java 安卓如何检查后台线程是否成功？

Question

我正试图用junRAR提取RAR文件。但正如我从这个问题上读到的：OutOfMemoryError when I decompress RAR file on Android，junRAR还没有针对Android进行优化。因此，我想做的是检查提取是否成功，如果失败，则给出错误消息。（因为如果提取不成功，我的应用程序将崩溃）。有人能告诉我怎么检查吗？我的线程正在这里完成：

public class MyTask extends AsyncTask<Void, Void, Void> {

  private ProgressDialog progress;
  public MyTask(ProgressDialog progress) {
      this.progress = progress;   
  }

  public void onPreExecute() {
    progress.show();
  }    
@Override
protected Void doInBackground(Void... params) {
    if(taskType==1){
         extractArchive(rarFile, destinationFolder);            
    }
return null;
}

public void onPostExecute(Void unused) {
    progress.dismiss();
    if(taskType==1){
        refreshFileList();
        Toast.makeText(MainActivity.this, "Extracted to " + targetPath, Toast.LENGTH_LONG).show();
    }
} 

以下是我的Logcat错误：

03-02 16:59:40.777: E/AndroidRuntime(28573): FATAL EXCEPTION: AsyncTask #1
03-02 16:59:40.777: E/AndroidRuntime(28573): java.lang.RuntimeException: An error occured while executing doInBackground()
03-02 16:59:40.777: E/AndroidRuntime(28573):    at 安卓.os.AsyncTask$3.done(AsyncTask.java:278)
03-02 16:59:40.777: E/AndroidRuntime(28573):    at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
03-02 16:59:40.777: E/AndroidRuntime(28573):    at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
03-02 16:59:40.777: E/AndroidRuntime(28573):    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
03-02 16:59:40.777: E/AndroidRuntime(28573):    at java.util.concurrent.FutureTask.run(FutureTask.java:137)
03-02 16:59:40.777: E/AndroidRuntime(28573):    at 安卓.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:208)
03-02 16:59:40.777: E/AndroidRuntime(28573):    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
03-02 16:59:40.777: E/AndroidRuntime(28573):    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
03-02 16:59:40.777: E/AndroidRuntime(28573):    at java.lang.Thread.run(Thread.java:856)
03-02 16:59:40.777: E/AndroidRuntime(28573): Caused by: java.lang.OutOfMemoryError
03-02 16:59:40.777: E/AndroidRuntime(28573):    at com.github.junrar.unpack.ppm.SubAllocator.startSubAllocator(SubAllocator.java:146)
03-02 16:59:40.777: E/AndroidRuntime(28573):    at com.github.junrar.unpack.ppm.ModelPPM.decodeInit(ModelPPM.java:216)
03-02 16:59:40.777: E/AndroidRuntime(28573):    at com.github.junrar.unpack.Unpack.readTables(Unpack.java:656)
03-02 16:59:40.777: E/AndroidRuntime(28573):    at com.github.junrar.unpack.Unpack.unpack29(Unpack.java:165)
03-02 16:59:40.777: E/AndroidRuntime(28573):    at com.github.junrar.unpack.Unpack.doUnpack(Unpack.java:120)
03-02 16:59:40.777: E/AndroidRuntime(28573):    at com.github.junrar.Archive.doExtractFile(Archive.java:501)
03-02 16:59:40.777: E/AndroidRuntime(28573):    at com.github.junrar.Archive.extractFile(Archive.java:443)
03-02 16:59:40.777: E/AndroidRuntime(28573):    at com.jearom.thesisfmanager.MainActivity.extractArchive(MainActivity.java:2270)
03-02 16:59:40.777: E/AndroidRuntime(28573):    at com.jearom.thesisfmanager.MainActivity$MyTask.doInBackground(MainActivity.java:1962)
03-02 16:59:40.777: E/AndroidRuntime(28573):    at com.jearom.thesisfmanager.MainActivity$MyTask.doInBackground(MainActivity.java:1)
03-02 16:59:40.777: E/AndroidRuntime(28573):    at 安卓.os.AsyncTask$2.call(AsyncTask.java:264)
03-02 16:59:40.777: E/AndroidRuntime(28573):    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
03-02 16:59:40.777: E/AndroidRuntime(28573):    ... 5 more
03-02 16:59:41.437: E/WindowManager(28573): Activity com.jearom.thesisfmanager.MainActivity has leaked window com.安卓.internal.policy.impl.PhoneWindow$DecorView@41d3a0c0 that was originally added here
03-02 16:59:41.437: E/WindowManager(28573): 安卓.view.WindowLeaked: Activity com.jearom.thesisfmanager.MainActivity has leaked window com.安卓.internal.policy.impl.PhoneWindow$DecorView@41d3a0c0 that was originally added here
03-02 16:59:41.437: E/WindowManager(28573):     at 安卓.view.ViewRootImpl.(ViewRootImpl.java:344)
03-02 16:59:41.437: E/WindowManager(28573):     at 安卓.view.WindowManagerImpl.addView(WindowManagerImpl.java:267)
03-02 16:59:41.437: E/WindowManager(28573):     at 安卓.view.WindowManagerImpl.addView(WindowManagerImpl.java:215)
03-02 16:59:41.437: E/WindowManager(28573):     at 安卓.view.WindowManagerImpl$CompatModeWrapper.addView(WindowManagerImpl.java:140)
03-02 16:59:41.437: E/WindowManager(28573):     at 安卓.view.Window$LocalWindowManager.addView(Window.java:537)
03-02 16:59:41.437: E/WindowManager(28573):     at 安卓.app.Dialog.show(Dialog.java:278)
03-02 16:59:41.437: E/WindowManager(28573):     at com.jearom.thesisfmanager.MainActivity$MyTask.onPreExecute(MainActivity.java:1867)
03-02 16:59:41.437: E/WindowManager(28573):     at 安卓.os.AsyncTask.executeOnExecutor(AsyncTask.java:561)
03-02 16:59:41.437: E/WindowManager(28573):     at 安卓.os.AsyncTask.execute(AsyncTask.java:511)
03-02 16:59:41.437: E/WindowManager(28573):     at com.jearom.thesisfmanager.MainActivity$6.onClick(MainActivity.java:752)
03-02 16:59:41.437: E/WindowManager(28573):     at com.安卓.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:166)
03-02 16:59:41.437: E/WindowManager(28573):     at 安卓.os.Handler.dispatchMessage(Handler.java:99)
03-02 16:59:41.437: E/WindowManager(28573):     at 安卓.os.Looper.loop(Looper.java:137)
03-02 16:59:41.437: E/WindowManager(28573):     at 安卓.app.ActivityThread.main(ActivityThread.java:4456)
03-02 16:59:41.437: E/WindowManager(28573):     at java.lang.reflect.Method.invokeNative(Native Method)
03-02 16:59:41.437: E/WindowManager(28573):     at java.lang.reflect.Method.invoke(Method.java:511)
03-02 16:59:41.437: E/WindowManager(28573):     at com.安卓.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:787)
03-02 16:59:41.437: E/WindowManager(28573):     at com.安卓.internal.os.ZygoteInit.main(ZygoteInit.java:554)
03-02 16:59:41.437: E/WindowManager(28573):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

onPostExecute（Result）在后台计算完成后在UI thread上调用。背景计算的result作为参数传递给此方法

有关更多信息：http://developer.android.com/reference/android/os/AsyncTask.html

这里有一个例子

  private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {
  protected Long doInBackground(URL... urls) {
     int count = urls.length;
     long totalSize = 0;
     for (int i = 0; i < count; i++) {
         totalSize += Downloader.downloadFile(urls[i]);
         publishProgress((int) ((i / (float) count) * 100));
         // Escape early if cancel() is called
         if (isCancelled()) break;
     }
     return totalSize;
  }

  protected void onProgressUpdate(Integer... progress) {
     setProgressPercent(progress[0]);
  }

  protected void onPostExecute(Long result) {
     showDialog("Downloaded " + result + " bytes");
  }
}

Answer 2

您可以使用SharedPreferences解决这个问题，方法是创建一个SharedPreference文件，该文件保存您在文件上执行的每个操作的状态，该文件使用文件名作为键，并创建一个boolean值，该值描述文件的状态，该文件是否成功提取。如果进程成功，请让方法返回^{，否则返回^{

按以下方式修改构造函数以保存应用程序的上下文

private ProgressDialog progress;
private Context mContext;
public MyTask(ProgressDialog progress, Context context) {
  this.progress = progress;   
  this.mContext = context;
}

将doInBackground方法替换为以下方法：

@Override
protected Void doInBackground(Void... params) {
if(taskType==1){
     if(extractArchive(rarFile, destinationFolder)){
        SharedPreferences myLog = mContext.getSharedPreferences("state_holder", Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = myLog.edit();
        editor.putBoolean("file_name", true);
        editor.commit();
   }            
}
return null;
}    

更多关于SharedPReference的信息，请点击本LINK