Android Custom Listener Example

Custom listener implemnatation in android with Full Sourcecode.
WorkHelper : Processing class  

package com.customlistener;

import android.location.Location;
import android.util.Log;

/**
 * @author piyush
 * Does data processing.
 */
public class WorkHelper {

 private HelperResult helperResult;
 private String tag="WorkHelper",resultString;
 private int randomNumber=-1,limit=1000;
 
 public WorkHelper(HelperResult helperResult) {
  this.helperResult=helperResult;
 }
 
 public void doProcessing()
 {
  //generate number between 0 to 1000
  randomNumber=(int)(Math.random()*limit);  
  Log.d(tag,"doProcessing:"+randomNumber);
  
  resultString="New RandomNumber is : "+randomNumber;
  //post data back to MainActivity
  helperResult.getResult(resultString);
 }
 
 public static abstract class HelperResult{
        public abstract void getResult(String resultString);
    }
}

MainActivity : UI Class

package com.customlistener;

import com.customlistener.WorkHelper.HelperResult;

import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;

/**
 * Main Activity 
 * @author piyush
 */
public class MainActivity extends Activity {
 
 private String tag="HelperResult",resultStr="";
 private Button startButton;
 private WorkHelper workHelper;
 private Context context;
 private TextView textViewData;
 
 /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        
        setContentView(R.layout.main);
        context=this;
        workHelper=new WorkHelper(helperResult);
        
        startButton=(Button)findViewById(R.id.button1);
        textViewData=(TextView)findViewById(R.id.textDetail);
        
        startButton.setOnClickListener(new OnClickListener() {
   
   @Override
   public void onClick(View v) 
   {
    //generate random number
    workHelper.doProcessing();
   }
  });
    }
    
    /**
     * Create Instance of HelperResult Class
     * and Implement getResult().
     */
    HelperResult helperResult=new HelperResult() 
    {
     @Override
  public void getResult(String resultString) {
   Log.d(tag,"in MainActivity");
   Log.d(tag,"Result Received :"+resultString);
   resultStr+=resultString+"\n";
   textViewData.setText(resultStr);   
  }
 };
    
}

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Android Tips : onClickListener:onClick()

In this post , we will learn "Easy/Effective way to write code in onClickListener's onClick() to know which Button is clicked"

Inside onClick(View view) : write a switch-case as shown in below code.

Android UI Thread & Massive Work Thread

Many times Android Application becomes in-responsive due to heavy load on UI thread & user gets "FORCE CLOSE" message.

Avoid performing long-running operations (such as network I/O) directly in the UI thread — the main thread of an application where the UI is run — or your application may be blocked and become unresponsive. Here is a brief summary of the recommended approach for handling expensive operations:

There is simple solution to make application that does Massive work & need to frequently update UI.
Solution is to create a mechanism using  android.os.handler ,

1. Create a Handler object in your UI thread
2. Spawn off worker threads to perform any required expensive operations
3. Post results from a worker thread back to the UI thread via Message Object.
4. Update the views on the UI thread as needed

Below is simple solution:

public class MyActivity extends Activity {

    [ . . . ]
    // Need handler for callbacks to the UI thread
    final Handler mHandler = new Handler();

    // Create runnable for posting
    final Runnable mUpdateResults = new Runnable() {
        public void run() {
            updateResultsInUi();
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        [ . . . ]
    }

    protected void startLongRunningOperation() {

        // Fire off a thread to do some work that we shouldn't do 

        // directly in the UI thread 

        Thread t = new Thread() {
            public void run() {
                mResults = doSomethingExpensive();
                mHandler.post(mUpdateResults);
            }
        };
        t.start();
    }

    private void updateResultsInUi() {

        // Back in the UI thread -- update our UI elements based on 

        //the data in mResults
        [ . . . ]
    }
}

Article on Android.com | Common Task