Undesired onItemSelected calls

Question

I have 36 spinners that I have initialized with some values. I have used onItemSelectedListener with them. As usual, the user can interact with these spinners, firing the on

Answer 1

Here's my solution to this problem. I extend AppCompatSpinner and add a method pgmSetSelection(int pos) that allows programmatic selection setting without triggering a selection callback. I've coded this with RxJava so that the selection events are delivered via an Observable.

package com.controlj.view;

import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.widget.AdapterView;

import io.reactivex.Observable;

/**
 * Created by clyde on 22/11/17.
 */

public class FilteredSpinner extends android.support.v7.widget.AppCompatSpinner {
    private int lastSelection = INVALID_POSITION;


    public void pgmSetSelection(int i) {
        lastSelection = i;
        setSelection(i);
    }

    /**
     * Observe item selections within this spinner. Events will not be delivered if they were triggered
     * by a call to setSelection(). Selection of nothing will return an event equal to INVALID_POSITION
     *
     * @return an Observable delivering selection events
     */
    public Observable<Integer> observeSelections() {
        return Observable.create(emitter -> {
            setOnItemSelectedListener(new OnItemSelectedListener() {
                @Override
                public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                    if(i != lastSelection) {
                        lastSelection = i;
                        emitter.onNext(i);
                    }
                }

                @Override
                public void onNothingSelected(AdapterView<?> adapterView) {
                    onItemSelected(adapterView, null, INVALID_POSITION, 0);
                }
            });
        });
    }

    public FilteredSpinner(Context context) {
        super(context);
    }

    public FilteredSpinner(Context context, int mode) {
        super(context, mode);
    }

    public FilteredSpinner(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public FilteredSpinner(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    public FilteredSpinner(Context context, AttributeSet attrs, int defStyleAttr, int mode) {
        super(context, attrs, defStyleAttr, mode);
    }
}

An example of its usage, called in onCreateView() in a Fragment for example:

    mySpinner = view.findViewById(R.id.history);
    mySpinner.observeSelections()
        .subscribe(this::setSelection);

where setSelection() is a method in the enclosing view that looks like this, and which is called both from user selection events via the Observable and also elsewhere programmatically, so the logic for handling selections is common to both selection methods.

private void setSelection(int position) {
    if(adapter.isEmpty())
        position = INVALID_POSITION;
    else if(position >= adapter.getCount())
        position = adapter.getCount() - 1;
    MyData result = null;
    mySpinner.pgmSetSelection(position);
    if(position != INVALID_POSITION) {
        result = adapter.getItem(position);
    }
    display(result);  // show the selected item somewhere
}

Answer 2

I don't know if this solution is as foolproof as the chosen one here, but it works well for me and seems even simpler:

boolean executeOnItemSelected = false;
spinner.setSelection(pos)

And then in the OnItemSelectedListener

public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
    if(executeOnItemSelected){
        //Perform desired action
    } else {
        executeOnItemSelected = true;
    }
}

Answer 3

I found a simple and, I think, elegant solution. Using tags. I first created a new XML file called 'tags' and put in the following code:

<resources xmlns:android="http://schemas.android.com/apk/res/android">
  <item name="pos" type="id" />
</resources>

Whenever I myself use spin.setSelection(pos), I also do spin.setTag(R.id.pos, pos), so I am setting the current position as a tag.

Then, in onItemSelected, I am executing code only if(spin.getTag(R.id.pos) != position), where position is the position variable supplied by the function. In this way, my code is executed only when the user is making a selection. Since the user has made a selection, the tag has not been updated, so after the processing is done, I update the tag as spin.setTag(R.id.pos, position).

NOTE: It is important to use the same adapter throughout, or the "position" variable might point to different elements.

EDIT: As kaciula pointed out, if you're not using multiple tags, you can use the simpler version, that is spin.setTag(pos) and spin.getTag() WITHOUT the need for an XML file.

Answer 4

The way I solved this is by saving the OnItemSelectedListener first. Then set the OnItemSelectedListener of the Spinner to the null value. After setting the item in the Spinner by code, restore the OnItemSelectedListener again. This worked for me.

See code below:

        // disable the onItemClickListener before changing the selection by code. Set it back again afterwards
        AdapterView.OnItemSelectedListener onItemSelectedListener = historyPeriodSpinner.getOnItemSelectedListener();
        historyPeriodSpinner.setOnItemSelectedListener(null);
        historyPeriodSpinner.setSelection(0);
        historyPeriodSpinner.setOnItemSelectedListener(onItemSelectedListener);

Answer 5

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

To avoid firing the code twice I use this solution:

     private Boolean 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) {
        }
    });