package a.a;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

public class AActivity extends Activity {
    /** Called when the activity is first created. */

    EditText Ev1;

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

        Ev1 = (EditText)findViewById(R.id.editText1);  

        //第一种方式  
        Button Btn1 = (Button)findViewById(R.id.button1);//获取按钮资源  
        Btn1.setOnClickListener(new Button.OnClickListener(){//创建监听  
            public void onClick(View v) {  
                String strTmp = "点击Button01";  
                Ev1.setText(strTmp);  
            }  

        });  

        //第二种方式  
        Button Btn2 = (Button) findViewById(R.id.button2);//获取按钮资源  
        Btn2.setOnClickListener(listener);//设置监听  

    }

    Button.OnClickListener listener = new Button.OnClickListener(){//创建监听对象  
        public void onClick(View v){  
            String strTmp="点击Button02";  
            Ev1.setText(strTmp);  
        }  

    };


    //第三种方式(Android1.6版本及以后的版本中提供了)  
    public void Btn3OnClick(View view){  
        String strTmp="点击Button03";
        Ev1.setText(strTmp);

    }  
}

<?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" >

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/hello" />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button1" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button2" />
    
 <Button
        android:id="@+id/button3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button3" 
        android:onClick="Btn3OnClick"/>

 <EditText
     android:id="@+id/editText1"
     android:layout_width="match_parent"
     android:layout_height="wrap_content" >

     <requestFocus />
 </EditText>

</LinearLayout>