Need some help. I used double click on back button for exit app with Toast with next code:
#Override
public void onBackPressed() {
if (back_pressed + 2000 > System.currentTimeMillis()) {
super.onBackPressed();
} else {
Toast.makeText(getBaseContext(), "Нажмите еще раз для выхода", Toast.LENGTH_SHORT).show();
}
back_pressed = System.currentTimeMillis();
}
Found that fragment code here at stackoverflow. I guess this is the best solution for issue. But there is one ecxeption - toast is still on screen after exiting app. How to kill the toast when user click back button twice and application closed?
We can't kill toast when application closes. We can use toast like below code. Toast.LENGTH_SHORT).show(); less duration of toast when your app closes.
Toast.makeText(this, "Press again to exit.. ", Toast.LENGTH_SHORT).show();
Or, you can set Duration of Toast by code below:
Toast toast = Toast.makeText(getApplicationContext(), "Press again to exit..", Toast.LENGTH_SHORT);
toast.show();
Handler handler = new Handler();
handler.postDelayed(new Runnable() {
#Override
public void run() {
toast.cancel();
}
}, 500);
Or, you can use this :
private Toast toast = null;
toast = Toast.makeText(getApplicationContext(), "", Toast.LENGTH_SHORT);
#Override
public void onBackPressed() {
if (doubleBackToExitPressedOnce) {
super.onBackPressed();
return;
}
this.doubleBackToExitPressedOnce = true;
//Toast.makeText(this, "Press again to exit..", Toast.LENGTH_SHORT).show();
toast.setText("Press again to exit..");
toast.show();
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
doubleBackToExitPressedOnce=false;
}
}, 2000);
}
#Override
protected void onStop () {
super.onStop();
toast.cancel();
}
You should be able to reach your goal by Using an helper class. In my applications I call this ToastManager.
In this class, you will manage every toast of your application and you can decide whether to dismiss or show them.
I did it to avoid the Toast queue, I'm dismissing the Toast when another one is shown.
You can implement it like below and call the dismissToast method in your custom application or Activity.
public class ToastManager {
private static Toast m_currentToast;
public static void showToast(Context ctx, String text)
{
try {
if (m_currentToast != null) {
m_currentToast.cancel();
}
m_currentToast = Toast.makeText(ctx, text, Toast.LENGTH_LONG);
m_currentToast.show();
}catch(Exception ex){
ex.printStackTrace();
}
}
public static void dismissToast(){
if(m_currentToast != null){
m_currentToast.cancel();
}
}
}
Obv you will have to create each tost by calling the showToast method.
hope this helps
Next code erase toast immediately after closing application:
#Override
protected void onStop () {
toast.cancel();
super.onStop();
}
I guess this is enough for my app, it's looking great.
Tnx Abhishek kumar )
I'm using Toast to show some informations to the user, because I want to show the newest message without delay regardless of the previous messages, I do it like this (learned from old projects):
public class MainActivity extends Activity {
private Toast mToast;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mToast = Toast.makeText(this, "", Toast.LENGTH_SHORT);
}
private void toast(final String message) {
runOnUiThread(new Runnable() {
#Override
public void run() {
mToast.setText(message);
mToast.show();
}
});
}
}
That is, the single Toast object is reused and showed multiple times, whenever I need show a new message, I just setText and show it again. It seems working fine, but after I did some searching on Google, I found most people will do it like this:
private void toast(final String message) {
runOnUiThread(new Runnable() {
#Override
public void run() {
mToast.cancel();
mToast = Toast.makeText(MainActivity.this, message, Toast.LENGTH_SHORT);
mToast.show();
}
});
}
Which cancel the previous Toast then make a new one by Toast.makeText.
Are there any differences? Which one should I prefer?
You can cache current Toast in Activity's variable, and then cancel it just before showing next toast. Here is an example:
Toast m_currentToast;
void showToast(String text)
{
if(m_currentToast != null)
{
m_currentToast.cancel();
}
m_currentToast = Toast.makeText(this, text, Toast.LENGTH_LONG);
m_currentToast.show();
}
Another way to instantly update Toast message:
void showToast(String text)
{
if(m_currentToast == null)
{
m_currentToast = Toast.makeText(this, text, Toast.LENGTH_LONG);
}
m_currentToast.setText(text);
m_currentToast.setDuration(Toast.LENGTH_LONG);
m_currentToast.show();
}
Reference : How to immediately replace the current toast with a second one without waiting for the current one to finish?
You should try code something like this to avoid visibility of multiple toast at a time.
private void toast(final String message) {
try{ mToast.getView().isShown(); // true if visible
mToast.setText(message);
} catch (Exception e) { // invisible if exception
mToast = Toast.makeText(theContext, message, toastDuration);
}
mToast.show(); //finally display it
}
code help me is here
What does the following exception mean; how can I fix it?
This is the code:
Toast toast = Toast.makeText(mContext, "Something", Toast.LENGTH_SHORT);
This is the exception:
java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
at android.os.Handler.<init>(Handler.java:121)
at android.widget.Toast.<init>(Toast.java:68)
at android.widget.Toast.makeText(Toast.java:231)
You need to call Toast.makeText(...) from the UI thread:
activity.runOnUiThread(new Runnable() {
public void run() {
Toast.makeText(activity, "Hello", Toast.LENGTH_SHORT).show();
}
});
This is copy-pasted from another (duplicate) SO answer.
You're calling it from a worker thread. You need to call Toast.makeText() (and most other functions dealing with the UI) from within the main thread. You could use a handler, for example.
Look up Communicating with the UI Thread in the documentation. In a nutshell:
// Set this up in the UI thread.
mHandler = new Handler(Looper.getMainLooper()) {
#Override
public void handleMessage(Message message) {
// This is where you do your work in the UI thread.
// Your worker tells you in the message what to do.
}
};
void workerThread() {
// And this is how you call it from the worker thread:
Message message = mHandler.obtainMessage(command, parameter);
message.sendToTarget();
}
Other options:
You could use Activity.runOnUiThread(). Straightforward if you have an Activity:
#WorkerThread
void workerThread() {
myActivity.runOnUiThread(() -> {
// This is where your UI code goes.
}
}
You could also post to the main looper. This works great if all you have is a Context.
#WorkerThread
void workerThread() {
ContextCompat.getMainExecutor(context).execute(() -> {
// This is where your UI code goes.
}
}
Deprecated:
You could use an AsyncTask, that works well for most things running in the background. It has hooks that you can call to indicate the progress, and when it's done.
It's convenient, but can leak contexts if not used correctly. It's been officially deprecated, and you shouldn't use it anymore.
UPDATE - 2016
The best alternative is to use RxAndroid (specific bindings for RxJava) for the P in MVP to take charge fo data.
Start by returning Observable from your existing method.
private Observable<PojoObject> getObservableItems() {
return Observable.create(subscriber -> {
for (PojoObject pojoObject: pojoObjects) {
subscriber.onNext(pojoObject);
}
subscriber.onCompleted();
});
}
Use this Observable like this -
getObservableItems().
subscribeOn(Schedulers.io()).
observeOn(AndroidSchedulers.mainThread()).
subscribe(new Observer<PojoObject> () {
#Override
public void onCompleted() {
// Print Toast on completion
}
#Override
public void onError(Throwable e) {}
#Override
public void onNext(PojoObject pojoObject) {
// Show Progress
}
});
}
----------------------------------------------------------------------------------------------------------------------------------
I know I am a little late but here goes.
Android basically works on two thread types namely UI thread and background thread. According to android documentation -
Do not access the Android UI toolkit from outside the UI thread to fix this problem, Android offers several ways to access the UI thread from other threads. Here is a list of methods that can help:
Activity.runOnUiThread(Runnable)
View.post(Runnable)
View.postDelayed(Runnable, long)
Now there are various methods to solve this problem.
I will explain it by code sample:
runOnUiThread
new Thread()
{
public void run()
{
myactivity.this.runOnUiThread(new Runnable()
{
public void run()
{
//Do your UI operations like dialog opening or Toast here
}
});
}
}.start();
LOOPER
Class used to run a message loop for a thread. Threads by default do
not have a message loop associated with them; to create one, call
prepare() in the thread that is to run the loop, and then loop() to
have it process messages until the loop is stopped.
class LooperThread extends Thread {
public Handler mHandler;
public void run() {
Looper.prepare();
mHandler = new Handler() {
public void handleMessage(Message msg) {
// process incoming messages here
}
};
Looper.loop();
}
}
AsyncTask
AsyncTask allows you to perform asynchronous work on your user
interface. It performs the blocking operations in a worker thread and
then publishes the results on the UI thread, without requiring you to
handle threads and/or handlers yourself.
public void onClick(View v) {
new CustomTask().execute((Void[])null);
}
private class CustomTask extends AsyncTask<Void, Void, Void> {
protected Void doInBackground(Void... param) {
//Do some work
return null;
}
protected void onPostExecute(Void param) {
//Print Toast or open dialog
}
}
Handler
A Handler allows you to send and process Message and Runnable objects
associated with a thread's MessageQueue.
Message msg = new Message();
new Thread()
{
public void run()
{
msg.arg1=1;
handler.sendMessage(msg);
}
}.start();
Handler handler = new Handler(new Handler.Callback() {
#Override
public boolean handleMessage(Message msg) {
if(msg.arg1==1)
{
//Print Toast or open dialog
}
return false;
}
});
Toast.makeText() can only be called from Main/UI thread. Looper.getMainLooper() helps you to achieve it:
JAVA
new Handler(Looper.getMainLooper()).post(new Runnable() {
#Override
public void run() {
// write your code here
}
});
KOTLIN
Handler(Looper.getMainLooper()).post {
// write your code here
}
An advantage of this method is that you can run UI code without Activity or Context.
Try this, when you see runtimeException due to Looper not prepared before handler.
Handler handler = new Handler(Looper.getMainLooper());
handler.postDelayed(new Runnable() {
#Override
public void run() {
// Run your task here
}
}, 1000 );
I ran into the same problem, and here is how I fixed it:
private final class UIHandler extends Handler
{
public static final int DISPLAY_UI_TOAST = 0;
public static final int DISPLAY_UI_DIALOG = 1;
public UIHandler(Looper looper)
{
super(looper);
}
#Override
public void handleMessage(Message msg)
{
switch(msg.what)
{
case UIHandler.DISPLAY_UI_TOAST:
{
Context context = getApplicationContext();
Toast t = Toast.makeText(context, (String)msg.obj, Toast.LENGTH_LONG);
t.show();
}
case UIHandler.DISPLAY_UI_DIALOG:
//TBD
default:
break;
}
}
}
protected void handleUIRequest(String message)
{
Message msg = uiHandler.obtainMessage(UIHandler.DISPLAY_UI_TOAST);
msg.obj = message;
uiHandler.sendMessage(msg);
}
To create the UIHandler, you'll need to perform the following:
HandlerThread uiThread = new HandlerThread("UIHandler");
uiThread.start();
uiHandler = new UIHandler((HandlerThread) uiThread.getLooper());
Hope this helps.
Reason for an error:
Worker threads are meant for doing background tasks and you can't show anything on UI within a worker thread unless you call method like runOnUiThread. If you try to show anything on UI thread without calling runOnUiThread, there will be a java.lang.RuntimeException.
So, if you are in an activity but calling Toast.makeText() from worker thread, do this:
runOnUiThread(new Runnable()
{
public void run()
{
Toast toast = Toast.makeText(getApplicationContext(), "Something", Toast.LENGTH_SHORT).show();
}
});
The above code ensures that you are showing the Toast message in a UI thread since you are calling it inside runOnUiThread method. So no more java.lang.RuntimeException.
that's what i did.
new Handler(Looper.getMainLooper()).post(new Runnable() {
#Override
public void run() {
Toast(...);
}
});
Visual components are "locked" to changes from outside threads.
So, since the toast shows stuff on the main screen that is managed by the main thread, you need to run this code on that thread.
Hope that helps:)
I was getting this error until I did the following.
public void somethingHappened(final Context context)
{
Handler handler = new Handler(Looper.getMainLooper());
handler.post(
new Runnable()
{
#Override
public void run()
{
Toast.makeText(context, "Something happened.", Toast.LENGTH_SHORT).show();
}
}
);
}
And made this into a singleton class:
public enum Toaster {
INSTANCE;
private final Handler handler = new Handler(Looper.getMainLooper());
public void postMessage(final String message) {
handler.post(
new Runnable() {
#Override
public void run() {
Toast.makeText(ApplicationHolder.INSTANCE.getCustomApplication(), message, Toast.LENGTH_SHORT)
.show();
}
}
);
}
}
runOnUiThread(new Runnable() {
public void run() {
Toast.makeText(mContext, "Message", Toast.LENGTH_SHORT).show();
}
});
Wonderful Kotlin solution:
runOnUiThread {
// Add your ui thread code here
}
first call Looper.prepare() and then call Toast.makeText().show() last call Looper.loop() like:
Looper.prepare() // to be able to make toast
Toast.makeText(context, "not connected", Toast.LENGTH_LONG).show()
Looper.loop()
This is because Toast.makeText() is calling from a worker thread. It should be call from main UI thread like this
runOnUiThread(new Runnable() {
public void run() {
Toast toast = Toast.makeText(mContext, "Something", Toast.LENGTH_SHORT);
}
});
The answer by ChicoBird worked for me. The only change I made was in the creation of the UIHandler where I had to do
HandlerThread uiThread = new HandlerThread("UIHandler");
Eclipse refused to accept anything else. Makes sense I suppose.
Also the uiHandler is clearly a class global defined somewhere. I still don't claim to understand how Android is doing this and what is going on but I am glad it works. Now I will proceed to study it and see if I can understand what Android is doing and why one has to go through all these hoops and loops. Thanks for the help ChicoBird.
For Rxjava and RxAndroid User:
public static void shortToast(String msg) {
Observable.just(msg)
.observeOn(AndroidSchedulers.mainThread())
.subscribe(message -> {
Toast.makeText(App.getInstance(), message, Toast.LENGTH_SHORT).show();
});
}
Coroutine will do it perfectly
CoroutineScope(Job() + Dispatchers.Main).launch {
Toast.makeText(context, "yourmessage",Toast.LENGTH_LONG).show()}
I was running into the same issue when my callbacks would try to show a dialog.
I solved it with dedicated methods in the Activity - at the Activity instance member level - that use runOnUiThread(..)
public void showAuthProgressDialog() {
runOnUiThread(new Runnable() {
#Override
public void run() {
mAuthProgressDialog = DialogUtil.getVisibleProgressDialog(SignInActivity.this, "Loading ...");
}
});
}
public void dismissAuthProgressDialog() {
runOnUiThread(new Runnable() {
#Override
public void run() {
if (mAuthProgressDialog == null || ! mAuthProgressDialog.isShowing()) {
return;
}
mAuthProgressDialog.dismiss();
}
});
}
Java 8
new Handler(Looper.getMainLooper()).post(() -> {
// Work in the UI thread
});
Kotlin
Handler(Looper.getMainLooper()).post{
// Work in the UI thread
}
GL
Handler handler2;
HandlerThread handlerThread=new HandlerThread("second_thread");
handlerThread.start();
handler2=new Handler(handlerThread.getLooper());
Now handler2 will use a different Thread to handle the messages than the main Thread.
To display a dialog or a toaster in a thread, the most concise way is to use the Activity object.
For example:
new Thread(new Runnable() {
#Override
public void run() {
myActivity.runOnUiThread(new Runnable() {
public void run() {
myActivity.this.processingWaitDialog = new ProgressDialog(myActivity.this.getContext());
myActivity.this.processingWaitDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
myActivity.this.processingWaitDialog.setMessage("abc");
myActivity.this.processingWaitDialog.setIndeterminate(true);
myActivity.this.processingWaitDialog.show();
}
});
expenseClassify.serverPost(
new AsyncOperationCallback() {
public void operationCompleted(Object sender) {
myActivity.runOnUiThread(new Runnable() {
public void run() {
if (myActivity.this.processingWaitDialog != null
&& myActivity.this.processingWaitDialog.isShowing()) {
myActivity.this.processingWaitDialog.dismiss();
myActivity.this.processingWaitDialog = null;
}
}
}); // .runOnUiThread(new Runnable()
...
Using lambda:
activity.runOnUiThread(() -> Toast.makeText(activity, "Hello", Toast.LENGTH_SHORT).show());
Toast, AlertDialogs needs to run on UI thread, you can use Asynctask to use them properly in android development.but some cases we need to customize the time outs, so we use Threads, but in threads we cannot use Toast,Alertdialogs like we using in AsyncTask.So we need separate Handler for popup those.
public void onSigned() {
Thread thread = new Thread(){
#Override
public void run() {
try{
sleep(3000);
Message message = new Message();
message.what = 2;
handler.sendMessage(message);
} catch (Exception e){
e.printStackTrace();
}
}
};
thread.start();
}
in Above example i want to sleep my thread in 3sec and after i want to show a Toast message,for that in your mainthread implement handler.
handler = new Handler() {
public void handleMessage(Message msg) {
switch(msg.what){
case 1:
Toast.makeText(getActivity(),"cool",Toast.LENGTH_SHORT).show();
break;
}
super.handleMessage(msg);
}
};
I used switch case here, because if you need to show different message in same way, you can use switch case within Handler class...hope this will help you
This usually happens when something on the main thread is called from any background thread. Lets look at an example , for instance.
private class MyTask extends AsyncTask<Void, Void, Void> {
#Override
protected Void doInBackground(Void... voids) {
textView.setText("Any Text");
return null;
}
}
In the above example , we are setting text on the textview which is in the main UI thread from doInBackground() method , which operates only on a worker thread.
I had the same problem and I fixed it simply by putting the Toast in onPostExecute() override function of the Asynctask<> and it worked.
You need to create toast on UI thread. Find the example below.
runOnUiThread(new Runnable() {
public void run() {
Toast.makeText(activity, "YOUR_MESSAGE", Toast.LENGTH_SHORT).show();
}
});
For displaying Toast message please refer to this article
Here is the solution for Kotlin using Coroutine:
Extend your class with CoroutineScope by MainScope():
class BootstrapActivity : CoroutineScope by MainScope() {}
Then simply do this:
launch {
// whatever you want to do in the main thread
}
Don't forget to add the dependencies for coroutine:
org.jetbrains.kotlinx:kotlinx-coroutines-core:${Versions.kotlinCoroutines}
org.jetbrains.kotlinx:kotlinx-coroutines-android:${Versions.kotlinCoroutines}
Create Handler outside the Thread
final Handler handler = new Handler();
new Thread(new Runnable() {
#Override
public void run() {
try{
handler.post(new Runnable() {
#Override
public void run() {
showAlertDialog(p.getProviderName(), Token, p.getProviderId(), Amount);
}
});
}
}
catch (Exception e){
Log.d("ProvidersNullExp", e.getMessage());
}
}
}).start();
Recently, I encounter this problem - It was happening because I was trying to call a function that was to do some UI stuff from the constructor. Removing the initialization from the constructor solved the problem for me.
I got the same problem and this code is working fine for me now.
As an example this is my code to do a task in the background and UI thread.
Observe how the looper is used:
new Thread(new Runnable() {
#Override
public void run() {
Looper.prepare();
// your Background Task here
runOnUiThread(new Runnable() {
#Override
public void run() {
// update your UI here
Looper.loop();
}
});
}
}).start();
i use the following code to show message from non main thread "context",
#FunctionalInterface
public interface IShowMessage {
Context getContext();
default void showMessage(String message) {
final Thread mThread = new Thread() {
#Override
public void run() {
try {
Looper.prepare();
Toast.makeText(getContext(), message, Toast.LENGTH_LONG).show();
Looper.loop();
} catch (Exception error) {
error.printStackTrace();
Log.e("IShowMessage", error.getMessage());
}
}
};
mThread.start();
}
}
then use as the following:
class myClass implements IShowMessage{
showMessage("your message!");
#Override
public Context getContext() {
return getApplicationContext();
}
}
I have an IntentService that downloads some files. The problem is that I create a Toast inside the IntentService like this
Toast.makeText(getApplicationContext(), "some message", Toast.LENGTH_SHORT).show();
The Toast will never disappear event if I exit the app. The only way to destroy it is to kill the process.
What am I doing wrong?
The problem is that IntentService is not running on the main application thread. you need to obtain a Handler for the main thread (in onCreate()) and post the Toast to it as a Runnable.
the following code should do the trick:
#Override
public void onCreate() {
super.onCreate();
mHandler = new Handler();
}
#Override
protected void onHandleIntent(Intent intent) {
mHandler.post(new Runnable() {
#Override
public void run() {
Toast.makeText(MyIntentService.this, "Hello Toast!", Toast.LENGTH_LONG).show();
}
});
}
This works for me:
public void ShowToastInIntentService(final String sText) {
final Context MyContext = this;
new Handler(Looper.getMainLooper()).post(new Runnable() {
#Override
public void run() {
Toast toast1 = Toast.makeText(MyContext, sText, Toast.LENGTH_LONG);
toast1.show();
}
});
};
IntentService will create a thread to handle the new intent, and terminated it immediately once the task has done. So, the Toast will be out of controlled by a dead thread.
You should see some exceptions in the console when the toast showing on the screen.
For people developing in Xamarin studio, this is how its done there:
Handler handler = new Handler ();
handler.Post (() => {
Toast.MakeText (_Context, "Your text here.", ToastLength.Short).Show ();
});
To show a toast when the user is in one of the application activity.
Just need a reference of the current activity, and call it with this sample code:
public void showToast(final String msg) {
final Activity a = currentActivity;
if (a != null ) {
a.runOnUiThread(new Runnable() {
#Override
public void run() {
Toast.makeText(a, msg, Toast.LENGTH_SHORT).show();
}
});
}
}
There is a lot of options to get the current activity, check this question:
How to get current foreground activity context in android?
But I use this approach:
The application must have:
private Activity currentActivity = null;
public Activity getCurrentActivity() {
return currentActivity;
}
public void setCurrentActivity(Activity mCurrentActivity) {
this.currentActivity = mCurrentActivity;
}
Each activity must have:
#Override
protected void onResume() {
super.onResume();
((MyApplication) getApplication()).setCurrentActivity(this);
}
#Override
protected void onPause() {
super.onPause();
((MyApplication) getApplication()).setCurrentActivity(null);
}
You shouldn't create Toasts from a Service. You should use a Notification instead.