EnqueueWork requiring Serialization causes AsyncTask to crash

Issue

The idea behind this project is to have a Progress bar running while uploading a Database to a webService

I have an AsyncTask that does some work, then calls a service and awaits for it to finish before calling onPostExecute()

private class UploadDatabaseAsyncTask extends AsyncTask<Void, Long, Void> {

    private AlertDialog dialog;
    private Activity activity;
    private TextView messageView;
    private String location;
    private long maxSize;
    private ProgressBar progressBar;

    UploadDatabaseAsyncTask(Activity activity, long maxSize, String location) {
        super();
        this.location = location;
        this.maxSize = maxSize;
        this.activity = activity;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();

        progressBar = new ProgressBar(activity);
        progressBar.setMax(100);
        progressBar.setProgress(0);

        dialog = new AlertDialog.Builder(activity).setTitle("Uploading").setView(progressBar).create();
        messageView = dialog.findViewById(android.R.id.message);

       // dialog.show();

        if (activity != null && activity.getView() != null)
        {
            activity.getView().setOnTouchListener(new View.OnTouchListener() {
                @Override
                public boolean onTouch(View v, MotionEvent event) {
                    return true;
                }
            });

            activity.getView().setBackgroundColor(ContextCompat.getColor(App.getAppContext(), R.color.grey));
        }
    }

    @Override
    protected void onProgressUpdate(Long... values) {
        messageView.setText(values[0] + " / " + maxSize);

        BigDecimal current = new BigDecimal(values[0]);
        BigDecimal max = new BigDecimal(maxSize);

        BigDecimal progress = current.divide(max, 3, RoundingMode.UP);

        progressBar.setProgress(Integer.valueOf(progress.multiply(new BigDecimal(100)).toString()));
    }

    @Override
    protected Void doInBackground(Void... voids) {

        Intent intent = new Intent();

        final Object lock = new Object();

        final boolean[] active = new boolean[]{true};

        DatabaseSyncService.SyncProgressCallback callback = new DatabaseSyncService.SyncProgressCallback() {
            @Override
            public void onProgress(long progress) {
                onProgressUpdate(progress);
            }

            @Override
            public void onFinish() {
                active[0] = false;
                lock.notify();
            }
        };


        intent.putExtra(DATABASE_ID, callback);
        intent.putExtra("LOCATION", location);
        DatabaseSyncService.enqueueWork(activity, intent);

        synchronized (lock)
        {
            while (active[0])
            {
                try {
                    lock.wait();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }

        return null;
    }

    @Override
    protected void onCancelled(Void aVoid) {
        if (activity != null && activity.getView() != null)
        {
            activity.getView().setOnTouchListener(null);
            activity.getView().setBackgroundColor(ContextCompat.getColor(App.getAppContext(), R.color.transparent));
        }
    }

    @Override
    protected void onCancelled() {
        if (activity != null && activity.getView() != null)
        {
            activity.getView().setOnTouchListener(null);
            activity.getView().setBackgroundColor(ContextCompat.getColor(App.getAppContext(), R.color.transparent));
        }
    }

    @Override
    protected void onPostExecute(Void aVoid) { 
        if (activity != null && activity.getView() != null) 
        {
            activity.getView().setOnTouchListener(null);
            activity.getView().setBackgroundColor(ContextCompat.getColor(App.getAppContext(), R.color.transparent))
        }

       AlertDialog.Builder builder = new AlertDialog.Builder(App.getAppContext());
       builder.setTitle("Upload Complete");
       builder.setMessage("You upload was completed!");
       builder.setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
           @Override
           public void onClick(DialogInterface dialog, int which) { }
       });

       builder.show();
    }
}

I'm running into an issue with the DatabaseSyncService.enqueueWork() method trying to serialize the AsyncTask, which won't work. Any idea why it is trying to do this?

StackTrace

E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #4
Process: com.app.app, PID: 15935
java.lang.RuntimeException: An error occurred while executing doInBackground()
    at android.os.AsyncTask$3.done(AsyncTask.java:353)
    at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:383)
    at java.util.concurrent.FutureTask.setException(FutureTask.java:252)
    at java.util.concurrent.FutureTask.run(FutureTask.java:271)
    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636)
    at java.lang.Thread.run(Thread.java:764)
 Caused by: java.lang.RuntimeException: Parcelable encountered IOException writing serializable object (name = com.app.app.api.SettingApi$UploadDatabaseAsyncTask$2)
    at android.os.Parcel.writeSerializable(Parcel.java:1786)
    at android.os.Parcel.writeValue(Parcel.java:1734)
    at android.os.Parcel.writeArrayMapInternal(Parcel.java:801)
    at android.os.BaseBundle.writeToParcelInner(BaseBundle.java:1506)
    at android.os.Bundle.writeToParcel(Bundle.java:1181)
    at android.os.Parcel.writeBundle(Parcel.java:841)
    at android.content.Intent.writeToParcel(Intent.java:10199)
    at android.app.job.JobWorkItem.writeToParcel(JobWorkItem.java:117)
    at android.app.job.IJobScheduler$Stub$Proxy.enqueue(IJobScheduler.java:205)
    at android.app.JobSchedulerImpl.enqueue(JobSchedulerImpl.java:53)
    at androidx.core.app.JobIntentService$JobWorkEnqueuer.enqueueWork(JobIntentService.java:343)
    at androidx.core.app.JobIntentService.enqueueWork(JobIntentService.java:523)
    at androidx.core.app.JobIntentService.enqueueWork(JobIntentService.java:501)
    at com.ascsoftware.ascora.sync.DatabaseSyncService.enqueueWork(DatabaseSyncService.java:37)
    at com.ascsoftware.ascora.api.SettingApi$UploadDatabaseAsyncTask.doInBackground(SettingApi.java:291)
    at com.ascsoftware.ascora.api.SettingApi$UploadDatabaseAsyncTask.doInBackground(SettingApi.java:212)
    at android.os.AsyncTask$2.call(AsyncTask.java:333)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245) 
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162) 
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636) 
    at java.lang.Thread.run(Thread.java:764) 
 Caused by: java.io.NotSerializableException: com.app.app.api.SettingApi$UploadDatabaseAsyncTask
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1233)
    at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1597)
    at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1558)
    at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1481)
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1227)
    at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:347)
    at android.os.Parcel.writeSerializable(Parcel.java:1781)
    at android.os.Parcel.writeValue(Parcel.java:1734) 
    at android.os.Parcel.writeArrayMapInternal(Parcel.java:801) 
    at android.os.BaseBundle.writeToParcelInner(BaseBundle.java:1506) 
    at android.os.Bundle.writeToParcel(Bundle.java:1181) 
    at android.os.Parcel.writeBundle(Parcel.java:841) 
    at android.content.Intent.writeToParcel(Intent.java:10199) 
    at android.app.job.JobWorkItem.writeToParcel(JobWorkItem.java:117) 
    at android.app.job.IJobScheduler$Stub$Proxy.enqueue(IJobScheduler.java:205) 
    at android.app.JobSchedulerImpl.enqueue(JobSchedulerImpl.java:53) 
    at androidx.core.app.JobIntentService$JobWorkEnqueuer.enqueueWork(JobIntentService.java:343) 
    at androidx.core.app.JobIntentService.enqueueWork(JobIntentService.java:523) 
    at androidx.core.app.JobIntentService.enqueueWork(JobIntentService.java:501) 
    at com.app.app.sync.DatabaseSyncService.enqueueWork(DatabaseSyncService.java:37) 
    at com.app.app.api.SettingApi$UploadDatabaseAsyncTask.doInBackground(SettingApi.java:291) 
    at com.app.app.api.SettingApi$UploadDatabaseAsyncTask.doInBackground(SettingApi.java:212) 
    at android.os.AsyncTask$2.call(AsyncTask.java:333) 
    at java.util.concurrent.FutureTask.run(FutureTask.java:266) 
    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245) 
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162) 
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636) 
    at java.lang.Thread.run(Thread.java:764) 
I/System.out: (HTTPLog)-Static: isSBSettingEnabled false
(HTTPLog)-Static: isSBSettingEnabled false

Here is the Callback

public interface SyncProgressCallback extends Serializable {
    void onProgress(long progress);
    void onFinish();
}

Solution

This line does not work:

intent.putExtra(DATABASE_ID, callback);

To put an object into an Intent, the object must implement Serializable/Parcelable interface. Moreover, the same requirement applies to all the fields of the object.

Though your callback object (which belongs to type DatabaseSyncService.SyncProgressCallback) implements Serializable, but it is instanced from an inner class callback = new DatabaseSyncService.SyncProgressCallback() {...}. According to this, java.io.NotSerializableException occurs in your case because:

• serializing such an inner class instance will result in serialization of its associated outer class instance as well
• Serialization of inner classes (i.e., nested classes that are not static member classes), including local and anonymous classes, is strongly discouraged

This means that you have to make your outer class UploadDatabaseAsyncTask implements Serializable which in turns must applies to all of its fields, and so on.

That's quite frustrating.

As a rule of thumb, please consider put something lightweight / pure data, not complex objects with complex dependencies, to an Intent.

Back to your code, one easy fix could be passing the callback object to the DatabaseSyncService.enqueueWork method:

    //intent.putExtra(DATABASE_ID, callback);
    intent.putExtra("LOCATION", location);
    DatabaseSyncService.enqueueWork(activity, intent, callback);

Inside enqueueWork() use callback directly instead of deserializing from the intent.

Answered By - Nghia Bui