使用Thread / Handler / Looper for Worker Thread Android

Question

Having some responsiveness issues when implementing the Thread/Handler/Looper ideology to process information in the background by passing messages. I really don't want to use the AsyncTask class, since i already know how to use that to accomplish what I am trying to do.

Can someone help me with the following code that downloads the Apache License using the GooglePlayServicesUtil class and displays it in a TextView inside a DialogFragment ?

My biggest issue is that when i launch it, sometimes it is fast but others it is very slow to show the DialogFragment. Maybe I am not following the best practice for loading the DialogFragment, i don't really know.

Update Added code that is now working, but for some reason I still get a UI Freeze once in a while. Does anyone know if this is device specific? I am currently on a Samsung GS3. . .

My DialogFragment:

public class ApacheLicenseDialog extends DialogFragment implements Handler.Callback{

// Message Constants
private static final int MSG_DO_WORK        = 0;
private static final int MSG_START          = 1;
private static final int MSG_DONE           = 2;
private static final int MSG_SHUTDOWN       = 3;

// UI Elements
private TextView m_textApacheLicense        = null;
private Button m_btnOk                      = null;
private ProgressBar m_apacheProgress        = null;

// Background Processing Objects
private BackgroundThread m_bgThread         = null;
protected Handler m_handler                 = null;

// Apache String Object
private String apacheLicense                = null;

// ----------------------------------------------------------------------------
// New Instance Method invokes DialogFragment constructor

public static ApacheLicenseDialog newInstance(int counter) 
{
    // Create the Apache License Dialog
    ApacheLicenseDialog dialog = new ApacheLicenseDialog();

    Bundle data = new Bundle();
    data.putInt("Counter", counter);
    Log.d("COUNTER", "New Instance called: "+ Integer.toString(counter)+" times.");

    // Set the Arguments for the Dialog
    dialog.setArguments(data);

    // Return the Dialog
    return dialog;
}

// ---------------------------------------------------------------------------
// Class Overrides

/* (non-Javadoc)
 * @see android.support.v4.app.DialogFragment#onCreate(android.os.Bundle)
 */
@Override public void onCreate(Bundle savedInstanceState) 
{
    // Perform the Default Behavior
    super.onCreate(savedInstanceState);
    setRetainInstance(true);

    // Create a new Handler, Background thread, and Start the Thread
    m_handler = new Handler(this);
    m_bgThread = new BackgroundThread();
    m_bgThread.start();
}

/*
 * (non-Javadoc)
 * 
 * @see
 * android.support.v4.app.Fragment#onCreateView(android.view.LayoutInflater,
 * android.view.ViewGroup, android.os.Bundle)
 */
@Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) 
{
    // Set the Layout from XML Resource
    return inflater.inflate(R.layout.apache_dialog_fragment, null);
}

/*
 * (non-Javadoc)
 * 
 * @see
 * android.support.v4.app.DialogFragment#onActivityCreated(android.os.Bundle
 * )
 */
@Override public void onActivityCreated(Bundle savedInstanceState) 
{
    // Perform Default Behavior
    super.onActivityCreated(savedInstanceState);

    // Reference this Dialog and Set its Title
    getDialog().setTitle(getActivity().getResources().getString(R.string.text_Apache_License_Title));


    // Reference the UI Elements
    m_textApacheLicense = (TextView)    getView().findViewById(R.id.textViewApacheLicense);
    m_apacheProgress    = (ProgressBar) getView().findViewById(R.id.apacheProgress);
    m_btnOk             = (Button)      getView().findViewById(R.id.btnOkay);

    // Add a Listener to the Button
    m_btnOk.setOnClickListener(OkListener);

    // Starts the Message Sending 
    init();

}   

/* (non-Javadoc)
 * @see android.support.v4.app.DialogFragment#onDismiss(android.content.DialogInterface)
 */
@Override public void onDismiss(DialogInterface dialog) 
{
    // Cleaned up this code, and Added some logging to test my message passing
            m_bgThread.m_workerHandler.obtainMessage(MSG_SHUTDOWN).sendToTarget();

    Log.d("DISMISSING", "Dismissed called on ApacheLicenseDialog");


    try {
        m_bgThread.join();
        Log.d("JOINING_THREAD", "Attempting to join the Thread");
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }finally{
        Log.d("JOINED_THREAD", "Thread successfully joined");
    }

    // Perform the default behavior
    super.onDismiss(dialog);
}

// ----------------------------------------------------------
// Handler.Callback Interface

@Override public boolean handleMessage(Message msg) 
{
    switch(msg.what)
    {
    case MSG_START:
        // Set the ProgressBar View to Visible
        m_apacheProgress.setVisibility(View.VISIBLE);
        break;
    case MSG_DONE:
        updateUI(msg);
        break;
    }
    // return true
    return true;
}

// ---------------------------------------------------------------------------
// Private Class Method

private void init()
{   
    // Send the Message to this Classes Handler
    m_bgThread.m_workerHandler.obtainMessage(MSG_DO_WORK).sendToTarget();

}

private void updateUI(Message msg) 
{
    // Set the ProgressBar View to Invisible
    m_apacheProgress.setVisibility(View.INVISIBLE);
    // Update the UI
    m_textApacheLicense.setText(msg.obj.toString());
}

private void obtainApacheLicense()
{   
    // Send message that the operation is Starting
    m_bgThread.m_workerHandler.obtainMessage(MSG_START).sendToTarget();

    // Fetch the ApacheLicense
    apacheLicense = GooglePlayServicesUtil.getOpenSourceSoftwareLicenseInfo(getActivity());

    // Send Message the the operation is Done
    m_handler.obtainMessage(MSG_DONE, apacheLicense).sendToTarget();
}

// ---------------------------------------------------------------------------
// Listeners

private OnClickListener OkListener = new OnClickListener()
{
    @Override public void onClick(View v) 
    {   
        // Dismiss the Dialog
        dismiss();

    }

};

// ---------------------------------------------------------------------------
// BackgroundThread Class used to Fetch the Apache License from GooglePlayServicesUtil Class

private class BackgroundThread extends Thread implements Handler.Callback{

    // Looper and Handler for the Background Thread
    private Looper      m_workerLooper;
    protected Handler   m_workerHandler;

    @Override public void run()
    {
        // Do background Processing
        Looper.prepare();
        m_workerLooper = Looper.myLooper();
        m_workerHandler = new Handler(m_workerLooper, BackgroundThread.this);
        Looper.loop();
    }

    @Override public boolean handleMessage(Message msg) 
    {
        switch(msg.what)
        {
        case MSG_DO_WORK:
            // Run the obtainApacheLicenseFunction in this Thread
            obtainApacheLicense();
            break;
        case MSG_SHUTDOWN:
            // Clean up the Looper by calling quit() on it
            m_workerLooper.quit();
            Log.d("BACKGROUND_THREAD","Looper is shut down");
            break;
        }
        // Return true
        return true;
    }

}
}

And i show this by using a switch statement as such:

// Runs the Apache Source Code in the Background
private void launchApacheDialogFragment(FragmentManager fm,FragmentTransaction ft) 
{
    counter++;

    // Check if the Dialog Already Exists
    m_dialogFragment = (ApacheLicenseDialog) fm.findFragmentByTag(APACHE_FRAGMENT);

    if(m_dialogFragment != null)
    {
        ft.remove(m_dialogFragment);
    }
    ft.addToBackStack(APACHE_FRAGMENT);

    m_dialogFragment = ApacheLicenseDialog.newInstance(counter);

    m_dialogFragment.show(fm, APACHE_FRAGMENT);

}

And finally my case statement which calls this method:

// Case 3 =  Show the Apache Open Source License information
        case 3:

            // Launch the DialogFragment
            launchApacheDialogFragment(fm, ft);

            // Break out of the Statement
            break;

Any help would be appreciated, this is kind of an annoying freeze delaying the experience, although its just to read the open source license.

Again, please help me using the Thread/Handler/Looper ideology. I am trying to understand this concept as opposed to just using AsyncTask.

Update

I have found this to be working using Debug perspective. My thread starts up and my handler processes all the messages and at the end of the lifecycle of my dialog fragment the background thread successfully joins. Am i forgetting something that needs to be cleaned up more?

Thanks

Answer 1

我找到了一种使用BroadcastReceiver做到这一点的更好方法，请参见此处的文章，以编程方式注册子类BroadcastReceiver onReceive（context，intent）不会在DialogFragment中被调用