在Android 7.0上PopupWindow.showAsDropDown不起作用的解决方法

/**
 * Created by twy on 2017/7/7.
 */

public class MyPopWindow extends PopupWindow {
    public MyPopWindow(final Activity context,View view){
        LayoutInflater inflater = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        int h = context.getWindowManager().getDefaultDisplay().getHeight();
        int w = context.getWindowManager().getDefaultDisplay().getWidth();
        this.setContentView(view);
        this.setWidth(ViewGroup.LayoutParams.MATCH_PARENT);
        this.setHeight(ViewGroup.LayoutParams.WRAP_CONTENT);
        this.setFocusable(true);
        this.setOutsideTouchable(true);
        this.update();
        ColorDrawable dw = new ColorDrawable(-00000);
        this.setBackgroundDrawable(dw);
        this.setAnimationStyle(R.style.AnimationPreview);
    }

    @Override
    public void showAsDropDown(View anchor) {
        if (Build.VERSION.SDK_INT == 24) {
            Rect rect = new Rect();
            anchor.getGlobalVisibleRect(rect);
            int h = anchor.getResources().getDisplayMetrics().heightPixels - rect.bottom;
            setHeight(h);
        }
        super.showAsDropDown(anchor);
    }
}