public class AlarmReceiver extends BroadcastReceiver {
  @Override
  public void onReceive(Context arg0, Intent arg1) {
    // TODO Auto-generated method stub
    Toast.makeText(arg0, "你设置的闹铃时间到了", Toast.LENGTH_LONG).show();
  }
}

<receiver
  android:name=".AlarmReceiver"
  android:process=":remote">
</receiver>

package cn.edu.pku;
import java.util.Calendar;
import android.app.Activity;
import android.app.AlarmManager;
import android.app.PendingIntent;
import android.app.TimePickerDialog;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.TimePicker;
public class AlarmActivity extends Activity {
  /** Called when the activity is first created. */
  Button mButton1;
  Button mButton2;
  TextView mTextView;
  Calendar calendar;
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    calendar=Calendar.getInstance();
    mTextView=(TextView)findViewById(R.id.TextView01);
    mButton1=(Button)findViewById(R.id.Button01);
    mButton2=(Button)findViewById(R.id.Button02);
    mButton1.setOnClickListener(new View.OnClickListener() {
      public void onClick(View v) {
        // TODO Auto-generated method stub
        calendar.setTimeInMillis(System.currentTimeMillis());
        int hour = calendar.get(Calendar.HOUR_OF_DAY);
        int minute = calendar.get(Calendar.MINUTE);
        new TimePickerDialog(AlarmActivity.this, new TimePickerDialog.OnTimeSetListener() {
          public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
            // TODO Auto-generated method stub
            calendar.setTimeInMillis(System.currentTimeMillis());
            calendar.set(Calendar.HOUR_OF_DAY, hourOfDay);
            calendar.set(Calendar.MINUTE, minute);
            calendar.set(Calendar.SECOND, 0);
            calendar.set(Calendar.MILLISECOND, 0);
            Intent intent = new Intent(AlarmActivity.this, AlarmReceiver.class);
            PendingIntent pendingIntent = PendingIntent.getBroadcast(AlarmActivity.this, 0, intent, 0);
            AlarmManager alarmManager = (AlarmManager)getSystemService(ALARM_SERVICE);
            alarmManager.set(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), pendingIntent);
            alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis() + (10 * 1000),
                (24 * 60 * 60 * 1000), pendingIntent);
            String tmps = "设置闹钟时间为" + format(hourOfDay) + ":" +format(minute);
            mTextView.setText(tmps);
          }
        }, hour, minute, true).show();
      }
    });
    mButton2.setOnClickListener(new View.OnClickListener() {
      public void onClick(View v) {
        // TODO Auto-generated method stub
        Intent intent = new Intent(AlarmActivity.this, AlarmReceiver.class);
        PendingIntent pendingIntent = PendingIntent.getBroadcast(AlarmActivity.this, 0, intent, 0);
        AlarmManager alarmManager = (AlarmManager)getSystemService(ALARM_SERVICE);
        alarmManager.cancel(pendingIntent);
        mTextView.setText("闹铃已取消！");
      }
    });
  }
  private String format(int time){
    String str = "" + time;
    if(str.length() == 1){
      str = "0" + str;
    }
    return str;
  }
}