Android have following Threads state:
Advantages of Multi-Threading1.Threads share the process' resources but are able to execute independently.
2.Applications responsibilities can be separated main thread runs UI, and slow tasks are sent to background threads.
3.Threading provides an useful abstraction of concurrent execution.
4.Particularly useful in the case of a single process that spawns multiple threads on top of a multiprocessor system. In this case real parallelism is achieved.
5.Consequently, a multithreaded program operates faster on computer systems that have multiple CPU's.
Handler Classhttp://developer.android.com/reference/android/os/Handler.html•When a process is created for your application, its main thread is dedicated to running a message queue that takes care of managing the top-level application objects (activities, intent receivers, etc) and any windows they create.
•You can create your own secondary threads, and communicate back with the main application thread through a Handler.
•When you create a new Handler, it is bound to the message queue of the thread that is creating it --from that point on, it will deliver messagesand runnablesto that message queue and execute them as they come out of the message queue.
Code for Multi-threading using Handler class
Code:
package com.android.multithreading;
import java.util.Random;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.DialogInterface.OnClickListener;
import android.inputmethodservice.Keyboard.Key;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.KeyEvent;
import android.view.View;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;
public class ThreadingActivity extends Activity implements Runnable
{
/*
* ThreadingActivity class for managing multi-tasking using message queue
*/
/** Called when the activity is first created. */
ProgressBar pb1;
ProgressBar pb2;
TextView msgWorking;
TextView msgReturned;
TextView pdTv;
Button pdBtn;
private String pi_string;
ProgressDialog pd;
boolean isRunning=false;
final int MAX_SEC=60;
String strTest="Global value seen by all threads";
int intTest=0;
Handler handler=new Handler()
{
@Override
public void handleMessage(Message msg)
{
String returnValue=(String)msg.obj;
Log.i(returnValue, " Return Value");
msgReturned.setText("returned by background thread: \n\n"+returnValue);
pb1.incrementProgressBy(2);
if(pb1.getProgress()==MAX_SEC)
{
msgReturned.setText("Done \n back thread has been stopped");
isRunning=false;
}
if(pb1.getProgress()==pb1.getMax())
{
msgWorking.setText("Done");
pb1.setVisibility(View.INVISIBLE);
pb2.setVisibility(View.INVISIBLE);
pb1.getLayoutParams().height=0;
pb2.getLayoutParams().height=0;
}
else
{
msgWorking.setText("Working..."+pb1.getProgress()+"%");
}
}
};// handler
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
pb1=(ProgressBar)findViewById(R.id.progress);
pb2=(ProgressBar)findViewById(R.id.progress2);
pb1.setMax(MAX_SEC);
pb1.setProgress(0);
msgWorking=(TextView)findViewById(R.id.TextView01);
msgReturned=(TextView)findViewById(R.id.TextView02);
pdTv=(TextView)findViewById(R.id.TextView03);
pdBtn=(Button)findViewById(R.id.pdBtn);
pdBtn.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
//Intent i=new //Intent(getApplicationContext(),ThreadsPosting.class);
//startActivity(i);
}
});
strTest+="-01";
intTest=1;
}
public void onStop()
{
super.onStop();
isRunning=false;
}
public void onStart()
{
super.onStart();
Thread background=new Thread(new Runnable() {
public void run()
{
// TODO Auto-generated method stub
try
{
for(int i=0;i<MAX_SEC && isRunning;i++)
{
Thread.sleep(1000);
Random rnd=new Random();
String data="Threads Value "+(int)rnd.nextInt(101);
data+="\n"+strTest+" "+intTest;
intTest++;
Message msg=handler.obtainMessage(1, (String)data);
if(isRunning)
{
handler.sendMessage(msg);
}
}
}
catch(Throwable e)
{
}
}//run
});// background
isRunning=true;
background.start();
}
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
// TODO Auto-generated method stub
pd = ProgressDialog.show(this, "Working..", "Calculating Pi", true,false);
Thread th=new Thread(this);
th.start();
return super.onKeyDown(keyCode, event);
}
public void run() {
// TODO Auto-generated method stub
Random rnd=new Random();
pi_string = Pi.computePi(800).toString();
handler2.sendEmptyMessage(0);
}
private Handler handler2=new Handler()
{
@Override
public void handleMessage(Message msg)
{
pd.dismiss();
pdTv.setText(pi_string);
}
};
}
Vaibhav Parkhi
Android Example
Neha Somany
