添加OnItemSelectedListener时应用程序崩溃

Question

I recently made an update to the iOS version of an app I made and I want to put that same functionality into the Android version. Basically, it takes user input of a year, which they select from a list and then the year previous to that is entered into the placeholder text of text field I specify. When I looked up how to do the same functionality in Android, I found out I needed an OnItemSelectedListener. However, that is when trouble arises. After adding the necessary code, and importing AdapterView into my Activity, my app keeps crashing on first launch. Since I am not sure where it keeps crashing, here is a link to my app's github page

Github Experimental branch

The code on the master branch works fine, so this is really strange.

Since the files are hard to decipher, here is the code I used to apply the OnItemSelectedListener:

// give Spinner a listener for new functionality to work
selection.setOnItemSelectedListener(new OnItemSelectedListener() {
    public void onItemSelected(AdapterView<?> parentView, 
                               View selectedItemView, int position, long id) {
        // get year selection for use with new functionality
        int iyear = Integer.parseInt(selection.getSelectedItem().toString()); 
        balance.setHint(R.string.balance + " from 12/31/" + pyear.getPrevYear(iyear)); 
    }
    // create empty method
    public void onNothingSelected(AdapterView<?> parentView) {}
});

Answer 1

Make sure the var balance is not null at the time of setHint. It could be that the id in findViewById is not right. Make sure that R.id.amount is a view inside of R.layout.main.

Answer 2

I still don't see the LogCat which is the most vital piece of information when tracking down an error...

So these are my guesses:

• I don't see where you define an adapter for selection so I assume that you do this in the XML. Have you confirmed that selection.getSelectedItem().toString() is a valid String for Integer.parseInt() ?

  If you have access to the array (call it selectionArray ) you can simply use:

   ... + pyear.getPrevYear(selectionArray[position]); 

• R.string.balance is an integer that references the String that you want. To display the String itself you want to use getString(R.string.balance) or probably getResources().getString(R.string.balance) .

• Verify none of your variables are null: selection , balance , and pyear .

---

To explain the first point a little more:

1. Create a class variable for the array and the String:

    int[] choicesArray; 

2. Initialize it in onCreate();

    choicesArray = getResources().getIntArray(R.array.choices_array); 

3. In OnItemSelectedListener use:

    balance.setHint(getResources().getString(R.string.balance) + " from 12/31/" + (choicesArray[position] - 1)); 

Answer 3

I went through and copied things from the master branch and things started working without crashing. Now, I am having issues with the hint, but since this question on why it kept crashing, I am not sure I can keep the question open.