Android自定义控件_让每一个Activity UI都具有弹性

前面我们已经介绍了如何让你的ScrollView，ListView具有弹性，

今天，我们在前面的基础上，做一下适当的修改，让那些既不是ScrollView，也不是ListView的Activity页面，也能具有弹性。

先上图：

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图中是最简单的一个Android测试程序。默认的效果TextView是无法划动的。

进过我们小小的改造，就能让整个UI具有弹性效果。

改动如下:

[java] view plaincopy在CODE上查看代码片派生到我的代码片
protected void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        View view = getLayoutInflater().inflate(R.layout.activity_main, null);  
        view.setOnTouchListener(new ElasticTouchListener());  
        setContentView(view);  
    }  
我们仅仅只需要在需要弹性的Root VIew 上加上监听。就能达到如果的效果了。
ElasticTouchListener源码：
[java] view plaincopy在CODE上查看代码片派生到我的代码片
public class ElasticTouchListener implements OnTouchListener {  
    private View inner;  
    View[] children;  
    private float y;  
    private Rect normal = new Rect();  
    private boolean animationFinish = true;  
    private int[] tops;  
    private int[] bottoms;  
  
    @Override  
    public boolean onTouch(View v, MotionEvent ev) {  
        if (inner == null && children == null) {  
            if (v instanceof ViewGroup) {  
                ViewGroup group = (ViewGroup) v;  
                int count = group.getChildCount();  
                if (count > 0) {  
                    children = new View[count];  
                    tops = new int[count];  
                    bottoms = new int[count];  
                    for (int i = 0; i < count; i++) {  
                        children[i] = group.getChildAt(i);  
                        tops[i] = children[i].getTop();  
                        bottoms[i] = children[i].getBottom();  
                    }  
                }  
            }  
            inner = v;  
        }  
        if (animationFinish && (inner != null || children != null)) {  
            int action = ev.getAction();  
            switch (action) {  
            case MotionEvent.ACTION_DOWN:  
//              System.out.println("ACTION_DOWN");  
                y = ev.getY();  
                break;  
            case MotionEvent.ACTION_UP:  
//              System.out.println("ACTION_UP");  
                y = 0;  
                if (isNeedAnimation()) {  
                    animation();  
                }  
                inner.invalidate();  
                break;  
            case MotionEvent.ACTION_MOVE:  
//              System.out.println("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()) {  
                    if (normal.isEmpty()) {  
                        // 保存正常的布局位置  
                        normal.set(inner.getLeft(), inner.getTop(), inner.getRight(), inner.getBottom());  
                    }  
                    if (children != null) {  
                        View view = null;  
                        for (int i = 0; i < children.length; i++) {  
                            view = children[i];  
                            view.layout(view.getLeft(), view.getTop() - deltaY / 2, view.getRight(), view.getBottom() - deltaY / 2);  
                        }  
                    } else {  
                        // 移动布局  
                        inner.layout(inner.getLeft(), inner.getTop() - deltaY / 2, inner.getRight(), inner.getBottom() - deltaY / 2);  
                    }  
                }  
                inner.invalidate();  
                break;  
            default:  
                break;  
            }  
        } else {  
            return false;  
        }  
        return true;  
    }  
  
    // 开启动画移动  
  
    public void animation() {  
        if (children == null) {  
            // 开启移动动画  
            TranslateAnimation trans = new TranslateAnimation(0, 0, 0, normal.top - inner.getTop());  
            trans.setDuration(200);  
            trans.setAnimationListener(new AnimationListener() {  
                @Override  
                public void onAnimationStart(Animation animation) {  
                    animationFinish = false;  
                }  
                @Override  
                public void onAnimationRepeat(Animation animation) {  
                }  
                @Override  
                public void onAnimationEnd(Animation animation) {  
                    inner.clearAnimation();  
                    // 设置回到正常的布局位置  
                    inner.layout(normal.left, normal.top, normal.right, normal.bottom);  
                    normal.setEmpty();  
                    animationFinish = true;  
                }  
            });  
            inner.startAnimation(trans);  
        } else {  
            for (int i = 0; i < children.length; i++) {  
                final View view = children[i];  
                if (view.getVisibility() == View.VISIBLE) {  
                    final int index = i;  
                    // 开启移动动画  
                    TranslateAnimation trans = new TranslateAnimation(0, 0, 0, tops[i] - view.getTop());  
                    trans.setDuration(200);  
                    trans.setAnimationListener(new AnimationListener() {  
                        @Override  
                        public void onAnimationStart(Animation animation) {  
                            animationFinish = false;  
                        }  
                        @Override  
                        public void onAnimationRepeat(Animation animation) {  
  
                        }  
                        @Override  
                        public void onAnimationEnd(Animation animation) {  
                            view.clearAnimation();  
                            // 设置回到正常的布局位置  
                            view.layout(view.getLeft(), tops[index], view.getRight(), bottoms[index]);  
                            normal.setEmpty();  
                            animationFinish = true;  
                        }  
                    });  
                    view.startAnimation(trans);  
                }  
            }  
        }  
  
    }  
  
    // 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() {  
//      int offset = inner.getMeasuredHeight() - getHeight();  
//      int scrollY = getScrollY();  
//      if (scrollY == 0 || scrollY == offset) {  
//          return true;  
//      }  
//      return false;  
          
//      if (children != null && children.length > 0  
//              && (children[children.length - 1].getBottom() <= inner.getPaddingTop()/*inner.getTop()*/  
//              || children[0].getTop() >= inner.getHeight()  
//              )) {  
//          return false;  
//      }  
          
        return true;  
    }  
}