TextView setText ignoring changes?

ClockworkAlchemist · by **ClockworkAlchemist** » Wed Mar 04, 2009 5:29 pm

I'm trying to put a simple timer at the top of my application. My idea was to dislpay it in a TextView and run a TimerTask and periodically update the timer. That all seems to work fine, but the text displayed in the TextView doesn't update after the first time I call setText. I've even tried calling invalidate and some other random voodoo, with no luck. I've tried spitting out the string to the debugger, and it is getting generated correctly roughly every second.
I assume I must be doing some very simple thing incorrectly. Is there some reason why my text view won't refresh?

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import stuff here
 
public class ClockActivity extends Activity 
 
{
 
        long start_time = System.currentTimeMillis();
 
        TextView text_timer = null;
 
    /** Called when the activity is first created. */
 
    @Override
 
    public void onCreate(Bundle savedInstanceState) 
 
    {
 
        super.onCreate(savedInstanceState);
 
        setContentView(R.layout.dttb_activity);
 
        start_time = System.currentTimeMillis();        
 
        text_timer = (TextView) findViewById(R.id.text_timer);
 
        Timer timer = new Timer();
 
        TimerTask task = new TimerTask()
 
        {
 
                public void run()
 
                {
 
                        updateClock();
 
                }
 
        };
 
        timer.scheduleAtFixedRate(task, 0, 1000);
 
    }
 
    public void updateClock()
 
    {
 
        long current_time = System.currentTimeMillis();
 
        long elapsed_time = current_time - start_time;
 
        Date elapsed = new Date(elapsed_time);
 
        int hours = elapsed.getHours();
 
        int minutes = elapsed.getMinutes();
 
        int seconds = elapsed.getSeconds();
 
        String message = String.format("%3d:%02d:%02d", hours, minutes, seconds);
 
        // This line works the first time this is called, 
 
        // but doesn't show changes on later calls....
 
        text_timer.setText( message );
 
        // uncomment for debugging
 
        //System.out.println(message);
 
    }
 
}
 
Parsed in 0.036 seconds,  using GeSHi 1.0.8.4

Here is my layout file, pretty simple....

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<?xml version="1.0" encoding="utf-8"?>
 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 
    android:orientation="vertical"
 
    android:layout_width="fill_parent"
 
    android:layout_height="fill_parent"
 
    android:background="#ffffffff"
 
    >
 
<TextView 
 
        android:id="@+id/text_timer"
 
        android:layout_width="wrap_content"
 
        android:layout_height="wrap_content"    
 
        android:text="000:00:00:00"
 
        android:textSize="24sp"
 
        android:textStyle="bold"
 
        android:layout_gravity="center_horizontal|top"
 
        android:textColor="#ff000000" />
 
</LinearLayout>
 
Parsed in 0.002 seconds,  using GeSHi 1.0.8.4

ClockworkAlchemist · by **ClockworkAlchemist** » Tue Mar 10, 2009 5:21 am

So I played around with this for awhile, and it turns out that you don't want to call setText on a thread other than the UI thread. I changed my code to this to get it to work:

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public class ClockActivity extends Activity 
 
{
 
        private class UpdateClock implements Runnable
 
        {
 
               ClockActivity act = null;
 
                public void run()
 
                {
 
                       if ( act != null && !act.isFinishing() )
 
                       {
 
                            act.updateClock();
 
                       }
 
                }
 
        }
 
        private class ClockTask extends TimerTask
 
        {
 
                ClockActivity act = null;
 
                public void run()
 
                {
 
                     if ( act != null && !act .isFinishing() )
 
                     {
 
                            UpdateClock update = new UpdateClock();
 
                            update.act = this.act ;
 
                            act .runOnUiThread(update);
 
                     }
 
                }
 
        }
 
        long start_time = System.currentTimeMillis();
 
        Timer clock_timer = null;
 
    /** Called when the activity is first created. */
 
    @Override
 
    public void onCreate(Bundle savedInstanceState) 
 
    {
 
        super.onCreate(savedInstanceState);
 
        setContentView(R.layout.clock_activity);               
 
        start_time = System.currentTimeMillis();
 
        clock_timer = new Timer();
 
        ClockTask clock_task = new ClockTask();
 
        clock_task.act = this;
 
        clock_timer.scheduleAtFixedRate(clock_task, 0, 1000);
 
    }
 
    public void updateClock()
 
    {
 
        long current_time = System.currentTimeMillis();
 
        long elapsed_time = current_time - start_time;
 
        Date elapsed = new Date(elapsed_time);
 
        int hours = elapsed.getHours();  
 
        int minutes = elapsed.getMinutes();
 
        int seconds = elapsed.getSeconds();
 
        String message = String.format("%3d:%02d:%02d", hours, minutes, seconds);
 
        TextView text_timer = (TextView) findViewById(R.id.text_timer);
 
        text_timer.setText(message);
 
        // uncomment for debugging
 
       // System.out.println(message);
 
    }
 
}
 
Parsed in 0.037 seconds,  using GeSHi 1.0.8.4

However, this just feels like a tremendous hack. Also, the virtual machine reports that its cleaning up around 10,000 objects and about 500kb every 30 seconds or so, which seems ridiculous for such a simple app. Can anybody suggest a better way of doing this?

powerdeng · by **powerdeng** » Tue Mar 10, 2009 7:47 pm

You should only update a UI object in the main thread.
send a message when you need to refresh the UI ,and use a handler to react.
the code below maybe do what you want.
[modified from your code,i use the default layout name .lazy

]

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public class ClockActivity extends Activity 
 
{ 
 
     long start_time = System.currentTimeMillis(); 
 
     TextView text_timer = null;
 
     /*in order to refer everywhere*/
 
     String message;
 
     /*Use handler to receive message from other thread*/
 
     Handler updateNow;
 
     /*Your Message 'what'*/
 
     public static final int TICK = 1;
 
    /** Called when the activity is first created. */ 
 
    @Override 
 
    public void onCreate(Bundle savedInstanceState) 
 
    { 
 
        super.onCreate(savedInstanceState); 
 
        setContentView(R.layout.main); 
 
        start_time = System.currentTimeMillis();         
 
        text_timer = (TextView) findViewById(R.id.text_timer); 
 
        /*You own handler hear*/
 
        updateNow = new Handler() {
 
            @Override
 
            public void handleMessage(Message msg) {
 
                switch (msg.what) {
 
                case TICK:
 
                    text_timer.setText(message);
 
                }
 
            }
 
        };
 
        Timer timer = new Timer(); 
 
        TimerTask task = new TimerTask() 
 
        { 
 
          public void run() 
 
          { 
 
               updateClock(); 
 
          } 
 
        }; 
 
        timer.scheduleAtFixedRate(task, 0, 1000);        
 
    } 
 
    public void updateClock() 
 
    { 
 
     long current_time = System.currentTimeMillis(); 
 
     long elapsed_time = current_time - start_time; 
 
     Date elapsed = new Date(elapsed_time); 
 
     int hours = elapsed.getHours(); 
 
     int minutes = elapsed.getMinutes(); 
 
     int seconds = elapsed.getSeconds(); 
 
     /*Change the message and tell the UI thread to update*/ 
 
     message = String.format("%3d:%02d:%02d", hours, minutes, seconds); 
 
     updateNow.sendEmptyMessage(TICK);
 
    } 
 
} 
Parsed in 0.040 seconds,  using GeSHi 1.0.8.4

TextView setText ignoring changes?

TextView setText ignoring changes?

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