Android中最常用也是最难用的控件——ListView

目标1：通过ListView来实现简单的滚动界面。

1. 代码：

   private String[] data={"Apple","Banana","Orange","Watermelon","Pear","Grape","Pineapple","Strawberry","Cherry","Mango","Apple","Banana","Orange","Watermelon","Pear","Grape","Pineapple","Strawberry","Cherry","Mango"};

   ArrayAdapter<String> adapter=new ArrayAdapter<String>(MainActivity.this,android.R.layout.simple_list_item_1,data);
   
   ListView listView=(ListView) findViewById(R.id.list_view);
   
   listView.setAdapter(adapter);

2. 运行结果截图：

   
3.  代码分析：

• ArrayAdapter<String> adapter=new ArrayAdapter<String>(MainActivity.this,android.R.layout.simple_list_item_1,data);
  MainActivity.this 本活动

  android.R.layout.simple_list_item_1     Android内置的一个TextView，里面只有一个。

  data 本地的数据

 目标2：定制ListView的界面，使得同时可以显示文本与图片。

1. 准备好与上面相对应的图片
2. 定义一个实体类，作为ListView适配器的适配类型。（理解重要）     

     （name表示水果名字 ImageId表示水果图片的id）  

代码：

public class Fruit {

    private String name;

    private int imageId;

    //构造方法

    public Fruit(String name,int imageId){

        this.name=name;

        this.imageId=imageId;

    }

    //内部方法

    public String getName(){

        return name;

    }

    //内部方法

    public int getImageId(){

        return imageId;

    }

}

3. 在layout目录下新建一个fruit_item.xml文件来自定义布局    
<?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="wrap_content">

<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>

4.创建一个自定义的适配器，这个适配器继承自ArrayAdapter,并将泛型指定为<Fruit>类

重写父类的构造函数与getView（）这个构造方法。
代码：

public class FruitAdapter extends ArrayAdapter<Fruit> {

    private int resourceId;

    public FruitAdapter(Context context,  int textViewResourceId, List<Fruit>object) {//继承自父类的构造方法

        super(context, textViewResourceId,object);

        resourceId=textViewResourceId;

    }

    public View getView(int position,  View convertView,  ViewGroup parent) {

        Fruit fruit = getItem(position);//获取当前项的Fruit实例

//        return super.getView(position, convertView, parent);

        View view = LayoutInflater.from(getContext()).inflate(resourceId, parent, false);

        ImageView fruitImage= (ImageView) view.findViewById(R.id.fruit_image);

        TextView  fruitName=(TextView)view.findViewById(R.id.fruit_name);

        fruitImage.setImageResource(fruit.getImageId());

        fruitName.setText(fruit.getName());

        return view;

    }

}

5.修改MainActivity中的代码：

For循环中将内容重复了两遍使得可以实现滚动效果。

代码：

public class MainActivity extends AppCompatActivity {
    private List<Fruit> fruitList=new ArrayList<>();
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initFruits();
        FruitAdapter adapter=new FruitAdapter(MainActivity.this,R.layout.fruit_item,fruitList);
        ListView listView=(ListView) findViewById(R.id.list_view);
        listView.setAdapter(adapter);

 }

    private void initFruits(){

        for (int i=0;i<2;i++){

            Fruit apple=new Fruit("Apple",R.drawable.apple_pic);

            fruitList.add(apple);

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

            fruitList.add(banana);

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

            fruitList.add(orange);

            Fruit watermelon=new Fruit("watermelon",R.drawable.watermelon_pic);

            fruitList.add(watermelon);

            Fruit pear=new Fruit("pear",R.drawable.pear_pic);

            fruitList.add(pear);

            Fruit grape=new Fruit("grape",R.drawable.grape_pic);

            fruitList.add(grape);

            Fruit pineapple=new Fruit("pineapple",R.drawable.pineapple_pic);

            fruitList.add(pineapple);

            Fruit strawberry=new Fruit("strawberry",R.drawable.strawberry_pic);

            fruitList.add(strawberry);

            Fruit cherry=new Fruit("cherry",R.drawable.cherry_pic);

            fruitList.add(cherry);

            Fruit mango=new Fruit("mango",R.drawable.mango_pic);

            fruitList.add(mango);

        }

    }

}

6.图片资源截图：

7.结果截图：

 

8. 优化：

增加点击事件的监听器：

//点击事件的监听器。

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();

   }

});

截图：