I have a service from where I want to send a broadcast using:
public class BackgroundService extends Service {
public BackgroundService() {
Log.i(MainActivity.TAG, "Background service started");
Intent broadcastIntent = new Intent("android.intent.action.CUSTOM_INTENT");
sendBroadcast(broadcastIntent);
}
The service is started from the Main Activity like so:
public void buttonClick(View view) {
Intent serviceIntent = new Intent(this, BackgroundService.class);
startService(serviceIntent);
}
However this does not work, it shows this error:
.BackgroundService: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.content.Context.sendBroadcast(android.content.Intent)' on a null object reference
Can anyone point out why? or provide a working example?
Thanks
You can do this with localBroadcastReceiver like below in service
val intent = Intent()
intent.setAction(YOUR_ACTION_STRING)
LocalBroadcastManager.getInstance(context).sendBroadcast(intent)
and on activity write below code
intentFilter.addAction(YOUR_ACTION_STRING);
LocalBroadcastManager.getInstance(context).registerReceiver(yourReceiver, intentFilter)
and yourReceiver param extends from broadcastReceiver
Related
So I've got this error code: Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
The line: Intent callMode = new Intent(MainActivity.this, IncallActivity.class);
What I'm trying to do is to set a new activity when I receive a call. The following function is what should "switch" to that activity.
public void callMode() {
Intent callMode = new Intent(MainActivity.this, IncallActivity.class);
startActivity(callMode);
}
And it is located inside of the MainActivity class, outside of the onCreate function.
When I try to put it inside of the onCreate function (without public void callMode() of course) it works, but that's not the goal.
I'm trying to activate this new activity from another class, which listens for calls.
public class CallReceiver extends BroadcastReceiver {
IncallActivity incallActivity = new IncallActivity();
public MainActivity mainActivity;
#Override
public void onReceive(Context context, Intent intent) {
if (intent.getStringExtra(TelephonyManager.EXTRA_STATE).equals(TelephonyManager.EXTRA_STATE_OFFHOOK)) {
mainActivity.callMode();
} else if (intent.getStringExtra(TelephonyManager.EXTRA_STATE).equals(TelephonyManager.EXTRA_STATE_IDLE)) {
incallActivity.endCallMode();
}
}
}
So why does this error show up?
I found a way to do it.
You need to add a public static Context context to your code, and then in onCreate, do context = getBaseContext();
From there you can launch the second activity from any class you'd like.
I have my application running a service for shake detect, however in my MainActivity, I have button for log out user, in which I must log out and terminate the service that detects the shake event.
my method for log out in my MainActivity is:
public void signOutAndFinish(){
//Stop Shakeservice
Intent intent = new Intent(this, ShakeService.class);
stopService(intent);
//Go to login activity
Intent iLoginView = new Intent(this, LoginActivity.class);
startActivity(iLoginView);
}
however if I shake my device after logging out, the service recognizes the shake, it is as if it will not kill it immediately:
Intent intent = new Intent(this, ShakeService.class);
stopService(intent);
The code in the method onDestroy is:
#Override
public void onDestroy() {
super.onDestroy();
}
How can I terminate the service so that when I log out the service dies?
Thanks for your help!
You can send a broadcast back your activity in the onDestroy() method of your service and then do the logout.
Here is some sample code of the above idea:
This for your service:
#Override
public void onDestroy() {
super.onDestroy();
Intent intent = new Intent();
intent.setAction("com.example.broadcast.MY_NOTIFICATION");
intent.putExtra("data","Notice for logout!");
sendBroadcast(intent);
}
And this is for your activity:
private BroadcastReceiver br = new MyBroadcastReceiver();
#Override
public void onCreate() {
IntentFilter filter = new IntentFilter("com.example.broadcast.MY_NOTIFICATION");
registerReceiver(br, filter);
}
#Override
public void onDestroy() {
unregisterReceiver(br);
}
// An inner class at your activity
public class MyBroadcastReceiver extends BroadcastReceiver {
private static final String TAG = "MyBroadcastReceiver";
#Override
public void onReceive(Context context, Intent intent) {
YourActivity.this.finish();
// or do anything you require to finish the logout...
}
}
however if I shake my device after logging out, the service recognizes the shake
Then presumably you did not clean up your Sensor stuff in the service's onDestroy() method.
How can I terminate the service so that when I log out the service dies?
You are doing that now. However, if you set up something in the service, such as listening to events from SensorManager, you need to clean that up, typically in onDestroy() of the service.
I have created a Broadcast receiver and it is working fine. but I need to pass a handler to that class.
public static class DataReceiver extends BroadcastReceiver {
Handler handler;
DataReceiver(Handler loghandler) {
this.handler = loghandler;
}
#Override
public void onReceive(Context context, Intent intent) {
//things goes here
}
}
Currently I am using like this & It is working if constructor override is not available.
Intent intent = new Intent(this, DataReceiver .class);
but I need to pass the handler too. How can I send the handler? Thanks
I don't really understand what you are trying to accomplish but i think this may help you. You don't need to make a whole new class for your broadcast receiver but you can use it inside your Main Activity like this:
BroadcastReceiver receiveLocationReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
// Your custom action
}
};
IntentFilter receiveLocationFilter = new IntentFilter();
receiveLocationFilter.addAction("android.intent.RECEIVE_LOCATION");
Register the receiver in "onStart":
registerReceiver(receiveLocationReceiver, receiveLocationFilter);
Unregister it in "onStop":
unregisterReceiver(receiveLocationReceiver);
Then when you need to send the broadcast all you need is :
Intent sendBroadcastIntent = new Intent("android.intent.RECEIVE_LOCATION");
sendBroadcast(sendBroadcastIntent);
I have a java Class that extends Plugin (PhoneGap), but when inside this class, i call another class that extends Activity, it just doesn't work !. i mean, it seems like it doesn't get called. To confirm this, i have change my second class, this time, not extending from Activity and it works fine. i need teh second one to extends from Activity because i am using this two utilities (getFileStreamPath and openFileOutput) to create a file
File filepath = getFileStreamPath("filename.CPCL"); and openFileOutput
FileOutputStream os = this.openFileOutput(fileName, Context.MODE_PRIVATE);
I have an app with a class which extends a custom Service that calls another class which extends Activity.
First I instantiate the Activity. In the onCreate of your Plugin class use:
// get a handle on your Application
Application app = getApplication();
Intent intent = new Intent(getApplicationContext(), YourActivity.class);
app.startActivity(intent);
This will start your Activity and call the standard Lifecycle events.
The way I handle continued communication with the running Activity is by using a Handler to send a broadcast from your plugin which the Activity picks up in its receiver. In the onCreate of your plugin:
mHandler.post(new Runnable() {
#Override
public void run() {
Log.d(TAG, "Call the Activity");
Intent intent = new Intent(YourActivity.CALL_FROM_PLUGIN);
intent.putExtra("request", <<Any extras you might want to send through>>);
sendBroadcast(intent);
}
});
In the Activity I declare the variable:
public static final String CALL_FROM_PLUGIN= "CALL_FROM_PLUGIN";
then in onCreate() I added the following;
IntentFilter filter = new IntentFilter();
filter.addAction(CALL_FROM_PLUGIN);
registerReceiver(mBroadcastReceiver, filter);
and then implemented a BroadcastReceiver:
BroadcastReceiver mBroadcastReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
Log.d(TAG, "BroadcastReceiver.onReceive()");
if (CALL_FROM_PLUGIN.equals(action)) {
Log.d(TAG, "Received call from Plugin");
// DO YOUR STUFF HERE
}
}
};
Someone else might be able to point out why this is necessary from a framework point of view, but this is the way I understand that Activities should be called. I hope this applies to your plugin class the way it does with my service class!
I want to start one of my existing activities and force the activity to call a specific method after it starts. Is this possible?
Can I define a method that should be called after creating the activity inside my Intent?
For example, something like:
Intent intent = new Intent(this, com.app.max.Home.class.myMethod);
No, I don't think you can have something like this:
Intent intent = new Intent(this, com.app.max.Home.class.method);
but you can do this:
Intent intent = new Intent(this, com.app.max.Home.class);
intent.putExtra("methodName","myMethod");
startActivity(intent);
and then in the called activity (where you need to start the method), you can take the intent and decide which method to call like this:
#Override
protected void onNewIntent(Intent intent) {
super.onNewIntent(intent);
if(intent.getStringExtra("methodName").equals("myMethod")){
mymethod();
}
}
Hello You can't call a particular method from intent but alternately you can use a service from intent and your requirement will be done.
Intent intent = new Intent(this, MyService.class);
and in MyService.class
public class MyService extends Service {
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
yourParticularMethod(); //do your task and stop the service when your task is done for battery saving purpose
context.stopService(new Intent(context, MyService.class));
return super.onStartCommand(intent, flags, startId);
}
#Override
public IBinder onBind(Intent intent) {
return null;
}
}
and register this service in your manifest file like this
<application>
<service android:name=".MyService" />
.
.
</application>
I solve this issue by using onCreate instead of onNewIntent.
Activity A:
Intent intent = new Intent(this, com.app.max.Home.class);
intent.putExtra("methodName","myMethod");
startActivity(intent);
com.app.max.Home Activity:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.home);
if(savedInstanceState == null)
{
Bundle extras = getIntent().getExtras();
if (extras == null)
{
//Extra bundle is null
}else{
String method = extras.getString("methodName");
if (method.equals("myMethod"))
{
//Call method here!
}
}
}
Hope this solution solve your problem
You question seems interesting, but there is no way you can do it using Intent. You have to understand that when you start an activity, it goes through a life cycle which is : onCreate()->onStart()->OnResume(). So what you can do is start that method from onResume() like this:
#Override
protected void onResume() {
super.onResume();
myMethod();//start your method from here
}
I'm just trying to help,give me some more information about your problem if this approach does not solve your problem.