请教下这个关机代码错哪了

package yu.bin;import android.app.Activity;import android.content.Intent;import android.net.Uri;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;public class poweroff extends Activity {    /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        Button t = (Button) findViewById(R.id.abc);        t.setOnClickListener(new OnClickListener() {            @Override            public void onClick(View v) {                // TODO Auto-generated method stub                Intent shutdown = new Intent(Intent.ACTION_SHUTDOWN);                startActivity(shutdown);            }        });    }}

<?xml version="1.0" encoding="utf-8"?><manifest    xmlns:android="http://schemas.android.com/apk/res/android"    package="yu.bin"    android:versionCode="1"    android:versionName="1.0">    <application        android:icon="@drawable/icon"        android:label="@string/app_name">        <activity            android:name=".poweroff"            android:label="@string/app_name">            <intent-filter>                <action                    android:name="android.intent.action.MAIN" />                <category                    android:sharedUserId="android.uid.system"                    android:name="android.intent.category.LAUNCHER" />            </intent-filter>        </activity>    </application>    <uses-sdk        android:minSdkVersion="8" />    <uses-permission        android:name="android.intent.action.ACTION_SHUTDOWN" /></manifest>