android获取屏幕像素

private void alertScreenDialog() {
		DisplayMetrics dm = new DisplayMetrics();
		getWindowManager().getDefaultDisplay().getMetrics(dm);
		String optStr = "手机屏幕分辨率为: "+dm.widthPixels+" x "+dm.heightPixels;
		Builder builder = new Builder(this);
		builder.setMessage(optStr);
		builder.setIcon(R.drawable.firefox);
		builder.setTitle("获取屏幕像素");
		//点击确定按钮
		builder.setPositiveButton("确定", new DialogInterface.OnClickListener(){
			@Override
			public void onClick(DialogInterface dialog, int which) {
				Toast.makeText(GetScreenActivity.this, "获取到像素", Toast.LENGTH_LONG).show();
			}
		});
		builder.setNegativeButton("返回", new DialogInterface.OnClickListener() {
			@Override
			public void onClick(DialogInterface dialog, int which) {
				Toast.makeText(GetScreenActivity.this, "返回", Toast.LENGTH_LONG).show();
			}
		});
		builder.create().show();
	}