HandlerThread

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <Button
        android:id="@+id/main"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="main" />

    <Button
        android:id="@+id/other"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="other" />

</LinearLayout>

MainActivity.java

package test.handler;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.HandlerThread;
import android.view.View;
import android.view.View.OnClickListener;

public class MainActivity extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        //------------------------------------
        // UI-Thread
        //------------------------------------
        // Handler(for UI-Thread)
        final Handler mainHandler = new Handler();

        findViewById(R.id.main).setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                mainHandler.post(new Runnable() {
                    @Override
                    public void run() {
                        System.out.println(Thread.currentThread().getName());
                    }
                });
            }
        });

        //------------------------------------
        // Other-Thread
        //------------------------------------
        // start Other-Thrad
        HandlerThread handlerThread = new HandlerThread("other");
        handlerThread.start();

        // Handler(for Other-Thread)
        final Handler otherHandler = new Handler(handlerThread.getLooper());

        findViewById(R.id.other).setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                otherHandler.post(new Runnable() {
                    @Override
                    public void run() {
                        System.out.println(Thread.currentThread().getName());
                    }
                });
            }
        });
    }
}