We Keep Coding

Not able to trigger the broadcast

I was learning concept of broadcast receivers and I wanted to make a project with which I can demonstrate triggering specific implicit receiver class which is kind of explicit broadcast.
I made 2 apps the sender app and receiver app for demonstration :
BROADCAST SENDER's MAIN ACTIVITY :
public class MainActivity extends AppCompatActivity {
//Declaring our views
TextView senderTextView;
Button sendButton;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//initializing views
senderTextView = findViewById(R.id.senderTextView);
sendButton = findViewById(R.id.sendButton);
//Setting onClick Listener on sendButton
sendButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
//Calling Broadcast Method
Broadcast();
}
});
}
//Broadcast Method
private void Broadcast(){
//Creating private broadcast intent
Intent intent = new Intent("com.example.broadcastreceiver.PRIVATE_BROADCAST");
//Here we are going to find all the apps in our mobile that have registered for this broadcast in their manifests
//This will help us to find packages or apps registered for com.example.PRIVATE_BROADCAST action
PackageManager packageManager = getPackageManager();
//queryBroadcastReceivers of package manager will query all the receivers having intent filter for "com.example.PRIVATE_BROADCAST" action
//and store receivers info in resolveInfoList
List<ResolveInfo> resolveInfoList = packageManager.queryBroadcastReceivers(intent,0);
//Now we will iterate over this list to find our specific receiver and trigger it
//for each info in resolveInfoList
for (ResolveInfo info : resolveInfoList){
//if info's receiver class name is com.example.broadcastreceiver.CustomBroadcastReceiver (which is our receiver class in receiver app)
if(info.activityInfo.name.equals("com.example.broadcastreceiver.CustomBroadcastReceiver")){
//then use this info to get package name and receiver class name to make a componentName
ComponentName componentName = new ComponentName(info.activityInfo.packageName,info.activityInfo.name);
//now set this componentName to our intent
intent.setComponent(componentName);
}
}
//Sending our private broadcast to our android mobile
sendBroadcast(intent);
//setting textView
senderTextView.setText("Broadcast Sent!");
}
BROADCAST RECEIVER'S MANIFEST :
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
package="com.example.broadcastreceiver">
<application
android:allowBackup="true"
android:dataExtractionRules="#xml/data_extraction_rules"
android:fullBackupContent="#xml/backup_rules"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="#style/Theme.BroadcastReceiver"
tools:targetApi="31">
<activity
android:name=".MainActivity"
android:exported="true">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<receiver
android:name=".CustomBroadcastReceiver"
android:exported="true">
<intent-filter>
<action android:name="com.example.broadcastreceiver.PRIVATE_BROADCAST"/>
</intent-filter>
</receiver>
</application>
</manifest>
BROADCAST RECEIVER's CustomBroadcastReceiver Class :
public class CustomBroadcastReceiver extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
//Making a toast when broadcast is received
Toast.makeText(context, "Broadcast Receiver App : Custom Broadcast Receiver Triggered" , Toast.LENGTH_SHORT).show();
}
BroadcastReceiver's Mainactivity has nothing.
This should trigger the toast in CustomBroadcastReciever class of Broadcast Receiver App but due to some reason toast is not appearing please help.
Thanks in advance :)

Just created a demo app that works:
In app1, send the broadcast like this (obviously change package names):
public void sendBroadcast() {
Intent broadcastIntent = new Intent("com.example.testimplicitbroadcastreceiver.PRIVATE_BROADCAST");
broadcastIntent.setComponent(new ComponentName("com.example.testimplicitbroadcastreceiver",
"com.example.testimplicitbroadcastreceiver.CustomBroadcastReceiver"));
sendBroadcast(broadcastIntent);
}
In app2's manifest, register the BroadcastReceiver:
<receiver
android:name=".CustomBroadcastReceiver"
android:exported="true">
<intent-filter>
<action android:name="com.example.testimplicitbroadcastreceiver.PRIVATE_BROADCAST"/>
</intent-filter>
</receiver>
Voila, now app2 will receive your Broadcast in the CustomBroadcastReceiver.

Broadcast receiver - send String between apps

I am trying to send string from app to app.
First app called "send" has only "MainActivity" class and layout:
private void sendMsg(){
final TextView msg = (TextView) findViewById(R.id.sendText);
Button snd = (Button)findViewById(R.id.sendButton);
snd.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if(!msg.getText().toString().trim().equals("")){
Intent intent = new Intent("Updated");
intent.setAction(Intent.ACTION_SEND);
intent.putExtra("TEXT", msg.getText().toString().trim());
intent.setType("text/plain");
intent.addFlags(Intent.FLAG_INCLUDE_STOPPED_PACKAGES);
intent.setComponent(new ComponentName("com.example.rec","com.example.rec.broadcastReciver"));
getApplicationContext().sendBroadcast(intent);
}else{
Toast.makeText(getApplicationContext(), "Write text that You want to broadcast!", Toast.LENGTH_LONG).show();
}
}
});
}
Second app called "rec" has two classes "broadcastReciver" and "MainActivity".
MainActivity:
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
zoviBroadCast();
}
private void zoviBroadCast(){
broadcastReciver brcv = new broadcastReciver();
registerReceiver(brcv,
new IntentFilter("action"));
}
}
broadcastReciver:
public class broadcastReciver extends BroadcastReceiver {
public void onReceive(Context context, Intent intent)
{
//String data = intent.getStringExtra("TEXT").trim();
if (intent != null)
{
String sIntentAction = intent.getAction();
if (sIntentAction != null && sIntentAction.equals("action"))
{
String data = intent.getStringExtra("TEXT").trim();
Toast.makeText(context, data, Toast.LENGTH_LONG).show();
}
else {
Toast.makeText(context,"Something went wrong",Toast.LENGTH_SHORT).show();
}
}
}
}
I also added lines between tag "receiver" in "AndroidManifest.xml":
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.rec">
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="#style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<receiver
android:name=".broadcastReciver"
android:enabled="true"
android:exported="true">
<intent-filter>
<action android:name="action" />
</intent-filter>
</receiver>
</application>
</manifest>
What application should do is when I type something in first application and send it another over button it should "broadcast" (show) toast at second app.
My second application is not showing any data when run.

Nowadays it is essential to specify an action in intent filter of your broadcast receiver.
<receiver android:name="MyReceiver" >
<intent-filter>
<action android:name="android.intent.action.MY_ACTION">
</action>
</intent-filter>
</receiver>
When sending the broadcast, you need to set exactly the same action to the intent you send.
Intent i = new Intent();
i.setAction("android.intent.action.MY_ACTION");
context.sendBroadcast(i);
Notation of action name may be not very important to get your code working, but I recommend to give names related to the package of your sending app.
For example: "com.username.example.myApplication.ACTION_EXAMPLE"

Get the current activity to handle NFC TAG discovered [duplicate]

This question already has an answer here:
Android: How do I temporarily handle an Intent in a different activity of my application?
(1 answer)
Closed 3 years ago.
I've got an android app with several activities. I want the current activity to handle the nfc discovered event, as the state of the app determines what i want to do with the tag
As can be seen in the attached code i've set up the intents on each activity and implemented the onResume, onPause and onNewIntent methods in each activty.
Yet, for some reason the MainActivty is the only one which gets called even though one of the other activities is the active one. Eg. it is the one with the current GUI.
You guys have any idea how to get the active activity to handle the NFC discovered?
Any help greatly appreciated :)
Here is the ApplicationManifest
<uses-permission android:name="android.permission.NFC" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<activity
android:name=".ConfigureStableNamesActivity"
android:label="#string/app_name"
android:theme="#style/AppTheme.NoActionBar">
<intent-filter>
<action android:name="android.nfc.action.NDEF_DISCOVERED " />
<category android:name="android.intent.category.DEFAULT" />
<data
android:host="www.nxp.com"
android:pathPrefix="/products/identification_and_security/smart_label_and_tag_ics/ntag/series/NT3H1101_NT3H1201.html"
android:scheme="http" />
</intent-filter>
</activity>
<activity
android:name=".MainActivity"
android:label="#string/app_name"
android:theme="#style/AppTheme.NoActionBar">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
<!-- <action android:name="android.nfc.action.ACTION_TAG_DISCOVERED"/>-->
<action android:name="android.nfc.action.NDEF_DISCOVERED " />
<category android:name="android.intent.category.DEFAULT" />
<data
android:host="www.nxp.com"
android:pathPrefix="/products/identification_and_security/smart_label_and_tag_ics/ntag/series/NT3H1101_NT3H1201.html"
android:scheme="http" />
</intent-filter>
</activity>
In each of my activities i have this code to handle the NFC discovered intent
#Override
protected void onResume() {
super.onResume();
ntagHandler.start();
}
#Override
protected void onPause() {
super.onPause();
ntagHandler.stop();
}
#Override
protected void onNewIntent(Intent intent) {
try {
Tag tag = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
nfcHandler = new NearFieldCommunicationHandler(tag);
nfcHandler.connect();
// DO SOMETHING HERE
// dataModel.readStableNames(nfcHandler);
} catch(IOException e) {
Toast.makeText(this, "Caught exception: " + e.toString(), Toast.LENGTH_LONG).show();
}
}

You need to implement "The foreground dispatch system". it allows an activity to intercept an intent and claim priority over other activities. Please refer: https://developer.android.com/guide/topics/connectivity/nfc/advanced-nfc#java
First create pendingIntent globally in your each activities as below:
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, new Intent(this, getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP), 0);
then take IntentFilter globally and init with null as below:
IntentFilter[] intentFiltersArray = null;
Write below code in onCreate() method:
IntentFilter ndef = new IntentFilter(NfcAdapter.ACTION_NDEF_DISCOVERED);
try {
ndef.addDataType("*/*"); /* YOU CAN TYPE HERE EITHER android.nfc.action.NDEF_DISCOVERED or
android.nfc.action.ACTION_TAG_DISCOVERED */
}
catch (IntentFilter.MalformedMimeTypeException e) {
throw new RuntimeException("fail", e);
}
IntentFilter[] intentFiltersArray = new IntentFilter[] {ndef, };
then take techListsArray globally as below:
String[][] techListsArray = new String[][] { new String[] { NfcF.class.getName() } };
Finally write below code to enable and disable the foreground dispatch when the activity loses (onPause()) and regains (onResume()) focus. enableForegroundDispatch() must be called from the main thread and only when the activity is in the foreground (calling in onResume() guarantees this)
public void onPause() {
super.onPause();
nfcadapter.disableForegroundDispatch(this);
}
public void onResume() {
super.onResume();
nfcadapter.enableForegroundDispatch(this, pendingIntent, intentFiltersArray, techListsArray);
}
public void onNewIntent(Intent intent) {
Tag tagFromIntent = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
//do something with tagFromIntent
}

Alarm Manager didn't Triggger to Broadcast Receiver

I'm going to build an Application with Alarm feature to remind the patients to take medicine on time.
But current issue is the alarm manager didn't trigger on the XiaoMi phone, and it work on the samsung note 4 in Android 6.0. And before implement the code to my project, I had create a new project and using the same code to test it. In the new project the code work perfectly as long as the Autostart permission has grant. The alarm will trigger on time, and even restart the phone, the boot receiver will also work recreate the alarm, but it only didn't work on my application.
And now below is my code.
OnAlarmReceiver.java
public class OnAlarmReceiver extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
Log.d("MyApp", "Received wake up from alarm manager.");
long rowid = intent.getExtras().getLong(RemindersDbAdapter.KEY_ROWID);
WakeReminderIntentService.acquireStaticLock(context);
Intent i = new Intent(context, ReminderService.class);
i.putExtra(RemindersDbAdapter.KEY_ROWID, rowid);
context.startService(i);
}
}
ReminderManager.java
public class ReminderManager {
private Context mContext;
private AlarmManager mAlarmManager;
public ReminderManager(Context context) {
mContext = context;
mAlarmManager = (AlarmManager)context.getSystemService(Context.ALARM_SERVICE);
}
public void setReminder(Long taskId, Calendar when) {
Intent i = new Intent(mContext, OnAlarmReceiver.class);
i.putExtra(RemindersDbAdapter.KEY_ROWID, (long)taskId);
int broadcastID = Integer.parseInt(taskId+""+when.getTime().getDate()+""+when.getTime().getYear()+""+taskId);
broadcastID = (int)when.getTimeInMillis();
System.out.println("Alarm when : "+ when.getTimeInMillis());
PendingIntent pi = PendingIntent.getBroadcast(mContext, broadcastID, i, PendingIntent.FLAG_ONE_SHOT);
System.out.println("Alarm Set ID : "+broadcastID);
if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
mAlarmManager = (AlarmManager)mContext.getSystemService(Context.ALARM_SERVICE);
AlarmManager.AlarmClockInfo ac= new AlarmManager.AlarmClockInfo(when.getTimeInMillis(), pi);
mAlarmManager.setAlarmClock(ac, pi);
System.out.println("Android 6.0 Marshmallow and above.");
}else if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
mAlarmManager.setExact(AlarmManager.RTC_WAKEUP, when.getTimeInMillis(), pi);
System.out.println("Android 4.4 Kikkat and above.");
}else{
mAlarmManager.set(AlarmManager.RTC_WAKEUP, when.getTimeInMillis(), pi);
System.out.println("Android 4.3 Jelly Bean and below.");
}
}
}
Manifest file:
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
<uses-permission android:name="android.permission.WAKE_LOCK" />
Forgot to mention, i had already register the .OnAlarmReceiver in manifest file
<receiver android:name=".OnBootReceiver">
<intent-filter>
<action android:name="android.intent.action.BOOT_COMPLETED" />
</intent-filter>
</receiver>
<receiver android:name=".OnAlarmReceiver" />
My main issue is with same code it work on the new project i had create to do testing, but didn't work on the my main project.
Can someone help me out. Thanks in advance.

Register OnAlarmReceiver in manifest
<receiver android:name=".OnAlarmReceiver" />

<receiver android:name=".OnAlarmReceiver">
<intent-filter>
<action android:name="android.intent.action.BOOT_COMPLETED"/>
</intent-filter>
</receiver>

NFC app crashing on enableForegroundDispatch

I am trying to get NFC foreground dispatch to work in my app using the tutorials
here and here. From what I can deduce all other functions seem to be working a it is just the NFC forground dispatch system that isn't working.
In my onCreate, I check NFC exists and initialise pending Intents and filters and get the NFC adapter:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Set some stuff
mTV = (TextView) findViewById(R.id.textView);
mButt = (Button) findViewById(R.id.button);
//mNfcAd = NfcAdapter.getDefaultAdapter(this);
//Init elsewhere
getAdapter();
//Hide button until its needed
mButt.setVisibility(View.INVISIBLE);
//Make sure NFC actually exists.....
if (mNfcAd == null) {
//Not going to work without NFC
Toast.makeText(this, "This device does not support NFC\nGet used to the pen and paper for now :/", Toast.LENGTH_LONG).show();
finish();
return;
}
Intent nfcIntent = new Intent(this, getClass());
nfcIntent.addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP);
nfcPendingIntent =
PendingIntent.getActivity(this, 0, nfcIntent, 0);
IntentFilter tagIntentFilter =
new IntentFilter(NfcAdapter.ACTION_NDEF_DISCOVERED);
try {
tagIntentFilter.addDataType("text/plain");
intentFiltersArray = new IntentFilter[]{tagIntentFilter};
}
catch (Throwable t) {
t.printStackTrace();
}
//Init the prefs
initPrefs();
}
public void initPrefs() {
prefs = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
}
private NfcAdapter getAdapter(){
if(mNfcAd ==null){
NfcManager manager = (NfcManager) getSystemService(NFC_SERVICE);
mNfcAd = manager.getDefaultAdapter();
}
return mNfcAd;
}
I then go on to check NFC is enabled (if not display a button that shows NFC settings) as well as checking if the app is in its first run. At the end of onResume(), I (attempt to) enable Foreground Dispatch for the adapter.
protected void onResume() {
super.onResume();
//Define the mButt action
mButt.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent dialogIntent = new Intent(Settings.ACTION_NFC_SETTINGS);
dialogIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(dialogIntent);
}
});
//If NFC exists, check if its turned on
if (!mNfcAd.isEnabled()) {
Toast.makeText(this, "You have NFC, but you haven't enabled it...", Toast.LENGTH_LONG).show();
mTV.setText("NFC not enabled");
mButt.setVisibility(View.VISIBLE);
}
//Check if first run
if (prefs.getInt("firstTime", 1) == 1 ||
prefs.getString("fullName", null) == null ||
prefs.getString("house", null) == null) {
Intent intent = new Intent(this, First_Run.class);
startActivity(intent);
prefs.edit().putInt("firstTime", 0);
prefs.edit().putString("fullName", getIntent().getExtras().getString("fullName"));
prefs.edit().putString("house", getIntent().getExtras().getString("house"));
prefs.edit().apply();
}
getAdapter().enableForegroundDispatch(this, nfcPendingIntent, intentFiltersArray, null);
handleIntent(getIntent());
}
The error is:
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.nfc.NfcAdapter.enableForegroundDispatch(android.app.Activity, android.app.PendingIntent, android.content.IntentFilter[], java.lang.String[][])' on a null object reference
However, all the arguments seem to be initialised;
It is being called in onResume, so the activity context is created;
nfcPendingIntent and intentFiltersArray are initialised in onCreate;
I do not have a techlist so I use null as the final argument;
The adapter itself is initialised in getAdapter.
I am currently combing through other tutorials to see the different methods that can be used, however I would really like to get this fixed.
Manifest:
<?xml version="1.0" encoding="utf-8"?>
<uses-feature
android:name="android.hardware.nfc"
android:required="true" />
<uses-permission android:name="android.permission.NFC" />
<application
android:fullBackupContent="false"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme">
<activity
android:name=".MainActivity"
android:label="#string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
<intent-filter>
<action android:name="android.nfc.action.NDEF_DISCOVERED" />
<category android:name="android.intent.category.DEFAULT" />
<data android:mimeType="text/plain" />
</intent-filter>
</activity>
<activity
android:name=".First_Run"
android:label="#string/title_activity_first__run">
</activity>
</application>

Try creating your NfcAdapter object like below.
NfcAdapter mNfcAdapter = NfcAdapter.getDefaultAdapter(this);