Example of using HandlerThread

android.os.HandlerThread is a handy class for starting a new thread that has a looper. The looper can then be used to create handler classes. Note that start() must still be called.

This is a example to implement our custom HandlerThread class, CustomHandlerThread. Start it in onResume() and stop it in onPause().

Example of using HandlerThread

package com.example.androidtesthandlerthread;

import android.os.Bundle;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.Message;
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 implements Handler.Callback{

 public class CustomHandlerThread extends HandlerThread implements Handler.Callback{
  
  public static final int MSG_FINISHED = 100;
  public static final int MSG_COUNT_UP = 101;
  public static final int MSG_COUNT_DOWN = 102;

  private Handler handler, callback;

  public CustomHandlerThread(String name) {
   super(name);
   // TODO Auto-generated constructor stub
  }

  public CustomHandlerThread(String name, int priority) {
   super(name, priority);
   // TODO Auto-generated constructor stub
  }
  
  public void setCallback(Handler cb){
   callback = cb;
  }

  @Override
  protected void onLooperPrepared() {
   handler = new Handler(getLooper(), this);
  }

  @Override
  public boolean handleMessage(Message msg) {
   
   int data1 = msg.arg1;
   int data2 = msg.arg2;
   int counter;
   
   switch(msg.what){
   case MSG_COUNT_UP:
    for(counter=data1; counter < data2; counter++){
     //...
    }
    callback.sendMessage(Message.obtain(null, MSG_FINISHED, counter));
    break;
   case MSG_COUNT_DOWN:
    for(counter=data1; counter > data2; counter--){
     //...
    }
    callback.sendMessage(Message.obtain(null, MSG_FINISHED, counter));
    break;
   }
   return true;
  }
  
  public void querySomething(int start, int end){
   if(start > end){
    Message msg = Message.obtain(
      null,   //Handler h 
      MSG_COUNT_DOWN, //int what 
      start,   //int arg1 
      end);   //int arg2
    handler.sendMessage(msg);
   }else if(start < end){
    Message msg = Message.obtain(
      null,   //Handler h 
      MSG_COUNT_UP, //int what 
      start,   //int arg1 
      end);   //int arg2
    handler.sendMessage(msg);
   }
  }
 }
 
 private final static String MyName = "My CustomHandlerThread";
 private CustomHandlerThread myCustomHandlerThread;
 private Handler myHandler;
 
 Button btnUp, btnDown;
 TextView textResult;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  btnUp = (Button)findViewById(R.id.buttonup);
  btnDown = (Button)findViewById(R.id.buttondown);
  textResult = (TextView)findViewById(R.id.result);
  
  btnUp.setOnClickListener(new OnClickListener(){

   @Override
   public void onClick(View arg0) {
    myCustomHandlerThread.querySomething(1, 100);
   }});
  
  btnDown.setOnClickListener(new OnClickListener(){

   @Override
   public void onClick(View arg0) {
    myCustomHandlerThread.querySomething(500, 10);
   }});
  
  myHandler = new Handler(this);
 }
 
 @Override
 protected void onResume() {
  super.onResume();
  
  myCustomHandlerThread = new CustomHandlerThread(MyName);
  myCustomHandlerThread.setCallback(myHandler);
  myCustomHandlerThread.start();
 }

 @Override
 protected void onPause() {
  super.onPause();
  
  myCustomHandlerThread.setCallback(null);
  myCustomHandlerThread.quit();
  myCustomHandlerThread = null;
 }

 @Override
 public boolean handleMessage(Message arg0) {
  int result = (Integer)arg0.obj;
  textResult.setText("result: " + result);
  return false;
 }

}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:orientation="vertical"
    tools:context=".MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="android-coding.blogspot.com" />
    
    <Button
        android:id="@+id/buttonup"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Count up from 1 to 100" />
    <Button
        android:id="@+id/buttondown"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Count down from 500 to 10" />
    <TextView
        android:id="@+id/result"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>