需要序列化的队列工作会导致 AsyncTask 崩溃

Question

这个项目背后的想法是在将数据库上传到Web服务时运行进度条

我有一个 AsyncTask 可以做一些工作，然后调用一个服务并等待它完成，然后再调用 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();
}
}

我在尝试序列化AsyncTask的DatabaseSyncService.enqueueWork()方法时遇到了问题，这不起作用。知道它为什么要这样做吗？

堆栈跟踪

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

这是回调

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

Answer 1

此行不起作用：

intent.putExtra(DATABASE_ID, callback);

要将对象放入Intent，该对象必须实现Serializable/Parcelable接口。此外，相同的要求适用于对象的所有字段。

虽然你的callback对象(属于类型DatabaseSyncService.SyncProgressCallback)实现了Serializable，但它是从内部类callback = new DatabaseSyncService.SyncProgressCallback() {...}实例化的。据此，java.io.NotSerializableException发生在您的案例中，因为：

• 序列化此类内部类实例也将导致其关联的外部类实例的序列化
• 强烈建议不要序列化内部类(即，不是静态成员类的嵌套类)，包括本地类和匿名类

这意味着您必须使外部类UploadDatabaseAsyncTask实现Serializable而该类又必须应用于其所有字段，依此类推。

这很令人沮丧。

根据经验，请考虑将轻量级/纯数据(而不是具有复杂依赖项的复杂对象)放入Intent。

回到你的代码，一个简单的解决方法是将callback对象传递给DatabaseSyncService.enqueueWork方法：

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

在内部enqueueWork()直接使用callback，而不是从意图中反序列化。