How to disable onItemSelectedListener to be invoked when setting selected item by code

user_273456 0
Viewed 42396

Just wondering how you handle the following problem: a result is calculated depending on two spinners' selected items. To handle the UI things, i.e. a user picks a new item in one of the spinners, I install a listener using setOnItemSelectedListener for the spinner in my onCreate() method of the activity.

Now: that works, of course, fine. The listener's work is to trigger a new calculation of the result.

The problem: because I intercept onPause() onResume() to save/restore the last state, I got a method that sets these two spinners' selected item programmatically like in here:

startSpinner.setSelection(pStart);
destSpinner.setSelection(pDest);

These two calls invoke the listeners, too! My calculation method for the result plus the notification of a new result set is invoked twice here!

A stupid direct approach for this would be to have a boolean variable disabling whatever the listener does inside, setting it before setting the selected items and resetting it afterwards. Okay. But is there a better method??

I don't want listeners to be called by code - actions, only by user actions! :-(

How do you do it? Thanks!

listener spinner android
12 Answers

Okay, I got it working the way I want to now.

The thing to understand here (and I did not when I was writing that question...) is that everything in Android runs in one thread - the UI thread.

Meaning: even though you set Spinner's values here and there: they are only updated (visually) and their listeners are only called after all methods you're currently in (like onCreate, onResume or whatever) are finished.

This allows the following:

  • keep the selected positions in field variables. (like currentPos1, currentPos2)
  • the listeners onItemSelectedListener() call a method like refreshMyResult() or whatever.
  • when setting positions programmatically, set the spinners and call your own refresh method manually right after that.

The refreshMyResult() method looks like this:

int newPos1 = mySpinner1.getSelectedItemPosition();
int newPos2 = mySpinner2.getSelectedItemPosition();
// only do something if update is not done yet
if (newPos1 != currentPos1 || newPos2 != currentPos2) {
    currentPos1 = newPos1;
    currentPos2 = newPos2;

    // do whatever has to be done to update things!

}

Because the listeners will be called later - and by then, the remembered position in currentPos is already updated - nothing will happen and no unnecessary update of anything else will take place. When a user selects a new value in one of the spinners, well - the update will be performed accordingly!

That's it! :-)

Ahh - one more thing: the answer to my question is: No. The listeners cannot be disabled (easily) and will be called whenever a value is changed.

user_2734560

My solution is very easy. First initialize a global boolean variable.

boolean shouldWork = true;

Then use below code in your onCreate() method.

Spinner spinner = findViewById(R.id.spinner);
spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
    @Override
    public void onItemSelected(AdapterView adapter, View v, int i, long lng) {
        if (shouldWork) {
               // Do your actions here
        }
        else
            shouldWork = true;
    }
    public void onNothingSelected(AdapterView<?> parentView)  {

    }
});

Now you can use the setSelection method in everwhere without invoking the onItemSelected() method by below code.

shouldWork = false;
spinner.setSelection(0);
user_77349450

Add the OnItemSelectedListener for each spinner after you have set any previous value in onResume.

user_2719740

In my case, since I'm triggering spinner programmatically, then I just have to add spinnerSelected flag after spinner.performClick() like below.

private var spinnerSelected = false

someView.setOnClickListener {
    spinner.performClick()
    spinnerSelected = true
}

spinner.onItemSelectedListener = object : AdapterView.OnItemSelectedListener {
    override fun onNothingSelected(parent: AdapterView<*>?) {
        // do nothing
    }

    override fun onItemSelected(
        parent: AdapterView<*>?,
        view: View?,
        position: Int,
        id: Long
    ) {
        if (spinnerSelected) {
            //... do something

            spinnerSelected = false
        }
      }
    }
user_58565470 
    This following method will help you to stop invoking automatically the selection listener


    yourspinnerobj.post(new Runnable() {
                @Override
                public void run() {
                    yourspinnerobj.setOnItemSelectedListener(yourspinnerlistener);
                }
            });
user_22863720
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