Develop Reference

Android - StartActivityForResult on finish() method freezes UI

I have the following situation:
Activity A starts Activity B, by using startActivityForResult
Activity B then returns an ArrayList of Strings to Activity A by using on finish().
Here is a code example of what exactly Activity B does:
ArrayList<String> urls = new ArrayList<>();
urls.add("Some string");
Intent intent = new Intent();
intent.putStringArrayListExtra(KEY, urls);
setResult(Activity.RESULT_OK, intent);
finish();
Then Activity A receive the data in onActivityResult(...)
The issue I have is that when the user taps the done button and Activity B's code example executes, Activity B freezes for about 3 seconds (when I have about 2 strings in the ArrayList). The more strings I have in the ArrayList the longer it freezes. I have more or less determined that it is finish() that causes the UI thread to freeze.
Is there a way to call finish() without freezing Activity B? If not, why is this happening?
EDIT:
Here is the full example:
/**
* Background task
*/
private class gatherUrlsTask extends AsyncTask<ArrayList<PictureEntry>, Integer, Intent> {
#Override
protected void onPreExecute() {
progressBar.setVisibility(View.VISIBLE);
bt_done.setVisibility(View.GONE);
fab_add_picture.setVisibility(View.GONE);
}
#SafeVarargs
#Override
protected final Intent doInBackground(ArrayList<PictureEntry>... params) {
ArrayList<String> imagePaths = new ArrayList<>();
for (PictureEntry pictureEntry : params[0]) {
if (pictureEntry.isSelected()) {
imagePaths.add(pictureEntry.getPath());
}
}
if (imagePaths.size() == 0) {
Toast.makeText(getApplicationContext(), R.string.please_select_atleast_one_image, Toast.LENGTH_LONG).show();
return null;
} else {
Intent intent = new Intent();
intent.putStringArrayListExtra(SELECTED_IMAGES_KEY, imagePaths);
return intent;
}
}
#Override
protected void onPostExecute(Intent intent) {
setResult(Activity.RESULT_OK, intent);
finish();
}
}
However I can remove everything from the AsyncTask since it did not have any effect on performance.

i don't know what is cause of that, but for prevent ui getting freezed, use asyncTask and then in the onPostExcecute call finish()

Can a Broadcast Receiver receive a Mobile Data CONNECTIVITY_CHANGE notification while WiFi is enabled?

For the many threads, blogs, examples and tutorials on the topic of Broadcast Receivers and mobile data connectivity i have not seen this question asked or answered.
I believe, based on experimenting with one of my Apps, that the answer to this question is a distinct NO, that while WiFi is enabled, a Broadcast Receiver listening for Mobile Data CONNECTIVITY_CHANGE does not receive a broadcast notification when that event occurs. If i am wrong and have missed something please let me know.
My App is a home screen Widget with two classes, ActiveMobileData is the AppWidgetProvider and ConnectivityChangeReceiver is the BroadcastReceiver. The AppWidgetProvider class is my first App which i put together earlier this year mainly from code widely available in a book, on StackOverflow and on various blogs etc. There is no App just the home screen widget. It simply toggles a home screen icon between red and green to indicate the current mobile data state. It has worked perfectly for several months with about 100 users.
I decided to add the BroadcastReceiver to pick up clicks from Settings. This code is also straight forward - it determines the current state of mobile data, and uses a global boolean variable set by AppWidgetProvider to determine if the home screen icon is red or green. Then it simply ensures that the icon color matches the mobile data state.
It all works except when WiFi is enabled it does not get a notification. If there is a way around this limitation i would appreciate hearing about it.
Following is the code for the widget and then for the receiver. I left out some details to keep it somewhat brief. iconEnabled is the shared global boolean variable ...
public class ActiveMobileData extends AppWidgetProvider {
static boolean iconEnabled;
#Override
public void onReceive(Context context, Intent intent) {
if (intent.getAction() != null)
super.onReceive(context, intent);
else {
context.startService(new Intent(context, ToggleService.class));
}
}
#Override
public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[]appWidgetIds) {
context.startService(new Intent(context, ToggleService.class));
}
public static class ToggleService extends IntentService {
public ToggleService() {
super("ActiveMobileData$ToggleService");
}
#Override
protected void onHandleIntent(Intent intent) {
ComponentName cn = new ComponentName(this, ActiveMobileData.class);
AppWidgetManager mgr = AppWidgetManager.getInstance(this);
mgr.updateAppWidget(cn, buildUpdate(this));
}
private RemoteViews buildUpdate(Context context) {
RemoteViews updateViews = new RemoteViews(context.getPackageName(), R.layout.widget);
if (!isMobileDataEnabled(getApplicationContext())) {
updateViews.setImageViewResource(R.id.mobileDataState, R.mipmap.ic_launcher_g);
enableMobileData(getApplicationContext(), true);
iconEnabled = true;
} else {
updateViews.setImageViewResource(R.id.mobileDataState, R.mipmap.ic_launcher_r);
enableMobileData(getApplicationContext(), false);
iconEnabled = false;
}
Intent i = new Intent(this, ActiveMobileData.class);
PendingIntent pi = PendingIntent.getBroadcast(context, 0, i, 0);
updateViews.setOnClickPendingIntent(R.id.mobileDataState, pi);
return updateViews;
}
public boolean isMobileDataEnabled(Context context) {
// ... the code here is the one that uses Java reflection
}
private void enableMobileData(Context context, boolean enabled) {
// ... the code here is the one that uses Java reflection
}
} // public static class ToggleService
} // public class ActiveMobileData
Following is the code for the BroadcastReceiver ...
public class ConnectivityChangeReceiver extends BroadcastReceiver {
#Override
public void onReceive (Context context, Intent intent) {
handleIntent(context);
}
protected void handleIntent(Context context) {
ComponentName cn = new ComponentName(context, ActiveMobileData.class);
AppWidgetManager mgr = AppWidgetManager.getInstance(context);
mgr.updateAppWidget(cn, buildUpdate(context));
}
private RemoteViews buildUpdate(Context context) {
RemoteViews updateViews = new RemoteViews(context.getPackageName(), R.layout.widget);
if (!ActiveMobileData.iconEnabled && isMobileDataEnabled(context)) {
ActiveMobileData.iconEnabled = true;
updateViews.setImageViewResource(R.id.mobileDataState, R.mipmap.ic_launcher_g);
Intent i = new Intent(context, ActiveMobileData.class);
PendingIntent pi = PendingIntent.getBroadcast(context, 0, i, 0);
updateViews.setOnClickPendingIntent(R.id.mobileDataState, pi);
} else
if (ActiveMobileData.iconEnabled && !isMobileDataEnabled(context)) {
ActiveMobileData.iconEnabled = false;
updateViews.setImageViewResource(R.id.mobileDataState, R.mipmap.ic_launcher_r);
Intent i = new Intent(context, ActiveMobileData.class);
PendingIntent pi = PendingIntent.getBroadcast(context, 0, i, 0);
updateViews.setOnClickPendingIntent(R.id.mobileDataState, pi);
}
return updateViews;
}
private boolean isMobileDataEnabled(Context context) {
// ... Identical code to that in the AppWidgetProvider
}
} // class ConnectivityChangeReceiver

I don't know offhand, but I can point you to the 2 best places to look.
Best bet would be to look in detail into the JavaDoc for ConnectivityManager.html#CONNECTIVITY_ACTION and then the source code for the ConnectivityManager that is online on GrepCode
In particular comments within the source code often have very informative information that doesn't exist elsewhere.
Update:
After reading the javadoc for CONNECTIVITY_ACTION again, I believe that you are correct because it say A change in network connectivity has occurred. A default connection has either been established or lost. NOTE: Default Conn. NOT 'A Conn.' So it only gets launched when the 'default' changes. So if you lose 3g/4g/etc while on WIFI then I don't think this gets launched.
However there 'is' something you 'can' do... (but only when your widget is running) (I'm actually not 100% sure a 'widget' CAN do this... b/c I generally work with teaching services/AIDL/ContentProviders/etc (aka. 'backend' stuff within the platform) But you can put a 'refresh' button on your widget that can query to GET ALL NETWORKS and then parse through all that data and display which networks 'are' active, etc.
Also there is the option. You could make pending intents for your broadcast receiver(s) (I'd recommend just 1 BR and have different payloads so you can sort them for what is being notified) then register each of those pending intents as a call back with the ConnectivityManager to notify it whenever a 'network' that 'matches' the NetworkRequest exists. This will notify you at least when they 'come alive'...
(this next idea would likely require you to make a service with a separate thread to prevent ANR)
now when they 'die'... you 'could' setup a TCP connection and see when it dies... (not 'good' but might be only 'viable' option) (and if you are are 'generous' with trying to not wake up the phone, the battery impact could be minimal)

Notifications not show up

I am working on a messaging app, it sends user notification when he is on a different activtyon my app or is on another app but if the user is on MessagingActivity.java it just updates the chat history and does not send any notifications which is perfectly fine, but the problem arises when the user is on MessagingActivity.java meanwhile an email or something else happen user leaves the MessagingActivity.java open and checks that app if in the meantime a message comes user does not receive any notifications
public void parseRequest(Bundle extras) {
if (extras.containsKey("for") && extras.containsKey("recipientID")) {
if (Integer.parseInt(extras.getString("recipientID")) == M.getID(this)) {
switch (extras.getString("for")) {
case "chat":
if (isRunning("MessagingActivity")) {
Intent intent = new Intent("update_messages_list");
intent.putExtra("data", extras);
sendBroadcast(intent);
} else {
Intent resultIntent = new Intent(this, MessagingActivity.class);
resultIntent.putExtra("conversationID", Integer.parseInt(extras.getString("conversationID")));
resultIntent.putExtra("recipientID", Integer.parseInt(extras.getString("ownerID")));
M.showNotification(getApplicationContext(), resultIntent,
extras.getString("ownerUsername"),
extras.getString("message"),
Integer.parseInt(extras.getString("conversationID")));
}

Let me know how you are checking that your MessageActivity is Running i.e. functioning of isRunning("MessagingActivity") method. If you are setting any global boolean variable for checking this and making isRunning value false in onDestroy() method of that activity then, according to life cycle of Activity it is not called until your activity is finished i.e. in your case user just switching from MessageActivity to Mail .

I am by no means an expert, but you could just set a boolean variable by overriding the Activity's onPause() and onResume() events.
Simply set msgActivityActive to true in onResume(), false in onPause(), and change your call to:
if (isRunning("MessagingActivity") && msgActivityActive)

Why calling a class that extends Activity does not work when called from one that extends Plugin?

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!

NullPointerException when using getInt(String)

I'm android beginner so please be easy on me. I'm doing some "exercises" and i'm writing simple app which will tell RSSI strength of home wifi network. Getting that number is pretty easy, but updating it and showing that on screen it's a little more complicated as i thought.
First this is my onCreate Activity. In this activity i'm launching another android component - Service. Because the code will run in background (i know i could use thread or something else, but this is for "practice" sake, and i have a few ideas what to do with this app, while running service and not interacting with UI )
public class MainActivity extends Activity {
TextView wifi_check;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
referenceViews();
startService(new Intent(this, CheckingWifiService.class));
//wifi_check.setText(""+getIntent().getExtras().getInt("RSSI"));
}
private void referenceViews() {
wifi_check = (TextView) findViewById(R.id.wifiCheck_TV);
}
}
Because my code will run every second or so, i will use TimerTask for this purpose. And here is my TimerTask class, which includes run() method, and code for executing inside
public class TimerTsk extends TimerTask {
Context act;
WifiManager wifiMan;
WifiInfo info;
Bundle sendInfo;
Intent intent;
int rssi;
public TimerTsk(Context context) {
act = context;
}
#Override
public void run() {
intent = new Intent();
sendInfo = new Bundle();
wifiMan = (WifiManager) act.getSystemService(Activity.WIFI_SERVICE);
info = wifiMan.getConnectionInfo();
rssi = info.getRssi();
Log.d("WORKED", "RUNNING SUCESSFULLY");
// i want to send info to my activity
sendInfo.putInt("RSSI", rssi);
intent.putExtras(sendInfo);
}
}
From this class , i want to send result of RSSI to my activity and then update a text. But when i call this code below, on activity i always get NullPointerException.
wifi_check.setText(""+getIntent().getExtras().getInt("RSSI"));
To be honest i had hard time figuring out which part of code is throwing an exepction. And i found that more exactly, this part of code is throwing an exepction.
getInt("RSSI")
Overall i see that service is running, because in my LOGCAT i see a message that i create with Log.d in TimerTsk class.
Any ideas why is this happening?
Here is my service class:
public class CheckingWifiService extends Service{
int rssi;
Timer time;
TimerTsk ttsk;
#Override
public IBinder onBind(Intent intent) {
return null;
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
time = new Timer();
time.schedule(new TimerTsk(getApplicationContext()), 500);
return START_STICKY;
}
}
Here is my LogCat:

I see a common mistake. Don't do this:
sendInfo.putInt("RSSI", rssi);
intent.putExtras(sendInfo); // This adds a Bundle to your existing Bundle!
You are creating an Intent, with a Bundle of extras, with a Bundle that holds rssi. Leave out this unnecessary Bundle:
intent.putExtras("RSSI", rssi);
Now in your next Activity you can use:
getIntent().getIntExtra("RSSI", 0);
However you should always check to make sure there aren't any surprise null variables:
Intent in = getIntent();
if(in != null) {
int rssi = in.getIntExtra("RSSI", -1);
if(rssi < 0)
wifi_check.setText(""+rssi);
else
wifi_check.setText("Unknown");
}

is your activity starting? I don't see any call to startActivity(). In any case as mentioned by Sam you just need to call putExtra for your intent. don't forget to call
is your activity starting? I don't see any call to startActivity(). In any case as mentioned by Sam you just need to call putExtra for your intent. don't forget to call
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
you need to put this flag when start activies from background