Listview优化

1.新建一个布局里面写

              

<ListView    android:layout_width="match_parent"    android:layout_height="match_parent"    android:id="@+id/list_main_a"></ListView>

2.再新建一个布局模型

        
<ImageView    android:layout_width="30dp"    android:layout_height="30dp"    android:id="@+id/Iv_main_a"    android:src="@drawable/icon_user"/><TextView    android:layout_width="match_parent"    android:layout_height="wrap_content"    android:id="@+id/tv_main_a"    android:textSize="30sp"    android:layout_weight="1"    android:text="XX"/><Button    android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:id="@+id/bt_main_a"    android:text="下载"    />
    在布局里加上一句代码可以点击任何一个地方，提供给点击事件用
android:descendantFocusability="blocksDescendants"

    布局模型效果如下：
第一一个实体类参数如下：
        
public ImageView imageView;public TextView textView;public Button button;
3.首先接收id 
          lv_main_a= (ListView) findViewById(R.id.list_main_a);

4.给 lv_main_a  设置点击事件
     
//给ListView设置点击事件
    
lv_main_a.setOnItemClickListener(new AdapterView.OnItemClickListener() {    @Override    public void onItemClick(AdapterView<?> parent, View view, int i, long id) {        Toast.makeText(MainActivity.this, "跳转到"+tityem[i%tityem.length], Toast.LENGTH_SHORT).show();    }});
5.定义两个全局变量的集合
private int[] images={R.drawable.icon_user,R.drawable.icon_user,R.drawable.icon_user,R.drawable.icon_user,R.drawable.icon_user};private String[] tityem={"西游记","三国演义","水浒传","少林寺传奇","雄霸天下"};

6.设置内部类
    
//OOM OutOfMemory 内存溢出
      
class My extends BaseAdapter{    @Override    public int getCount() {        return 100;    }    @Override    public Object getItem(int i) {        return tityem[i%tityem.length];    }    @Override    public long getItemId(int i) {        return i;    }    @Override    public View getView(final int i, View view, ViewGroup parent) {        if(view==null){                                                  //view如果为空            view=getLayoutInflater().inflate(R.layout.layout_mx,null);      ////把布局文件转成View            layoutActivity layout=new layoutActivity();            layout.button= (Button) view.findViewById(R.id.bt_main_a);            layout.imageView= (ImageView) view.findViewById(R.id.Iv_main_a);            layout.textView= (TextView) view.findViewById(R.id.tv_main_a);            view.setTag(layout);        }        layoutActivity layout= (layoutActivity) view.getTag();           //获取view的值
     //设值                 layout.textView.setText(tityem[i%tityem.length]+i);        layout.imageView.setImageResource(images[i%tityem.length]);        layout.button.setOnClickListener(new View.OnClickListener() {   //给按钮设置点击事件            @Override            public void onClick(View v) {                Toast.makeText(MainActivity.this, "正在下载"+tityem[i%tityem.length], Toast.LENGTH_SHORT).show();            }        });        return view;    }}
  
全部代码如下：
package com.example.g160628_android08_widgetplus2;import android.content.pm.LabeledIntent;import android.os.AsyncTask;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.view.ViewGroup;import android.widget.AdapterView;import android.widget.BaseAdapter;import android.widget.Button;import android.widget.ImageView;import android.widget.ListView;import android.widget.TextView;import android.widget.Toast;public class MainActivity extends AppCompatActivity {    private ListView lv_main_a;    private int[] images={R.drawable.icon_user,R.drawable.icon_user,R.drawable.icon_user,R.drawable.icon_user,R.drawable.icon_user};    private String[] tityem={"西游记","三国演义","水浒传","少林寺传奇","雄霸天下"};    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.layout);         lv_main_a= (ListView) findViewById(R.id.list_main_a);        lv_main_a.setAdapter(new My());        lv_main_a.setOnItemClickListener(new AdapterView.OnItemClickListener() {            @Override            public void onItemClick(AdapterView<?> parent, View view, int i, long id) {                Toast.makeText(MainActivity.this, "跳转到"+tityem[i%tityem.length], Toast.LENGTH_SHORT).show();            }        });    }    class My extends BaseAdapter{        @Override        public int getCount() {            return 100;        }        @Override        public Object getItem(int i) {            return tityem[i%tityem.length];        }        @Override        public long getItemId(int i) {            return i;        }        @Override        public View getView(final int i, View view, ViewGroup parent) {            if(view==null){                view=getLayoutInflater().inflate(R.layout.layout_mx,null);                layoutActivity layout=new layoutActivity();                layout.button= (Button) view.findViewById(R.id.bt_main_a);                layout.imageView= (ImageView) view.findViewById(R.id.Iv_main_a);                layout.textView= (TextView) view.findViewById(R.id.tv_main_a);                view.setTag(layout);            }            layoutActivity layout= (layoutActivity) view.getTag();            layout.textView.setText(tityem[i%tityem.length]+i);            layout.imageView.setImageResource(images[i%tityem.length]);            layout.button.setOnClickListener(new View.OnClickListener() {                @Override                public void onClick(View v) {                    Toast.makeText(MainActivity.this, "正在下载"+tityem[i%tityem.length], Toast.LENGTH_SHORT).show();                }            });            return view;        }    }}
效果如下：
点击书名
  
点击下载：