在onCreate()中获取View宽高

两种方法：

1.使用View.post(Runable runable)方法

        imageView.post(new Runnable() {
            @Override
            public void run() {
                Log.d(TAG, "run: width = " + imageView.getWidth());
                Log.d(TAG, "run: measuredWidth = " + imageView.getMeasuredWidth());
            }
        }); 

2.使用ViewTreeObserver：

ViewTreeObserver observer = imageView.getViewTreeObserver();
        observer.addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
            @Override
            public void onGlobalLayout() {
                Log.d(TAG, "onGlobalLayout: width = " + imageView.getWidth());
                Log.d(TAG, "onGlobalLayout: measuredWidth = " + imageView.getMeasuredWidth());
            }
        });

3.可以覆写onWindowFocusChanged方法

    @Override
    public void onWindowFocusChanged(boolean hasFocus) {
        super.onWindowFocusChanged(hasFocus);
        Log.d(TAG, "onWindowFocusChanged: width = " + imageView.getWidth());
        Log.d(TAG, "onWindowFocusChanged: measuredWidth = " + imageView.getMeasuredWidth());
    }

==注意==：ViewTreeObserver和onWindowFocusChanged会被调用多次