Thanks for your help. This reply is one month late as I haven't had
time for further Android development learning until now. This is what
I've got so far. It successfully increments from 0 to 1, however, I
want to know how I can continuously call handler.postDelayed to
increment all the way up to 500. Can't seem to figure it out. This is
probably more of a Java question than an Android question. Any ideas?
package com.mhuang.stop;
import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;
import android.os.Handler;
public class StopAt500 extends Activity {
private Handler handler = new Handler();
public TextView tv;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);;
final TextView tv = new TextView(this);
setContentView(tv);
tv.setText("0");
count();
}
public void count() {
final Runnable increment = new Runnable() {
public void run() {
String counter = (String) tv.getText();
int i = Integer.parseInt(counter);
tv.setText(Integer.toString(i+=1));
}
};
handler.postDelayed(increment, 4000);
}
}
On Jan 26, 2:08 pm, Mark Murphy <mmur...@commonsware.com> wrote:
> coolbho3k wrote:
> > Okay, so I am creating a test program (my version of "hello world"
> > every time I start developing on a new platform) that flashes the
> > numbers 0 through 500 on the screen rapidly. Here's what I have in my
> > main Java file so far. Problem is, it won't display anything. Anyone
> > know what is wrong?
>
> > I have some experience in C/C++ but I'm almost completely new to Java.
> > Thanks!
>
> > package com.mh.test;
>
> > import android.app.Activity;
> > import android.os.Bundle;
> > import android.widget.TextView;
>
> > public class AndroidTest extends Activity {
> > /** Called when the activity is first created. */
> > @Override
> > public void onCreate(Bundle savedInstanceState) {
> > TextView tv = new TextView(this);
> > super.onCreate(savedInstanceState);
> > for(int i=0; i >= 500; i++)
> > {
> > tv.setText(Integer.toString(i));
> > setContentView(tv);
> > try {
> > Thread.sleep(4000);
> > } catch (InterruptedException e) {
> > // TODO Auto-generated catch block
> > e.printStackTrace();
> > }
>
> > }
>
> > }
> > }
>
> Simple answer: you're not letting Android do anything.
>
> Somewhat more complicated answer:
>
> Writing for Android is a little like writing for other UI toolkits that
> have the notion of a "UI thread". Java/Swing and 16-bit Windows come to
> mind from personal experience, though I assume other systems use a
> similar pattern.
>
> All your calls to the activity (e.g., setContentView()) and all your
> changes to the widgets (e.g., setText()) queue up messages in a message
> loop. These messages will not get processed until you leave the callback
> method you are in (onCreate()).
>
> What I would expect to happen if you ran this would be to get a "process
> not responding" error, since this implementation seems to want to run
> for 2,000 seconds (500 passes with a 4-second sleep), which is a wee bit
> longer than Android wants to be tied up in one of the callbacks.
>
> So, here's what you do:
>
> In onCreate(), set up the TextView, make it be the activity's UI via
> setContentView(), set the TextView to "0", and call postDelayed() on the
> TextView to queue up an event 4,000ms later. In that event (a Java
> Runnable object's run() method), you would increment the TextView and
> call postDelayed() again to queue up another event 4,000ms later.
> Lather, rinse, and repeat until you get to 500, then don't call
> postDelayed() again. The most important thing, though, is after your
> first call to postDelayed() is to return out of onCreate(), so Android
> can start doing what you're telling it to.
>
> If you want it to run as fast as possible, instead of a 4-second delay,
> use post() instead of postDelayed().
>
> There are other approaches to this -- my book has a similar sample app,
> updating a progress bar and using a Handler to manage a background thread.
>
> --
> Mark Murphy (a Commons Guy)http://commonsware.com
> _The Busy Coder's Guide to Android Development_ Version 2.0 Published!
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