CODEWITHSUNDEEP
androidandroid-alertdialog
Born Again
Born Again

Reputation: 2179

AlertDialog getButton() method returns null

I have set up an AlertDialog like this:

AlertDialog.Builder noteAlert = new AlertDialog.Builder(ClassName.this);
noteAlert.setTitle("Title");
noteAlert.setMessage("Message");
noteAlert.setPositiveButton("Positive", new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int whichButton) {
        // some code
    }
});
noteAlert.setNeutralButton("Positive", new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int whichButton) {
        // some code
    }
});
noteAlert.setNegativeButton("Positive", new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int whichButton) {
        // some code
    }
});

AlertDialog alertDialog = noteAlert.create();                                   
Button deleteButton = alertDialog.getButton(AlertDialog.BUTTON_NEGATIVE);
if (someCondition != 1)
    // code runs till here
    deleteButton.setEnabled(false); // code works on deleting this line

noteAlert.show();

When I run the above code, it works till the if statement. Then the app crashes (I am assuming getButton() throws an NPE). I have seen many other answers on SO which give the same code as solution to disabling a button.

And when I comment out the setEnabled() line, the app works fine (only the button is not disable). So basically I am trying to disable this NegativeButton and it is not working. Can you guys suggest some solution?

LogCat:

07-13 08:01:14.378: D/ViewRootImpl(19779): ViewRoot TouchDown(Absolute) DOWN (380 , 691)

07-13 08:01:14.495: E/dialog(19779): AlertDiablog begins

07-13 08:01:14.495: E/hasnote(19779): 0

07-13 08:01:14.511: E/hasnote(19779): 0

07-13 08:01:14.511: D/AndroidRuntime(19779): Shutting down VM

07-13 08:01:14.511: W/dalvikvm(19779): threadid=1: thread exiting with uncaught exception (group=0x40e392a0)

07-13 08:01:14.519: E/AndroidRuntime(19779): FATAL EXCEPTION: main

07-13 08:01:14.519: E/AndroidRuntime(19779): java.lang.NullPointerException

07-13 08:01:14.519: E/AndroidRuntime(19779): at com.example.sherlockcaldroid2.TestSubjectCalendar$1$2.onClick(TestSubjectCalendar.java:250)

07-13 08:01:14.519: E/AndroidRuntime(19779): at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:1 66)

07-13 08:01:14.519: E/AndroidRuntime(19779): at android.os.Handler.dispatchMessage(Handler.java:99)

07-13 08:01:14.519: E/AndroidRuntime(19779): at android.os.Looper.loop(Looper.java:137)

07-13 08:01:14.519: E/AndroidRuntime(19779): at android.app.ActivityThread.main(ActivityThread.java:4849)

07-13 08:01:14.519: E/AndroidRuntime(19779): at java.lang.reflect.Method.invokeNative(Native Method)

07-13 08:01:14.519: E/AndroidRuntime(19779): at java.lang.reflect.Method.invoke(Method.java:511)

07-13 08:01:14.519: E/AndroidRuntime(19779): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)

07-13 08:01:14.519: E/AndroidRuntime(19779): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)

07-13 08:01:14.519: E/AndroidRuntime(19779): at dalvik.system.NativeStart.main(Native Method)

07-13 08:01:34.089: I/Process(19779): Sending signal. PID: 19779 SIG: 9

Upvotes: 1

Views: 4708

Answers (4)

Rakesh
Rakesh

Reputation: 1236

Access the button after dialog.show. Else it will be null.

AlertDialog.Builder builder = new AlertDialog.Builder(MyActivity.this);
                builder.setTitle("Title");
                builder.setMessage("message");
                builder.setPositiveButton("Ok", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //Do Something
                    }
                });
 builder.setNegativeButton(context.getResources().getString(R.string.no_text), (dialog, which) -> {
                            dialog.cancel();
                            listener.onNoButtonClick();
                        });
                AlertDialog dialog = builder.create();
                dialog.show();
               dialog.getButton(AlertDialog.BUTTON_NEGATIVE).setEnabled(false);

Upvotes: 0

Denys Makhov
Denys Makhov

Reputation: 382

This is because the button does not exist at the time of the call deleteButton.setEnabled(false). You should move the call noteAlert.show() before deleteButton.setEnabled(false).

Upvotes: 1

Michal
Michal

Reputation: 6683

Try this solution:

AlertDialog.Builder noteAlert = new AlertDialog.Builder(ClassName.this); 
noteAlert.setPositiveButton("Positive", new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int whichButton) {
        // some code
    }
});
noteAlert.setOnShowListener(new DialogInterface.OnShowListener() {
            @Override
            public void onShow(DialogInterface dialog) {
                if(**some condition**)
                {
                    Button button = builder.getButton(AlertDialog.BUTTON_POSITIVE);
                    if (button != null) {
                        button.setEnabled(false);
                    }
                }
            }
        });

Upvotes: 0

Corey Scott
Corey Scott

Reputation: 2440

I am pretty sure the view is not inflated until later in the life-cycle (i.e. on calling show()).

I took a quick look at the docs and couldn't find a build() or inflate() method but I would expect that the easiest way is just to move the noteAlert.show() before the button manipulation logic

EDIT: Did you try changing:

noteAlert.setPositiveButton("Positive", new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int whichButton) {
        // some code
    }
});

to

noteAlert.setButton(DialogInterface.BUTTON_POSITIVE, "Positive", new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int whichButton) {
        // some code
    }
});

Upvotes: 1

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