Develop Reference

How to pend flutter method channel callback (android native java code) for an android listener

I have a flutter app that run a java code in some situations.
I wrote java code in method call handler in MethodCahnnel.
In this callback I call another method that is communicate with a serial port using usb-serial-for-android and wait for data in onNewData listener. I want to send back this data to flutter. and I am using a class variable for it and fill it in onNewData method. and use result.success conditionaly when the variable is not empty! but result.success never called and if I delete the if statement, result.success called when the variable is empty.
Here is the section of my code:
public class MainActivity extends FlutterActivity implements SerialInputOutputManager.Listener {
private static final String CHANNEL = "channel";
private UsbSerialPort connectionPort;
private String response = "";
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public void configureFlutterEngine(#NonNull FlutterEngine flutterEngine) {
super.configureFlutterEngine(flutterEngine);
new MethodChannel(flutterEngine.getDartExecutor().getBinaryMessenger(), CHANNEL)
.setMethodCallHandler(
(call, result) -> {
select();
if (!response.isEmpty()) result.success(response);
}
);
}
#Override
protected void onNewIntent(Intent intent) {
if (intent.getAction().equals("android.hardware.usb.action.USB_DEVICE_ATTACHED")) {
Toast.makeText(this, "new usb device detected!", Toast.LENGTH_SHORT).show();
}
super.onNewIntent(intent);
}
private void select() {
connectionPort.write(...);
}
#Override
public void onNewData(byte[] data) {
response = Utils.byteArrayToHexString(data);
}
#Override
public void onRunError(Exception e) {
status("error onRunError" + e.getMessage());
}
}

How to update UI on external asynctask on android

MainActivity execute external asynctask class
Here my code
public class MainActivity extends AppCompatActivity implements View.OnClickListener
...
public void onFirstBtnClick()
{
AysncClass ac = new AyncClass();
ac.execute();
}
and external asynctask
public class AysncClass extends AsyncTask<String, String, Integer>
#Override
protected Integer doInBackground(String... strings) {
Method1(strings[0], Integer.parseInt(strings[1]));
return null;
}
public Method1(Strins s, int i)
{
onProgressUpdate("first start");
publishProgress();
// do more work
onProgressUpdate("second start");
publishProgress();
}
public void Method2()
{
onProgressUpdate("Method2 here");
publishProgress();
}
...
#Override
protected void onProgressUpdate(final String... values) {
super.onProgressUpdate(values);
// what can i do here?
}
}
I use runOnUiThread like this in onProgressUpdate
((MainActivity)context).runOnUiThread(new Runnable()
{
#Override
public void run()
{
((MainActivity)context).tvRead.append(values[0]);
}
});*
but It occur 'java.lang.ArrayIndexOutOfBoundsException: length=0; index=0' even though values[0] is not null.
Also I use interface
this.context.WriteText(values[0]);
It occur same error
And I do this...
((MainActivity)context).tvRead.append(values[0]);
It occur 'java.lang.RuntimeException: An error occured while executing doInBackground()' and 'CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.'
...How can I resolve?

Do not call onProgressUpdate(). Instead just call publishProgress("The String").
By calling publishProgress without a parameter you will have no values in onProgressUpdate. That's why you get an IndexOutOfBondException.

Don't call onProgressUpdate on your own.
Call publishProgress("My Message");
In onProgressUpdate, don't use runOnUIThread.
OnProgressUpdate runs on the Ui thread only.
Instead of this
onProgressUpdate("Method2 here");
publishProgress();
Do this
publishProgress("Method2 here");

On ProgressUpdate will be in UIThread, no need again specify in UI thread. From DoInbackGround you have to make call publishProgress method for invoking OnProgressUpdate.

Use an interface as communicator between your Activity and AsyncTask
Create Interface
interface MyInterface {
void callActivityUi(String progress); // use float maybe
}
Initialize AsyncTask like this:
AysncClass as = new AysncClass(new MyInterface() {
#Override
void callActivityUi (String progress) {
// you will receive data here
}
});
Create a constructor in your AysncClass
private MyInterface myInterface;
public AysncClass (MyInterface myInterface) {
this.myInterface = myInterface;
}
Call Activity in onProgressUpdate(String... values)
myInterface.callActivityUi(values[0]);

Based on your code, you can use an interface to post the progress to the activity. I modified your code like this:
AsyncTask class
public class AysncClass extends AsyncTask<String, String, Integer> {
public interface SomeListener {
public void onSomething(Object mObject);
}
private SomeListener sl;
public AysncClass(SomeListener sl) {
this.sl = sl;
}
#Override
protected Integer doInBackground(String... strings) {
Method1(strings[0], Integer.parseInt(strings[1]));
return null;
}
public Method1(Strins s, int i) {
onProgressUpdate("first start");
publishProgress();
// do more work
onProgressUpdate("second start");
publishProgress();
}
public void Method2() {
onProgressUpdate("Method2 here");
publishProgress();
}
...
#Override
protected void onProgressUpdate(final String... values) {
super.onProgressUpdate(values);
// what can i do here?
sl.onSomething(mObject);
}
}
MainActivity class
public class MainActivity extends AppCompatActivity implements View.OnClickListener,
AysncClass.SomeListener {
...
public void onFirstBtnClick() {
AysncClass ac = new AyncClass(this);
ac.execute();
}
#Override
public void onSomething(Object mObject) {
//Do your UI work here
}
}

Loading multiple AdMob videos

For demonstration purposes, the app has one activity that simply offers this:
You click a button, view a rewarded video, and you are rewarded with whatever.
The Problem
How can I load the videos? From what I have seen you can only call mAd.loadAd() once. There are 3 videos, each with their own AD UNIT ID. Each ad unit can have its own listener, but only one video loads so it doesn't matter...
When trying to load multiple videos
For example:
mAd1.loadAd("AD_UNIT_1", new AdRequest.Builder().build());
mAd2.loadAd("AD_UNIT_2", new AdRequest.Builder().build());
mAd3.loadAd("AD_UNIT_3", new AdRequest.Builder().build());
results in only the last video being loaded and this in log:
W/Ads: Loading already in progress, saving this object for future refreshes.
onCreate()
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mAd1 = MobileAds.getRewardedVideoAdInstance(this);
mAd2 = MobileAds.getRewardedVideoAdInstance(this);
mAd3 = MobileAds.getRewardedVideoAdInstance(this);
listeners...
mAd1.loadAd() etc
}
Thank you for your help
Edit: It's clear I am thinking about this problem wrong. I have 5+ ad zones that each will play a rewarded video and give a different reward (for example, one gives coins, one gives a level up, and so on..). There is no reason to load 5 videos. I should load one in onCreate(), so it's ready when needed, then load it again after the item is rewarded so it's ready for next time.
So the question remains, if there is just the one video, and thus one ad zone, being loaded onCreate() then how can I track what reward to give?

Here's a simple solution...
MainActivity.java
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mAd = MobileAds.getRewardedVideoAdInstance(this);
mAd.setRewardedVideoAdListener(new RewardedVideoAdListener() {
#Override
public void onRewarded(RewardItem rewardItem) {
switch(Constants.currentAd) {
case("REWARD1"):
//do something
Constants.currentAd = "";
break;
case("REWARD2"):
//do something
Constants.currentAd = "";
break;
case("REWARD3"):
//do something
Constants.currentAd = "";
break;
}
}
});
mAd.loadAd("REWARDED_VIDEO_UNIT_ID", new AdRequest.Builder().build());
}
public void showRewardedVideo() {
if (mAd.isLoaded()) {
mAd.show();
}
}
Constants.java
public class Constants {
public static String currentAd = "";
}
Showing the ad after button click
rewardButton1.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Constants.currentAd = "REWARD1";
dismiss();
((MainActivity) getActivity()).showRewardedVideo();
}
});
REWARDED_VIDEO_UNIT_ID is one ad unit for rewarded video in AdMob...remove the rest. No need for other units, you can track whatever you like in the listener.

Other simple soluction...
AbstractRewardVideo.java
public abstract class AbstractRewardVideo {
private RewardedVideoAd mAd;
private String adId = "ca-app-pub...";
private Activity activity;
abstract protected RewardedVideoAdListener getListener();
public void init(Activity activity) {
this.activity = activity;
mAd = MobileAds.getRewardedVideoAdInstance(activity);
setAdId(adId);
loadRewardedVideoAd();
}
public Activity getActivity(){
return this.activity;
}
public void loadRewardedVideoAd() {
mAd.loadAd(adId, new AdRequest.Builder().build());
}
public void showVideo(){
setListener(getListener());
if (mAd.isLoaded()) {
mAd.show();
} else {
Utils.exibirToast("Don't loaded!");
}
}
public void setAdId(#NonNull String id){
this.adId = id;
}
public void setListener(RewardedVideoAdListener listener){
mAd.setRewardedVideoAdListener(listener);
}
}
Reward1.java
public class Reward1 extends AbstractRewardVideo {
public Reward1(Activity activity) {
init(activity);
}
#Override
protected RewardedVideoAdListener getListener() {
return new Listener();
}
private class Listener implements RewardedVideoAdListener {
#Override
public void onRewarded(RewardItem rewardItem) {
//Do something...
}
public void onRewardedVideoAdLoaded() {}
public void onRewardedVideoAdOpened() {}
public void onRewardedVideoStarted() {}
public void onRewardedVideoAdClosed() { loadRewardedVideoAd(); }
public void onRewardedVideoAdLeftApplication() {}
public void onRewardedVideoAdFailedToLoad(int i) {}
}
}
Reward2.java
public class Reward2 extends AbstractRewardVideo {
public Reward2(Activity activity) {
init(activity);
}
#Override
protected RewardedVideoAdListener getListener() {
return new Listener();
}
private class Listener implements RewardedVideoAdListener {
#Override
public void onRewarded(RewardItem rewardItem) {
//Do something...
}
public void onRewardedVideoAdLoaded() {}
public void onRewardedVideoAdOpened() {}
public void onRewardedVideoStarted() {}
public void onRewardedVideoAdClosed() { loadRewardedVideoAd(); }
public void onRewardedVideoAdLeftApplication() {}
public void onRewardedVideoAdFailedToLoad(int i) {}
}
}
MainActivity.java
public class MainActivity extends AppCompatActivity{
Reward1 reward1;
Reward2 reward2;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
reward1 = new Reward1(this);
reward2 = new Reward1(this);
...
reward1.showVideo();
...
reward2.showVideo();
}
}

MobileAds.initialize ( this, "ca-app-pub-4761500786576152~8215465788" );
RewardedVideoAd mAd = MobileAds.getRewardedVideoAdInstance(this);
mAd.setRewardedVideoAdListener(Video_Ad.this);
}
#Override
public void onRewardedVideoAdLoaded() {
}
#Override
public void onRewardedVideoAdOpened() {
}
#Override
public void onRewardedVideoStarted() {
}
#Override
public void onRewardedVideoAdClosed() {
}
#Override
public void onRewarded(RewardItem rewardItem) {
}
#Override
public void onRewardedVideoAdLeftApplication() {
}
#Override
public void onRewardedVideoAdFailedToLoad(int i) {
}
#Override
public void onRewardedVideoCompleted() {
}

AsyncTask data communication with nested Classes

I have a specific scenario and I need your help.
I'm trying to build an App in Android that involves network communication.
I am using AsyncTask for the http POST requests.
I have another class called Proxy (not a good one.. will be changed) which holds different kinds of functionalities (registerUser, setUserName, getUserPermission...)
And Of course, I have an Activity.
My Activity holds an instance of Proxy class.
My goal, is to push a button in the activity, it will call a method from Proxy class, which in its turn calls the AsyncTask's execute() method that actually run the http POST.
I was wondering how to get the data from AsyncTask's onPostExecute to my activity.
What I have in mind is to have an interface in AsyncTask, which will be implemented in Proxy class, and another interface in Proxy class which will be implemented in my Activity class.
Roll the data all the way to my Activity.
I want to hear your thoughts about whether this is the way to go, or another approach is preffered.
Thanks a lot for your help.
Adding some code
public class RegisterActivity extends FragmentActivity implements Proxy.OnProxyHttpPostResponseListener {
private Proxy proxy;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_register);
this.proxy = new Proxy();
this.proxy.setHttpPostResponseListener(this);
}
#Override
public void onProxyHttpPostResponse(String response) {
//Do something when http post returns
}
}
public class Proxy {
public interface OnProxyHttpPostResponseListener {
void onProxyHttpPostResponse(String response);
}
private OnProxyHttpPostResponseListener httpPostResponseListener;
public void setHttpPostResponseListener(OnProxyHttpPostResponseListener listener) {
this.httpPostResponseListener = listener;
}
private class HttpPostAsync extends AsyncTask<Pair<String, ArrayList<Pair<String, String>>>, Void, String> {
#Override
protected String doInBackground(Pair<String, ArrayList<Pair<String, String>>>... params) {
return this.httpPost(params[0].first, params[0].second);
}
protected void onPostExecute(String response) {
httpPostResponseListener.onProxyHttpPostResponse(response);
}
}

If you're just needing HTTP POST functionality then an AsyncTask might not be the best choice. AsyncTask really shines if you need to get progress updates as the task is executing (with onProgressUpdate(Progress... progress)). If you'd like to use AsyncTask nonetheless, iroiroys' reply should help.
A bit more simply, you could just use a Handler thread straight up. Something like this:
public class HandlerExampleActivity extends Activity {
private Button postButton;
private Button getButton;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_handler_example);
backgroundThread = new BackgroundThread();
backgroundThread.start();
postButton = (Button) findViewById(R.id.button_post);
postbutton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
backgroundThread.post("DATA_HERE");
}
});
getButton = (Button) findViewById(R.id.button_get);
getbutton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
backgroundThread.get("URL_HERE");
}
});
}
#Override
protected void onDestroy() {
super.onDestroy();
backgroundThread.exit();
}
private class BackgroundThread extends Thread {
private Handler backgroundHandler;
public void run() {
Looper.prepare();
backgroundHandler = new Handler();
Looper.loop();
}
public void post(DataType data) {
backgroundHandler.post(new Runnable() {
#Override
public void run() {
// pull data and do the POST
uiMsg = uiHandler.obtainMessage(POST_COMPLETE, whatever_data_passing_back, 0, null);
uiHandler.sendMessage(uiMsg);
}
});
}
public void get(URL data) {
backgroundHandler.post(new Runnable() {
#Override
public void run() {
// GET data
uiMsg = uiHandler.obtainMessage(GET_COMPLETE, whatever_data_passing_back, 0, null);
uiHandler.sendMessage(uiMsg);
}
});
}
public void exit() {
backgroundHandler.getLooper().quit();
}
}
private final Handler uiHandler = new Handler() {
public void handleMessage(Message msg) {
switch(msg.what) {
case POST_COMPLETE:
// handle it
break;
case GET_COMPLETE:
// handle it
break
case MESSAGE_BACK_TO_UI_THREAD:
// do something
break;
case OPERATION_FAIL:
// oh no!
break;
case OPERATION_SUCCESS:
// yay!
break;
}
}
};
}

I suggest you try Handler and Handler.Callback.
Below I made it simple example..
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.os.Handler.Callback;
import android.os.Message;
public class MainActivity extends Activity implements Callback {
Handler handler;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
handler = new Handler(this);
Proxy proxy = new Proxy(handler);
proxy.foo();
}
private class Proxy {
Handler handler;
public Proxy(Handler handler) {
this.handler = handler;
}
private void foo() {
new myAsync().execute();
}
private class myAsync extends AsyncTask<Void, Void, Void> {
#Override
protected Void doInBackground(Void... params) {
return null;
}
#Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
Message msg = handler.obtainMessage();
msg.obj = result;
handler.sendMessage(msg);
}
}
}
#Override
public boolean handleMessage(Message msg) {
// Handle Message here!
return false;
}
}

Android: toast inside AsyncTask

I have an AsyncTask class SearchForQuestions that is called from an Activity QuizMap. When looping through an array in SearchForQuestions I can't find the correct context for toast to appear within the AsynTask.
The standard Toast.makeText(getApplicationContext(), "This is Toast!!!", Toast.LENGTH_SHORT).show(); gives error getApplicationContext() undefined.
I have tried some of the solutions to this offerred by SO, most of them are listed here and concern getting UiThread and running on that.
I can't get this to work however. Here's example code snippets of what i have tried. I have put a method in QuizMap and try calling it from SearchForQuestions but SearchForQuestions isn't recognised. How can I get around this? )Still a newbie at java...)
// QuizMap activity
public class QuizMap extends FragmentActivity
implements OnMarkerClickListener {
private GoogleMap map;
private static final String TAG = "QuizMap"; // debugging
...
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_quizmap);
map = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map))
.getMap();
...
}
// make toast inside AsyncTask
public void showNotNearToast(final String toast) {
QuizMap.this.runOnUiThread(new Runnable() {
public void run() {
Toast.makeText(QuizMap.this, "This is Toast!!!", Toast.LENGTH_SHORT).show();
}});
}
.
// SearchForQuestions class
private class SearchForQuestions extends AsyncTask<String, Void, DataHandler> {
// checks for proximity to question locations
Location location =
locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
#Override
protected DataHandler doInBackground(String... pointsList) {
String result = pointsList[0];
...
}
#Override
protected void onPostExecute(DataHandler result) {
ArrayList<String> resultsArray = result.results;
Integer numPoints = resultsArray.size();
for (int i =0;i<numPoints;i++){
String[] pointDetails = resultsArray.get(i).split("::");
...
// we can make use of the Android distanceTo function to calculate the distances
float distance = location.distanceTo(fixedLoc);
if (i > DIST) { // this is UCL
showNotNearToast("My Message"); // showNotNearToast undefined
if (distance < DIST) {
...
}
};

I'm going t close this question. I haven't solved my problem but the number of answers provided that apparently work in other situations suggest there's something else going on. I'm going to re-structure the classes to get around having to call from within AsyncTask.

Just Toast it, why do you want to create a function for it? onPostExecute() is already on UI thread.
You are not able to access because inner Class can not call functions of Outer class unless you pass instance of the outer class.

Call your toast in onPostExecute
Create an interface for a callback.
public interface ToastCallback {
public void invoke(String text);
}
Your AsyncTask constructor
private ToastCallback toastCallback;
public SearchQuestions(ToastCallback callback) {
this.toastCallback = callback;
}
// in doInBackground() {
toastCallback.invoke("Toast from background");
}
In Your Activity,
private void showNotNearToast(String text) {
runOnUiThread(new Runnable() {
#Override
public void run() {
Toast.makeText(getApplicationContext(), text, Toast.LENGTH_SHORT).show();
}
});
}
public class MyToastCallback implements ToastCallback {
#Override
public void invoke(String text) {
showNotNearToast(text);
}
}
// Asynctask call
new SearchQuestion(new MyTosatCallback()).execute(<Your params here>);

Try this from inside your AsyncTask:
myActivity.this.runOnUiThread(new Runnable() {
public void run() {
Toast.makeText(activity, "Hello", Toast.LENGTH_SHORT).show();
}
});
Where you have your
showNotNearToast("My Message"); // showNotNearToast undefined
Replace myActivity with the name of your Activity.

(Ab)use the publishProgress method
private class ToastAsyncTask extends AsyncTask<Void, String, Void>{
#Override
protected Void doInBackground(Void... voids) {
SystemClock.sleep(1000);
publishProgress("Toast msg string");
SystemClock.sleep(1000);
return null;
}
#Override
protected void onProgressUpdate(String... values) {
Toast.makeText(getApplicationContext(), values[0], Toast.LENGTH_SHORT).show();
}
}
**UPDATE: ** since you are having problems with context for some reason, use this version. Tough the implementation above works for me.
private class ToastAsyncTask extends AsyncTask<Void, String, Void> {
private WeakReference<Context> contextRef;
public ToastAsyncTask(Context context) {
contextRef = new WeakReference<Context>(context);
}
#Override
protected Void doInBackground(Void... voids) {
SystemClock.sleep(1000);
publishProgress("Toast msg string");
SystemClock.sleep(1000);
return null;
}
#Override
protected void onProgressUpdate(String... values) {
if (contextRef.get() != null) {
Toast.makeText(contextRef.get(), values[0], Toast.LENGTH_SHORT).show();
} else {
// The context was destroyed.. check what you are doing
}
}
}
Use it like this
new ToastAsyncTask(MainActivity.this).execute();

Pass the activity into the AsyncTask. See below.
private class SearchForQuestions extends AsyncTask<String, Void, DataHandler> {
Activity activity;
public void SearchForQuestions(Activity activity){
this.activity = activity;
}
//... rest of the code
public class QuizMap extends FragmentActivity implements OnMarkerClickListener {
/*...*/
new SearchForQuestions(this).execute();
/*...*/
/*When calling the toast:*/
Toast.makeText(this.activity, "This is Toast!!!", Toast.LENGTH_SHORT).show();