官方API：

A structure describing general information about a display, such as its size, density, and font scaling.

To access the DisplayMetrics members, initialize an object like this:

 DisplayMetrics metrics = new DisplayMetrics();
 getWindowManager().getDefaultDisplay().getMetrics(metrics);

应用实例：

WindowManager windowManager = (WindowManager) getSystemService(Context.WINDOW_SERVICE);
DisplayMetrics displayMetrics = new DisplayMetrics();
windowManager.getDefaultDisplay().getMetrics(displayMetrics);
int width = displayMetrics.widthPixels;
int height = displayMetrics.heightPixels;