Question

I have a method public void writeEntry(Activity ctx, Entry entry) which get some data and have to call a native method, which takes longer to finish.
So I created an AsyncTask which handles the ProgressDialog and the native method. It works great in an own Activity to test it, in that Activity I used a callback interface and so on.

In my case I have the above described method and have to execute the AsyncTask. The executing can’t be in that method because it doesn’t halt the further execution.
I need the result from the native method before I can continue with the execution.
Is there any possibility to wait for the AsyncTask til it is finished? The method wait() isn’t an option because the UI Thread will wait, too and so the sense of a ProgressDialog will be lost.

Can I use the method runOnUiThread() from the given parameters or is the only solution to start an own Activity?

Answer 1

My first solution was to use callback methods with an interface implementation see the example https://stackoverflow.com/a/6396376/390177.

After chatting a while in the Android chat I heard that there is a more praticable solution.
You can use of an IntentService in combination with a PendingIntent.
The communication is realized with Intent‘s.
If you want to use a ProgressDialog, you need an own Activity for it, which register for example a BroadcastReciever and the IntentService sends it actual status per Broadcast.

But lets start now.
First we create the Activity, which contains the ProgressDialog and a registered BroadcastReceiver. The BroadcastReceiver listen for messages about updating and finishing the dialog.

For the Activity we needs the layout …

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent" android:layout_height="match_parent"
    android:background="#80000000">
</LinearLayout>

… and the related code:

public class ProgressActivity extends Activity {
    /**
     * ProgressDialog which is shown
     */
    private ProgressDialog progessDialog_g;

    /**
     * Instance of the BroadcastReceiver
     */
    private BroadcastReceiver receiver_g;

    /**
     * Identifier for the different settings of the ProgressDialog
     */
    public static final String PROGRESS_DIALOG_BOOL_HORIZONTAL_BAR = "pbar_horizontal_bar";
    public static final String PROGRESS_DIALOG_BOOL_CANCELABLE = "pbar_horizontal_cancelable";
    public static final String PROGRESS_DIALOG_STR_MESSAGE = "pbar_message";
    public static final String PROGRESS_DIALOG_INT_MAX = "pbar_max_bar";
    public static final String PROGRESS_DIALOG_INT_VALUE = "pbar_value";
    protected static final int PROGRESS_DIALOG_INT_MAX_VALUE = 100;

    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);

        setContentView(R.layout.progress);

        progessDialog_g = new ProgressDialog(this);

        // Reads and sets the settings for the ProgressDialog
        Intent i = getIntent();
        progessDialog_g.setCancelable(i.getBooleanExtra(
                PROGRESS_DIALOG_BOOL_CANCELABLE, false));
        if (i.getBooleanExtra(
                PROGRESS_DIALOG_BOOL_HORIZONTAL_BAR, false)) {
            progessDialog_g.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        } else {
            progessDialog_g.setProgressStyle(ProgressDialog.STYLE_SPINNER);
        }
        progessDialog_g
                .setMessage(i
                        .getStringExtra(PROGRESS_DIALOG_STR_MESSAGE));
        progessDialog_g.setMax(i.getIntExtra(
                PROGRESS_DIALOG_INT_MAX, 100));

        // Create the IntentFilter for the different broadcast messages
        IntentFilter iFilter =
                new IntentFilter(
                        ExampleProgressService.PROGRESS_DIALOG_BROADCAST_INIT);
        iFilter.addAction(ExampleProgressService.PROGRESS_DIALOG_BROADCAST_UPDATE);
        iFilter.addAction(ExampleProgressService.PROGRESS_DIALOG_BROADCAST_FINISH);

        // Creates the BroadcastReceiver
        receiver_g = new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent){
                Log.d(DefaultPreferences.DEBUG_PREFIX + "ProgressActivity",
                        intent.getAction());

                if (ExampleProgressService.PROGRESS_DIALOG_BROADCAST_INIT
                        .equals(intent.getAction())) {
                    // Sets the ProgressDialog style
                    if (intent
                            .getBooleanExtra(
                                    PROGRESS_DIALOG_BOOL_HORIZONTAL_BAR,
                                    false)) {
                        progessDialog_g
                                .setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
                    } else {
                        progessDialog_g
                                .setProgressStyle(ProgressDialog.STYLE_SPINNER);
                    }

                    // Shows the ProgressDialog    
                    progessDialog_g.show();
                } else if (ExampleProgressService.PROGRESS_DIALOG_BROADCAST_UPDATE
                        .equals(intent.getAction())) {
                    // Updates the ProgressDialog
                    int value =
                            intent.getIntExtra(
                                    PROGRESS_DIALOG_INT_VALUE,
                                    -1);
                    if (value != -1) {
                        progessDialog_g.setProgress(value);
                    }
                } else if (ExampleProgressService.PROGRESS_DIALOG_BROADCAST_FINISH
                        .equals(intent.getAction())) {
                    // Finishs the ProgressDialog
                    progessDialog_g.cancel();
                    finish();
                }
            }
        };

        // Registers the BroadcastReceiver
        registerReceiver(receiver_g, iFilter);
    }

    @Override
    protected void onDestroy(){
        unregisterReceiver(receiver_g);
        super.onDestroy();
    }
}

Now we want to use the Activity, so lets start with calling it:

final Intent i = new Intent(parentActivity, <packages>.ProgressActivity);
i.putExtra(ProgressActivity.PROGRESS_DIALOG_BOOL_CANCELABLE, cancelable_g);
i.putExtra(ProgressActivity.PROGRESS_DIALOG_BOOL_HORIZONTAL_BAR, showProgress_g);
i.putExtra(ProgressActivity.PROGRESS_DIALOG_STR_MESSAGE, message_g);
i.putExtra(ProgressActivity.PROGRESS_DIALOG_INT_MAX, ProgressActivity.PROGRESS_DIALOG_INT_MAX_VALUE);

parentActivity.startActivity(i);

So we habe a running ProgressActivity, which waits for different broadcasts. But first we need the IntentService, which sends the broadcasts.
So lets go:

public class ExampleProgressService extends IntentService {
    /**
     * PendingIntent for callback.
     */
    protected PendingIntent pi_g = null;

    private static final String DEBUG_TAG = "ExampleProgressService";

    /**
     * Message identifier for ProgressDialog init
     */
    public static final String PROGRESS_DIALOG_BROADCAST_INIT = "Dialog.Progress.Init";
    /**
     * Message identifier for ProgressDialog finish
     */
    public static final String PROGRESS_DIALOG_BROADCAST_FINISH = "Dialog.Progress.Finish";
    /**
     * Message identifier for ProgressDialog update
     */
    public static final String PROGRESS_DIALOG_BROADCAST_UPDATE = "Dialog.Progress.Update";

    /**
     * Identifier of the result for intent content
     */
    public static final String PROGRESS_DATA_RESULT = "Result";
    /**
     * Identifier of the result error for intent content
     */
    public static final String PROGRESS_DATA_RESULT_ERROR_MESSAGE = "Result.Error.Message";
    /**
     * Identifier of the result error exception for intent content
     */
    public static final String PROGRESS_DATA_RESULT_ERROR_EXCEPTION = "Result.Error.Exception";
    /**
     * Identifier of the result status for intent content
     */
    public static final String PROGRESS_DATA_RESULT_STATUS_BOOL = "Result.Status.boolean";

    /**
     * Identifier of the pending intent for intent content
     */
    public static final String PROGRESS_DATA_PENDING_RESULT = "PendingResult";

    public ExampleProgressService() {
        super("ExampleProgressService");
    }

    /**
     * Send the finish message.
     */
    private void closeProgressActivity() {
        Intent intent = new Intent(PROGRESS_DIALOG_BROADCAST_FINISH);

        sendBroadcast(intent);
    }

    /**
     * Do some magic with the intent content
     */
    private void extractVariablesFromIntentAndPrepare(Intent intent)
            throws Exception {
        pi_g = (PendingIntent) intent
                .getParcelableExtra(PROGRESS_DATA_PENDING_RESULT);

        if (pi_g == null) {
            throw new Exception("There is no pending intent!");
    }

    /**
     * Sends an error message.
     */
    private void failed(Exception e, String message) {
        Intent i = new Intent();
        i.putExtra(PROGRESS_DATA_RESULT_ERROR_EXCEPTION, e);
        i.putExtra(PROGRESS_DATA_RESULT_ERROR_MESSAGE, message);

        send(i, false);
    }

    /**
     * Sends the init message.
     */
    private void initProgressActivity() {
        Intent intent = new Intent(PROGRESS_DIALOG_BROADCAST_INIT);

        intent.putExtra(PROGRESS_DIALOG_BOOL_HORIZONTAL_BAR,
                multipart_g);

        sendBroadcast(intent);
    }

    /**
     * (non-Javadoc)
     * 
     * @see android.app.IntentService#onHandleIntent(android.content.Intent)
     */
    @Override
    protected void onHandleIntent(Intent intent) {
        extractVariablesFromIntentAndPrepare(intent);

        initProgressActivity();

        // do your calculation here and implements following code
        Intent intent = new Intent(PROGRESS_DIALOG_BROADCAST_UPDATE);

        intent.putExtra(PROGRESS_DIALOG_INT_VALUE, progressValue);

        sendBroadcast(intent);

        // If you finished, use one of the two methods to send the result or an error
        success(result);
        failed(exception, optionalMessage);
    }

    /**
     * Sends the data to the calling Activity
     */
    private void send(Intent resultData, boolean status) {
        resultData.putExtra(PROGRESS_DATA_RESULT_STATUS_BOOL, status);

        closeProgressActivity();

        try {
            pi_g.send(this, Activity.RESULT_OK, resultData);
        } catch (PendingIntent.CanceledException e) {
            Log.e(DEBUG_TAG,
                    "There is something wrong with the pending intent", e);
        }
    }

    /**
     * Sends the result message.
     */
    private void success(String result) {
        Intent i = new Intent();
        i.putExtra(PROGRESS_DATA_RESULT, result);

        send(i, true);
    }
}

The result of the calculation progress shall be available in the parentActivity, so we create the PendingIntent in that Activity and call the IntentService.

// Some identifier for the call
int requestCode = 12345;

final Intent sI = new Intent(ExampleProgressService.PROGRESS_SERVICE_ACTION);

// Callback
sI.putExtra(ExampleProgressService.PROGRESS_DATA_PENDING_RESULT, parentActivity
        .createPendingResult(requestCode, null,
                PendingIntent.FLAG_CANCEL_CURRENT));

// Service start
parentActivity.startService(sI);

For receiving the results, we have to override the method onActivityResult(int requestCode, int resultCode, Intent data).

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data){
    // Compares the requestCode with the requestCode from above
    if (requestCode == ...) {
        if (data.getBooleanExtra(ExampleProgressService.PROGRESS_DATA_RESULT_STATUS_BOOL, false)) {
            // Calculation was success
            data.getStringExtra(ExampleProgressService.PROGRESS_DATA_RESULT);
        } else
        {
            // Calculation is failed
            data.getStringExtra(ExampleProgressService.PROGRESS_DATA_RESULT_ERROR_MESSAGE);
            ((Exception) data.getSerializableExtra(ExampleProgressService.PROGRESS_DATA_RESULT_ERROR_EXCEPTION));
        }
    }
}

That was the magic, I hope it will help you.