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possible alternative to static inner classes to prevent memory leaks in android/java?

lately i have been researching about memory leaks in java/android and pretty much everywhere it says that instead of anonymous classes i should use static inner classes with weak references.
so, in my android app i started doing that but very quickly got tired of it because it's a lot of boilerplate code... i think have an alternative solution which i would prefer to use, but i'm juts not sure that it is a valid alternative to static inner classes in terms of preventing memory leaks. as i said before, i haven't seen this solution suggested anywhere else (all say to use static inner classes) so thats why im not sure my alternative will work.
ill use a simple example from my app:
i have a class called WebClient which handles asynchronous web requests and it accepts an interface called iCallback which returns the response from the server to the caller, and in my activity once i get this callback i need to dismiss a dialog, and maybe perform some activity related things (like trigger onBackPressed() and setResult()).
so here is my static inner class i have created:
private static class CallBack implements WebClient.ICallback
{
private WeakReference<ProgressDialog> mProgDiag;
private WeakReference<BaseActivity> mActivity;
public CallBack(BaseActivity activity, ProgressDialog progDiag)
{
this.mProgDiag = new WeakReference<>(progDiag);
this.mActivity = new WeakReference<>(activity);
}
#Override
public void onCallback(String data)
{
String responseAsString = Utils.extractStringFromResponse(...);
final BaseActivity parentActivity = mActivity.get();
ProgressDialog dialog = mProgDiag.get();
if(dialog != null)
{
dialog.dismiss();
}
if (responseAsString == null)
{
if(parentActivity != null)
{
Utils.makeServerErrorDialog(parentActivity,
new iDialogButtonClickedListener()
{
#Override
public void onDialogButtonClicked()
{
parentActivity.onBackPressed();
}
});
}
return;
}
//everything is ok
if (responseAsString.equals("1"))
{
if(parentActivity != null)
{
Intent result = new Intent();
result.putExtra(...);
parentActivity.setResult(Activity.RESULT_OK, result);
}
}
else
{
Utils.reportErrorToServer(...);
if(parentActivity != null)
{
parentActivity.setResult(Activity.RESULT_CANCELED);
}
}
if(parentActivity != null)
{
parentActivity.onBackPressed();
}
}
}
so for every variable i need in this static inner class i have to create a new weak reference, then retrieve the object itself, and then every time i want to access it i need to check whether it's null... that seems like a lot of code to me.
and here is my suggested alternative:
public abstract class BaseActivity extends AppCompatActivity
implements WebClient.ICallback
{
private static final String TAG = "BaseActivity";
WebClient.ICallback mCallBack;
ProgressDialog mProgDiag;
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(...);
mCallBack = this;
//some code to invoke a server request on button click
//and passing mCallBack to the request
}
#Override
public void onCallback(String data)
{
String responseAsString = Utils.extractStringFromResponse(...);
mProgDiag.dismiss();
if (responseAsString == null)
{
Utils.makeServerErrorDialog(this,
new iDialogButtonClickedListener()
{
#Override
public void onDialogButtonClicked()
{
onBackPressed();
}
});
return;
}
//everything is ok
if (responseAsString.equals("1"))
{
Intent result = new Intent();
result.putExtra(...);
setResult(Activity.RESULT_OK, result);
}
else
{
Utils.reportErrorToServer(...);
setResult(Activity.RESULT_CANCELED);
}
onBackPressed();
}
#Override
protected void onPause()
{
mCallBack = null;
super.onPause();
}
#Override
protected void onResume()
{
super.onResume();
mCallBack = this;
}
}
to me this seems much cleaner: no creating and retrieving instances of weak references for every variable i need access to, i can directly invoke activity methods (e.g. onBackPressed()), and no checking for null everywhere.
the only place i would now have to check for null is inside WebClient class before invoking the callBack method.
so my question is, does this approach achieve the same result in terms of preventing memory leaks? is it a "worthy" alternative to static inner classes?

Unfortunately, your approach does not work. By implementing the WebClient.ICallback in your activity, rather than an inner class, you don't get rid of the leak. The leak happens not because the references to activity and dialog are implicit in an anonymous class, or in lambda, or in a non-static inner class instance; the happens when the WebClient keeps this reference while the activity is gone (it is not destroyed, because there is a strong reference to it).
The special mCallBack that you set to null when the activity is paused, gains nothing. Just as well, you can simply pass your activity instance to the WebClient. Now there is a strong reference to your activity, which is managed by someone (async handlers of the WebClient), who is not under your control. If you are unlucky, the async handler will get stuck somewhere and will never release this reference.
Please read this detailed explanation.
Note that WebView itself can cause a memory leak, if special measures are not undertaken!

Android : Inform adapter that data-set has changed from a static method

I am working on an Android project in which I am trying to integrate PUSH service offered by Cometd framework.
Now, whenever a new message arrives for a Conversation, I would like to inform ChatMessagesActivity which contains the list of messages between the two users.
Now, when the other user sends a message to the Android app, I would like to update the view of the user. I tried doing that by calling notifyDataSetHasChanged() on the adapter, but because I was calling it outside of View thread, I am getting an error.
The method is static, because new messages are received in Conversation class, while the messages are going-on in ChatMessagesActivity class. For communication between both classes, I have created 2 static methods which act like a bi-directional bridge for sending & receiving messages.
I hope I was clear, if there are any doubts, kindly let me know.
ChatMessagesActivity.java :
public class ChatMessagesActivity extends ApplicationDrawerLoader {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_chat_messages);
chatList = (ListView)findViewById(R.id.chatList);
new getPrivateChatsForUser(this).execute();
}
// IN the method below, I receive information from another activity.
public static void recieveUpdatedMessage(String channelName, Map<String, Object> input){
Boolean found = Arrays.asList(channelName.split(" ")).contains("chat");
if(found){
int processedChannelName = Integer.valueOf(channelName.replace("/chat/",""));
if(processedChannelName == groupAccountId){
// Here i tried calling adapter.NotifyDataSetchanged();.. Didn't fly.
}
}
}
// Async method retrieving messages.
public class getPrivateChatsForUser extends AsyncTask<Void, Void, ResponseEntity<RestReplies[]>> {
ChatMessagesActivity chatMessagesActivity = null;
getPrivateChatsForUser(ChatMessagesActivity chatMessagesActivity) {
this.chatMessagesActivity = chatMessagesActivity;
}
#Override
protected ResponseEntity<RestReplies[]> doInBackground(Void... params) {
// network connection related stuff, not relevant to problem
}
#Override
protected void onPostExecute(ResponseEntity<RestReplies[]> responseEntity) {
super.onPostExecute(responseEntity);
RestReplies[] restRepliesArray = responseEntity.getBody();
Collections.addAll(restRepliesList, restRepliesArray);
ArrayList<HashMap<String, String>> chatMessagesHashMapList = new ArrayList<HashMap<String, String>>();
for (RestReplies restReplies : restRepliesList) {
HashMap<String, String> chatMap = new HashMap<>();
chatMap.put(chatText, restReplies.getReplyText());
chatMap.put(firstName, restReplies.getReplyingPersonName());
chatMap.put(chatImage, restReplies.getSenderImage());
chatMap.put(privateChannel,"/service/person/"+String.valueOf(conversationId));
chatMessagesHashMapList.add(chatMap);
}
chatList = (ListView) findViewById(R.id.chatList);
chatMessagesAdapter = new ChatMessagesAdapter(chatMessagesActivity, chatMessagesHashMapList);
chatList.setAdapter(chatMessagesAdapter);
chatList.scrollTo(0, chatList.getHeight());
}
}
So, how should I instruct that the data-set has been changed.. And how does the adapter knows where and how to get the data-set which has changed. Can anyone help me with this problem. Thanks a lot... :-)

Use broadcast receiver at your adapter and fire a local broadcast with android LocalBroadcast in your push service
private BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent)
{
if(intent.getAction().equals("MYREFRESH"))
{
notifiyDataSetChanged();
}
}
};
In your constructor in adapter register this reciever
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction("MYREFRESH");
LocalBroadcastManager.getInstance(context).registerReceiver(broadReceiver, intentFilter);
In your push if you get a push notification trigger this
Intent intent = new Intent();
intent.putExtra(...) //send any data to your adapter
Intent.setAction("myaction");
LocalBroadcastManager.getInstance(context).sendBroadcast(intent);

The way to deal with this is using a broadcast or bus pattern. You can use some good bus libraries such as http://square.github.io/otto/ or a LocalBroadcast
This past answer from me shows how to use the LocalBroadcast system: Refreshing fragments in FragmentActivity after sync service runs

Displaying Toast notifications from Java class

I want to create a separate class within my application to handle error reporting and send specific errors to a database. However, I'm unable to figure out what the Context should be and how this should be properly coded. I assume it should still be possible, I just need to code it differently, if that is not the case, what is the best solution for me?
public class SendError implements Runnable
{
private String url;
public SendError(String errors, String form, String database, String SQL)
{
url = string;
Handler handler = new Handler();
handler.post(new Runnable() {
public void run() {
Toast toast = Toast.makeText(getContext, msg, Toast.LENGTH_LONG);
toast.show();
}
});
}
}
EDIT:
What I'm trying to do is create one class for my entire application that handles recording of SQL errors when submitting data to the database. The class needs to do 2 simple things. Submit information based on what form, database, time submitted, and the SQL code that created the error. The other thing I would like this class to do is to display a toast giving basic error information back to the user. I have the data submission portion of this worked out properly (hence the reason for the Runnable), but am still getting errors for the Toast.

Shouldn't do the work in your constructor, this makes your separate class useless.
public class SendError implements Runnable
{
private final Context context;
private final String url;
public SendError(Context context, String string) {
this.context = context;
this.url = string;
}
public void makeToast(String msg, String errors, String form, String database, String SQL) {
Handler handler = new Handler();
handler.post(new Runnable() {
public void run() {
Toast toast = Toast.makeText(context, msg, Toast.LENGTH_LONG);
toast.show();
}
});
}
}
Your context needs to be the relevant context, from using a Toast the Context is usually an Activity which can take the form of:
this (in an Activity)
ActivityName.this (in a inner class of an Activity)
getActivity (in a Fragment inside an Activity)
For example:
new SendError(YourActivity.this, "something").makeToast("Hello", "errors", "form", "database", "sql");

Just need to pass Context in the constructor when you create this class.
I would advise you rethink this class though - it's called "SendError" which sounds like a method name, it implements Runnable for some reason, and it's notifying the user with Toasts - sounds like too much for one class.

Toast toast = Toast.makeText(getApplicationContext(), msg, Toast.LENGTH_LONG).show();
or
Toast toast = Toast.makeText(SendError.this, msg, Toast.LENGTH_LONG).show();

Instantiating TextToSpeech inside GCMIntentService

So I have a bit of a problem. I am trying to make my app do things based on the message it receives through GCM. In this case it's supposed to make a sound by using the TextToSpeech class. It kind of works, but not the first time I send the message. I realise this is probably because TextToSpeech hasn't been instantiated, but I'm not sure how go to about and do that? I tried onInit(), but that didn't work at all.
Also, what is the best way to shut down TTS in my example?
Disclaimer: I come from a PHP background, and know very little Java. I try to learn by doing, so please forgive me if this is a silly question. Thanks in advance!
public class GCMIntentService extends GCMBaseIntentService {
private static final String TAG = "GCMIntentService";
public static TextToSpeech mtts;
public GCMIntentService() {
super(SENDER_ID);
}
#Override
protected void onMessage(Context context, Intent intent) {
Log.i(TAG, "Received message");
String message = intent.getExtras().getString("message");
mtts = new TextToSpeech(context, null);
if (message.startsWith("makeSound")) {
mtts = new TextToSpeech(context, null);
mtts.setLanguage(Locale.US);
mtts.speak(message, TextToSpeech.QUEUE_FLUSH, null);
}
}
}

It doesn't work the first time because the initialization of TextToSpeech is asynchronous. You can not simple instantiate it and use it as you are doing. You should provide a callback to be called once the TextToSpeech has been initialized if you want to use it right away.
mTextToSpeech = new TextToSpeech( this, new TextToSpeech.OnInitListener()
{
#Override
public void onInit( int status )
{
// Check for status might not be initialized due to errors
// Configure language/speed
}
} );
It does work the rest of the times, because mtts is static. This means that is a class variable and is not destroyed/initialized when creating new instances of the service. By the second time you use this service, this variable was already initialized in the first service execution.

Appcelerator custom module receiving callback for onActivityResult

I'm trying to create a custom module in Appcelerator for the new Square API for Android. I have everything the way I want it, but the main problem is that I want to be able to notify the caller that the payment was successful for if it failed. The Square API says this:
After Square finishes, Android invokes Activity.onActivityResult() on the activity passed to the constructor. The request code passed to this method will be passed to onActivityResult(). The result code is Activity.RESULT_CANCELED if the payment was canceled or Activity.RESULT_OK if the payment succeeded.
I've been passing the TiContext.currentActivity to the constructor:
public SquareModule(TiContext tiContext) {
super(tiContext);
ourSquare = new Square(tiContext.getActivity());
}
And then in the method that actually runs the payment, I have this that basically tries to set the passed in callback to the onResult handlers of the current activity using the registerResultHandler in the TiActivitySupportHelper class.
public void runPayment(KrollInvocation invocation, int price, String description, KrollCallback handler) {
Log.i(LCAT, "runPayment called");
// Register the passed in function as a handler on the onResult stack
this.resultCallback = handler;
Activity activity = invocation.getTiContext().getActivity();
TiActivitySupportHelper support = new TiActivitySupportHelper(activity);
int code = support.getUniqueResultCode();
support.registerResultHandler(code, this);
// Some of the payment work here
ourSquare.squareUp(Bill.containing(advice), code);
}
The main module class implements TiActivityResultHandler and implements onResult and onError. These methods are not being called at all. And of course the passed in method isn't being called either.
For completeness, see the implementation of the onResult and onError handlers:
#Override
public void onResult(Activity activity, int requestCode, int resultCode, Intent data)
{
Log.i(LCAT, "onResult Called");
if (resultCallback == null) return;
KrollDict event = new KrollDict();
event.put(TiC.EVENT_PROPERTY_REQUEST_CODE, requestCode);
event.put(TiC.EVENT_PROPERTY_RESULT_CODE, resultCode);
event.put(TiC.EVENT_PROPERTY_INTENT, new IntentProxy(getTiContext(), data));
event.put(TiC.EVENT_PROPERTY_SOURCE, this);
resultCallback.callAsync(event);
}
#Override
public void onError(Activity activity, int requestCode, Exception e)
{
Log.i(LCAT, "onError Called");
if (resultCallback == null) return;
KrollDict event = new KrollDict();
event.put(TiC.EVENT_PROPERTY_REQUEST_CODE, requestCode);
event.put(TiC.EVENT_PROPERTY_ERROR, e.getMessage());
event.put(TiC.EVENT_PROPERTY_SOURCE, this);
resultCallback.callAsync(event);
}
And also see the Appcelerator JS calling the method in the module:
square.runPayment(2, 'Testing123', function(e) {
label1.text = 'Payment Successful!';
});

For those that come upon this question. The answer can be found in the module here:
https://github.com/hidef/Appcelerator-Square-Module (see the LaunchSquare.java class)
Basically, I used an Activity object that I created to receive the Square API's onResult update. I then was able to pass that back cleanly to the module class and hand it back via callback to the calling application.