ListView讨论

 1.ListView简单用法

第一步：

在activity_main.xml中增加：

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

 

第二步：

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

 

2.定制LIstView界面（MVC）

V层：

在activity_main.xml建立一个ListView控件

新建立一ListView的页面子布局

（绘制V层的时候会自动调用getView())

 

Ｍ层：

建立一需要展示的实体类

 

Ｃ层：

建立一自定义Adapter（继承ArrayAdapter）

 

例子如下：

public class FruitAdapter extends ArrayAdapter<Fruit> {

    private int resourceId;

    /***
     *
     * @param context  域，上下文
     * @param textViewResourceId  布局ID
     * @param objects  实体对象
     */
    public FruitAdapter(Context context,int textViewResourceId, List<Fruit> objects ) {
        super(context, textViewResourceId, objects);
        resourceId = textViewResourceId;
    }

 

　　＊Provides the metrics for the shadow image. These include the dimensions of
         * the shadow image, and the point within that shadow that should
         * be centered under the touch location while dragging.

    //控制展示，相当于DAO类，获得数据

　@Override
    public View getView(int position, View convertView, ViewGroup parent) {
        Fruit fruit = getItem(position); //自动将List<Fruit>中的值解出，获取当前项的Fruit实例

        //new 出布局、控件
        View view = LayoutInflater.from(getContext()).inflate(resourceId,null); （布局）
        ImageView fruitImage = (ImageView) view.findViewById(R.id.fruit_image);  （控件）
        TextView fruitName = (TextView) view.findViewById(R.id.fruit_name);   （控件）
        //赋值 

        fruitImage.setImageResource(fruit.getImageId());  
        fruitName.setText(fruit.getName());  
        return view;

    }
}

 

在MainActivity中调用，相当于Action类

例子如下：

private List<Fruit> fruitList = new ArrayList<Fruit>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //初始化fruitList

        initFruits();
        FruitAdapter adapter = new FruitAdapter(MainActivity.this, R.layout.fruit_item, fruitList);
        ListView listView = (ListView) findViewById(R.id.list_view);
        //返回数据至V层

        listView.setAdapter(adapter);

    }

    private void initFruits() {
        Fruit apple = new Fruit("Apple",R.drawable.a);
        fruitList.add(apple);
        Fruit banana = new Fruit("Banana",R.drawable.b);
        fruitList.add(banana);
        Fruit orange = new Fruit("Orange",R.drawable.c);
        fruitList.add(orange);
        Fruit watermelon = new Fruit("Watermelon",R.drawable.d);
        fruitList.add(watermelon);
        Fruit pear = new Fruit("Pear",R.drawable.e);
        fruitList.add(pear);
        Fruit grape = new Fruit("Grape",R.drawable.f);
        fruitList.add(grape);
        Fruit pineapple = new Fruit("Pineapple",R.drawable.g);
        fruitList.add(pineapple);
        Fruit strawberry = new Fruit("Strawberry",R.drawable.h);
        fruitList.add(strawberry);
        Fruit cherry = new Fruit("Cherry",R.drawable.i);
        fruitList.add(cherry);
        Fruit mango = new Fruit("Mango",R.drawable.j);
        fruitList.add(mango);

    }

 

getView：

getView()方法是ListView的每个列表项目绘制在屏幕上时被调用

 

3.提升listview的运行效率

View view;
        if (convertView == null) {
            view = LayoutInflater.from(getContext()).inflate(resourceId, null);
        } else {
            view = convertView;
        }

  ConvertView是对之前加载好的布局进行缓存

 

 4.Android获取LayoutInflater对象的方法总结

获取context对象

一：

LayoutInflater inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View child = inflater.inflate(R.layout.child, null);

 二：

LayoutInflater inflater = LayoutInflater.from(context);
View child = inflater.inflate(R.layout.child, null);

 

方法1和方法2其实都是对context().getSystemService()的使用