Android —页面下拉刷新（ListView与SwipeRefreshLayout）

　　相信大家在使用淘宝的时候应该都看到过下拉刷新的效果。这种效果看起来会感觉比较难做，一起来看下下拉刷新。

ListView

思路：

通过FrameLayout底层为下拉刷新的Header，上面一层是ListView，监听手指滑动设置动画效果，移动ListView。

使用：

1、编写ListView顶部下拉刷新的header

<?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"
android:orientation="vertical" >
<TextView
android:layout_width="match_parent"
android:gravity="center"
android:layout_height="wrap_content"
android:text="下拉刷新"
/>

</LinearLayout>

2、ListView(后面将会进行动态添加)

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

3、自定义FrameLayout动态添加ListView与header

public class MyFrameLayout extends FrameLayout{
ListView listview;
public MyFrameLayout(Context context) {
super(context);
}
public MyFrameLayout(Context context, AttributeSet attrs) {
super(context, attrs);
//先创建LayoutInflater 用于获得布局
LayoutInflater inflater=(LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
//添加顶部布局
View header=inflater.inflate(R.layout.header, null);
//向布局中添加header（下拉加载）
addView(header);
//ListView的Adapter
ArrayAdapter<String> adapter=new ArrayAdapter<String>(context, android.R.layout.simple_list_item_1,new String[]{"a","b","c","d","e","f","g","h","i","j","k","l","m","n"});

listview=(ListView) inflater.inflate(R.layout.mylistview, null);
listview.setAdapter(adapter);
//向布局中添加ListView
addView(listview);

}

//拦截事件
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {

if(ev.getAction()==MotionEvent.ACTION_DOWN){

}
if(listview.getFirstVisiblePosition()==0){
View firstview=listview.getChildAt(listview.getFirstVisiblePosition());
if(firstview.getY()>=0){

return true;

}

}

return super.onInterceptTouchEvent(ev);
}
//设置动画时使用
private float oldy;
//处理事件
@Override
public boolean onTouchEvent(MotionEvent event) {
Log.d("onTouchEvent", ""+super.onTouchEvent(event));
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
//手指落下监听
oldy=event.getY();

case MotionEvent.ACTION_MOVE:
float y=event.getY();
float distance=y-oldy;
//设置listview移动
listview.setTranslationY(listview.getTranslationY()+distance);
oldy=y;
invalidate();

return true;

case MotionEvent.ACTION_UP:
//手指抬起时，设置动画效果，使ListView回到顶部
ObjectAnimator.ofFloat(listview, "translationY", listview.getTranslationY(),0).setDuration(300).start();

break;
default:
break;
}
return super.onTouchEvent(event);
}
}

4、布局引用

<?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"
android:orientation="vertical" >
<com.example.administrator.myapplication2.MyFrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
>
</com.example.administrator.myapplication2.MyFrameLayout>

</LinearLayout>

5、在MainActivity中使用该布局即可。

SwipeRefreshLayout

　　实际上Android已经为我们实现一种下拉刷新，那就是通过SwipeRefreshLayout，看下新出的SwipeRefreshLayout的实现方式。

使用：

1、布局

注：SwipeRefreshLayout类似于ScrollView，内部只能有一个组件。

<?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"
android:orientation="vertical" >

<android.support.v4.widget.SwipeRefreshLayout
android:id="@+id/swiperefresh"
android:layout_width="match_parent"
android:layout_height="match_parent" >

<ListView
android:id="@+id/listview2"
android:layout_width="match_parent"
android:layout_height="match_parent" >
</ListView>
</android.support.v4.widget.SwipeRefreshLayout>

</LinearLayout>

2、MainActivity

public class MainActivity extends Activity {
private SwipeRefreshLayout refresh;
private ListView mlistview;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
mlistview=(ListView) findViewById(R.id.listview2);
refresh=(SwipeRefreshLayout) findViewById(R.id.swiperefresh);
ArrayAdapter<String> adapter=new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1,new String[]{"a","b","c","d","e","f","g","h","i","j","k","l","m","n"});
mlistview.setAdapter(adapter);
//设置监听事件
refresh.setOnRefreshListener(new OnRefreshListener() {

@Override
public void onRefresh() {

refresh.setRefreshing(false);
}
});

}

}