android static Handler

package com.example.orm;

import java.lang.ref.WeakReference;

import android.app.Activity;

import android.os.Bundle;

import android.os.Handler;

import android.os.Message;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.Toast;

public class Welcom extends Activity {

String myText = "";
Button bt_test;

public static class MyHandler extends Handler {
WeakReference<Welcom> mWeak;

public MyHandler(Welcom mm) {

mWeak = new WeakReference<Welcom>(mm);
}

@Override
public void handleMessage(Message msg) {
// TODO Auto-generated method stub
super.handleMessage(msg);
Welcom mm = mWeak.get();
switch (msg.what) {
case 0:
mm.myText = "dfsf";
mm.bt_test.setText("换行");

break;
}

}
}

MyHandler mmHandler = new MyHandler(this);

@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.welcom);

bt_test = (Button) findViewById(R.id.bt_test);
bt_test.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
mmHandler.sendEmptyMessage(0);
}
});
}

}