Develop Reference

App crashed : Attempt to invoke virtual method on a null object reference

I'm working on an app that shows status bar notifications to the user. The user can turn on and off the notifications and the notification sound by 2 switches. I run the app and tried to switch on the notification and it crashed. The stack trace said on line 60(i marked it so that youcan find it easily):
Attempt to invoke virtual method 'void android.app.NotificationManager.notify(int, android.app.Notification)' on a null object reference
import android.annotation.TargetApi;
import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Intent;
import android.os.Build;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.CompoundButton;
import android.widget.Switch;
import androidx.annotation.RequiresApi;
import static android.app.PendingIntent.getActivity;
import static android.content.Context.NOTIFICATION_SERVICE;
public class Settings extends AppCompatActivity {
Switch simpleswitch1;
Switch simpleswitch2;
private Notification notification;
NotificationManager manager;
Notification myNotication;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_settings);
simpleswitch1 = (Switch) findViewById(R.id.simpleswitch1);
simpleswitch2 = (Switch) findViewById(R.id.simpleswitch2);
simpleswitch1.setChecked(false);
simpleswitch2.setChecked(false);
simpleswitch1.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
#RequiresApi(api = Build.VERSION_CODES.JELLY_BEAN)
#Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
if (isChecked){{
Intent intent = new Intent("com.rj.notitfications.SECACTIVITY");
PendingIntent pendingIntent = PendingIntent.getActivity(Settings.this, 1, intent, 0);
Notification.Builder builder = new Notification.Builder(Settings.this);
builder.setAutoCancel(false);
builder.setTicker("this is ticker text");
builder.setContentTitle("WhatsApp Notification");
builder.setContentText("You have a new message");
builder.setSmallIcon(R.drawable.notification);
builder.setContentIntent(pendingIntent);
builder.setOngoing(true);
builder.setSubText("This is subtext...");
builder.setNumber(100);
builder.build();
myNotication = builder.getNotification();
manager.notify(11, myNotication);//THE ERROR LED HERE
}
}
simpleswitch2.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
#Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
if (isChecked){
notification.defaults |= Notification.DEFAULT_SOUND;
}}
});}});}}

The reason you're getting a crash is because you don't initialize the manager property. You can do it before you use manager like this:
manager = getSystemService(Context.NOTIFICATION_SERVICE)

setRepeating of AlarmManager is only triggering for the first time and not repeating

I am trying to implement an alarm manager that will be called every day to update a database. I started by trying the set Function of the alarmManager and it worked to trigger the alarm at a certain time. Then I moved on to try and use setRepeating to trigger the alarm on a daily basis. The setRepeating function which is done to Repeat every minute just for testing is only working the first time and is not doing the function repeatedly.
Here is my BroadcastReceiver:
package com.example.bleh.myapplication;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.util.Log;
import android.widget.TextView;
import android.widget.Toast;
import com.example.bleh.myapplication.DB.AppDatabase;
import com.example.bleh.myapplication.DB.Plan;
import com.example.bleh.myapplication.DB.User;
import com.example.bleh.myapplication.Utils1.FormulaUtils;
import com.github.lzyzsd.circleprogress.DonutProgress;
public class AlarmReceiver extends BroadcastReceiver {
private static final String DEBUG_TAG = "AlarmReceiver";
public AppDatabase mydb;
Plan plan;
#Override
public void onReceive(Context context, Intent intent) {
Toast.makeText(context, "Alarm worked.", Toast.LENGTH_LONG).show();
mydb = AppDatabase.getInstance(context);
final long planid = intent.getExtras().getLong("planid");
final long userid = intent.getExtras().getLong("uid");
final String requirements = intent.getExtras().getString("requirements");
Log.wtf("PlanId: ",planid+"");
Log.wtf("UserId: ",userid+"");
Log.wtf("Requirements",requirements);
plan = mydb.getPlanDao(context).getPlanById((int) planid);
final User user = mydb.getUserDao(context).getUserById((int) userid);
plan.setCurrentWeight(FormulaUtils.reCalculateWeight(plan.getCurrentWeight(), Double.parseDouble(requirements)));
plan.setBmr(Double.parseDouble(FormulaUtils.calculateBmr(user.getSex(), plan.getCurrentWeight(), user.getHeight(), user.getBirthDay())));
plan.setNbOfDays(plan.getNbOfDays() - 1);
mydb.getPlanDao(context).update(plan);
String requirement = FormulaUtils.CalulcateDailyRequirements(plan.getWorkoutPerWeek(), plan.getBmr());
String day = plan.getNbOfDays() + "";
float progress = 0F;
// Start feature2 activity with updated data
Intent updateFeature2Intent = new Intent(context, feature2.class);
updateFeature2Intent.addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP | Intent.FLAG_ACTIVITY_CLEAR_TOP); // Add this flag
updateFeature2Intent.putExtra("requirement", requirement);
updateFeature2Intent.putExtra("day", day);
updateFeature2Intent.putExtra("progress", progress);
context.startActivity(updateFeature2Intent);
}
}
Here is my Feature Activity:
package com.example.bleh.myapplication;
import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.graphics.Color;
import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.TimePicker;
import android.widget.Toast;
import com.example.bleh.myapplication.DB.AppDatabase;
import com.example.bleh.myapplication.DB.Exercise;
import com.example.bleh.myapplication.DB.Food;
import com.example.bleh.myapplication.DB.Plan;
import com.example.bleh.myapplication.DB.User;
import com.example.bleh.myapplication.Utils1.FormulaUtils;
import com.github.lzyzsd.circleprogress.DonutProgress;
import java.text.DecimalFormat;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.List;
import java.util.TimeZone;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
public class feature2 extends AppCompatActivity {
public AppDatabase mydb;
TextView BMR,requirements,days;
Button addfood,addex,nextday;
LinearLayout mainLayout;
Button Meas,Bluetooth;
DonutProgress donutProgress;
Plan plan;
// Add this method
#Override
protected void onNewIntent(Intent intent) {
super.onNewIntent(intent);
// Get data from intent
String requirement = intent.getStringExtra("requirement");
String day = intent.getStringExtra("day");
float progress = intent.getFloatExtra("progress", 0F);
// Update UI
TextView requirements = findViewById(R.id.requirements);
TextView Days = findViewById(R.id.days);
DonutProgress dailyProgress = findViewById(R.id.donut_progress);
requirements.setText(requirement);
Days.setText(day);
dailyProgress.setProgress(progress);
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_feature2);
Intent intent = getIntent();
requirements = findViewById(R.id.requirements);
donutProgress = findViewById(R.id.donut_progress);
days = findViewById(R.id.days);
final long planid = intent.getExtras().getLong("planid");
final long userid = intent.getExtras().getLong("uid");
mydb = AppDatabase.getInstance(feature2.this);
plan = mydb.getPlanDao(feature2.this).getPlanById((int) planid);
try {
requirements.setText(FormulaUtils.CalulcateDailyRequirements(plan.getWorkoutPerWeek(), plan.getBmr()));
}
catch (Exception ex)
{
Log.wtf("There is no plan","!");
}
Intent intent1 = new Intent(this, AlarmReceiver.class);
intent1.putExtra("uid", userid);
intent1.putExtra("planid", planid);
intent1.putExtra("requirements",requirements.getText().toString());
Calendar updateTime = Calendar.getInstance();
updateTime.setTimeZone(TimeZone.getTimeZone("GMT"));
updateTime.set(Calendar.HOUR_OF_DAY, 8);
updateTime.set(Calendar.MINUTE, 3);
updateTime.set(Calendar.SECOND,0);
Date milliseconds = updateTime.getTime();
long millis = milliseconds.getTime();
PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0,
intent1, PendingIntent.FLAG_ONE_SHOT);
AlarmManager alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);
alarmManager.setRepeating(AlarmManager.RTC, millis ,60000, pendingIntent);
Toast.makeText(this, "Alarm set", Toast.LENGTH_LONG).show();
}
}
Here is my Manifest Part:
<receiver android:name=".AlarmReceiver"
android:enabled="true"
android:exported="true">
</receiver>

I had encountered this problem earlier with my app
Repeating alarms will not trigger for api > 23 if phone is in idle state. Refer Schedue Repeating alarms
Doze mode also blocks the alarm.
What you can do is to use setExact and setExactAndAllowWhileIdle for api > 23 and use your own logic to repeat the alarm.
if (Build.VERSION.SDK_INT >= 23) {
alarmManager.setExactAndAllowWhileIdle(RTC_WAKEUP, calendar.getTimeInMillis(), alarmIntent);
} else {
alarmManager.setExact(RTC_WAKEUP, calendar.getTimeInMillis(), alarmIntent);
}
Trigger the alarm again in the receiver or in the activity which is triggered by the alarm manager.
In your case set the alarm again in the AlarmReceiver for next day.

I'd recommend you to read about Doze mode and this topic. Also you can use this lib by Evernote. It helps to handle scheduling of background tasks.

Hot to set alarm and notification when new message arrives from Firebase Realtime Database to android Device [duplicate]

This question already has answers here:
How to sound notifications sound when new Message arrives from Firebase Realtime Data base
(4 answers)
Closed 4 years ago.
I'm using firebase data base to create my chat applicaiton. Now that I have sucessfully completed my chat application, but when new message arrives I would like to notify user with sound and NOtification in Notification bar even when the app is not running.
I used the below code to do that
NotificationCompat.Builder builder = new NotificationCompat.Builder(this)
.setSmallIcon(R.drawable.ic_launcher)
.setContentTitle("Notifications Example")
.setContentText("This is a test notification");
Intent notificationIntent = new Intent(this, MenuScreen.class);
PendingIntent contentIntent = PendingIntent.getActivity(this, 0, notificationIntent,
PendingIntent.FLAG_UPDATE_CURRENT);
builder.setContentIntent(contentIntent);
builder.setAutoCancel(true);
builder.setLights(Color.BLUE, 500, 500);
long[] pattern = {500,500,500,500,500,500,500,500,500};
builder.setVibrate(pattern);
builder.setStyle(new NotificationCompat.InboxStyle());
builder.setSound(Settings.System.DEFAULT_NOTIFICATION_URI)
NotificationManager manager = (NotificationManager)
getSystemService(Context.NOTIFICATION_SERVICE);
manager.notify(1, builder.build());
But it only set alarm when i open the chat activity, then aftearwards when new message arrives it does nothing.
Here is my chat activity code
package com.nepalpolice.mnemonics.chat;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.graphics.Color;
import android.media.AudioManager;
import android.media.RingtoneManager;
import android.media.ToneGenerator;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.net.Uri;
import android.os.Bundle;
import android.os.Vibrator;
import android.provider.Settings;
import android.support.annotation.Nullable;
import android.support.v4.app.NotificationCompat;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import com.google.firebase.database.ChildEventListener;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.iid.FirebaseInstanceId;
import com.google.firebase.messaging.RemoteMessage;
import com.nepalpolice.mnemonics.R;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
/**
* Created by filipp on 6/28/2016.
*/
public class Chat_Room extends AppCompatActivity{
private Button btn_send_msg;
private EditText input_msg;
private TextView chat_conversation;
private Toolbar mainToolbar;
private String user_name,room_name;
private DatabaseReference root ;
private String temp_key;
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.chat_room);
btn_send_msg = (Button) findViewById(R.id.btn_send);
input_msg = (EditText) findViewById(R.id.msg_input);
chat_conversation = (TextView) findViewById(R.id.textView);
user_name = getIntent().getExtras().get("user_name").toString();
room_name = getIntent().getExtras().get("room_name").toString();
mainToolbar = (Toolbar) findViewById(R.id.main_chat);
setSupportActionBar(mainToolbar);
getSupportActionBar().setTitle(" Room - "+room_name);
root = FirebaseDatabase.getInstance().getReference().child(room_name);
btn_send_msg.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Map<String,Object> map = new HashMap<String, Object>();
temp_key = root.push().getKey();
root.updateChildren(map);
DatabaseReference message_root = root.child(temp_key);
Map<String,Object> map2 = new HashMap<String, Object>();
map2.put("name",user_name);
map2.put("msg",input_msg.getText().toString());
message_root.updateChildren(map2);
input_msg.getText().clear();
}
});
root.addChildEventListener(new ChildEventListener() {
#Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
append_chat_conversation(dataSnapshot);
}
#Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
append_chat_conversation(dataSnapshot);
}
#Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
#Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
private String chat_msg,chat_user_name;
private void append_chat_conversation(DataSnapshot dataSnapshot) {
Iterator i = dataSnapshot.getChildren().iterator();
while (i.hasNext()){
chat_msg = (String) ((DataSnapshot)i.next()).getValue();
chat_user_name = (String) ((DataSnapshot)i.next()).getValue();
chat_conversation.append(chat_user_name +" : "+chat_msg +" \n");
}
}
}
Here is my Firebase Data structure file
Firebase Data Structure
Any help is appreciated. Thanks in advance.

If you are using FCM, you need to understand this part of the doc before proceeding:
The onMessageReceived is provided for most message types, with the following exceptions which are listed below:
Notification messages delivered when your app is in the background. In this case, the notification is delivered to the device’s system tray. A user tap on a notification opens the app launcher by default
Messages with both notification and data payload, both background and foreground. In this case, the notification is delivered to the device’s system tray, and the data payload is delivered in the extras of the intent of your launcher Activity.
So if you need to decide the type of payload you re sending to the android device. You may want to go for Message with both Notifications and data payload so that onMessageRecieved() is invoked at all times.
You can find more details Here

cannot find symbol in push Notification error "notificationBuilder.setContentText(currentText).setNumber(++numMessages);"

Below is my code,I am using cordova Push Notification,I am trying to merge multiple push notification but its give me error, for single notification its working, i am unable to find what went wrong, kindly suggest
package org.apache.cordova.firebase;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.media.RingtoneManager;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.NotificationCompat;
import android.util.Log;
import android.text.TextUtils;
import com.google.firebase.messaging.FirebaseMessagingService;
import com.google.firebase.messaging.RemoteMessage;
import java.util.Map;
import java.util.Random;
private void sendNotification(String id, String title, String messageBody, Map<String, String> data, boolean showNotification)
{
Bundle bundle = new Bundle();
int notifyID = 1;
for (String key : data.keySet()) {
bundle.putString(key, data.get(key));
}
if (showNotification) {
Intent intent = new Intent(this, OnNotificationOpenReceiver.class);
intent.putExtras(bundle);
PendingIntent pendingIntent = PendingIntent.getBroadcast(this, id.hashCode(), intent,
PendingIntent.FLAG_UPDATE_CURRENT);
Uri defaultSoundUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this)
.setContentTitle(title)
.setContentText(messageBody)
.setAutoCancel(true)
.setSound(defaultSoundUri);
int numMessages = 0;
//This line gives me error:error: cannot find symbol
notificationBuilder.setContentText(currentText).setNumber(++numMessages);
notificationManager.notify(notifyID, notificationBuilder.build());
} else {
bundle.putBoolean("tap", false);
FirebasePlugin.sendNotification(bundle);
}
}

It looks like currentText that is used in the setContextText method isn't instantiated anywhere in your code.

OnClickListener cannot be resolved to a type

I'm diving into Java (this is day 1) and I'm trying to create a button that will trigger a notification when I click it...
This code is based off of the notification documentation here, and UI events documentation here
package com.example.contactwidget;
import android.app.Activity;
import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.widget.Button;
public class ContactWidget extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Button calc1 = (Button) findViewById(R.id.calc_button_1);
calc1.setOnClickListener(buttonListener);
setContentView(R.layout.main);
}
private static final int HELLO_ID = 1;
//Error: OnClickListener cannot be resolved to a type
private OnClickListener buttonListener = new OnClickListener() {
public void onClick (View v) {
String ns = Context.NOTIFICATION_SERVICE;
NotificationManager mNotificationManager = (NotificationManager) getSystemService(ns);
int icon = R.drawable.icon;
CharSequence ticketBrief = "Button Pressed Brief";
CharSequence ticketTitle = "Button pressed";
CharSequence ticketText = "You pressed button 1";
long when = System.currentTimeMillis();
Notification notification = new Notification(icon, ticketBrief, when);
Intent notificationIntent = new Intent(this, ContactWidget.class);
PendingIntent contentIntent = PendingIntent.getActivity(this, 0, notificationIntent, 0);
notification.setLatestEventInfo(getApplicationContext(), ticketTitle, ticketText, contentIntent);
mNotificationManager.notify(HELLO_ID, notification);
}
}
}
I'm running into a problem: OnClickListener cannot be resolved to a type. The problem here is that I don't see any problems with my code in relation to the example I'm using

Add this import:
import android.view.View.OnClickListener;
If you are using Eclipse, you can use Ctrl+Shift+O to make it import those clases or interfaces automagically.

Make sure you have both these imports:
import android.view.View;
import android.view.View.OnClickListener;

setContentView(R.layout.main);
Should be above the button declaration, just below
super.onCreate(savedInstanceState);