android獲取屏幕的高度和寬度用到WindowManager這個類民镜，兩種方法：
1、WindowManager wm = (WindowManager) getContext()
.getSystemService(Context.WINDOW_SERVICE);
int width = wm.getDefaultDisplay().getWidth();
int height = wm.getDefaultDisplay().getHeight();
2寥粹、WindowManager wm = this.getWindowManager();
int width = wm.getDefaultDisplay().getWidth();
int height = wm.getDefaultDisplay().getHeight();