How to update UI on external asynctask on android

Question

MainActivity execute external asynctask class

Here my code

public class MainActivity extends AppCompatActivity implements View.OnClickListener
...
public void onFirstBtnClick()
{
    AysncClass ac = new AyncClass();
    ac.execute();
}

and external asynctask

public class AysncClass extends AsyncTask<String, String, Integer>

    @Override
    protected Integer doInBackground(String... strings) {
        Method1(strings[0], Integer.parseInt(strings[1]));
        return null;
    }

    public Method1(Strins s, int i)
    {
        onProgressUpdate("first start");
        publishProgress();
        // do more work
        onProgressUpdate("second start");
        publishProgress();
    }

    public void Method2()
    {
        onProgressUpdate("Method2 here");
        publishProgress();
    }
    ...
     @Override
    protected void onProgressUpdate(final String... values) {
    super.onProgressUpdate(values);
    // what can i do here?
    }
}

I use runOnUiThread like this in onProgressUpdate

    ((MainActivity)context).runOnUiThread(new Runnable()
    {
        @Override
        public void run()
        {
            ((MainActivity)context).tvRead.append(values[0]);
        }
    });*

but It occur 'java.lang.ArrayIndexOutOfBoundsException: length=0; index=0' even though values[0] is not null.

Also I use interface

this.context.WriteText(values[0]);

It occur same error

And I do this...

((MainActivity)context).tvRead.append(values[0]);

It occur 'java.lang.RuntimeException: An error occured while executing doInBackground()' and 'CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.'

...How can I resolve?

Answer 1

Do not call onProgressUpdate() . Instead just call publishProgress("The String") .

By calling publishProgress without a parameter you will have no values in onProgressUpdate . That's why you get an IndexOutOfBondException.

Answer 2

Don't call onProgressUpdate on your own. Call publishProgress("My Message");

In onProgressUpdate, don't use runOnUIThread.

OnProgressUpdate runs on the Ui thread only.

Instead of this

onProgressUpdate("Method2 here");
publishProgress();

Do this

publishProgress("Method2 here");

Answer 3

On ProgressUpdate will be in UIThread, no need again specify in UI thread. From DoInbackGround you have to make call publishProgress method for invoking OnProgressUpdate.

Answer 4

Use an interface as communicator between your Activity and AsyncTask

Create Interface

interface MyInterface {
    void callActivityUi(String progress);  // use float maybe
}

Initialize AsyncTask like this:

AysncClass as = new AysncClass(new MyInterface() {
    @Override
    void callActivityUi (String progress) {
        // you will receive data here
    }

});

Create a constructor in your AysncClass

private MyInterface myInterface;
public AysncClass (MyInterface myInterface) {
    this.myInterface = myInterface;
}

Call Activity in onProgressUpdate(String... values)

myInterface.callActivityUi(values[0]);

Answer 5

Based on your code, you can use an interface to post the progress to the activity. I modified your code like this:

AsyncTask class

public class AysncClass extends AsyncTask<String, String, Integer> {

    public interface SomeListener {
        public void onSomething(Object mObject);
    }

    private SomeListener sl;

    public AysncClass(SomeListener sl) {
        this.sl = sl;
    }

    @Override
    protected Integer doInBackground(String... strings) {
        Method1(strings[0], Integer.parseInt(strings[1]));
        return null;
    }

    public Method1(Strins s, int i) {
        onProgressUpdate("first start");
        publishProgress();
        // do more work
        onProgressUpdate("second start");
        publishProgress();
    }

    public void Method2() {
        onProgressUpdate("Method2 here");
        publishProgress();
    }
    ...
    @Override
    protected void onProgressUpdate(final String... values) {
        super.onProgressUpdate(values);
        // what can i do here?
        sl.onSomething(mObject);
    }
}

MainActivity class

public class MainActivity extends AppCompatActivity implements View.OnClickListener,
    AysncClass.SomeListener {
    ...
    public void onFirstBtnClick() {
        AysncClass ac = new AyncClass(this);
        ac.execute();
    }

    @Override
    public void onSomething(Object mObject) {
        //Do your UI work here
    }
}