首先，废话少说，先上效果图：

代码：

public class MainActivity extends Activity implements OnClickListener{

	private Button showBtn1;
	private Button showBtn2;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		showBtn1 = (Button) findViewById(R.id.showBtn1);
		showBtn2 = (Button) findViewById(R.id.showBtn2);
		showBtn1.setOnClickListener(this);
		showBtn2.setOnClickListener(this);
	}

	@Override
	public void onClick(View v) {
		// TODO Auto-generated method stub
		View popupView = LayoutInflater.from(this).inflate(R.layout.popup, null);
		PopupWindow popupWindow = new PopupWindow(popupView, ViewGroup.LayoutParams.WRAP_CONTENT, 
				ViewGroup.LayoutParams.WRAP_CONTENT, true);
		popupWindow.setBackgroundDrawable(new BitmapDrawable());
		popupView.measure(MeasureSpec.UNSPECIFIED, MeasureSpec.UNSPECIFIED);
		int popupWidth = popupView.getMeasuredWidth();
		int popupHeight =  popupView.getMeasuredHeight();
		int[] location = new int[2];
		switch (v.getId()) {
		case R.id.showBtn1:
		    v.getLocationOnScreen(location);
		    popupWindow.showAtLocation(v, Gravity.NO_GRAVITY, (location[0]+v.getWidth()/2)-popupWidth/2,
		    		location[1]-popupHeight);
			break;
		case R.id.showBtn2:
		    v.getLocationOnScreen(location);
		    popupWindow.showAtLocation(v, Gravity.NO_GRAVITY, (location[0]+v.getWidth()/2)-popupWidth/2,
		    		location[1]-popupHeight);
			break;

		default:
			break;
		}
	}
}

Demo下载：http://download.csdn.net/detail/u011494050/7787359