Ошибка developer warning for package

If you get this error should be paid attention to 2 items and them order:

1. NotificationChannel mChannel = new NotificationChannel(id, name, importance);
2. builder = new NotificationCompat.Builder(context, id);

Also NotificationManager notifManager and NotificationChannel mChannel are created only once.

There are required setters for Notification:

• builder.setContentTitle() // required
• .setSmallIcon() // required
• .setContentText() // required

See example:

private NotificationManager notifManager;
public void createNotification(String aMessage, Context context) {
    final int NOTIFY_ID = 0; // ID of notification
    String id = context.getString(R.string.default_notification_channel_id); // default_channel_id
    String title = context.getString(R.string.default_notification_channel_title); // Default Channel
    Intent intent;
    PendingIntent pendingIntent;
    NotificationCompat.Builder builder;
    if (notifManager == null) {
        notifManager = (NotificationManager)context.getSystemService(Context.NOTIFICATION_SERVICE);
    }
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        int importance = NotificationManager.IMPORTANCE_HIGH;
        NotificationChannel mChannel = notifManager.getNotificationChannel(id);
        if (mChannel == null) {
            mChannel = new NotificationChannel(id, title, importance);
            mChannel.enableVibration(true);
            mChannel.setVibrationPattern(new long[]{100, 200, 300, 400, 500, 400, 300, 200, 400});
            notifManager.createNotificationChannel(mChannel);
        }
        builder = new NotificationCompat.Builder(context, id);
        intent = new Intent(context, MainActivity.class);
        intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_SINGLE_TOP);
        pendingIntent = PendingIntent.getActivity(context, 0, intent, 0);
        builder.setContentTitle(aMessage)                            // required
               .setSmallIcon(android.R.drawable.ic_popup_reminder)   // required
               .setContentText(context.getString(R.string.app_name)) // required
               .setDefaults(Notification.DEFAULT_ALL)
               .setAutoCancel(true)
               .setContentIntent(pendingIntent)
               .setTicker(aMessage)
               .setVibrate(new long[]{100, 200, 300, 400, 500, 400, 300, 200, 400});
    }
    else {
        builder = new NotificationCompat.Builder(context, id);
        intent = new Intent(context, MainActivity.class);
        intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_SINGLE_TOP);
        pendingIntent = PendingIntent.getActivity(context, 0, intent, 0);
        builder.setContentTitle(aMessage)                            // required
               .setSmallIcon(android.R.drawable.ic_popup_reminder)   // required
               .setContentText(context.getString(R.string.app_name)) // required
               .setDefaults(Notification.DEFAULT_ALL)
               .setAutoCancel(true)
               .setContentIntent(pendingIntent)
               .setTicker(aMessage)
               .setVibrate(new long[]{100, 200, 300, 400, 500, 400, 300, 200, 400})
               .setPriority(Notification.PRIORITY_HIGH);
    }
    Notification notification = builder.build();
    notifManager.notify(NOTIFY_ID, notification);
}

How to completely solve Android8.0 (API26 +) and the above version of the simulator Run Notad Times Developer Warning for Package «com.example.my» failed to post notification on channel ‘Default’ See log for more detail

Error problem

—- Andr Wind QQ1652102745

First, run the notification bar (Notification) error in the simulator Demo:

PS: Declaring that my mainActivity program code is not any problem, this error occurred.

Second, the normal operation after solving the problem:

1 Effect 1 (Android8.0 API26 below version of the effect)NOTIFICAMPAT.BUILDER class to implement the announcement

②Effect 2 (Android 8.0 API26 and above) renderingsNotificationCompat.Builder classTo achieve the announcement

Third, solution:

1, analyze the reason

This error is mainly because we generally use the NotificationsCompat.Builder class to implement the announcement.

NotificationCompat.Builder builder=new NotificationCompat.Builder(getApplicationContext(),"default");

Run the notification bar on your phone before Android8.0 (API26) Either shields the notification bar (prevent harassment), or all normal operation notification bar. We don’t have problems with NOTIFICAPMPAT.BUILDER class.

Since Android 8.0 (API26), in order to make users better experience, then new channel functions (that is, NotificationChannel class)The channel function (that is, the NotificationChannel class) enables the user to have the right to choose, the user can set the shield-independent navigation notice, and the user can set an important notice.

  NotificationChannel Mchannel = New NotificationChannel (ID, "123", Importance); // Establish a notification bar channel class (you need to have ID, important properties)

That is to say we realize the fence function in Android8.0 (API26) and above.NOTIFICATIONCOMPAT.BUILDER class, it will not function properly, which will cause us to appear error:

Developer warning for package «com.example.my»Failed to post notification on channel ‘default’ See log for more details

Error problem

2, solution:

1 If your emulator runs system version is used android8.0 or lessNOTIFICAMPAT.BUILDER class to implement the announcement

Layout design Source code: https://www.cnblogs.com/adf520/p/12601872.html

2-1, MainActivity.java function realizes source code

  1 package com.example.my;
  2 
  3 import androidx.annotation.RequiresApi;
  4 import androidx.appcompat.app.AppCompatActivity;
  5 import androidx.core.app.NotificationCompat;
  6 
  7 import android.app.Notification;
  8 import android.app.NotificationChannel;
  9 import android.app.NotificationManager;
 10 import android.content.Context;
 11 import android.content.ContextWrapper;
 12 import android.content.Intent;
 13 import android.content.pm.PackageManager;
 14 import android.graphics.Bitmap;
 15 import android.graphics.BitmapFactory;
 16 import android.graphics.Color;
 17 import android.os.Build;
 18 import android.os.Bundle;
 19 import android.provider.Settings;
 20 import android.text.Layout;
 21 import android.view.LayoutInflater;
 22 import android.view.View;
 23 import android.widget.Button;
 24 import android.widget.CheckBox;
 25 import android.widget.TextView;
 26 import android.widget.Toast;
 27 
 28 public class MainActivity extends AppCompatActivity implements View.OnClickListener {
 29 CheckBox cb1,cb2,cb3;
 30 Button pay;
 31 int count=0;
 32     @RequiresApi(api = Build.VERSION_CODES.O)
 33     @Override
 34     protected void onCreate(Bundle savedInstanceState) {
 35         super.onCreate(savedInstanceState);
 36         setContentView(R.layout.activity_main);
 37         
 38         cb1=findViewById(R.id.cb1);
 39         cb2=findViewById(R.id.cb2);
 40         cb3=findViewById(R.id.cb3);
 41         pay=findViewById(R.id.pay);
 42         pay.setOnClickListener(this);
 43 
 44 
 45     }
 46 
 47     @RequiresApi(api = Build.VERSION_CODES.O)
 48     @Override
 49     public void onClick(View v) {
 50         if (cb1.isChecked())
 51             count+=45;
 52         if (cb2.isChecked())
 53             count+=60;
 54         if (cb3.isChecked())
 55             count+=55;
 56 
 57 
 58 //        final NotificationManager manager = (NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);//Notification Bar Manager (get system service)
 59 //        String id = "channel_1"; //Custom Set Channel ID Property
 60 //        String description = "123";//Custom Set Channel Description Property
 61 //        int importance = NotificationManager.IMPORTANCE_HIGH;//Notification bar management Important prompt message sound setting
 62 //        /**
 63 //                  * Oreo does not have priority, use importance
 64 //                  * Importance_none Close Notification
 65 //                  * Importance_min opens the notification, not popping, but no prompt sound, no display in the status bar
 66 //                  * Importance_low opens notifications, no pop-up, does not post a tone, display in the status bar
 67 //                  * Importance_default opens notifications, no pop-up, prompt tone, display in the status bar
 68 //                  * Importance_high opens notification, pop-up, issue a tone, display in the status bar
 69 //         */
 70 //        NotificationChannel mChannel = new NotificationChannel(id, "123", importance);//Establish a notification bar channel class (you need to have ID, important properties)
 71 //// mchannel.setdescription (description); // Configure the properties of the notification channel
 72 //// mchannel.EnableLights (TRUE); // Setting the flashlight when notification (if Android device supports)
 73 //// mchannel.setlightcolor (color.red); // Set the flash color is red
 74 //// mchannel.enablevibration (TRUE); // Setting the vibration when the notification (if Android device supports)
 75 ////        mChannel.setVibrationPattern(new long[]{100, 200, 300, 400, 500, 400, 300, 200, 400});
 76 //       manager.createNotificationChannel(mChannel);////Finally create this notification channel in NotificationManager
 77 //        Notification notification = new Notification.Builder(this, id)//Create a Notification object.
 78 //                                .SETCONTENTTITLE ("Payment Notice")  //Set notification title
 79 //                .setSmallIcon(R.drawable.q)//Set notification small icon
 80 //                .setLargeIcon(BitmapFactory.decodeResource(getResources(), R.drawable.q))//Set notification big icon
 81 //                                .SETCONTENTTEXT ("You have paid" + count + "yuan")//Set the notification content
 82 //                .setAutoCancel(true)//Set automatic deletion notification
 83 //                .build();//Run
 84 //
 85 //        manager.notify((int) System.currentTimeMillis(),notification); //Notification column retain multiple notifications
 86 //        count=0;//Empty amount
 87 
 88 //
 89 //     LayoutInflater inflater=getLayoutInflater();
 90 //     View layout=inflater.inflate(R.layout.activity_main2,null);
 91 //     TextView tv= layout.findViewById(R.id.tv);
 92 //          TV.Settext ("You pay" + count + "yuan");
 93 //     Toast toast=new Toast(MainActivity.this);
 94 //     toast.setView(layout);
 95 //     toast.setDuration(Toast.LENGTH_SHORT);
 96 //     toast.show();
 97 //     count=0;
 98 
 99         
100 
101         //Step 1: Create a notification constructor NotificationCompat.Builder object.
102         NotificationCompat.Builder builder=new NotificationCompat.Builder(getApplicationContext(),"default");
103         //Step 2: Call the method settings of the NotificationCompat.Builder object notification related content.
104         builder.setSmallIcon(R.drawable.q);//Set notification small icon
105         builder.setLargeIcon(BitmapFactory.decodeResource(getResources(), R.drawable.q));//Set notification big icon
106         builder.setContentTitle("Payment Notification");//Set notification title
107         builder.setContentText("You have paid"+count+"yuan");//Set the notification content
108         builder.setAutoCancel(true);//Set automatic deletion notification
109         Notification notification=builder.build();//: Create a Notification object.
110         NotificationManager manager= (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);//Notification Bar Manager (get system service)
111 //        manager.notify(1,notification); //Notification bar keeps single notice
112         manager.notify((int) System.currentTimeMillis(),notification); //Notification column retain multiple notifications
113         count=0;//Empty amount
114 
116         
117     }
118 }

2 If your simulator runs system version is Android 8.0 and aboveNotificationChannel class to implement the announcement

2-1, MainActivity.java function realizes source code

  1 package com.example.my;
  2 
  3 import androidx.annotation.RequiresApi;
  4 import androidx.appcompat.app.AppCompatActivity;
  5 import androidx.core.app.NotificationCompat;
  6 
  7 import android.app.Notification;
  8 import android.app.NotificationChannel;
  9 import android.app.NotificationManager;
 10 import android.content.Context;
 11 import android.content.ContextWrapper;
 12 import android.content.Intent;
 13 import android.content.pm.PackageManager;
 14 import android.graphics.Bitmap;
 15 import android.graphics.BitmapFactory;
 16 import android.graphics.Color;
 17 import android.os.Build;
 18 import android.os.Bundle;
 19 import android.provider.Settings;
 20 import android.text.Layout;
 21 import android.view.LayoutInflater;
 22 import android.view.View;
 23 import android.widget.Button;
 24 import android.widget.CheckBox;
 25 import android.widget.TextView;
 26 import android.widget.Toast;
 27 
 28 public class MainActivity extends AppCompatActivity implements View.OnClickListener {
 29 CheckBox cb1,cb2,cb3;
 30 Button pay;
 31 int count=0;
 32     @RequiresApi(api = Build.VERSION_CODES.O)
 33     @Override
 34     protected void onCreate(Bundle savedInstanceState) {
 35         super.onCreate(savedInstanceState);
 36         setContentView(R.layout.activity_main);
 37 
 38         cb1=findViewById(R.id.cb1);
 39         cb2=findViewById(R.id.cb2);
 40         cb3=findViewById(R.id.cb3);
 41         pay=findViewById(R.id.pay);
 42         pay.setOnClickListener(this);
 43 
 44 
 45     }
 46 
 47     @RequiresApi(api = Build.VERSION_CODES.O)
 48     @Override
 49     public void onClick(View v) {
 50         if (cb1.isChecked())
 51             count+=45;
 52         if (cb2.isChecked())
 53             count+=60;
 54         if (cb3.isChecked())
 55             count+=55;
 56 
 57 
 58         final NotificationManager manager = (NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);//Notification Bar Manager (get system service)
 59         String id = "channel_1"; //Custom Set Channel ID Property
 60         String description = "123";//Custom Set Channel Description Property
 61         int importance = NotificationManager.IMPORTANCE_HIGH;//Notification bar management Important prompt message sound setting
 62         /**
 63                   * Oreo does not have priority, use importance
 64                   * Importance_none Close Notification
 65                   * Importance_min opens the notification, not popping, but no prompt sound, no display in the status bar
 66                   * Importance_low opens notifications, no pop-up, does not post a tone, display in the status bar
 67                   * Importance_default opens notifications, no pop-up, prompt tone, display in the status bar
 68                   * Importance_high opens notification, pop-up, issue a tone, display in the status bar
 69          */
 70         NotificationChannel mChannel = new NotificationChannel(id, "123", importance);//Establish a notification bar channel class (you need to have ID, important properties)
 71 //        mChannel.setDescription(description); //  Configuration Notification Channel properties
 72 //        mChannel.enableLights(true);//  Set the flashlight when notification (if Android device supports)
 73 //        mChannel.setLightColor(Color.RED);//Set the flash color for red
 74 //        mChannel.enableVibration(true);   //  Set the vibration when notification (if Android device supports)
 75 //        mChannel.setVibrationPattern(new long[]{100, 200, 300, 400, 500, 400, 300, 200, 400});
 76        manager.createNotificationChannel(mChannel);//// Finally create this notification channel in NotificationManager
 77         Notification notification = new Notification.Builder(this, id)//Create a Notification object.
 78                 .setContentTitle("Payment Notification")  //Set notification title
 79                 .setSmallIcon(R.drawable.q)//Set notification small icon
 80                 .setLargeIcon(BitmapFactory.decodeResource(getResources(), R.drawable.q))//Set notification big icon
 81                 .setContentText("You have paid"+count+"yuan")//Set the notification content
 82                 .setAutoCancel(true)//Set automatic deletion notification
 83                 .build();//run
 84 
 85         manager.notify((int) System.currentTimeMillis(),notification); //Notification column retain multiple notifications
 86         count=0;//Empty amount
 87 
 88 //
 89 //     LayoutInflater inflater=getLayoutInflater();
 90 //     View layout=inflater.inflate(R.layout.activity_main2,null);
 91 //     TextView tv= layout.findViewById(R.id.tv);
 92 //          TV.Settext ("You pay" + count + "yuan");
 93 //     Toast toast=new Toast(MainActivity.this);
 94 //     toast.setView(layout);
 95 //     toast.setDuration(Toast.LENGTH_SHORT);
 96 //     toast.show();
 97 //     count=0;
 98 
 99 
100 
101 //        //Step 1: Create a notification constructor NotificationCompat.Builder object.
102 //        NotificationCompat.Builder builder=new NotificationCompat.Builder(getApplicationContext(),"default");
103 //        //Step 2: Call the method settings of the NotificationCompat.Builder object notification related content.
104 //        builder.setSmallIcon(R.drawable.q);//Set notification small icon
105 //        builder.setLargeIcon(BitmapFactory.decodeResource(getResources(), R.drawable.q));//Set notification big icon
106 //                Builder.SetContentTitle ("Payment Notice");//Set notification title
107 //                Builder.setContentText ("You have paid" + count + "yuan");//Set the notification content
108 //        builder.setAutoCancel(true);//Set automatic deletion notification
109 //        Notification notification=builder.build();//: Create a Notification object.
110 //        NotificationManager manager= (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);//Notification Bar Manager (get system service)
111 //// manager.notify (1, notification); // Notification bar keeps a single notice
112 //        manager.notify((int) System.currentTimeMillis(),notification); //Notification column retain multiple notifications
113 //        count=0;//Empty amount
114 
115 
116 
117     }
118 }

The above code is only a reference, I hope to bring you help, I am Antife, thank you for your attention and support, there is a problem welcome to leave a message below; see the next one answer.

i was made up my mp3 player.

it’s working but i always got a toast message

enter image description here

so i think i need to notification channel in my code.

but i don’t know how to add code. help me !!

here is my code

public class MusicController extends MediaController {

public MusicController(Context c){
    super(c);
}

public void hide(){}
}

public class MusicService extends Service implements
    MediaPlayer.OnPreparedListener, MediaPlayer.OnErrorListener,
    MediaPlayer.OnCompletionListener {

//media player
private MediaPlayer player;
//song list
private ArrayList<Song> songs;
//current position
private int songPosn;
//binder
private final IBinder musicBind = new MusicBinder();
//title of current song
private String songTitle="";
//notification id
private static final int NOTIFY_ID=1;
//shuffle flag and random
private boolean shuffle=false;
private Random rand;

public void onCreate(){
    //create the service
    super.onCreate();
    //initialize position
    songPosn=0;
    //random
    rand=new Random();
    //create player
    player = new MediaPlayer();
    //initialize
    initMusicPlayer();
}

public void initMusicPlayer(){
    //set player properties
    player.setWakeMode(getApplicationContext(),
            PowerManager.PARTIAL_WAKE_LOCK);
    player.setAudioStreamType(AudioManager.STREAM_MUSIC);
    //set listeners
    player.setOnPreparedListener(this);
    player.setOnCompletionListener(this);
    player.setOnErrorListener(this);
}

//pass song list
public void setList(ArrayList<Song> theSongs){
    songs=theSongs;
}

//binder
public class MusicBinder extends Binder {
    MusicService getService() {
        return MusicService.this;
    }
}

//activity will bind to service
@Override
public IBinder onBind(Intent intent) {
    return musicBind;
}

//release resources when unbind
@Override
public boolean onUnbind(Intent intent){
    player.stop();
    player.release();
    return false;
}

//play a song
public void playSong(){
    //play
    player.reset();
    //get song
    Song playSong = songs.get(songPosn);
    //get title
    songTitle=playSong.getTitle();
    //get id
    long currSong = playSong.getID();
    //set uri
    Uri trackUri = ContentUris.withAppendedId(
            android.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
            currSong);
    //set the data source
    try{
        player.setDataSource(getApplicationContext(), trackUri);
    }
    catch(Exception e){
        Log.e("MUSIC SERVICE", "Error setting data source", e);
    }
    player.prepareAsync();
}

//set the song
public void setSong(int songIndex){
    songPosn=songIndex;
}

@Override
public void onCompletion(MediaPlayer mp) {
    //check if playback has reached the end of a track
    if(player.getCurrentPosition()>0){
        mp.reset();
        playNext();
    }
}

@Override
public boolean onError(MediaPlayer mp, int what, int extra) {
    Log.v("MUSIC PLAYER", "Playback Error");
    mp.reset();
    return false;
}

@Override
public void onPrepared(MediaPlayer mp) {
    //start playback
    mp.start();
    //notification
    Intent notIntent = new Intent(this, MainActivity.class);
    notIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
    PendingIntent pendInt = PendingIntent.getActivity(this, 0,
            notIntent, PendingIntent.FLAG_UPDATE_CURRENT);

    Notification.Builder builder = new Notification.Builder(this);

    builder.setContentIntent(pendInt)
            .setSmallIcon(R.drawable.android_music_player_play)
            .setTicker(songTitle)
            .setOngoing(true)
            .setContentTitle("Playing")
            .setContentText(songTitle);
    Notification not = builder.build();
    startForeground(NOTIFY_ID, not);
}

//playback methods
public int getPosn(){
    return player.getCurrentPosition();
}

public int getDur(){
    return player.getDuration();
}

public boolean isPng(){
    return player.isPlaying();
}

public void pausePlayer(){
    player.pause();
}

public void seek(int posn){
    player.seekTo(posn);
}

public void go(){
    player.start();
}

//skip to previous track
public void playPrev(){
    songPosn--;
    if(songPosn<0) songPosn=songs.size()-1;
    playSong();
}

//skip to next
public void playNext(){
    if(shuffle){
        int newSong = songPosn;
        while(newSong==songPosn){
            newSong=rand.nextInt(songs.size());
        }
        songPosn=newSong;
    }
    else{
        songPosn++;
        if(songPosn>=songs.size()) songPosn=0;
    }
    playSong();
}

@Override
public void onDestroy() {
    stopForeground(true);
}

//toggle shuffle
public void setShuffle(){
    if(shuffle) shuffle=false;
    else shuffle=true;
}

}

public class MainActivity extends Activity implements MediaPlayerControl {

//song list variables
private ArrayList<Song> songList;
private ListView songView;

//service
private MusicService musicSrv;
private Intent playIntent;
//binding
private boolean musicBound=false;

//controller
private MusicController controller;

//activity and playback pause flags
private boolean paused=false, playbackPaused=false;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
        if (checkSelfPermission(Manifest.permission.READ_EXTERNAL_STORAGE)
                != PackageManager.PERMISSION_GRANTED) {

            requestPermissions(new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},1);


            return;
        }}

    //retrieve list view
    songView = (ListView)findViewById(R.id.song_list);
    //instantiate list
    songList = new ArrayList<Song>();
    //get songs from device
    getSongList();
    //sort alphabetically by title
    Collections.sort(songList, new Comparator<Song>(){
        public int compare(Song a, Song b){
            return a.getTitle().compareTo(b.getTitle());
        }
    });
    //create and set adapter
    SongAdapter songAdt = new SongAdapter(this, songList);
    songView.setAdapter(songAdt);

    //setup controller
    setController();
}

//connect to the service
private ServiceConnection musicConnection = new ServiceConnection(){

    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
        MusicBinder binder = (MusicBinder)service;
        //get service
        musicSrv = binder.getService();
        //pass list
        musicSrv.setList(songList);
        musicBound = true;
    }

    @Override
    public void onServiceDisconnected(ComponentName name) {
        musicBound = false;
    }
};

//start and bind the service when the activity starts
@Override
protected void onStart() {
    super.onStart();
    if(playIntent==null){
        playIntent = new Intent(this, MusicService.class);
        bindService(playIntent, musicConnection, Context.BIND_AUTO_CREATE);
        startService(playIntent);
    }
}

//user song select
public void songPicked(View view){
    musicSrv.setSong(Integer.parseInt(view.getTag().toString()));
    musicSrv.playSong();
    if(playbackPaused){
        setController();
        playbackPaused=false;
    }
    controller.show(0);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    //menu item selected
    switch (item.getItemId()) {
        case R.id.action_shuffle:
            musicSrv.setShuffle();
            break;
        case R.id.action_end:
            stopService(playIntent);
            musicSrv=null;
            System.exit(0);
            break;
    }
    return super.onOptionsItemSelected(item);
}

//method to retrieve song info from device
public void getSongList(){
    //query external audio
    ContentResolver musicResolver = getContentResolver();
    Uri musicUri = android.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
    Cursor musicCursor = musicResolver.query(musicUri, null, null, null, null);
    //iterate over results if valid
    if(musicCursor!=null && musicCursor.moveToFirst()){
        //get columns
        int titleColumn = musicCursor.getColumnIndex
                (android.provider.MediaStore.Audio.Media.TITLE);
        int idColumn = musicCursor.getColumnIndex
                (android.provider.MediaStore.Audio.Media._ID);
        int artistColumn = musicCursor.getColumnIndex
                (android.provider.MediaStore.Audio.Media.ARTIST);
        //add songs to list
        do {
            long thisId = musicCursor.getLong(idColumn);
            String thisTitle = musicCursor.getString(titleColumn);
            String thisArtist = musicCursor.getString(artistColumn);
            songList.add(new Song(thisId, thisTitle, thisArtist));
        }
        while (musicCursor.moveToNext());
    }
}

@Override
public boolean canPause() {
    return true;
}

@Override
public boolean canSeekBackward() {
    return true;
}

@Override
public boolean canSeekForward() {
    return true;
}

@Override
public int getAudioSessionId() {
    return 0;
}

@Override
public int getBufferPercentage() {
    return 0;
}

@Override
public int getCurrentPosition() {
    if(musicSrv!=null && musicBound && musicSrv.isPng())
        return musicSrv.getPosn();
    else return 0;
}

@Override
public int getDuration() {
    if(musicSrv!=null && musicBound && musicSrv.isPng())
        return musicSrv.getDur();
    else return 0;
}

@Override
public boolean isPlaying() {
    if(musicSrv!=null && musicBound)
        return musicSrv.isPng();
    return false;
}

@Override
public void pause() {
    playbackPaused=true;
    musicSrv.pausePlayer();
}

@Override
public void seekTo(int pos) {
    musicSrv.seek(pos);
}

@Override
public void start() {
    musicSrv.go();
}

//set the controller up
private void setController(){
    controller = new MusicController(this);
    //set previous and next button listeners
    controller.setPrevNextListeners(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            playNext();
        }
    }, new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            playPrev();
        }
    });
    //set and show
    controller.setMediaPlayer(this);
    controller.setAnchorView(findViewById(R.id.song_list));
    controller.setEnabled(true);
}

private void playNext(){
    musicSrv.playNext();
    if(playbackPaused){
        setController();
        playbackPaused=false;
    }
    controller.show(0);
}

private void playPrev(){
    musicSrv.playPrev();
    if(playbackPaused){
        setController();
        playbackPaused=false;
    }
    controller.show(0);
}

@Override
protected void onPause(){
    super.onPause();
    paused=true;
}

@Override
protected void onResume(){
    super.onResume();
    if(paused){
        setController();
        paused=false;
    }
}

@Override
protected void onStop() {
    controller.hide();
    super.onStop();
}

@Override
protected void onDestroy() {
    stopService(playIntent);
    musicSrv=null;
    super.onDestroy();
   }
}

how can i fix it ? ! help me !

On Android 8.1 API 27 notification does not display

I get Toast on Android 8.1 API 27:

Developer warning for package «my_package_name»
Failed to post notification on …

Logcat includes next strings:

Notification: Use of stream types is deprecated for operations other
than volume control

W/Notification: See the documentation of setSound() for what to use
instead with android.media.AudioAttributes to qualify your playback
use case

E/NotificationService: No Channel found for pkg=my_package_name

The full information in the Toast and in Logcat can help in the localization this problem.

Solution 1:

If you get this error should be paid attention to 2 items and them order:

1. NotificationChannel mChannel = new NotificationChannel(id, name, importance);
2. builder = new NotificationCompat.Builder(context, id);

Also NotificationManager notifManager and NotificationChannel mChannel are created only once.

There are required setters for Notification:

• builder.setContentTitle() // required
• .setSmallIcon() // required
• .setContentText() // required

See example:

private NotificationManager notifManager;
public void createNotification(String aMessage, Context context) {
    final int NOTIFY_ID = 0; // ID of notification
    String id = context.getString(R.string.default_notification_channel_id); // default_channel_id
    String title = context.getString(R.string.default_notification_channel_title); // Default Channel
    Intent intent;
    PendingIntent pendingIntent;
    NotificationCompat.Builder builder;
    if (notifManager == null) {
        notifManager = (NotificationManager)context.getSystemService(Context.NOTIFICATION_SERVICE);
    }
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        int importance = NotificationManager.IMPORTANCE_HIGH;
        NotificationChannel mChannel = notifManager.getNotificationChannel(id);
        if (mChannel == null) {
            mChannel = new NotificationChannel(id, title, importance);
            mChannel.enableVibration(true);
            mChannel.setVibrationPattern(new long[]{100, 200, 300, 400, 500, 400, 300, 200, 400});
            notifManager.createNotificationChannel(mChannel);
        }
        builder = new NotificationCompat.Builder(context, id);
        intent = new Intent(context, MainActivity.class);
        intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_SINGLE_TOP);
        pendingIntent = PendingIntent.getActivity(context, 0, intent, 0);
        builder.setContentTitle(aMessage)                            // required
               .setSmallIcon(android.R.drawable.ic_popup_reminder)   // required
               .setContentText(context.getString(R.string.app_name)) // required
               .setDefaults(Notification.DEFAULT_ALL)
               .setAutoCancel(true)
               .setContentIntent(pendingIntent)
               .setTicker(aMessage)
               .setVibrate(new long[]{100, 200, 300, 400, 500, 400, 300, 200, 400});
    }
    else {
        builder = new NotificationCompat.Builder(context, id);
        intent = new Intent(context, MainActivity.class);
        intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_SINGLE_TOP);
        pendingIntent = PendingIntent.getActivity(context, 0, intent, 0);
        builder.setContentTitle(aMessage)                            // required
               .setSmallIcon(android.R.drawable.ic_popup_reminder)   // required
               .setContentText(context.getString(R.string.app_name)) // required
               .setDefaults(Notification.DEFAULT_ALL)
               .setAutoCancel(true)
               .setContentIntent(pendingIntent)
               .setTicker(aMessage)
               .setVibrate(new long[]{100, 200, 300, 400, 500, 400, 300, 200, 400})
               .setPriority(Notification.PRIORITY_HIGH);
    }
    Notification notification = builder.build();
    notifManager.notify(NOTIFY_ID, notification);
}

Solution 2:

Andy’s answer is working however I wanted to avoid to deprecated Builder and follow the FireBase Quickstart Project. I just added code before notify from manager.

String channelId = "default_channel_id";
String channelDescription = "Default Channel";
// Since android Oreo notification channel is needed.
//Check if notification channel exists and if not create one
if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
    NotificationChannel notificationChannel = notificationManager.getNotificationChannel(channelId);
    if (notificationChannel == null) {
        int importance = NotificationManager.IMPORTANCE_HIGH; //Set the importance level
        notificationChannel = new NotificationChannel(channelId, channelDescription, importance);
        notificationChannel.setLightColor(Color.GREEN); //Set if it is necesssary
        notificationChannel.enableVibration(true); //Set if it is necesssary
        notificationManager.createNotificationChannel(notificationChannel);
    }
}

//notificationManager.notify as usual

Edit:
They removed the channel exist check from example I am not sure why.

Solution 3:

I have set channel id, but notification still not shown.

Finally i found my problem is had not invoke «setContentText()» method.

It was really help me that @Andy Sander mentioned «required setters»!

here are required setters for Notification on Android 8 Oreo API 26 and later:

builder.setContentTitle() // required
.setSmallIcon() // required
.setContentText() // required
.setChannelId(id) // required for deprecated in API level >= 26 constructor .Builder(this)