Question

I have a problem I can’t set the text of a button during a countdown, this is the code:

begin.setText("Start level 1");
begin.setOnClickListener(new OnClickListener(){
public void onClick(View arg0) {

final int delay = 0000; // delay for 5 sec.
final int period = 1000; // repeat every sec.
final Timer timer = new Timer();
timer.scheduleAtFixedRate(new TimerTask() {
    public  void run() {
        begin.setText("" + t);
        t--;
        if(t == 0) {
            timer.cancel()
        }
    }
}, delay, period);

this is the logcat:

android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
07-30 17:27:05.273: E/AndroidRuntime(22543):    at android.view.ViewRoot.checkThread(ViewRoot.java:2802)
07-30 17:27:05.273: E/AndroidRuntime(22543):    at android.view.ViewRoot.requestLayout(ViewRoot.java:594)
07-30 17:27:05.273: E/AndroidRuntime(22543):    at android.view.View.requestLayout(View.java:8128)
07-30 17:27:05.273: E/AndroidRuntime(22543):    at android.view.View.requestLayout(View.java:8128)
07-30 17:27:05.273: E/AndroidRuntime(22543):    at android.view.View.requestLayout(View.java:8128)
07-30 17:27:05.273: E/AndroidRuntime(22543):    at android.widget.RelativeLayout.requestLayout(RelativeLayout.java:254)
07-30 17:27:05.273: E/AndroidRuntime(22543):    at android.view.View.requestLayout(View.java:8128)
07-30 17:27:05.273: E/AndroidRuntime(22543):    at android.view.View.requestLayout(View.java:8128)
07-30 17:27:05.273: E/AndroidRuntime(22543):    at android.widget.TextView.checkForRelayout(TextView.java:5405)
07-30 17:27:05.273: E/AndroidRuntime(22543):    at android.widget.TextView.setText(TextView.java:2712)
07-30 17:27:05.273: E/AndroidRuntime(22543):    at android.widget.TextView.setText(TextView.java:2580)
07-30 17:27:05.273: E/AndroidRuntime(22543):    at android.widget.TextView.setText(TextView.java:2555)
07-30 17:27:05.273: E/AndroidRuntime(22543):    at it.bisemanuDEV.piano.livello1$1$1.run(livello1.java:134)
07-30 17:27:05.273: E/AndroidRuntime(22543):    at java.util.Timer$TimerImpl.run(Timer.java:289)

I hope you can help.
Thanks

Answer 1

As @Jug6ernaut mentioned, you shouldn’t use a TimerTask.
Instead, you could try using a Handler. This is how I do things like that in a timer.

For example, in your timer when you want to call .setText(), do this:

mHandler.post(new Runnable() {
    @Override
    public void run() {
        begin.setText(gcalendar.get(Calendar.MINUTE)+":"+gcalendar.get(Calendar.SECOND));   
    }
});

It is initialized simply as Handler mHandler = new Handler().

Edit: Just noticed this is the same idea as the other SO question links posted in the comments below your answer… well, here it is anyways.