今天又在iOS上看到列表的”阻尼”效果，就是列表拉到表頭或者表尾時，還可以繼續往上或往下拉，松開手後，整個列表會彈回去，來看效果圖：
整個實現重點在overScrollBy這個方法上，當你滾動listview時會觸發此事件，它會根據表頭或表尾的坐標，及你所給的maxOverScrollY最大滾動縱坐標值來計算listview的表頭或表尾的坐標。
Android默認的ListView的overScrollBy方法中maxOverScrollY=0；所以你只能看到在表頭或表尾有一條帶顏色的線閃燈，據說，這是為了避免IOS的專利….
下面來看實現方式：
activity_main.xml：
<com.example.tt.BaseListView
android:id="@+id/mylistview"
android:layout_width="match_parent"
android:layout_height="match_parent" >
</com.example.tt.BaseListView>
MainActivity.java：
public class MainActivity extends Activity {
private BaseListView listview;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_main);
listview = (BaseListView) findViewById(R.id.mylistview);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_expandable_list_item_1, new String[] { "A", "A", "A", "A", "A", "A", "A", "A", "A"});
listview.setAdapter(adapter);
}
}
這個是重點
BaseListView.java
public class BaseListView extends ListView
{
private static final int MAX_Y_OVERSCROLL_DISTANCE = 200;
private Context mContext;
private int mMaxYOverscrollDistance;
public BaseListView(Context context)
{
super(context);
mContext = context;
initBounceListView();
}
public BaseListView(Context context, AttributeSet attrs)
{
super(context, attrs);
mContext = context;
initBounceListView();
}
public BaseListView(Context context, AttributeSet attrs, int defStyle)
{
super(context, attrs, defStyle);
mContext = context;
initBounceListView();
}
private void initBounceListView()
{
final DisplayMetrics metrics = mContext.getResources().getDisplayMetrics();
final float density = metrics.density;
mMaxYOverscrollDistance = (int) (density * MAX_Y_OVERSCROLL_DISTANCE);
}
@Override
protected boolean overScrollBy(int deltaX, int deltaY, int scrollX, int scrollY, int scrollRangeX, int scrollRangeY, int maxOverScrollX, int maxOverScrollY, boolean isTouchEvent)
{
return super.overScrollBy(deltaX, deltaY, scrollX, scrollY, scrollRangeX, scrollRangeY, maxOverScrollX, mMaxYOverscrollDistance, isTouchEvent);
}
}
更多Android相關信息見Android 專題頁面 http://www.linuxidc.com/topicnews.aspx?tid=11
