【转】Android广播事件机制及应用(实现简单的定时提醒功能)

Admin · 发表于 2013-2-26 15:53:22

涉及的主要内容：1) AlarmManager 和 PendingIntent 2) BroadReceiver 3) Notification and NotificationManager

  1.Android广播事件机制
   Android的广播事件处理类似于普通的事件处理。不同之处在于，后者是靠点击按钮这样的组件行为来触发，而前者是通过构建Intent对象，使用sentBroadcast()方法来发起一个系统级别的事件广播来传递信息。广播事件的接收是通过定义一个继承Broadcast Receiver的类实现的，继承该类后覆盖其onReceive()方法,在该方法中响应事件。Android系统中定义了很多标准的Broadcast Action来响应系统广播事件。例如：ACTION_TIME_CHANGED（时间改变时触发）。但是，我们也可以自己定义Broadcast Receiver接收广播事件。
  2.实现简单的定时提醒功能
   主要包括三部分部分：
   1）定时 - 通过定义Activity发出广播
   2）接收广播 - 通过实现BroadcastReceiver接收广播
   3) 提醒 - 并通过Notification提醒用户
   现在我们来具体实现这三部分：
   2.1 如何定时，从而发出广播呢？
   现在的手机都有闹钟的功能，我们可以利用系统提供的闹钟功能，来定时，即发出广播。具体地，在Android开发中可以用AlarmManager来实现。
   AlarmManager 提供了一种系统级的提示服务，允许你安排在某个时间执行某一个服务。
   AlarmManager的使用步骤说明如下：
   1）获得AlarmManager实例： AlarmManager对象一般不直接实例化，而是通过Context.getSystemService(Context.ALARM_SERVIECE) 方法获得
   2）定义一个PendingIntent来发出广播。
   3）调用AlarmManager的相关方法，设置定时、重复提醒等功能。
   详细代码如下(ReminderSetting.java)：

Java代码
package com.Reminder;
import java.util.Calendar;
import android.app.Activity;
import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
/**
* trigger the Broadcast event and set the alarm
*/
public class ReminderSetting extends Activity {
Button btnEnable;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
/* create a button. When you click the button, the alarm clock is enabled */
btnEnable=(Button)findViewById(R.id.btnEnable);
btnEnable.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
setReminder(true);
}
});
}
/**
* Set the alarm
*
* @param b whether enable the Alarm clock or not
*/
private void setReminder(boolean b) {
// get the AlarmManager instance
AlarmManager am= (AlarmManager) getSystemService(ALARM_SERVICE);
// create a PendingIntent that will perform a broadcast
PendingIntent pi= PendingIntent.getBroadcast(ReminderSetting.this, 0, new Intent(this,MyReceiver.class), 0);
if(b){
// just use current time as the Alarm time.
Calendar c=Calendar.getInstance();
// schedule an alarm
am.set(AlarmManager.RTC_WAKEUP, c.getTimeInMillis(), pi);
}
else{
// cancel current alarm
am.cancel(pi);
}
}
}

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package com.Reminder;
import java.util.Calendar;
import android.app.Activity;
import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
/**
* trigger the Broadcast event and set the alarm
*/
public class ReminderSetting extends Activity {
Button btnEnable;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
/* create a button. When you click the button, the alarm clock is enabled */
btnEnable=(Button)findViewById(R.id.btnEnable);
btnEnable.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
setReminder(true);
}
});
}
/**
* Set the alarm
*
* @param b whether enable the Alarm clock or not
*/
private void setReminder(boolean b) {
// get the AlarmManager instance
AlarmManager am= (AlarmManager) getSystemService(ALARM_SERVICE);
// create a PendingIntent that will perform a broadcast
PendingIntent pi= PendingIntent.getBroadcast(ReminderSetting.this, 0, new Intent(this,MyReceiver.class), 0);
if(b){
// just use current time as the Alarm time.
Calendar c=Calendar.getInstance();
// schedule an alarm
am.set(AlarmManager.RTC_WAKEUP, c.getTimeInMillis(), pi);
}
else{
// cancel current alarm
am.cancel(pi);
}
}
}

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2.2 接收广播
新建一个class 继承BroadcastReceiver，并实现onReceive()方法。当BroadcastReceiver接收到广播后，就会去执行OnReceive()方法。所以，我们在OnReceive()方法中加上代码，当接收到广播后就跳到显示提醒信息的Activity。具体代码如下( MyReceiver.java)：

package com.Reminder;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
/**
* Receive the broadcast and start the activity that will show the alarm
*/
public class MyReceiver extends BroadcastReceiver {
/**
* called when the BroadcastReceiver is receiving an Intent broadcast.
*/
@Override
public void onReceive(Context context, Intent intent) {
/* start another activity - MyAlarm to display the alarm */
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
intent.setClass(context, MyAlarm.class);
context.startActivity(intent);
}
}

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package com.Reminder;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
/**
* Receive the broadcast and start the activity that will show the alarm
*/
public class MyReceiver extends BroadcastReceiver {
/**
* called when the BroadcastReceiver is receiving an Intent broadcast.
*/
@Override
public void onReceive(Context context, Intent intent) {
/* start another activity - MyAlarm to display the alarm */
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
intent.setClass(context, MyAlarm.class);
context.startActivity(intent);
}
}

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注意：创建完BroadcastReceiver后，需要在AndroidManifest.xml中注册：
<receiver android:name=".MyReceiver">
   <intent-filter>
      <action android:name= "com.Reminder.MyReceiver" />
</intent-filter>
</receiver>
2.3 提醒功能
   新建一个Activity，我们在这个Activity中通过Android的Notification对象来提醒用户。我们将添加提示音,一个TextView来显示提示内容和并一个button来取消提醒。
   其中，创建Notification主要包括：
   1）获得系统级得服务NotificationManager，通过 Context.getSystemService(NOTIFICATION_SERVICE)获得。
   2）实例化Notification对象，并设置各种我们需要的属性，比如:设置声音。
   3）调用NotificationManager的notify()方法显示Notification
   详细代码如下：MyAlarm.java

package com.Reminder;
import android.app.Activity;
import android.app.Notification;
import android.app.NotificationManager;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore.Audio;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
/**
* Display the alarm information
*/
public class MyAlarm extends Activity {
/**
* An identifier for this notification unique within your application
*/
public static final int NOTIFICATION_ID=1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.my_alarm);
// create the instance of NotificationManager
final NotificationManager nm=(NotificationManager) getSystemService(NOTIFICATION_SERVICE);
// create the instance of Notification
Notification n=new Notification();
/* set the sound of the alarm. There are two way of setting the sound */
// n.sound=Uri.parse("file:///sdcard/alarm.mp3");
n.sound=Uri.withAppendedPath(Audio.Media.INTERNAL_CONTENT_URI, "20");
// Post a notification to be shown in the status bar
nm.notify(NOTIFICATION_ID, n);
/* display some information */
TextView tv=(TextView)findViewById(R.id.tvNotification);
tv.setText("Hello, it's time to bla bla...");
/* the button by which you can cancel the alarm */
Button btnCancel=(Button)findViewById(R.id.btnCancel);
btnCancel.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
nm.cancel(NOTIFICATION_ID);
finish();
}
});
}
}

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package com.Reminder;
import android.app.Activity;
import android.app.Notification;
import android.app.NotificationManager;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore.Audio;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
/**
* Display the alarm information
*/
public class MyAlarm extends Activity {
/**
* An identifier for this notification unique within your application
*/
public static final int NOTIFICATION_ID=1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.my_alarm);
// create the instance of NotificationManager
final NotificationManager nm=(NotificationManager) getSystemService(NOTIFICATION_SERVICE);
// create the instance of Notification
Notification n=new Notification();
/* set the sound of the alarm. There are two way of setting the sound */
// n.sound=Uri.parse("file:///sdcard/alarm.mp3");
n.sound=Uri.withAppendedPath(Audio.Media.INTERNAL_CONTENT_URI, "20");
// Post a notification to be shown in the status bar
nm.notify(NOTIFICATION_ID, n);
/* display some information */
TextView tv=(TextView)findViewById(R.id.tvNotification);
tv.setText("Hello, it's time to bla bla...");
/* the button by which you can cancel the alarm */
Button btnCancel=(Button)findViewById(R.id.btnCancel);
btnCancel.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
nm.cancel(NOTIFICATION_ID);
finish();
}
});
}
}

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注：关于提示音设置（Notification.sound），可以参考：http://developer.android.com/guide/topics/ui/notifiers/notifications.html 中的相关部分。

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【转】Android广播事件机制及应用(实现简单的定时提醒功能)

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