BaseAdapter使用

package com.example.user.android2lesson_03_baseadapter;


import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ListView;


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


import bean.News;


public class MainActivity extends AppCompatActivity {
    //  BaseAdapter使用
    //第一步.创建一个布局文件，对Item控件进行布局


    //第二步.在对应的Activity中添加ListView控件


    //第三步.声明属性并进行初始化


    //第四步.创建一个类，继承自BaseAdapter


    //第五步.创建Adapter并进行绑定


    private ListView mListView;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mListView= (ListView) findViewById(R.id.listView);
        MyAdapter adapter=new MyAdapter(this,getData());
        mListView.setAdapter(adapter);


    }
    private List getData(){
        List list=new ArrayList<>();
        News new1=new News(R.drawable.image,"逗逼","大狗");
        list.add(new1);
        News new2=new News(R.drawable.image1,"逗逼","二狗");
        list.add(new2);
        News new3=new News(R.drawable.image2,"逗逼","狗狗");
        list.add(new3);




        return list;
    }


}




package com.example.user.android2lesson_03_baseadapter;


import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;


import java.util.List;


import bean.News;




/**
 * Created by user on 2016/7/6.
 */
public class MyAdapter extends BaseAdapter{


    //声明属性，保存数据和上下文对象
    private List list;
    private Context context;


    public MyAdapter(Context context,List list){
        this.context=context;
        this.list=list;
    }




    @Override
    public int getCount() {
        return list.size();
    }


    @Override
    public Object getItem(int i) { return list.get(i);
    }


    @Override
    //获取Item对应的ID
    public long getItemId(int i) {
        return i;
    }


    @Override
    //获取i对应位置的视图
    public View getView(int i, View view, ViewGroup viewGroup) {
        /**优化前
        //去获取指定的layout文件中指定id的控件
        View v=LayoutInflater.from(context).inflate(R.layout.item_layout,null);
        ImageView image= (ImageView) v.findViewById(R.id.image);
        TextView titleView= (TextView) v.findViewById(R.id.text1);
        TextView infoView= (TextView) v.findViewById(R.id.text2);


        //拿到数据
        News news= (News) getItem(i);


        //根据数据对界面进行赋值
        image.setBackgroundResource(news.getImg());
        titleView.setText(news.getTitle().toString());
        infoView.setText(news.getInfo().toString());
         return v;


        */
        //优化后
        //利用缓存
        ViewHolder Holder;
        if (view==null){
            //将指定的的布局文件转换成视图文件


            //这里是缓存的界面控件
            view= View.inflate(context,R.layout.item_layout,null);


            Holder=new ViewHolder();
            Holder.imageView= (ImageView) view.findViewById(R.id.image);
            Holder.titleView= (TextView) view.findViewById(R.id.text1);
            Holder.infoView= (TextView) view.findViewById(R.id.text2);
            view.setTag(Holder);
        }else {
            Holder= (ViewHolder) view.getTag();


        }
        News news= (News) getItem(i);
        Holder.imageView.setBackgroundResource(news.getImg());
        Holder.titleView.setText(news.getTitle().toString());
        Holder.infoView.setText(news.getInfo().toString());
        return view;
    }
}




package com.example.user.android2lesson_03_baseadapter;


import android.widget.ImageView;
import android.widget.TextView;


/**
 * Created by user on 2016/7/6.
 */
public class ViewHolder {
    //这里罗列的是所有的控件
    public ImageView imageView;
    public TextView titleView;
    public TextView infoView;












}




package bean;




/**
 * Created by user on 2016/7/6.
 */
public class News {
    //存放图片,资源都是采用id的形式
    private  int img;
    private String title;
    private String info;


    //初始化方法
    public News(int img, String title, String info){
        this.img=img;
        this.title=title;
        this.info=info;
    }


    public int getImg() {
        return img;
    }


    public void setImg(int img) {
        this.img = img;
    }


    public String getTitle() {
        return title;
    }


    public void setTitle(String title) {
        this.title = title;
    }


    public String getInfo() {
        return info;
    }


    public void setInfo(String info) {
        this.info = info;
    }




}





    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.user.android2lesson_03_baseadapter.MainActivity">
    
    


            android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+idstView">










    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" 
    android:layout_width="match_parent"
    android:layout_height="match_parent">


            android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/image"/>
            android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical">
            android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="标题"
        android:id="@+id/text1"/>
            android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="我是一条消息"
        android:id="@+id/text2"/>