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
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>