<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" //1.5以后默认的是LinearLayout布局
  android:orientation="vertical"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  >
<TextView
  android:id="@+id/textview1" //定义Id方便Java类找到它,并且控制它
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:text="@string/hello"
  />
<Button
  android:id="@+id/button1"
  android:layout_width="60px"
  android:layout_height="wrap_content"
  android:layout_gravity="right" //让Button放在右面
  android:text="确定"
/>
</LinearLayout>

package com.android.test;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
public class ButtonDemo extends Activity {
  private TextView textview1;
  private Button button1;
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    //通过ID在找到定义在main.xml里的TextView和Button控件
    textview1 = (TextView)findViewById(R.id.textview1);
    button1 = (Button)findViewById(R.id.button1);
    //增加事件响应
    button1.setOnClickListener(new Button.OnClickListener(){
      public void onClick(View v)
      {
        //Toast提示控件
        Toast.makeText(ButtonDemo.this,
            "TextView里的文字发生了改变,你注意到了吗?",
            Toast.LENGTH_LONG).show();
        //将TextView的文字发生改变
        textview1.setText("欢迎来到魏祝林的博客!");
      }
    });
  }
}