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);            }        });    }}