listView 的用法

1.Fruit.class 定义为水果实体类

    

public class Fruit {
    private String name;
    private int imageId;

    public Fruit(String name,int imageId)
    {
        this.name = name;
        this.imageId = imageId;
    }
    public String  getName(){
        return name;
    }
    public  int getImageId()
    {
        return imageId;
    }


}

2.fruit_item 为listview的子项定义一个布局

xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="match_parent"
              android:layout_height="match_parent">

      <ImageView
          android:id="@+id/fruit_image"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"/>
     <TextView
         android:id="@+id/fruit_name"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_gravity="center_vertical"
         android:layout_marginLeft="10dp"
         />

LinearLayout>

3.FruitAdapter.class  定义一个自定义的适配器，并将泛型指定为Fruit类

/**
 *  自定义的适配器
*/
public class FruitAdapter extends ArrayAdapter {
     private int resourceId;
     public FruitAdapter(Context context,int textViewResourceId,
                         List objects)
    {
        super(context,textViewResourceId,objects);
        resourceId = textViewResourceId;
    }

    @Override
    public View getView(int postion, View convertView, ViewGroup parent )
    {
        Fruit fruit = getItem(postion);//获取当前的的实例
        View view;
        ViewHolder  viewHolder;
        if (convertView ==null)
        {
            view =  LayoutInflater.from(getContext()).inflate(resourceId,parent,false); //false表不增父布局
            viewHolder = new ViewHolder();
            viewHolder.fruitImageId = (ImageView)view.findViewById(R.id.fruit_image);
            viewHolder.fruitName = (TextView) view.findViewById(R.id.fruit_name);
            view.setTag(viewHolder);//将viewHolder储存在view中
        }
        else
        {
            view = convertView;
            viewHolder = (ViewHolder) view.getTag();//重新获取ViewHolder;

        }

        viewHolder.fruitImageId.setImageResource(fruit.getImageId());
        viewHolder.fruitName.setText(fruit.getName());
        return view;
    }

    class ViewHolder{
        ImageView fruitImageId;
        TextView  fruitName;
    }
}

4.MainActivity.java 主活动

public class MainActivity extends AppCompatActivity {
 private List fruitList = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initFruit();
       FruitAdapter adapter =  new FruitAdapter(MainActivity.this,R.layout.fruit_item,fruitList);
        ListView listView =   (ListView)findViewById(R.id.list_view);
        listView.setAdapter(adapter);
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView parent, View view, int position, long id) {
                  Fruit fruit = fruitList.get(position);
                Toast.makeText(MainActivity.this, fruit.getName(), Toast.LENGTH_SHORT).show();
            }
        });
    }
    public void initFruit()
    {
        for (int i =0;i< 4 ; i ++ ){
      Fruit apple =  new Fruit("apple",R.drawable.apple);
        fruitList.add(apple);

        Fruit banana =  new Fruit("banana",R.drawable.banana);
        fruitList.add(banana);

        Fruit orange =  new Fruit("orange",R.drawable.orange);
        fruitList.add(orange);

        Fruit pear =  new Fruit("pear",R.drawable.pear);
        fruitList.add(pear);
        Fruit watermelon =  new Fruit("pear",R.drawable.watermelon);
        fruitList.add(watermelon);
        }

    }
}

6.activity_layout.xml 主布局文件

<LinearLayout
    android:id="@+id/activity_main"
    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"
    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.sh.customlistviewtest.MainActivity">

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

    ListView>
LinearLayout>