How to disable onItemSelectedListener to be invoke

问题:

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!

回答1:

I have an easier, and I think, better solution. Since I had to refresh the spinners even after initialization, this is a more generic approach. Please refer the accepted answer:

Undesired onItemSelected calls

回答2:

A cleaner solution, in my opinion, to differentiate between programmatic and user-initiated changes is the following:

Create your listener for the spinner as both an OnTouchListener and OnItemSelectedListener

public class SpinnerInteractionListener implements AdapterView.OnItemSelectedListener, View.OnTouchListener {

    boolean userSelect = false;

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        userSelect = true;
        return false;
    }

    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) {
        if (userSelect) { 
            // Your selection handling code here
            userSelect = false;
        }
    }

}

Add the listener to the spinner registering for both event types

SpinnerInteractionListener listener = new SpinnerInteractionListener();
mSpinnerView.setOnTouchListener(listener);
mSpinnerView.setOnItemSelectedListener(listener);

This way, any unexpected calls to your handler method due to initialization or re-initialization will be ignored.

回答3:

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.

回答4:

First add boolean values for stopping spinner listener call

  Boolean check = false;

Then you add on Touch listener and on Item click Listener Like below code

 holder.filters.setOnTouchListener(new View.OnTouchListener() {
               @Override
               public boolean onTouch(View v, MotionEvent event) {

                   check = true;
                   return false;
               }
           });

           holder.filters.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener()
           {

               @Override
               public void onItemSelected(AdapterView<?> parent, View arg1, int position, long id)
               {
                   flag = filterids.get(position);

                   if(check)
                   {
                       check = false;
                       new Applyfilters().execute(flag,"3");
                   }else{

                   }

               }

               @Override
               public void onNothingSelected(AdapterView<?> arg0)
               {
                   // TODO Auto-generated method stub
               }
           });

Its simple working good for stopping server call multiple times.

回答5:

It is very easy you can call the Spinner.setSelection(int position, boolean animate) method with false so the listeners will not react on the change.

回答6:

Spinner.setSelection(int position, boolean animate) does trigger the listener on 4.3

回答7:

I created a library that help for all, that no need to call item onClick action in Spinner For example:

spinner.setSelection(withAction,position);

where withAction is a boolean flag, that used for call or not item action

Link on Github: https://github.com/scijoker/spinner2

回答8:

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

回答9:

When Spinner.setSelection(position) is used, it always activates setOnItemSelectedListener()

To avoid firing the code twice I use this solution:

private mIsSpinnerFirstCall=true;

...
Spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
        //If a new value is selected (avoid activating on setSelection())
        if(!mIsSpinnerFirstCall) {
            // Your code goes gere
        }
        mIsSpinnerFirstCall = false;
    }

    public void onNothingSelected(AdapterView<?> arg0) {
    }
});

This solution is valid when you are sure that Spinner.setSelection(position) us used. Also, it is important to set mIsSpinnerFirstCall=true each time before using Spinner.setSelection(position)

回答10:

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);

回答11:

    This following method will help you to stop invoking automatically the selection listener


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