【转】Android自定义控件（三）——有弹性的ListView

原文地址：http://blog.csdn.net/a105865708/article/details/17959459

上一次我们试验了有弹性的ScrollView。详情

这一次，我们来试验有弹性的ScrollView。

国际惯例，效果图：

主要代码：

　　

 import android.content.Context;
 import android.graphics.Rect;
 import android.util.AttributeSet;
 import android.view.MotionEvent;
 import android.view.animation.Animation;
 import android.view.animation.Animation.AnimationListener;
 import android.view.animation.TranslateAnimation;
 import android.widget.AbsListView;
 import android.widget.ListView;

 /**
  * ElasticScrollView有弹性的ListView
  */
 public class ElasticListView extends ListView {
     private float y;
     private Rect normal = new Rect();
     private boolean animationFinish = true;

     public ElasticListView(Context context) {
         super(context);
         init();
     }

     public ElasticListView(Context context, AttributeSet attrs) {
         super(context, attrs);
         init();
     }

     protected void onScrollChanged(int l, int t, int oldl, int oldt) {

     }

     boolean overScrolled = false;
     private void init() {
         setOnScrollListener(new OnScrollListener() {
             @Override
             public void onScrollStateChanged(AbsListView view, int scrollState) {
             }

             @Override
             public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
                 overScrolled = false;
             }
         });
     }

     @Override
     protected void onOverScrolled(int scrollX, int scrollY, boolean clampedX, boolean clampedY) {
         overScrolled = true;
     }

     @Override
     public boolean onTouchEvent(MotionEvent ev) {
         commOnTouchEvent(ev);
         return super.onTouchEvent(ev);
     }

     public void commOnTouchEvent(MotionEvent ev) {
         if (animationFinish) {
             int action = ev.getAction();
             switch (action) {
             case MotionEvent.ACTION_DOWN:
                 y = ev.getY();
                 break;
             case MotionEvent.ACTION_UP:
                 y = 0;
                 if (isNeedAnimation()) {
                     animation();
                 }
                 break;
             case MotionEvent.ACTION_MOVE:
                 final float preY = y == 0 ? ev.getY() : y;
                 float nowY = ev.getY();
                 int deltaY = (int) (preY - nowY);

                 y = nowY;
                 // 当滚动到最上或者最下时就不会再滚动，这时移动布局
                 if (isNeedMove(deltaY)) {
                     if (normal.isEmpty()) {
                         // 保存正常的布局位置
                         normal.set(getLeft(), getTop(), getRight(), getBottom());
                     }
                     // 移动布局
                     layout(getLeft(), getTop() - deltaY / 2, getRight(), getBottom() - deltaY / 2);
                 }
                 break;
             default:
                 break;
             }
         }
     }

     // 开启动画移动
     public void animation() {
         // 开启移动动画
         TranslateAnimation ta = new TranslateAnimation(0, 0, 0, normal.top - getTop());
         ta.setDuration(200);
         ta.setAnimationListener(new AnimationListener() {
             @Override
             public void onAnimationStart(Animation animation) {
                 animationFinish = false;

             }

             @Override
             public void onAnimationRepeat(Animation animation) {

             }

             @Override
             public void onAnimationEnd(Animation animation) {
                 clearAnimation();
                 // 设置回到正常的布局位置
                 layout(normal.left, normal.top, normal.right, normal.bottom);
                 normal.setEmpty();
                 animationFinish = true;
             }
         });
         startAnimation(ta);
     }

     // 是否需要开启动画
     public boolean isNeedAnimation() {
         return !normal.isEmpty();
     }

     // 是否需要移动布局
     public boolean isNeedMove(float deltaY) {
         if (overScrolled && getChildCount() > 0) {
             if (getLastVisiblePosition() == getCount() - 1 && deltaY > 0) {
                 return true;
             }
             if (getFirstVisiblePosition() == 0 && deltaY < 0) {
                 return true;
             }
         }
         return false;
     }
 }

测试代码：

 public class MainActivity extends Activity {
     ElasticListView listView;
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);

         listView = (ElasticListView) findViewById(R.id.listview);

         String[] listValues = new String[20];
         for (int i=0;i<listValues.length;i++) {
             listValues[i] = "TextView" + i;
         }
         listView.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, listValues));
     }
 }

 public class MainActivity extends Activity {
     ElasticListView listView;
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);

         listView = (ElasticListView) findViewById(R.id.listview);

         String[] listValues = new String[20];
         for (int i=0;i<listValues.length;i++) {
             listValues[i] = "TextView" + i;
         }
         listView.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, listValues));
     }
 }