AndroidRunnable, with Runnable Thread

It's a very simple exercise to implament a activity with a Runnable Thread.



Modify main.xml to add a TextView, as a counter used to monitor the Runnable Thread. It count-up in every 1000ms.

main.xml

<?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"
>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/hello"
/>
<TextView
android:id="@+id/i"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
/>
</LinearLayout>

Modify AndroidRunnable.java

package com.exercise.AndroidRunnable;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.widget.TextView;

public class AndroidRunnable extends Activity{
 
 int i = 0;
 TextView myi;
 
 Handler handler = new Handler(){

  @Override
  public void handleMessage(Message msg) {
   // TODO Auto-generated method stub
   update_i();
  }
 };
 
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        myi =(TextView)findViewById(R.id.i);
    }
    
    @Override
 protected void onStart() {
  // TODO Auto-generated method stub
  super.onStart();
  
  Thread myThread=new Thread(new Runnable() {
   public void run() {
    while(true){
     try {
      handler.sendMessage(handler.obtainMessage());
      Thread.sleep(1000);
     }
     catch (Throwable t) {
     }
    }
   }
  });
   
  myThread.start();
 }

 private void update_i()
    {
     i++;
     myi.setText(String.valueOf(i));
    }
}

AndroidRunnable.java can be downloaded here.

Note that update_i() cannot be called inside myThread directly, because only the Thread create the View can touch it. Otherwise, Exception will be generated. That's why I have to implement a Handler to call update_i() indirectly.