Android background thread, by extending Thread

Android background thread, by extending Thread

In this exercise, a new class, BackgroundThread, was created by extending Thread class. The object of this class run in background thread. A TextView will be toggled between on and off by this background thread. In Android, only the UI thread can modify UI elements, the method run in background thread cannot modify UI elements directly. So we have to implement a Handler, the background thread will send a Message to the Handler to change Visibility of the TextView.



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/mytext"
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:text="This Text will be Turn ON/OFF triggered by a background thread."
   />
</LinearLayout>

AndroidBackgroundThread.java

package com.exercise.AndroidBackgroundThread;

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

public class AndroidBackgroundThread extends Activity {

BackgroundThread backgroundThread;
TextView myText;
boolean myTextOn = true;


public class BackgroundThread extends Thread {

 boolean running = false;

 void setRunning(boolean b){
  running = b;
 }

 @Override
 public void run() {
  // TODO Auto-generated method stub
  //super.run();
  while(running){
   try {
    sleep(1000);
   } catch (InterruptedException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
   handler.sendMessage(handler.obtainMessage());
  }
 }

}

Handler handler = new Handler(){

 @Override
 public void handleMessage(Message msg) {
  // TODO Auto-generated method stub
  //super.handleMessage(msg);
  if (myTextOn){
   myTextOn = false;
   myText.setVisibility(View.GONE);
  }
  else{
   myTextOn = true;
   myText.setVisibility(View.VISIBLE);
  }
 }

};



   /** Called when the activity is first created. */
   @Override
   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.main);
      
       myText = (TextView)findViewById(R.id.mytext);
      
       Toast.makeText(this, "onCreate()", Toast.LENGTH_LONG).show();
      
   }
  
  

@Override
protected void onStart() {
 // TODO Auto-generated method stub
 super.onStart();

 backgroundThread = new BackgroundThread();
 backgroundThread.setRunning(true);
       backgroundThread.start();
       Toast.makeText(this, "onStart()", Toast.LENGTH_LONG).show();
}

@Override
protected void onStop() {
 // TODO Auto-generated method stub
 super.onStop();

 boolean retry = true;
 backgroundThread.setRunning(false);

 while(retry){
  try {
   backgroundThread.join();
   retry = false;
  } catch (InterruptedException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
 
 }

 Toast.makeText(this, "onStop()", Toast.LENGTH_LONG).show();

}
}

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another version: Android background thread, by implementing Thread object, provided with a Runnable object.

Related article:
- ProgressDialog + Thread