<?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">
<Button android:id="@+id/btn" 
android:text="设置闹钟"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.ljq.activity" android:versionCode="1"
android:versionName="1.0">
<application android:icon="@drawable/icon"
android:label="@string/app_name">
<activity android:name=".MainActivity"
android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category
android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".AlarmActivity" />
<!-- android:process=":remote": 新开一个进程 -->
<receiver android:name=".AlarmReceiver" android:process=":remote"/>
</application>
<uses-sdk android:minSdkVersion="7" />
</manifest>

package com.ljq.activity;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;

public class AlarmReceiver extends BroadcastReceiver{

@Override
public void onReceive(Context context, Intent intent) {
Intent i=new Intent(context, AlarmActivity.class);
i.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
context.startActivity(i);
}
}

package com.ljq.activity;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.DialogInterface.OnClickListener;
import android.os.Bundle;


public class AlarmActivity extends Activity {

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

//显示对话框
new AlertDialog.Builder(AlarmActivity.this).
setTitle("闹钟").//设置标题
setMessage("时间到了！").//设置内容
setPositiveButton("知道了", new OnClickListener(){//设置按钮
public void onClick(DialogInterface dialog, int which) {
AlarmActivity.this.finish();//关闭Activity
}
}).create().show();


}



}

import java.util.Calendar;

import android.app.Activity;
import android.app.AlarmManager;
import android.app.Dialog;
import android.app.PendingIntent;
import android.app.TimePickerDialog;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TimePicker;
import android.widget.Toast;

public class MainActivity extends Activity{
private Button btn=null;
private AlarmManager alarmManager=null;
Calendar cal=Calendar.getInstance();
final int DIALOG_TIME = 0; //设置对话框id

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

alarmManager=(AlarmManager)getSystemService(Context.ALARM_SERVICE);
btn=(Button)findViewById(R.id.btn);
btn.setOnClickListener(new View.OnClickListener(){
public void onClick(View view) {
showDialog(DIALOG_TIME);//显示时间选择对话框
}
});

}

@Override
protected Dialog onCreateDialog(int id) {
Dialog dialog=null;
switch (id) {
case DIALOG_TIME:
dialog=new TimePickerDialog(
this,
new TimePickerDialog.OnTimeSetListener(){
public void onTimeSet(TimePicker timePicker, int hourOfDay,int minute) {
Calendar c=Calendar.getInstance();//获取日期对象 
c.setTimeInMillis(System.currentTimeMillis()); //设置Calendar对象
c.set(Calendar.HOUR, hourOfDay); //设置闹钟小时数
c.set(Calendar.MINUTE, minute); //设置闹钟的分钟数
c.set(Calendar.SECOND, 0); //设置闹钟的秒数
c.set(Calendar.MILLISECOND, 0); //设置闹钟的毫秒数
Intent intent = new Intent(MainActivity.this, AlarmReceiver.class); //创建Intent对象
PendingIntent pi = PendingIntent.getBroadcast(MainActivity.this, 0, intent, 0); //创建PendingIntent
//alarmManager.set(AlarmManager.RTC_WAKEUP, c.getTimeInMillis(), pi); //设置闹钟
alarmManager.set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), pi); //设置闹钟，当前时间就唤醒
Toast.makeText(MainActivity.this, "闹钟设置成功", Toast.LENGTH_LONG).show();//提示用户
}
},
cal.get(Calendar.HOUR_OF_DAY),
cal.get(Calendar.MINUTE),
false);

break;
}
return dialog;
}
}