获取Android控件的宽高

/**
     * view 初始化完毕，宽高已经确定。<br/>
     * 当 Activity 的窗口得到和失去焦点的时候，这个方法均会被调用。<br/>
     * 频繁调用 onResume 和 onPause 这个方法也会被频繁调用。
     * @param hasFocus
 */
@Override
public void onWindowFocusChanged(boolean hasFocus) {
    super.onWindowFocusChanged(hasFocus);
    if (hasFocus) {
        int width = view.getMeasuredWidth();
        int height = view.getMeasuredHeight();
    }
}

@Override	
protected void onStart() {
    super.onStart();

    /* 通过 post 可以将一个 Runnable 投递到消息队列的尾部。等到用的时候 view 也初始化好了。 */
    view.post(new Runnable() {
        @Override
        public void run() {
            int width = view.getMeasuredWidth();
            int height = view.getMeasuredHeight();
        }
    });
}

@Override
protected void onStart() {
    super.onStart();
    /* 当 view树 的状态发生改变或者 View 树内部的 View 可见性发生改变时， onGlobalLayout 会被回调。*/
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
        ViewTreeObserver viewTreeObserver = view.getViewTreeObserver();
        viewTreeObserver.addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
            @Override
            public void onGlobalLayout() {
                view.getViewTreeObserver().removeOnGlobalLayoutListener(this);
                int width = view.getMeasuredWidth();
                int height = view.getMeasuredHeight();
            }
        });
    }
}

/* 比如宽高是100px */
    int widthMeasureSpec = View.MeasureSpec.makeMeasureSpec(100, View.MeasureSpec.EXACTLY);
    int heightMeasureSpec = View.MeasureSpec.makeMeasureSpec(100, View.MeasureSpec.EXACTLY);
    view.measure(widthMeasureSpec, heightMeasureSpec);
    int width = view.getMeasuredWidth();
    int height = view.getMeasuredHeight();

/* view 的尺寸是使用20位二进制表示（最大是30个1，即 2的30次方-1 ，也就是 (1 << 30) - 1 */
    int widthMeasureSpec = View.MeasureSpec.makeMeasureSpec((1 << 30) - 1, View.MeasureSpec.AT_MOST);
    int heightMeasureSpec = View.MeasureSpec.makeMeasureSpec((1 << 30) - 1, View.MeasureSpec.AT_MOST);
    view.measure(widthMeasureSpec, heightMeasureSpec);
    int width = view.getMeasuredWidth();
    int height = view.getMeasuredHeight();