public class MainActivity extends Activity {

 private AlarmManager alarmManager;
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  //获取AlarmManager对象
  alarmManager= (AlarmManager) getSystemService(ALARM_SERVICE);
 }

 public void btn(View view) {
  final Calendar c = Calendar.getInstance();
  TimePickerDialog dialog = new TimePickerDialog(this,
    new OnTimeSetListener() {
   //延迟意图（即闹钟的意图）
   PendingIntent paIntent = PendingIntent.getActivity(MainActivity.this, 
     1, new Intent(MainActivity.this,SecondActivity.class), 
     PendingIntent.FLAG_UPDATE_CURRENT);
     @Override
     public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
      //设置你所选择的时间
      c.set(Calendar.HOUR_OF_DAY, hourOfDay);
      c.set(Calendar.MINUTE, minute);
      //第一个参数指定闹钟服务的类型
      //第二个参数指定闹钟间隔的时间
      //第三个参数指跳转闹钟的延迟意图
      alarmManager.set(AlarmManager.RTC_WAKEUP, c.getTimeInMillis(), paIntent);
     }
    }, 
    //闹钟的初始值（时和分）
    c.get(Calendar.HOUR_OF_DAY),
    c.get(Calendar.MINUTE), 
    true);
  dialog.show();
 }
}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:paddingBottom="@dimen/activity_vertical_margin"
 android:paddingLeft="@dimen/activity_horizontal_margin"
 android:paddingRight="@dimen/activity_horizontal_margin"
 android:paddingTop="@dimen/activity_vertical_margin"
 tools:context="com.example.alarmmanager.MainActivity" >

 <Button
  android:onClick="btn"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:text="@string/btntext" />

</RelativeLayout>