Share object between threads with Synchronized Statements

Last post show how to create synchronized code with Synchronized Method. Alternatively, we can synchronize block of code with Synchronized Statements.


Example code:

package com.example.androidthread;

import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
import android.app.Activity;

public class MainActivity extends Activity {

 Button buttonStart;
 TextView textInfoA, textInfoB;

 String infoMsgA;
 String infoMsgB;

 ShareClass shareObj = new ShareClass(10);

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  buttonStart = (Button) findViewById(R.id.buttonstart);
  textInfoA = (TextView) findViewById(R.id.infoa);
  textInfoB = (TextView) findViewById(R.id.infob);

  buttonStart.setOnClickListener(new OnClickListener() {

   @Override
   public void onClick(View arg0) {

    infoMsgA = "Thread A\n";
    infoMsgB = "Thread B\n";
    textInfoA.setText(infoMsgA);
    textInfoB.setText(infoMsgB);

    new Thread(new Runnable() {

     boolean stop = false;

     @Override
     public void run() {

      while (!stop) {
       if (shareObj.getCounter() > 0) {

        infoMsgA += "A: "
          + shareObj.delayDecCounter(2500) + "\n";
        
        try {
         Thread.sleep(3000);
        } catch (InterruptedException e) {
         // TODO Auto-generated catch block
         e.printStackTrace();
        }

        MainActivity.this.runOnUiThread(new Runnable() {

         @Override
         public void run() {
          textInfoA.setText(infoMsgA);
         }

        });

       } else {
        stop = true;
       }
      }
     }
    }).start();

    new Thread(new Runnable() {

     boolean stop = false;

     @Override
     public void run() {

      while (!stop) {
       if (shareObj.getCounter() > 0) {

        infoMsgB += "B: "
          + shareObj.delayDecCounter(500) + "\n";
        
        try {
         Thread.sleep(500);
        } catch (InterruptedException e) {
         // TODO Auto-generated catch block
         e.printStackTrace();
        }

        MainActivity.this.runOnUiThread(new Runnable() {

         @Override
         public void run() {
          textInfoB.setText(infoMsgB);
         }

        });

       } else {
        stop = true;
       }
      }
     }
    }).start();

   }
  });

 }

 public class ShareClass {

  int counter;

  ShareClass(int c) {
   counter = c;
  }

  public int getCounter() {
   return counter;
  }

  public int delayDecCounter(int delay) {
   
   //do something not access the share obj
   try {
    Thread.sleep(100);
   } catch (InterruptedException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }

   synchronized (this) {
    int tmpCounter = counter;

    try {
     Thread.sleep(delay);
    } catch (InterruptedException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
    }

    tmpCounter--;
    counter = tmpCounter;
    
    return counter;
   }
   
  }
 }

}

The layout XML, refer to last post.

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- More example about Thread