我无法改变这种感觉：安卓开发人员再次推出了新功能，并让所有人对如何使用该功能感到茫然。
我说的是安卓 O 中的通知渠道。
多年来，我一直在使用兼容性支持库来避免处理特定平台细节，即：NotificationCompat。
现在，Builder 要求我提供一个通知渠道 ID，这很好，但完全让我自己创建这样的渠道。 我找不到任何用于创建渠道的兼容性支持，也找不到在正确时间创建它们的合理方法。
文档简单地说明应该在“某个地方”进行创建，而且“可能不是在发布通知时”。 但我应该做什么？我讨厌为简单的任务编写特定版本的代码 - 这就是我使用兼容性库的原因。
有人有处理它的建议吗？每次想要显示通知时创建它们是否“昂贵”？
这是我在Android O上生成通知并保持向后兼容的解决方案：
String idChannel = "my_channel_01";
Intent mainIntent;
mainIntent = new Intent(context, LauncherActivity.class);
PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, mainIntent, 0);
NotificationManager mNotificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
NotificationChannel mChannel = null;
// The id of the channel.
int importance = NotificationManager.IMPORTANCE_HIGH;
NotificationCompat.Builder builder = new NotificationCompat.Builder(context, null);
builder.setContentTitle(context.getString(R.string.app_name))
.setSmallIcon(getNotificationIcon())
.setContentIntent(pendingIntent)
.setContentText(context.getString(R.string.alarm_notification) + ManagementDate.getIstance().hourFormat.format(getAlarm(context, 0)));
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
mChannel = new NotificationChannel(idChannel, context.getString(R.string.app_name), importance);
// Configure the notification channel.
mChannel.setDescription(context.getString(R.string.alarm_notification));
mChannel.enableLights(true);
mChannel.setLightColor(Color.RED);
mChannel.setVibrationPattern(new long[]{100, 200, 300, 400, 500, 400, 300, 200, 400});
mNotificationManager.createNotificationChannel(mChannel);
} else {
builder.setContentTitle(context.getString(R.string.app_name))
.setPriority(NotificationCompat.PRIORITY_HIGH)
.setColor(ContextCompat.getColor(context, R.color.transparent))
.setVibrate(new long[]{100, 250})
.setLights(Color.YELLOW, 500, 5000)
.setAutoCancel(true);
}
mNotificationManager.notify(1, builder.build());
这并不像你想象的那么昂贵！你需要做的就是创建一个通知渠道并将其绑定到通知上。
有两种方法可以解决这个问题，但无论哪种方法，你都需要创建一个具有特定通道ID的通知渠道。
NotificationManager mNotificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
String id = "my_channel_01";
int importance = NotificationManager.IMPORTANCE_LOW;
NotificationChannel mChannel = new NotificationChannel(id, name,importance);
mChannel.enableLights(true);
mNotificationManager.createNotificationChannel(mChannel);
第一种方法是在构造函数中设置通知渠道：
Notification notification = new Notification.Builder(MainActivity.this , id).setContentTitle("Title");
mNotificationManager.notify("your_notification_id", notification);
第二种方式是通过Notificiation.Builder.setChannelId()设置通道。
Notification notification = new Notification.Builder(MainActivity.this).setContentTitle("Title").
setChannelId(id);
mNotificationManager.notify("your_notification_id", notification);
如果您想要支持 Android 的旧版本（< Oreo），我们可以使用 NotificationHelper 来包装 NotificationManager，并创建和构建 Notification.Builder 实例，如下所示：
/**
* Helper class to manage notification channels, and create notifications.
* <p>
* Created by teocci.
*
* @author teocci@yandex.com on 2018-Oct-02
*/
public class NotificationHelper extends ContextWrapper
{
public static final String NOTIFICATION_CHANNEL_PRIMARY = "notification_channel_primary";
public static final int NOTIFICATION_ID_PRIMARY = 1100;
private NotificationManager manager;
/**
* Registers notification channels, which can be used later by individual notifications.
*
* @param ctx The application context
*/
public NotificationHelper(Context ctx)
{
super(ctx);
// For API 26+ create notification channels
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
NotificationChannel channel = new NotificationChannel(NOTIFICATION_CHANNEL_PRIMARY,
getString(R.string.channel_name),
NotificationManager.IMPORTANCE_DEFAULT
);
channel.setLightColor(Color.BLUE);
channel.setLockscreenVisibility(Notification.VISIBILITY_PRIVATE);
channel.setDescription(getString(R.string.channel_description));
getManager().createNotificationChannel(channel);
}
}
/**
* Cancel a previously shown notification. If it's transient, the view
* will be hidden. If it's persistent, it will be removed from the status
* bar.
*
* @param id The ID of the notification
*/
public void remove(int id){
manager.cancel(id);
}
/**
* Get a notification of type 1
* <p>
* Provide the builder rather than the notification it's self as useful for making notification
* changes.
*
* @return the builder as it keeps a reference to the notification (since API 24)
*/
public Notification getNotification()
{
return getNotification(getTitle(), getBody()).build();
}
/**
* Get a notification of type 1
* <p>
* Provide the builder rather than the notification it's self as useful for making notification
* changes.
*
* @param title the title of the notification
* @param body the body text for the notification
* @return the builder as it keeps a reference to the notification (since API 24)
*/
public Notification.Builder getNotification(String title, String body)
{
Notification.Builder builder = new Notification.Builder(getApplicationContext())
.setOngoing(true) // Persistent notification!
.setAutoCancel(true)
.setTicker(title)
.setContentTitle(title)
.setContentText(body)
.setSmallIcon(getSmallIcon());
// Set the Channel ID for Android O.
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
builder.setChannelId(NOTIFICATION_CHANNEL_PRIMARY); // Channel ID
}
return builder;
}
/**
* Send a notification.
*
* @param id The ID of the notification
* @param notification The notification object
*/
public void notify(int id, Notification.Builder notification)
{
getManager().notify(id, notification.build());
}
/**
* Get the notification manager.
* <p>
* Utility method as this helper works with it a lot.
*
* @return The system service NotificationManager
*/
private NotificationManager getManager()
{
if (manager == null) {
manager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
}
return manager;
}
/**
* Get the small icon for this app
*
* @return The small icon resource id
*/
private int getSmallIcon()
{
return R.drawable.ic_smart_audio_noti_icon;
}
/**
* Get the notification title for this app
*
* @return The notification title as string
*/
private String getTitle()
{
return getString(R.string.notification_title);
}
/**
* Get the notification content for this app
*
* @return The notification content as string
*/
private String getBody()
{
return getString(R.string.notification_content);
}
}
@Override
public void onCreate()
{
...
notificationHelper = new NotificationHelper(this);
notificationHelper.notify(NotificationHelper.NOTIFICATION_ID_PRIMARY, "App is running");
...
}
@Override
public void onDestroy()
{
notificationHelper.remove(NotificationHelper.NOTIFICATION_ID_PRIMARY)
}
这里有一种替代方案，使用反射创建通知渠道，因此您可以将compileSdkVersion设置为低于26的版本。
private void createNotificationChannel(NotificationManager notificationManager) {
// Channel details
String channelId = "myChannelId";
String channelName = "Notifications";
// Channel importance (3 means default importance)
int channelImportance = 3;
try {
// Get NotificationChannel class via reflection (only available on devices running Android O or newer)
Class notificationChannelClass = Class.forName("android.app.NotificationChannel");
// Get NotificationChannel constructor
Constructor<?> notificationChannelConstructor = notificationChannelClass.getDeclaredConstructor(String.class, CharSequence.class, int.class);
// Instantiate new notification channel
Object notificationChannel = notificationChannelConstructor.newInstance(channelId, channelName, channelImportance);
// Get notification channel creation method via reflection
Method createNotificationChannelMethod = notificationManager.getClass().getDeclaredMethod("createNotificationChannel", notificationChannelClass);
// Invoke method on NotificationManager, passing in the channel object
createNotificationChannelMethod.invoke(notificationManager, notificationChannel);
// Log success to console
Log.d("MyApp", "Notification channel created successfully");
}
catch (Exception exc) {
// Log exception to console
Log.e("MyApp", "Creating notification channel failed", exc);
}
}
当您构建通知时，只需调用NotificationCompat.Builder的.setChannelId()方法：
builder.setChannelId("myChannelId");
注意: 您需要在 build.gradle 文件中将你的 appcompat-v7 库更新到版本 26.x.x:
compile 'com.android.support:appcompat-v7:26.1.0'
使用NotificationChannel非常简单。
NotificationChannel实际上将多个通知分组到通道中。它基本上为用户提供了更多的通知行为控制。您可以在使用示例 | Working with Notification Channel中了解有关Notification Channel及其实现的更多信息。
创建Notification Channel
// This is the Notification Channel ID. More about this in the next section
public static final String NOTIFICATION_CHANNEL_ID="channel_id";
//User visible Channel Name
public static final String CHANNEL_NAME="Notification Channel";
// Importance applicable to all the notifications in this Channel
int importance=NotificationManager.IMPORTANCE_DEFAULT;
//Notification channel should only be created for devices running Android 26
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
NotificationChannel notificationChannel = new NotificationChannel(NOTIFICATION_CHANNEL_ID, CHANNEL_NAME, importance);
//Boolean value to set if lights are enabled for Notifications from this Channel
notificationChannel.enableLights(true);
//Boolean value to set if vibration is enabled for Notifications from this Channel
notificationChannel.enableVibration(true);
//Sets the color of Notification Light
notificationChannel.setLightColor(Color.GREEN);
//Set the vibration pattern for notifications. Pattern is in milliseconds with the format {delay,play,sleep,play,sleep...}
notificationChannel.setVibrationPattern(new long[]{500,500,500,500,500});
//Sets whether notifications from these Channel should be visible on Lockscreen or not
notificationChannel.setLockscreenVisibility(
Notification.VISIBILITY_PUBLIC);
}
// Creating the Channel
NotificationManager notificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
notificationManager.createNotificationChannel(notificationChannel);
现在，在创建通知时，只需将频道 ID 传递给如下所示的通知构建器构造函数即可
//We pass the unique channel id as the second parameter in the constructor
NotificationCompat.Builder notificationCompatBuilder=new NotificationCompat.Builder(this,NOTIFICATION_CHANNEL_ID);
//Title for your notification
notificationCompatBuilder.setContentTitle("This is title");
//Subtext for your notification
notificationCompatBuilder.setContentText("This is subtext");
//Small Icon for your notificatiom
notificationCompatBuilder.setSmallIcon(R.id.icon);
//Large Icon for your notification
notificationCompatBuilder.setLargeIcon( BitmapFactory.decodeResource(getResources(),R.id.icon));
notificationManager.notify( NOTIFICATION_ID,notificationCompatBuilder.build());
通过这个通知，它将成为在第一步创建的通知渠道的一部分，并且其行为现在将与渠道设置相关。