Question

Good afternoon everyone

So, I’m trying to dynamically change textview’s properties.
basically, I defined a Duration. and I want to my handler/runnable to append text to a textView until I reach the duration.

public class Dynamic_testActivity extends Activity
{
    public Context      context         = null;
    public TextView     view            = null;
    public Handler      mHandler        = null;
    public long         startTime       = 0L;
    public final int    duration_millis = 10000;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        context = getApplicationContext();

        view    = (TextView)    findViewById(R.id.textView1);
        view.append("\n");

        mHandler = new Handler();
    }

    @Override
    protected void onStart() {
        super.onStart();

        startTime = System.currentTimeMillis();

        mHandler.post(new Runnable() {
            @Override
            public void run() {
                view.append("Hell_yeah_!\n");
                // 10 character lenght
            }
        });
    }
}

So yes, it append the text once, because the run do so.
But how could I make some kind of loop, without blocking the UI Thread, and append text until the end of the duration.

That was the first step …

The second part now … In fact, I Want to change the color of the text.
using

Spannable WordtoSpan = new SpannableString(view.getText());        
WordtoSpan.setSpan(new ForegroundColorSpan(Color.BLUE), 0, view.getText().length(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);

I want to the color changing to be dynamic for the duration … like a karaoke …
So, is it possible to make that in the runnable without having the UI Thread blocked until the end of the duration ? and How ?

If anyone could explain the complet process ? or post some source code

---

Solved.
Here is a basic example…
There is still a little trouble … at the very beginning of the application, the whole textview is yellow, and after a second, it updates the display as it should be .
If any one knows why, advices are welcome =)

Note : there’s only two simple Textview in the layout… Duration is in milliseconds… and there is 10 character in the dynamic textview to fit the duration … So basically, one char = one second …

public class Dynamic_testActivity extends Activity
{
    public Context      context                                 = null;
    public TextView     view                                    = null;
    public TextView     view2                                   = null;
    public Handler      handler                                 = null;
    public long         start_time, current_time, elapsed_time  = 0L;
    public final int    duration                                = 10000;
    public int          end                                     = 0;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        context = getApplicationContext();
        view    = (TextView)    findViewById(R.id.textView1);
        view2   = (TextView)    findViewById(R.id.textView2);
        handler = new Handler();
    }

    @Override
    protected void onStart() {
        super.onStart();

        start_time   = Long.valueOf( System.currentTimeMillis() );
        current_time = start_time;

        handler.postDelayed(new Runnable() {
            @Override
            public void run() {

                current_time = Long.valueOf( System.currentTimeMillis() );
                elapsed_time = Long.valueOf(current_time) - Long.valueOf(start_time);

                if ( elapsed_time >= duration + 30 ) {
                    Toast.makeText(context, "Done", Toast.LENGTH_LONG).show();
                    //finish();
                } else {
                    end = (int) (elapsed_time / 1000);
                    Spannable WordtoSpan = new SpannableString(view.getText());
                    WordtoSpan.setSpan(new ForegroundColorSpan(Color.YELLOW), 0, end, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);

                    view.setText(WordtoSpan);
                    view2.setText("time : " + elapsed_time);
                    handler.postDelayed(this, 10);
                }
            }
        }, 10);
    }
}

Answer 1

In your run() methond, you can call mHandler.post(this) (or use postDelayed to delay it)

There is property change animation in API level 14, but if you are targetting a lower version, use postDelayed repetively to change progressively the color of the text.