Dialogs AlertDialogs How to block execution while dialog is up NET-style

Question

Coming from the  NET-environment  I m now looking to understand how Dialogs work in Android   In  NET  when calling MessageBox Show      that creates and shows a popup dialog  In the call to Show I can specify what buttons should be available in the popup  for example   DialogResult myDialogResult   MessageBox Show  My text here    My caption here   MessageBoxButtons YesNoCancel     As you can see  the call to Show returns a DialogResult when a button is pressed in the popup  informing me what button was clicked  Note that in  NET  execution is halted at the line where the call to Show      is made  so it can return the value when a button is pressed   If I in the above example press  No  the myDialogResult will be equal to   myDialogResult    DialogResult No   Since I find the  NET-way of using creating popups very easy and intuitive  I would like that way of creating popups in Android too    So  the question is if anyone know how to  halt execution  like with the MessageBox Show  and then return a value whenever the Button is pressed  and the dialog goes away    Edit 1  To be a little bit more clear   I need for the execution to halt and wait until the user has chosen a button to click in the popup  The code that follow the call to show the Dialog is dependent on what button is clicked in the Dialog   That s why I cannot use what Erich and Alex suggest  since writing code in the onClick-methods as suggested below is not going to work  The reason is that I cannot continue the  normal execution   Let me take an example   Let me take an example   int nextStep   0     this variable will not be reached from within the onClick-methods  AlertDialog Builder builder   new AlertDialog Builder this   builder setMessage  Hello            setPositiveButton  Ok   new DialogInterface OnClickListener                 public void onClick DialogInterface dialog  int id                    nextStep   1         COMPILER ERROR                                         setNegativeButton  Cancel   new DialogInterface OnClickListener                 public void onClick DialogInterface dialog  int id                    nextStep   2         COMPILER ERROR                                         create   show     if  nextStep    1           then do some damage   else if  nextStep    2        dont do damage   If I wanted the execution to be dependent on the choice in the popup  I would somehow have to make all the variables in the  normal execution   in this case nextStep  available in the onClick-methods  and that sounds like hell to me   Edit 2  Another obvious example would be a popup asking  Do you want to continue  with the options  Yes  and  No    If the user presses  Yes   the whole method should be aborted otherwise it should continue execution  How do you solve that nicely

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UserSelect  null  AlertDialog Builder builder   new Builder ImonaAndroidApp LoginScreen               builder setMessage  you message                builder setPositiveButton  OK   new OnClickListener                       Override                 public void onClick DialogInterface dialog  int which                        UserSelect   true                                                   builder setNegativeButton  Cancel   new OnClickListener                       Override                 public void onClick DialogInterface dialog  int which                        UserSelect   false                                                    in UI thread         builder show                            wait until the user select             while UserSelect   null

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Developers of Android and iOS decided that they are powerful and smart enough to reject Modal Dialog conception  that was on market for many-many years already and didn t bother anyone before   unfortunately for us  I believe that there is work around for Android - since you can show dialog from non-ui thread using Runnable class  there should be a way to wait in that thread  non-ui  until dialog is finished   Edit  Here is my solution  it works great       int pressedButtonID      private final Semaphore dialogSemaphore   new Semaphore 0  true       final Runnable mMyDialog   new Runnable                 public void run                         AlertDialog errorDialog   new AlertDialog Builder   your activity object here    create                errorDialog setMessage  My dialog                 errorDialog setButton  My Button1   new DialogInterface OnClickListener                      Override                 public void onClick DialogInterface dialog  int which                        pressedButtonID   MY BUTTON ID1                      dialogSemaphore release                                                          errorDialog setButton2  My Button2   new DialogInterface OnClickListener                      Override                 public void onClick DialogInterface dialog  int which                        pressedButtonID   MY BUTTON ID2                      dialogSemaphore release                                                          errorDialog setCancelable false               errorDialog show                          public int ShowMyModalDialog      should be called from non-UI thread               pressedButtonID   MY BUTTON INVALID ID          runOnUiThread mMyDialog           try                       dialogSemaphore acquire                      catch  InterruptedException e                              return pressedButtonID

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A simplified version of Daniel s answer above  This function gets a yes or no from user in an alert dialog but could easily be modified to get other input   private boolean mResult  public boolean getYesNoWithExecutionStop String title  String message  Context context           make a handler that throws a runtime exception when a message is received     final Handler handler   new Handler              Override         public void handleMessage Message mesg                throw new RuntimeException                              make a text input dialog and show it     AlertDialog Builder alert   new AlertDialog Builder context       alert setTitle title       alert setMessage message       alert setPositiveButton  Yes   new DialogInterface OnClickListener             public void onClick DialogInterface dialog  int whichButton                mResult   true              handler sendMessage handler obtainMessage                           alert setNegativeButton  No   new DialogInterface OnClickListener             public void onClick DialogInterface dialog  int whichButton                mResult   false              handler sendMessage handler obtainMessage                           alert show            loop till a runtime exception is triggered      try   Looper loop          catch RuntimeException e2          return mResult

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In Android Dialogs are asynchronous so you re going to have to structure your code a little differently   So in C  your logic ran something like this in pseudocode   void doSomeStuff         int result   showDialog  Pick Yes or No         if  result    YES              do stuff for yes           else if  result    NO              do stuff for no              finish off here     For Android it s going to have to be less neat   Think of it like so   You ll have an OnClickListener like this   public void onClick DialogInterface dialog  int whichButton       if  whichButton    BUTTON POSITIVE          doOptionYes            else if  whichButton    BUTTON NEGATIVE          doOptionNo             Which is then supported by the following methods   void doOptionYes           do stuff for yes     endThings       void doOptionNo           do stuff for no     endThings       void endThings           clean up here     So what was one method is now four   It may not seem as neat but that s how it works I m afraid

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Ted  as you probably found out  you unfortunately can t do that on Android  Dialogs are modal  but asynchronous  and it will definitely disrupt the sequence you re trying to establish as  you would have done on  NET  or Windows for that matter   You will have to twist your code around and break some logic that would have been very easy to follow based on your example    Another very simple example is to save data in a file  only to find out that the file is already there and asking to overwrite it or not  Instead of displaying a dialog and having an if statement to act upon the result  Yes No   you will have to use callbacks  called listeners in Java  and split your logic into several functions   On Windows  when a dialog is shown  the message pump continues in the background  only the current message being processed is on hold   and that works just fine  That allows users to move your app and let is repaint while you re displaying a dialog box for example  WinMo supports synchronous modal dialogs  so does BlackBerry but just not Android

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I am using Xamarin Android  MonoDroid   and I have requirments for developing UI Blocking confirm box  I am not going to argue with the client because I can see good reasons for why they want that  details here   so I need to implement this  I tried  Daniel and  MindSpiker above  but these did not work on MonoForAndroid  the moment the message is sent between the threads  the app is crashed  I assume it is something to do with Xamarin mapping    I ended up creating a separate thread from the UI thread and then blocking that and waiting for the user response as follows       since the controllers code is shared cross-platforms  protected void RunConfirmAction Action runnableAction        if  runnableAction    null                if  Core Platform IsAndroid                        var confirmThread   new Thread      gt  runnableAction                 confirmThread Start                      else                       runnableAction                          The call to the logout method has now changed like this  RunConfirmAction Logout       the implemtation of the MessageBox waiting is like this  public DialogResult MessageBoxShow string message  string caption  MessageBoxButtons buttons  MessageBoxIcon icon  MessageBoxDefaultButton defaultButton        if   CurrentContext    null  amp  amp   CurrentContext Screen    null  amp  amp  MainForm MainActivity    null                Action lt bool gt  callback   OnConfirmCallBack           IsCurrentlyInConfirmProcess   true          Action messageBoxDelegate        gt  MessageBox Show   Activity MainForm MainActivity   callback  message  caption  buttons           RunOnMainUiThread messageBoxDelegate           while   IsCurrentlyInConfirmProcess                        Thread Sleep 1000                                      else               LogHandler LogError  Trying to display a Message box with no activity in the CurrentContext  Message was      message             return  ConfirmBoxResult   DialogResult OK   DialogResult No      private void OnConfirmCallBack bool confirmResult         ConfirmBoxResult   confirmResult       IsCurrentlyInConfirmProcess   false     private bool  ConfirmBoxResult   false  private bool  IsCurrentlyInConfirmProcess   false    Full details on how to do this can be found in my blog post here

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just to answer your question   btw sry that i m 9 months late D   there s a  workaround  4 this kind of problems  i e    new AlertDialog Builder some class this  setTitle  bla   setMessage  bla bla   show    wait      simply add wait     and them in the OnClickListener start the class again with notify   something like this   Override     public void onClick DialogInterface dialog  int item            Toast makeText getApplicationContext     test   Toast LENGTH LONG  show              notify              dialog cancel            the same workaround goes 4 toasts and other async calls in android

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let me as a thank you to the StackOverflow community  share something nice with you  where I have used the above example in Android code for HTTP calls  which now turns MODAL instead of the usual extra thread and the complexities of merging the threads by use of the a bit peculiar threading   This is working in our app right now - 15 Oct 2020  public JSONArray genericHttpModal Context context  final String url  final JSONObject request         this url   url          genericHttpRequestQueue   Volley newRequestQueue context             class MyJsonReturn           JSONArray returnJsonArray           public void set JSONArray i                returnJsonArray   i                     public void set String i                try                   returnJsonArray put 0  i                 catch  JSONException e                    e printStackTrace                                     public JSONArray get                 return returnJsonArray                       final MyJsonReturn mymy   new MyJsonReturn            Positive Response   HTTP OK      final Handler handler   new Handler              Override         public void handleMessage  NonNull Message msg                throw new RuntimeException                          final Response Listener responseListener   new Response Listener lt String gt               Override         public void onResponse String response                try                   mymy set new JSONArray response                  catch  JSONException e                    mymy set  quot     quot JSONException   quot  quot    e getMessage      quot   quot    quot                              handler sendMessage handler obtainMessage                              Negative Response   HTTP NOT OK     final Response ErrorListener errorListener   new Response ErrorListener              Override         public void onErrorResponse VolleyError error                result    quot fail quot                try                   mymy set new JSONArray  quot     quot JSONException   quot  quot    result    quot   quot    quot                   catch  JSONException e                    mymy set  quot     quot JSONException   quot  quot    e getMessage      quot   quot    quot                              handler sendMessage handler obtainMessage                            final StringRequest httpRequest   new StringRequest Request Method POST  URL POINTER   url              responseListener              errorListener                Here the mRequestQueue handler will get the parameters for this request here             Ref  https   stackoverflow com questions 33573803 how-to-send-a-post-request-using-volley-with-string-body 33578202            Ref  Multi Threaded solution 14 Oct 2020  David Svarrer    https   stackoverflow com questions 2028697 dialogs-alertdialogs-how-to-block-execution-while-dialog-is-up-net-style  This stackoverflow here           Override         protected java util Map lt String  String gt  getParams   throws AuthFailureError               return jsonObjectToMap request                        httpRequest setShouldCache false      Elijah  Could work on dropping the cache         genericHttpRequestQueue add httpRequest            try           Looper loop          catch  RuntimeException re              return mymy get

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I am new to the Android Java world and was surprised to find out here  unless I don t understand what I read  that modal dialogs don t work  For some very obscure reasons for me at the moment  I got this  ShowMessage  equivalent with an ok button that works on my tablet in a very modal manner   From my TDialogs java module   class DialogMes       AlertDialog alertDialog     private final Message NO HANDLER   null    public DialogMes Activity parent String aTitle  String mes          alertDialog   new AlertDialog Builder parent  create        alertDialog setTitle aTitle           alertDialog setMessage mes          alertDialog setButton  OK  NO HANDLER            alertDialog show               Here s part of the test code   public class TestDialogsActivity extends Activity implements DlgConfirmEvent        Override   public void onCreate Bundle savedInstanceState          super onCreate savedInstanceState       setContentView R layout main       Button btShowMessage    Button  findViewById R id btShowMessage       btShowMessage setOnClickListener new View OnClickListener           public void onClick View view                   DialogMes dlgMes   new DialogMes  TestDialogsActivity this  Message   life is good                                          I also implemented a modal Yes No dialog following the interface approach suggested above by JohnnyBeGood  and it works pretty good too    Correction   My answer is not relevant to the question that I misunderstood  For some reason  I interpreted M  Romain Guy  you don t want to do that  as a no no to modal dialogs  I should have read   you don t want to do that   this way    I apologize

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In Android  the structure is different from  NET   AlertDialog Builder builder   new AlertDialog Builder this   builder setMessage  Hello            setPositiveButton  Ok   new DialogInterface OnClickListener                public void onClick DialogInterface dialog  int id                      Handle Ok                                setNegativeButton  Cancel   new DialogInterface OnClickListener                public void onClick DialogInterface dialog  int id                      Handle Cancel                                create      Will get you a dialog with two buttons and you handle the button clicks with callbacks   You might be able to write some code to make the syntax more closely resemble  NET  but the dialog lifecycle  is pretty intertwined with Activity  so in the end  it might be more trouble than it s worth   Additional dialog references are here

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Rewriting    There are radical differences between mobile and desktop environment  as well as between the way in which applications were developed to a handful of years ago and today    a  mobile devices need to conserve energy  Part of the value they offer  So you need to save resources  Threads are an expensive resource  Halt the progress of a thread is an unacceptable waste of this resource    b  Nowadays the user is much more demanding  To assist them  we believe that it deserves to have full working CPU and the smallest possible expenditure of energy  Its application is not alone on the device  there is an unknow number of another apps running at same time and your app is not necessarily the most urgent    c  system-level locks are not an option  a mobile device works with a number of events and services in the background and it is not right for any of them can be locked by an application    Think about the user receiving a phone call while your  system lock  is working     Based on the above facts  the answer to the proposed question are     There is a viable way to build a dialog that blocks the main thread until a response from the user     No  Workarounds do user experience get worse and it may make the mistake of blaming the system itself  This is unfair and penalizes the platform and all its developers     Is there a way to block the entire system with a dialogue     No  This is strictly forbidden on the platform  No application can interfere with the operation of the system or other applications     I need to refactor my application  or rethink my way of programming to suit me on the Android mobile system architecture     Yes  Including this aspect

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Hu  Damn I was struggling whole day for this  Somehow I got workaround though I would t recommend it  You will have to use Handler to achieve this  call getDialogBack function to get boolean result    getDialogBack this   Log d TAG   quot onCreate   quot  result       In getDialogBack write dialog and handler code to make it synchronous public int getDialogBack Context context int i            final Handler handler   new Handler Looper getMainLooper                    Override             public void handleMessage Message mesg                    throw new RuntimeException                                      AlertDialog Builder alert   new AlertDialog Builder context           alert setTitle  quot Title quot            alert setMessage  quot Message quot            alert setPositiveButton  quot Want to print next quot   new                 DialogInterface OnClickListener                         public void onClick DialogInterface dialog  int id                            handler sendMessage handler obtainMessage                                                       alert setNegativeButton  quot Return False quot   new DialogInterface OnClickListener                 public void onClick DialogInterface dialog  int id                    handler sendMessage handler obtainMessage                                       alert show             try               Looper loop              catch  RuntimeException e                       return true

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you set onclick listeners to you buttons  dissmis dialog and do your action  Don t need to halt anything  protected Dialog onCreateDialog int id      return new AlertDialog Builder this  setTitle R string no connection  setIcon android R drawable ic dialog alert  setView textEntryView  setPositiveButton R string exit  new DialogInterface OnClickListener          public void onClick DialogInterface dialog  int whichButton          Here goes what you want to do             to call -   ex - showDialog DIALOG ERROR PREF    More  http   developer android com guide topics ui dialogs html

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The cleanest and simplest solution is to use your own listener interface so that when the user clicks on the ok button your listener is called with the return value  This method does nothing fancy or complicated and respects android principles   Define your listener interface as follows   public interface EditListener    Used to get an integer return value from a dialog            void returnValue int value        For my application I created an EditValue class which uses AlertDialog and which I call whenever I want to edit an integer value  Note how the EditListener interface is passed as an argument to this code  When the user clicks on the OK button the value will be returned to your calling code via the EditListener method   public final class EditValue    Used to edit a value using an alert dialog    The edited value is returned via the returnValue method of the supplied EditListener             interface    Could be modified with different constructors to edit double float etc        public EditValue final Activity parent  int value  String title  String message                    final EditListener editListener    AlertDialog Builder alert  new AlertDialog Builder parent     if title  null  title  message    else if message  null  message  title    if title  null  alert setTitle title     if message  null  alert setMessage message         Set an EditText view to get user input    final EditText input   new EditText parent     input setText String valueOf value      input setInputType InputType TYPE CLASS NUMBER     alert setView input      alert setPositiveButton  OK  new DialogInterface OnClickListener      public void onClick DialogInterface dialog  int which      try      int newValue  Integer valueOf input getText   toString          editListener returnValue newValue        dialog dismiss         catch NumberFormatException err                    alert setNegativeButton  Cancel   new DialogInterface OnClickListener      public void onClick DialogInterface dialog  int which      dialog dismiss                   alert show           Finally when you use EditValue you need to declare your EditListener and you can now access the return value and do what you want to do    new EditValue main AnchorManager anchorageLimit                 main res getString R string config anchorage limit  null                 new EditListener     public void returnValue int value   AnchorManager anchorageLimit  value

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PasswordDialog dlg   new PasswordDialog this    if dlg showDialog      DialogResult OK            blabla  anything your self      public class PasswordDialog extends Dialog       int dialogResult      Handler mHandler        public PasswordDialog Activity context  String mailName  boolean retry                 super context           setOwnerActivity context           onCreate            TextView promptLbl    TextView  findViewById R id promptLbl           promptLbl setText  Input password n    mailName             public int getDialogResult                 return dialogResult            public void setDialogResult int dialogResult                this dialogResult   dialogResult                Called when the activity is first created          public void onCreate             setContentView R layout password dialog           findViewById R id cancelBtn  setOnClickListener new android view View OnClickListener                   Override             public void onClick View paramView                                endDialog DialogResult CANCEL                                         findViewById R id okBtn  setOnClickListener new android view View OnClickListener                   Override             public void onClick View paramView                                endDialog DialogResult OK                                                public void endDialog int result                dismiss            setDialogResult result           Message m   mHandler obtainMessage            mHandler sendMessage m              public int showDialog                 mHandler   new Handler                  Override               public void handleMessage Message mesg                         process incoming messages here                   super handleMessage msg                   throw new RuntimeException                                         super show            try               Looper getMainLooper   loop                      catch RuntimeException e2                              return dialogResult

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This is the simplest way   new AlertDialog Builder this  setTitle  title   setMessage  message   create   show

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Try this in a Thread  not the UI-Thread    final CountDownLatch latch   new CountDownLatch 1   handler post new Runnable        Override   public void run         OnClickListener okListener   new OnClickListener          Override     public void onClick DialogInterface dialog  int which          dialog dismiss          latch countDown                  AlertDialog dialog   new AlertDialog Builder context  setTitle title       setMessage msg  setPositiveButton  OK   okListener  create      dialog show          try     latch await      catch  InterruptedException e      e printStackTrace

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Use android app Dialog setOnDismissListener OnDismissListener listener

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In an attempt to optimize memory and performance dialogs in Android are asynchronous  they are also managed for this reason    Comming from the Windows world  you are used to modal dialogs   Android dialogs are modal but more like non-modal when it comes to execution  Execution does not stop after displaying a dialog   The best description of Dialogs in Android I have seen is in  Pro Android  http   www apress com book view 1430215968  This is not a perfect explanation but it should help you to wrap your brain around the differences between Dialogs in Windows and Android   In Windows you want to do A  ask a question with a dialog  and then do B or C   In android design A with all the code you need for B and C in the onClick   of the OnClickListener s  for the dialog   Then do A and launch the dialog   You   re done with A   When the user clicks a button B or C will get executed   Windows ------- A code launch dialog user picks B or C B or C code done   Android ------- OnClick for B code  does not get executed yet  OnClick for C code  does not get executed yet  A code launch dialog done  user picks B or C

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Ted  you don t want to do this  really    The biggest reason is that if you block the UI thread while you are displaying a Dialog  you will block the thread that s in charge of drawing and handling the events of your Dialog  Which means your dialog will be unresponsive  You will also cause ANRs if the user takes more than a few seconds to click the dialog   Erich s answer is exactly what you need  I know it s not what you want  but that doesn t matter  We ve designed Android to prevent developers from writing synchronous dialogs so you don t really have much of a choice

[android] Dialogs / AlertDialogs: How to "block execution" while dialog is up (.NET-style)

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