How to handle screen orientation change when progr

Question

My program does some network activity in a background thread. Before starting, it pops up a progress dialog. The dialog is dismissed on the handler. This all works fine, except when screen orientation changes while the dialog is up (and the background thread is going). At this point the app either crashes, or deadlocks, or gets into a weird stage where the app does not work at all until all the threads have been killed.

How can I handle the screen orientation change gracefully?

The sample code below matches roughly what my real program does:

public class MyAct extends Activity implements Runnable {
    public ProgressDialog mProgress;

    // UI has a button that when pressed calls send

    public void send() {
         mProgress = ProgressDialog.show(this, "Please wait", 
                      "Please wait", 
                      true, true);
        Thread thread = new Thread(this);
        thread.start();
    }

    public void run() {
        Thread.sleep(10000);
        Message msg = new Message();
        mHandler.sendMessage(msg);
    }

    private final Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            mProgress.dismiss();
        }
    };
}

Stack:

E/WindowManager(  244): Activity MyAct has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@433b7150 that was originally added here
E/WindowManager(  244): android.view.WindowLeaked: Activity MyAct has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@433b7150 that was originally added here
E/WindowManager(  244):     at android.view.ViewRoot.<init>(ViewRoot.java:178)
E/WindowManager(  244):     at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:147)
E/WindowManager(  244):     at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:90)
E/WindowManager(  244):     at android.view.Window$LocalWindowManager.addView(Window.java:393)
E/WindowManager(  244):     at android.app.Dialog.show(Dialog.java:212)
E/WindowManager(  244):     at android.app.ProgressDialog.show(ProgressDialog.java:103)
E/WindowManager(  244):     at android.app.ProgressDialog.show(ProgressDialog.java:91)
E/WindowManager(  244):     at MyAct.send(MyAct.java:294)
E/WindowManager(  244):     at MyAct$4.onClick(MyAct.java:174)
E/WindowManager(  244):     at android.view.View.performClick(View.java:2129)
E/WindowManager(  244):     at android.view.View.onTouchEvent(View.java:3543)
E/WindowManager(  244):     at android.widget.TextView.onTouchEvent(TextView.java:4664)
E/WindowManager(  244):     at android.view.View.dispatchTouchEvent(View.java:3198)

I have tried to dismiss the progress dialog in onSaveInstanceState, but that just prevents an immediate crash. The background thread is still going, and the UI is in partially drawn state. Need to kill the whole app before it starts working again.

Answer 1

I faced this same problem, and I came up with a solution that didn't invole using the ProgressDialog and I get faster results.

What I did was create a layout that has a ProgressBar in it.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<ProgressBar
    android:id="@+id/progressImage"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerInParent="true"
    />
</RelativeLayout>

Then in the onCreate method do the following

public void onCreate(Bundle icicle) {
    super.onCreate(icicle);
    setContentView(R.layout.progress);
}

Then do the long task in a thread, and when that's finished have a Runnable set the content view to the real layout you want to use for this activity.

For example:

mHandler.post(new Runnable(){

public void run() {
        setContentView(R.layout.my_layout);
    } 
});

This is what I did, and I've found that it runs faster than showing the ProgressDialog and it's less intrusive and has a better look in my opinion.

However, if you're wanting to use the ProgressDialog, then this answer isn't for you.

Answer 2

When you switch orientations, Android will create a new View. You're probably getting crashes because your background thread is trying to change the state on the old one. (It may also be having trouble because your background thread isn't on the UI thread)

I'd suggest making that mHandler volatile and updating it when the orientation changes.