Android 控件 - 最简单的 Notification、Application Context 应用于 Notification

最简单的 Notification

1、演示

java 复制代码

final String CHANNEL_ID = "my_test_channel";
int notificationId = 1;

NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
    CharSequence name = "my test channel";
    int importance = NotificationManager.IMPORTANCE_DEFAULT;

    NotificationChannel channel = new NotificationChannel(CHANNEL_ID, name, importance);

    notificationManager.createNotificationChannel(channel);
}

Notification notification = new NotificationCompat.Builder(this, CHANNEL_ID)
        .setContentTitle("系统通知")
        .setContentText("Hello World")
        .setSmallIcon(R.drawable.ic_notification)
        .build();

notificationManager.notify(notificationId, notification);

java 复制代码

NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

2、解读

java 复制代码

NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

获取通知管理器

java 复制代码

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {

    ...

}

如果系统版本大于 Android 8.0（API 26），必须创建通知渠道才能发送通知

java 复制代码

CharSequence name = "my test channel";
int importance = NotificationManager.IMPORTANCE_DEFAULT;

NotificationChannel channel = new NotificationChannel(CHANNEL_ID, name, importance);

创建通知渠道，所需参数：通知渠道的唯一标识符、通知渠道的显示名称、通知渠道的重要等级

java 复制代码

notificationManager.createNotificationChannel(channel);

将通知渠道注册到系统，这个操作只需在应用首次运行时执行一次即可

java 复制代码

Notification notification = new NotificationCompat.Builder(this, CHANNEL_ID)

创建通知，传入通知渠道的唯一标识符，指明该通知属于哪个通知渠道

java 复制代码

.setContentTitle("系统通知")
.setContentText("Hello World")
.setSmallIcon(R.drawable.ic_notification)

设置通知的标题，设置通知的正文内容，设置通知的图标

java 复制代码

notificationManager.notify(notificationId, notification);

发送通知，传入通知的唯一标识符

Application Context 应用于 Notification

1、演示

java 复制代码

Context context = getApplicationContext();

final String CHANNEL_ID = "my_test_channel";

NotificationManager notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
    NotificationChannel channel = new NotificationChannel(CHANNEL_ID, "my test channel", NotificationManager.IMPORTANCE_DEFAULT);
    notificationManager.createNotificationChannel(channel);
}

Notification notification = new NotificationCompat.Builder(context, CHANNEL_ID)
        .setContentTitle("系统通知")
        .setContentText("Hello World")
        .setSmallIcon(R.drawable.ic_notification)
        .build();

notificationManager.notify(1, notification);

java 复制代码

Context context = getApplicationContext();

final String CHANNEL_ID = "my_test_channel";

NotificationManager notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
    NotificationChannel channel = new NotificationChannel(CHANNEL_ID, "my test channel", NotificationManager.IMPORTANCE_DEFAULT);
    notificationManager.createNotificationChannel(channel);
}

Intent intent = new Intent(context, TargetActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TOP);
PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, intent, PendingIntent.FLAG_IMMUTABLE);

Notification notification = new NotificationCompat.Builder(context, CHANNEL_ID)
        .setContentTitle("系统通知")
        .setContentText("Hello World")
        .setSmallIcon(R.drawable.ic_notification)
        .setContentIntent(pendingIntent)
        .build();

notificationManager.notify(1, notification);

2、小结

通知系统会持有 Notification Builder 中的 Context
如果使用 Activity Context，即使 Activity 被销毁，通知系统仍会持有它的引用
通知的生命周期通常比 Activity 更长，即使应用在后台，通知也应能正常显示
Application Context 能保证通知系统在整个应用生命周期内正常工作