Pass a Message From Thread to Update UI

Question

Ive created a new thread for a file browser. The thread reads the contents of a directory. What I want to do is update the UI thread to draw a graphical representation of the files and folders. I know I can't update the UI from within a new thread so what I want to do is:

whilst the file scanning thread iterates through a directories files and folders pass a file path string back to the UI thread. The handler in the UI thread then draws the graphical representation of the file passed back.

public class New_Project extends Activity implements Runnable {

    private Handler handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            Log.d("New Thread","Proccess Complete.");
            Intent intent = new Intent();
            setResult(RESULT_OK, intent);
            finish();
        }
    };


    public void fileScanner(){
        //if (!XMLEFunctions.canReadExternal(this)) return;
        pd = ProgressDialog.show(this, "Reading Directory.",
                "Please Wait...", true, false);

        Log.d("New Thread","Called");
        Thread thread = new Thread(this);
        thread.start();
    }


    public void run() {
        Log.d("New Thread","Reading Files");
        getFiles();
        handler.sendEmptyMessage(0);
    }


    public void getFiles() {
        for (int i=0;i<=allFiles.length-1;i++){
            //I WANT TO PASS THE FILE PATH BACK TU A HANDLER IN THE UI
            //SO IT CAN BE DRAWN.
            **passFilePathBackToBeDrawn(allFiles[i].toString());**
        } 
    }

}

Solution 1

Check out AsyncTask for this kind of stuff. It's really much more elegant than rolling your own handler and passing messages back and forth.

http://developer.android.com/reference/android/os/AsyncTask.html

Solution 2

It seems passing simple messages is int based... What I needed to do was pass a Bundle

using Message.setData(Bundle) and Message.getData(Bundle)

So Happy =0)

//Function From Within The Thread

public void newProjectCreation() {

Message msg =  new Message();
Bundle bundle = new Bundle();

bundle.putString("Test", "test value");
msg.setData(bundle);

handler2.sendMessage(msg);
}

//Handler in The UI Thread Retreieves The Data
//And Can Update the GUI as Required

private Handler handler2 = new Handler() {
    @Override
    public void handleMessage(Message msg) {

    Bundle bundle = msg.getData();
    Toast.makeText(New_Project.this,bundle.getString("Test"),Toast.LENGTH_SHORT).show();

}

};