Đời cơ bản là buồn

The following assumes that you have already basic knowledge in Android development. Please check the Android development tutorial to learn the basics.

2. Notification Manager

2.1. Notification Manager

Android allows to put notification into the titlebar of your application. The user can expand the notification bar and by selecting the notification the user can trigger another activity.

2.2. Setting up Notifications

Notifications in Android are represented by the Notification class. To create notifications you use the NotificationManager class which can be received from the Context, e.g. an activity or a service, via the getSystemService() method.

NotificationManager notificationManager = (NotificationManager) 
  getSystemService(NOTIFICATION_SERVICE);

The Notification.Builder provides an builder interface to create an Notification object. You use a PendingIntent to specify the action which should be performed once the user select the notification. Notification.Builder allows to add up two three buttons with definable actions to the notification.

// Prepare intent which is triggered if the
// notification is selected

Intent intent = new Intent(this, NotificationReceiver.class);
PendingIntent pIntent = PendingIntent.getActivity(this, 0, intent, 0);

// Build notification
// Actions are just fake
Notification noti = new Notification.Builder(this)
        .setContentTitle("New mail from " + "test@gmail.com")
        .setContentText("Subject")
        .setSmallIcon(R.drawable.icon)
        .setContentIntent(pIntent)
        .addAction(R.drawable.icon, "Call", pIntent)
        .addAction(R.drawable.icon, "More", pIntent)
        .addAction(R.drawable.icon, "And more", pIntent).build();
    
  
NotificationManager notificationManager = 
  (NotificationManager) getSystemService(NOTIFICATION_SERVICE);

// Hide the notification after its selected
noti.flags |= Notification.FLAG_AUTO_CANCEL;

notificationManager.notify(0, noti);

Showing the Notification bar with the created notification

Android 4.1 supports expandable notifications. In addition to normal notification view it is possible to define a big view which gets shown when notification is expanded. There are three styles to be used with the big view: big picture style, big text style, Inbox style. The following code demonstrates the usage of the BigTextStyle() which allows to use up to 256 dp.

String longText = "...";

Notification noti = new Notification.Builder(this).
.....
.setStyle(new Notification.BigTextStyle().bigText(longText))

2.3. Canceling Notifications

The user can dismiss all notification or if you set your notification to auto-cancel it is also removed once the user selects it.
You can also call the cancel() for a specific notification ID on the NotificationManager. The cancelAll() method call removes all of the notifications you previously issued.

3. Pending Intent

A PendingIntent is a token that you give to another application (e.g. Notification Manager, Alarm Manager or other 3rd party applications), which allows this other application to use the permissions of your application to execute a predefined piece of code.
To perform a broadcast via a pending intent so get a PendingIntent via the getBroadcast() method of the PendingIntent class. To perform an activity via an pending intent you receive the activity via PendingIntent.getActivity().

4. Example: NotificationManager

Create a new project called de.vogella.android.notificationmanager with the activity class called CreateNotificationActivity. This activity should use the main.xml layout file.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <Button
        android:id="@+id/button1"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:onClick="createNotification"
        android:text="Create Notification" >
    </Button>

</LinearLayout>

Create the following result.xml layout file.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="This is the result activity opened from the notification" >
    </TextView>

</LinearLayout>

Create a new activity called NotificationReceiverActivity with the following coding. Don't forget to register the activity in the AndroidManfest.mf.

package de.vogella.android.notificationmanager;

import android.app.Activity;
import android.os.Bundle;

public class NotificationReceiverActivity extends Activity {
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.result);
  }
}

Change the CreateNotificationActivity class to the following coding.

package de.vogella.android.notificationmanager;

import android.app.Activity;
import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;

public class CreateNotificationActivity extends Activity {
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
  }

  public void createNotification(View view) {
    // Prepare intent which is triggered if the
    // notification is selected
    Intent intent = new Intent(this, NotificationReceiverActivity.class);
    PendingIntent pIntent = PendingIntent.getActivity(this, 0, intent, 0);

    // Build notification
    // Actions are just fake
    Notification noti = new Notification.Builder(this)
        .setContentTitle("New mail from " + "test@gmail.com")
        .setContentText("Subject").setSmallIcon(R.drawable.icon)
        .setContentIntent(pIntent)
        .addAction(R.drawable.icon, "Call", pIntent)
        .addAction(R.drawable.icon, "More", pIntent)
        .addAction(R.drawable.icon, "And more", pIntent).build();
    NotificationManager notificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
    // Hide the notification after its selected
    noti.flags |= Notification.FLAG_AUTO_CANCEL;

    notificationManager.notify(0, noti);

  }
}

Run your application and press the button. A new notification is created. If you select it your second activity will be displayed.

5. Thank you

Please help me to support this article:

6. Questions and Discussion

Before posting questions, please see the vogella FAQ. If you have questions or find an error in this article please use the www.vogella.com Google Group. I have created a short list how to create good questions which might also help you.

7. Links and Literature

7.1. Source Code

Source Code of Examples

7.2. Android Resources

Android Location API and Google Maps
Android and Networking
Android Homepage
Android Issues / Bugs
Android Google Groups

7.3. vogella Resources

vogella Training Android and Eclipse Training from the vogella team
Android Tutorial Introduction to Android Programming
GWT Tutorial Program in Java and compile to JavaScript and HTML
Eclipse RCP Tutorial Create native applications in Java
JUnit Tutorial Test your application
Git Tutorial Put everything you have under distributed version control system

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Đời cơ bản là buồn

Thứ Tư, 10 tháng 4, 2013

Android Notifications - Tutorial

Lars Vogel

1. Prerequisites for this tutorial