1. ListView的用法流程

1.1 新建activity_main.xml

此页面作为主页布局页面，添加了一个ListView标签，显示全部数据。

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >
    <ListView
        android:id="@+id/list_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >
    </ListView>
</LinearLayout>

1.2 新建fruit_item.xml

此页面作为item单项的布局文件，显示单项的内容。

<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"
                android:layout_marginLeft="10dip" />
    </LinearLayout>

1.3 定义一个数据类文件Fruit.java

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;
    }
}

1.4 定义一个适配器类文件FruitAdapter.java

public class FruitAdapter extends ArrayAdapter<Fruit> {
    private int resourceId;
    public FruitAdapter(Context context, int textViewResourceId,
        List<Fruit> objects) {
        super(context, textViewResourceId, objects);
        resourceId = textViewResourceId;
    }
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        Fruit fruit = getItem(position); // 获取当前项的Fruit实例
        View view = LayoutInflater.from(getContext()).inflate(resourceId, null);
        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;
    }
}

1.5 创建活动MainActivity.java

public class MainActivity extends Activity {
    private List<Fruit> fruitList = new ArrayList<Fruit>();
        @Override
        protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initFruits(); //  初始化水果数据
        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() {
        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);
    }
}

2. 使用ViewHolder模式优化ListView

这里主要修改了getView()方法。
在子项被滚动到屏幕内的时候，会调用getView()。原始的getView()方法如下：

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    Fruit fruit = getItem(position); // 获取当前项的Fruit实例
    View view = LayoutInflater.from(getContext()).inflate(resourceId, null);
    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;
}

通过getItem(position) 获取当前项的Fruit实例，然后通过LayoutInflater来为这个子项加载我们传入的布局。接着调用View的findViewById()方法获得控件实例。

缺点：每次在调用getView()时都通过findViewById()实例化控件。

ViewHolder模式充分利用了ListView的视图缓存机制，避免了每次在调用getView()时都去通过findViewById()实例化控件。提高效率50%以上！！

只需要修改适配器类FruitAdapter.java中的getView()方法就可以。

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    Fruit fruit = getItem(position);
    ViewHolder holder = null;
    View view;
    if(convertView == null){
        view = LayoutInflater.from(getContext()).inflate(resourceId, null);
        viewHolder = new ViewHolder();
        viewHolder.fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
        viewHolder.fruitName = (TextView) view.findViewById(R.id.fruit_name);
        view.setTag(viewHolder); //  将ViewHolder 存储在View 
    }else{
        view = convertView;
        viewHolder = (ViewHolder)view.getTag();
    }

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

public final class ViewHolder{
    public ImageView fruitImage;
    public TextView fruitName;
}

3. ListView小技巧

分隔线，在ListView标签中设置如下就会在ListView中得到一个颜色为灰色，高为10dp的分隔线。
```
android:divider="@android:color/darker_gray"
android:dividerHeight="10dp"
```
滚动条
```
android:scrollbars="none"
```

取消点击后的回馈效果

android:listSelector="#00000000"
或者 android:listSelector="@android:color/transparent"

设置显示在第N项

listView.setSelection(N); //瞬间完成移动
//以下为平滑移动
listView.smoothScrollBy(offset);
listView.smoothScrollBy(index);
listView.smoothScrollBy(distance, duration);

设置空ListView，当数据为空时，可以显示的一个View

在ListView标签的同级添加一个id为empty_view的View

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<ListView
    android:id="@+id/list_view"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >
</ListView>
<TextView
        android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="这是无数据时显示的信息"
/>
</LinearLayout>

然后在MainActivity.java中设置

listView.setEmptyView(findViewById(R.id.empty_view));

4. 动态修改ListView

笨方法是重新设置adapter，但这样效率特别低。所以，要用notifyDataSetChanged()方法。

Fruit mango = new Fruit("Mango", R.drawable.mango_pic);
fruitList.add(mango);
adapter.notifyDataSetChanged();

注意：此fruitList必须和之前是同一个对象！！！如果新建了一个对象fruitList2，然后fruitList = fruitList2，这样是行不通的！！！因为并没有改变原始的对象。

5. 滑动监听

View.OnTouchListener

listView.setOnTouchListener(new View.OnTouchListener(){
      @Override
      public boolean onTouch(View v, MotionEvent event){
                switch(event.getAction()){
                      case MotionEvent.ACTION_DOWN:
                              //触摸时
                              break;
                      case MotionEvent.ACTION_MOVE:
                              //移动时
                              break;
                      case MotionEvent.ACTION_UP:
                              //离开时
                              break;
                }     
     }
});

AbsListView.OnScrollListener

listView.setOnScrollListener(new OnScrollListener(){
      @Override
      public boolean onScrollStateChanged(AbsListView view, int scrollState){
                switch(scrollState){
                       case OnScrollListener.SCROLL_STATE_IDLE:
                              //滑动停止时
                              break;
                       case OnScrollListener.SCROLL_STATE_IDLE:
                              //正在滚动时
                              break;
                       case OnScrollListener.SCROLL_STATE_IDLE:
                              //手指抛动时，手指离开后随着惯性继续滑动的状态
                              break;
                }
     }   
     @Override
      public boolean onScroll(AbsListView view,
                          int firstVisibleItem,  //第一个能看见的item的ID
                          int visibleItemCount,  //当前能看见的item总数
                          int totalItemCount){  //整个ListView的item总数
              //滚动时一直调用
              //do something
      }

}