑定一个adapter用来实现listview中的item view资源申请和item view的数据绑定。

2.3 ListView的过滤和排序

ListView也可以实现对每一个item进行过滤或者排序，当然在开发的工程中也需要对adapter进行设计才能实现该项功能。

2.4 动态更新

notifyDataSetChanged()：这个方法将在数据被改变，或者数据新创建的时候会被调用。这个时候你可以在这个方法中重写方

法以至于达到动态更新数据的目的。

3.默认适配器

3.1 默认平台适配器

Android提供了默认的适配器，最主要的两个是：ArrayAdapter和CursorAdapter。其中ArrayAdapter可基于Arrays

或java.util.List来处理数据。而SimpleCursorAdapter可以处理相关数据库。

3.2使用ArrayAdapter的一个例子：

package com.example.zhengxie.demo_testcase;

import android.content.Context;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.BaseAdapter;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.ListView;
import android.widget.TextView;

import java.security.KeyStore;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    ListView listView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        listView = (ListView) findViewById(R.id.listview);
        String[] values = new String[]{"中国移动", "中国联通", "中国电信"};
        final ArrayList arrayList = new ArrayList();
        for (int i = 0; i < values.length; i++) {
            arrayList.add(values[i]);
        }
        //设置adapter(context,listview中的样式，数据)
        final StableArrayAdapter adapter = new StableArrayAdapter(this, R.layout.rowbuttonlayout, arrayList);
        listView.setAdapter(adapter);
        //当用户点击了一个Item时，对Item的监听事件
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView parent, final View view, int position, long id) {
                final String item = (String) parent.getItemAtPosition(position);
                view.animate().setDuration(2000).alpha(0).withEndAction(new Runnable() {//对view的渐变显示
                    @Override
                    public void run() {
                        arrayList.remove(item);
                        adapter.notifyDataSetChanged();//记：View refresh
                        view.setAlpha(1);//0为透明，1为不透明
                    }
                });
            }
        });
    }

    private class StableArrayAdapter extends ArrayAdapter {
        HashMap mInMap = new HashMap();
        private Context context;
        private List list;

        public StableArrayAdapter(Context context, int resource, List objects) {
            super(context, resource, objects);
            this.context = context;
            this.list = objects;
            for (int i = 0; i < objects.size(); i++) {
                mInMap.put(objects.get(i), i);
            }
        }

        @Override
        public long getItemId(int position) {
            String item = getItem(position);
            return mInMap.get(item);
        }

        @Override
        public boolean hasStableIds() {
            return true;
        }

        @NonNull
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            View view;
            LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            view = inflater.inflate(R.layout.rowbuttonlayout,null);
            final ViewHolder viewHolder ;
            if (convertView == null){//布局缓存是否为空
                viewHolder = new ViewHolder();
                viewHolder.textView = (TextView) view.findViewById(R.id.label);
                viewHolder.checkBox = (CheckBox) view.findViewById(R.id.check);
                viewHolder.checkBox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
                    @Override
                    public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                        viewHolder.checkBox.setSelected(buttonView.isChecked());
                    }
                });
                view.setTag(viewHolder);//将viewHolder加载到view中
            }
            else {
                view = convertView;
                viewHolder = (ViewHolder) view.getTag();
            }
            viewHolder.textView.setText(list.get(position));
            viewHolder.checkBox.setSelected(false);
            return view;
        }

        class ViewHolder{
            private TextView textView;
            private CheckBox checkBox;
        }
    }
}

3.3 使用ArrayActivity实现的例子

1.新建List数据集合
package com.example.zhengxie.demo_testcase;

/**
 * 
 */

public class Model {
    private String name;
    private boolean selected;

    public Model(String name) {
        this.name = name;
        selected = false;
    }

    public String getName() {
        return name;
    }

    public boolean isSelected() {
        return selected;
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setSelected(boolean selected) {
        this.selected = selected;
    }
}

2.新建ListActivity
package com.example.zhengxie.demo_testcase;

import android.app.ListActivity;
import android.os.Bundle;
import android.widget.ArrayAdapter;

import java.util.ArrayList;
import java.util.List;

/**
 * 
 */

public class MyList extends ListActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ArrayAdapter adapter = new myArrayAdapter(this, getModel());
        setListAdapter(adapter);
    }

    private List getModel() {
        List list = new ArrayList();
        list.add(get("电信"));
        list.add(get("移动"));
        list.add(get("联通"));
        list.get(1).setSelected(true);
        return list;
    }

    private Model get(String s) {
        return new Model(s);
    }
}

3.创建adater类：myArrayAdapter.java
package com.example.zhengxie.demo_testcase;

import android.app.Activity;
import android.content.Context;
import android.support.annotation.NonNull;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.TextView;

import java.util.List;

/**
 * 
 */
public class myArrayAdapter extends ArrayAdapter {

    private final List list;
    private final Activity context;

    public myArrayAdapter(Activity context, List model) {
        super(context, R.layout.rowbuttonlayout, model);
        this.list = model;
        this.context = context;
    }

    static class ViewHolder {
        protected TextView textView;
        protected CheckBox checkBox;
    }

    @NonNull
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View view;
        if (convertView == null) {
            LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            view = inflater.inflate(R.layout.rowbuttonlayout, null);
            final ViewHolder viewHolder = new ViewHolder();
            viewHolder.textView = (TextView) view.findViewById(R.id.label);
            viewHolder.checkBox = (CheckBox) view.findViewById(R.id.check);
            viewHolder.checkBox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
                @Override
                public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                    if (!buttonView.isPressed()) return;
                    Model element = (Model) viewHolder.checkBox.getTag();
                    element.setSelected(buttonView.isChecked());
                }
            });
            view.setTag(viewHolder);
            viewHolder.checkBox.setTag(list.get(position));
        } else {
            view = convertView;
            ((ViewHolder) view.getTag()).checkBox.setTag(list.get(position));
        }
        ViewHolder holder = (ViewHolder) view.getTag();
        holder.textView.setText(list.get(position).getName());
        holder.checkBox.setChecked(list.get(position).isSelected());
        return view;
    }
}

4.RecyclerView

上面介绍完了ListView的常用显示方式和技巧。下面进行一个当前最火的RecyclerView，这个实现类拥有着很多有点，

基本解决了ListView的一些缺陷，比如：需要手动重写ViewHolder，对于item的动画操作也需要很复杂的逻辑去实现等等。

下面我将用自己实现的一个实例为大家介绍：

1.新建RecyclerView的xml资源：


    
    

2.新建类，对于RecyclerView进行初始化：
package com.example.zhengxie.recyclerview;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.animation.Animation;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private RecyclerView mRecyclerView;
    private MyAdapter mMyAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //第一步：声明RecyclerView
        mRecyclerView = (RecyclerView) findViewById(R.id.rw_main);
        //第二步：设置布局的格式：LinearLayoutManager是水平显示(如果要创建一个自定义布局管理器，请扩展 RecyclerView.LayoutManager 类别)
        mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
        //第三步：声明一个Adapter
        mMyAdapter = new MyAdapter(this, initData());
        //绑定一个自定义的分割线
        mRecyclerView.addItemDecoration(new MyItemDivider(this,R.drawable.shape));
        //第四步：绑定adapter
        mRecyclerView.setAdapter(mMyAdapter);
    }

    //第五步：声明一个ArrayList数组存储数据
    private List initData() {
        List datas = new ArrayList<>();
        for (int i = 0; i <= 40; i++) {
            datas.add("Item:"+i);
        }
        return datas;
    }
}

3.初始化adapter：MyAdapter.java类

package com.example.zhengxie.recyclerview;

import android.content.Context;
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.List;

/**
 * 
 */

public class MyAdapter extends RecyclerView.Adapter {

    private List datas;
    private LayoutInflater inflater;

    //第一步：创建构造函数需要的参数
    public MyAdapter(Context context, List datas) {
        this.datas = datas;
        //记第二步：初始化inflate
        inflater = LayoutInflater.from(context);
    }

    //第三步：声明MyViewHolder这个类,初始化每个资源
    public class MyViewHolder extends RecyclerView.ViewHolder {
        private TextView title;

        //第五步：声明每个item
        public MyViewHolder(View itemView) {
            super(itemView);
            title = (TextView) itemView.findViewById(R.id.rv_main_item_title);
        }
    }

    //第四步：重写createView
    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        MyViewHolder holder = new MyViewHolder(inflater.inflate(R.layout.rv_main_item, parent, false));
        return holder;
    }

    //第六步：这里对数据进行赋值操作
    @Override
    public void onBindViewHolder(MyViewHolder holder, int position) {
        holder.title.setText(datas.get(position));
    }

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

4.添加一个Decoratoin的shape：


    
    
    

    

5.添加addItemDecoration类：MyItemDivider.java
package com.example.zhengxie.recyclerview;

import android.content.Context;
import android.content.res.Configuration;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.support.v7.widget.RecyclerView;
import android.view.View;

/**
 * 
 */

public class MyItemDivider extends RecyclerView.ItemDecoration{
    private Drawable mDrawable;

    public MyItemDivider(Context context, int resId) {
        mDrawable = context.getResources().getDrawable(resId);
    }

    @Override
    public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
        int left = parent.getPaddingLeft();//左边距
        int right = parent.getWidth() - parent.getPaddingRight();//右边距
        int childCount = parent.getChildCount();//获得当前首次刷新时页面的item个数
        for (int i = 0; i < childCount; i++) {
            View child = parent.getChildAt(i);
            RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
            int top = child.getBottom() + params.bottomMargin;//获得要画decoration的上高度
            int bottom = top + mDrawable.getIntrinsicHeight();//获得要画decoration下高度
            mDrawable.setBounds(left, top, right, bottom);
            mDrawable.draw(c);
        }
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        outRect.set(0,0,0,mDrawable.getIntrinsicWidth());
    }
}

5.附加

对于RecyclerView中实现的Drawable的left,top,right,botton这里做一下说明：

这样大家就更容易更方便的理解Drawable方法在Android系统里的绘制图片的模式和坐标位置了。