通过单击按钮两次足够快来绕过模式Android对话框？

Question

Let's say we have two buttons, each with a OnClickListener. Each of listeners show a ProgressDialog and do some background work. (Behind the scene is an AsyncTask, the dialog is opened in onPreExecute. I don't think it matters, just for the record...). Let's say there is some rule saying no more than one background worker may be active at any given time.

My assumption was that the Dialog prevents two background workers running at the same time. I thought the modal dialog blocks the UI and it's not possible to click another button after the show() method of the dialog is called. I was wrong.

If you click the buttons fast enough, it's possible to trigger both background workers (almost) at the same time. The log shows that it's possible to click two Buttons within a 150 ms time span despite the Dialog:

04-14 18:34:04.390: DEBUG/greenrobot(1860): Clicked: 2131034112
04-14 18:34:04.470: DEBUG/greenrobot(1860): doInBackground2: 2131034112
04-14 18:34:04.540: DEBUG/greenrobot(1860): Clicked: 2131034113
04-14 18:34:04.570: DEBUG/greenrobot(1860): doInBackground2: 2131034113

The dialog code looks like this:

progressDialog = new ProgressDialog(currentActivity);
progressDialog.setMessage(msg);
progressDialog.show(); 

What did I miss? I hope I missed something really stupid, because if not, I cannot think of a nice and solution preventing UI interaction after the click. Synchronizing the background workers is not a solution because the UI and scenario is more complex.

Answer 1

Disable the button after it is clicked, until it is safe to be clicked again.

show() is asynchronous. The dialog will not appear immediately upon the call to show() . It will occur moments later.