StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

PO
text
Body
copied!<p>I met the same problem. My activity needs to parse some data from a URL and it's slow. So I create a thread to do so then show a progressdialog. I let the thread post a msg back to UI thread via Handler when it's finished. In Handler.handleMessage, I get the data object (ready now) from thread and populate it to UI. So it's very similar to your example.</p> <p>After many trial and error it looks like I found a solution. At least now I can rotate screen at any moment, before or after the thread is done. In all tests, the dialog is properly closed and all behaviors are as expected.</p> <p>What I did is shown below. The goal is to fill my data model (mDataObject) and then populate it to UI. Should allow screen rotation at any moment without surprise.</p> <pre><code>class MyActivity { private MyDataObject mDataObject = null; private static MyThread mParserThread = null; // static, or make it singleton OnCreate() { ... Object retained = this.getLastNonConfigurationInstance(); if(retained != null) { // data is already completely obtained before config change // by my previous self. // no need to create thread or show dialog at all mDataObject = (MyDataObject) retained; populateUI(); } else if(mParserThread != null && mParserThread.isAlive()){ // note: mParserThread is a static member or singleton object. // config changed during parsing in previous instance. swap handler // then wait for it to finish. mParserThread.setHandler(new MyHandler()); } else { // no data and no thread. likely initial run // create thread, show dialog mParserThread = new MyThread(..., new MyHandler()); mParserThread.start(); showDialog(DIALOG_PROGRESS); } } // http://android-developers.blogspot.com/2009/02/faster-screen-orientation-change.html public Object onRetainNonConfigurationInstance() { // my future self can get this without re-downloading // if it's already ready. return mDataObject; } // use Activity.showDialog instead of ProgressDialog.show // so the dialog can be automatically managed across config change @Override protected Dialog onCreateDialog(int id) { // show progress dialog here } // inner class of MyActivity private class MyHandler extends Handler { public void handleMessage(msg) { mDataObject = mParserThread.getDataObject(); populateUI(); dismissDialog(DIALOG_PROGRESS); } } } class MyThread extends Thread { Handler mHandler; MyDataObject mDataObject; public MyHandler(..., Handler h) {...; mHandler = h;} // constructor with handler param public void setHandler(Handler h) { mHandler = h; } // for handler swapping after config change public MyDataObject getDataObject() { return mDataObject; } // return data object (completed) to caller public void run() { mDataObject = new MyDataObject(); // do the lengthy task to fill mDataObject with data lengthyTask(mDataObject); // done. notify activity mHandler.sendEmptyMessage(0); // tell activity: i'm ready. come pick up the data. } } </code></pre> <p>That's what works for me. I don't know if this is the "correct" method as designed by Android -- they claim this "destroy/recreate activity during screen rotation" actually makes things easier, so I guess it shouldn't be too tricky.</p> <p>Let me know if you see a problem in my code. As said above I don't really know if there is any side effect.</p>

Querying!

Guidance

An individual column

Larger individual text columns get their own page to allow for proper reading.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload