居中+循环滚动的listview(2)

接上上一篇所说，最后是一个自定义的listview：

package com.example.mylistview;import android.content.Context;import android.util.AttributeSet;import android.view.KeyEvent;import android.view.View;import android.widget.ListAdapter;import android.widget.ListView;import android.widget.TextView;public class MyListView extends ListView {private TextView mFocus;private MyListView instance;public MyListView(Context context, AttributeSet attrs) {super(context, attrs);instance = this;instance.setOnKeyListener(mOnKeyListener);}private View.OnKeyListener mOnKeyListener=new View.OnKeyListener() {@Overridepublic boolean onKey(View arg0, int arg1, KeyEvent arg2) {// TODO 自动生成的方法存根switch(arg2.getAction()){case KeyEvent.ACTION_DOWN: if(arg1==KeyEvent.KEYCODE_DPAD_UP||(arg1==KeyEvent.KEYCODE_DPAD_DOWN)) moveFocus(arg1,arg0); break; }return false;}private void moveFocus(int direction,View focus) {int index=instance.getSelectedItemPosition();//丢失焦点的时候返回。if(index==-1){return;}//获取下一个焦点int position;if(index<instance.getAdapter().getCount()-1&&direction==KeyEvent.KEYCODE_DPAD_DOWN)position =index+1-getFirstVisiblePosition();else if(index>0&&direction==KeyEvent.KEYCODE_DPAD_UP)position =index-1-getFirstVisiblePosition();elseposition = index-getFirstVisiblePosition();mFocus=(TextView) instance.getChildAt(position);//焦点为空返回if(mFocus==null)return;int[] loc = new int[2];instance.getLocationOnScreen(loc);int[] screenLocation = new int[2];mFocus.getLocationOnScreen(screenLocation);//这里的高度需要有一个调整值，不知道为什么。int height = ((TextView)mFocus).getHeight()+2;if (screenLocation[1] < loc[1] + 8*height) {instance.smoothScrollBy(instance.getScrollY() - height, 0);}if (screenLocation[1] > loc[1] + 8*height) {instance.smoothScrollBy(instance.getScrollY() + height, 0);}}};}

至此，就实现了基本的居中+循环滚动的listview，当然会存在不少bug，日后有机会改善。