<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<TextView  
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="@string/hello"
    />
<Button
 android:id="@+id/bt"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:text="Presse Me Look Log"
/>
</LinearLayout>

package com.android.test;
import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
public class LogDemo extends Activity {
 private static final String ACTIVITY_TAG="LogDemo";
 private Button bt;
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        //通过findViewById找到Button资源
        bt = (Button)findViewById(R.id.bt);
        //增加事件响应
        bt.setOnClickListener(new Button.OnClickListener(){
    @Override
   public void onClick(View v) {
    Log.v(LogDemo.ACTIVITY_TAG, "This is Verbose.");
    Log.d(LogDemo.ACTIVITY_TAG, "This is Debug.");
    Log.i(LogDemo.ACTIVITY_TAG, "This is Information");
    Log.w(LogDemo.ACTIVITY_TAG, "This is Warnning.");
    Log.e(LogDemo.ACTIVITY_TAG, "This is Error.");
   }
        });
    }
}