截至2019年7月
Android compileSdkVersion 28，buildToolsVersion 28.0.3和firebase-messaging：19.0.1
在研究了所有其他其他StackOverflow问题和答案并尝试了无数过时的解决方案许多小时之后，该解决方案设法在以下3种情况下显示通知：
-应用位于前台：
通过MyFirebaseMessagingService类的onMessageReceived方法接收通知
-应用已被终止（它未在后台运行）：
FCM自动将通知发送到通知托盘。当用户触摸通知时，将通过调用清单中具有android.intent.category.LAUNCHER的活动来启动应用。您可以通过在onCreate（）方法中使用getIntent（）。getExtras（）来获取通知的数据部分。
-应用程序在后台：
FCM自动将通知发送到通知托盘。当用户触摸通知时，通过启动清单中具有android.intent.category.LAUNCHER的活动，将应用程序置于前台。由于我的应用程序在该活动中具有launchMode =“ singleTop”，因此不会调用onCreate（）方法，因为已经创建了同一类的一个活动，而是调用了该类的onNewIntent（）方法，并且您获得了数据的一部分通过使用intent.getExtras（）获得通知。
步骤：1-如果您定义应用的主要活动是这样的：
<activity
android:name=".MainActivity"
android:label="@string/app_name"
android:largeHeap="true"
android:screenOrientation="portrait"
android:launchMode="singleTop">
<intent-filter>
<action android:name=".MainActivity" />
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
2-将这些行添加到MainActivity.class的onCreate（）方法中
Intent i = getIntent();
Bundle extras = i.getExtras();
if (extras != null) {
for (String key : extras.keySet()) {
Object value = extras.get(key);
Log.d(Application.APPTAG, "Extras received at onCreate: Key: " + key + " Value: " + value);
}
String title = extras.getString("title");
String message = extras.getString("body");
if (message!=null && message.length()>0) {
getIntent().removeExtra("body");
showNotificationInADialog(title, message);
}
}
和这些方法相同的MainActivity.class：
@Override
public void onNewIntent(Intent intent){
//called when a new intent for this class is created.
// The main case is when the app was in background, a notification arrives to the tray, and the user touches the notification
super.onNewIntent(intent);
Log.d(Application.APPTAG, "onNewIntent - starting");
Bundle extras = intent.getExtras();
if (extras != null) {
for (String key : extras.keySet()) {
Object value = extras.get(key);
Log.d(Application.APPTAG, "Extras received at onNewIntent: Key: " + key + " Value: " + value);
}
String title = extras.getString("title");
String message = extras.getString("body");
if (message!=null && message.length()>0) {
getIntent().removeExtra("body");
showNotificationInADialog(title, message);
}
}
}
private void showNotificationInADialog(String title, String message) {
// show a dialog with the provided title and message
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle(title);
builder.setMessage(message);
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
}
3-创建类MyFirebase，如下所示：
package com.yourcompany.app;
import android.content.Intent;
import android.util.Log;
import com.google.firebase.messaging.FirebaseMessagingService;
import com.google.firebase.messaging.RemoteMessage;
public class MyFirebaseMessagingService extends FirebaseMessagingService {
public MyFirebaseMessagingService() {
super();
}
@Override
public void onMessageReceived(RemoteMessage remoteMessage) {
Log.d(Application.APPTAG, "myFirebaseMessagingService - onMessageReceived - message: " + remoteMessage);
Intent dialogIntent = new Intent(this, NotificationActivity.class);
dialogIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
dialogIntent.putExtra("msg", remoteMessage);
startActivity(dialogIntent);
}
}
4-创建一个新的类NotificationActivity.class像这样：
package com.yourcompany.app;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.util.Log;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.view.ContextThemeWrapper;
import com.google.firebase.messaging.RemoteMessage;
public class NotificationActivity extends AppCompatActivity {
private Activity context;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
context = this;
Bundle extras = getIntent().getExtras();
Log.d(Application.APPTAG, "NotificationActivity - onCreate - extras: " + extras);
if (extras == null) {
context.finish();
return;
}
RemoteMessage msg = (RemoteMessage) extras.get("msg");
if (msg == null) {
context.finish();
return;
}
RemoteMessage.Notification notification = msg.getNotification();
if (notification == null) {
context.finish();
return;
}
String dialogMessage;
try {
dialogMessage = notification.getBody();
} catch (Exception e){
context.finish();
return;
}
String dialogTitle = notification.getTitle();
if (dialogTitle == null || dialogTitle.length() == 0) {
dialogTitle = "";
}
AlertDialog.Builder builder = new AlertDialog.Builder(new ContextThemeWrapper(context, R.style.myDialog));
builder.setTitle(dialogTitle);
builder.setMessage(dialogMessage);
builder.setPositiveButton(getResources().getString(R.string.accept), new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
}
}
5-将这些行添加到标签内的应用清单中
<service
android:name=".MyFirebaseMessagingService"
android:exported="false">
<intent-filter>
<action android:name="com.google.firebase.MESSAGING_EVENT" />
</intent-filter>
</service>
<meta-data android:name="com.google.firebase.messaging.default_notification_channel_id" android:value="@string/default_notification_channel_id"/>
<activity android:name=".NotificationActivity"
android:theme="@style/myDialog"> </activity>
<meta-data
android:name="com.google.firebase.messaging.default_notification_icon"
android:resource="@drawable/notification_icon"/>
<meta-data
android:name="com.google.firebase.messaging.default_notification_color"
android:resource="@color/color_accent" />
6-将这些行添加到Application.java onCreate（）方法或MainActivity.class onCreate（）方法中：
// notifications channel creation
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
// Create channel to show notifications.
String channelId = getResources().getString("default_channel_id");
String channelName = getResources().getString("General announcements");
NotificationManager notificationManager = getSystemService(NotificationManager.class);
notificationManager.createNotificationChannel(new NotificationChannel(channelId,
channelName, NotificationManager.IMPORTANCE_LOW));
}
做完了
现在，要使其在上述3个方案中都能正常工作，您必须通过以下方式从Firebase Web控制台发送通知：
在“通知”部分中：通知标题=要在通知对话框中显示的标题（可选）通知文本=要向用户显示的消息（必填）然后在“目标”部分：App =您的Android应用程序，在“其他选项”部分：Android通知频道= default_channel_id自定义数据键：标题值：（此处与“通知”部分的“标题”字段中的文本相同）键：主体值：（此处与“通知”部分的“消息”字段中的文本相同）键：click_action值：.MainActivity声音=失效
期限= 4周
您可以使用带有Google Play的API 28在仿真器中对其进行调试。
编码愉快！
Not getting messages here? See why this may be: goo.gl/39bRNJ。与以下答案一样，该解决方案可在带有通知和数据有效负载的消息