Data Binding giving NullPointerException when used with static method

Question

I am getting a NullPointerException when I use to format date with my StringUtils class. If I use it without StringUtils, it just works fine.

I have added the import statement for StringUtils

I have this:

<TextView
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_weight="1"
    android:text="@{StringUtils.getFormattedDate(user.date)}" />

This gives me an error in my StringUtils method:

public static String getFormattedDate(String unformattedDate) {
        // unformattedDate will be in format of yyyy-mm-dd
        // Convert it to d mmm, yyyy
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
        String date = null;
        try {
            Date d = df.parse(unformattedDate);   // <<--------- Here
            SimpleDateFormat dateFormat = new SimpleDateFormat("d MMM, yyyy");
            date = dateFormat.format(d.getTime());
        } catch (ParseException e) {
            e.printStackTrace();
        }
        return date;
    }

When I checked with debugger, unformattedDate is null from the beginning. The correct method is called but the value passed is null. This is strange.

When I use it like this in the layout file:

<TextView
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_weight="1"
    android:text="@{user.date}" />

It gives me no error, and date is displayed on screen!

I have tried cleaning the project and re-run it. But no success.

It is fetched async using firebase database. Is that causing issue? — kirtan403
– kirtan403, Commented Sep 6, 2016 at 6:45

tynn · Accepted Answer · 2016-09-06 06:54:54Z

1

Data bindings are null-safe itself, but this doesn't hold for using the values as parameter. Since the getFormattedDate() is yours to change, just make sure it's null-safe as well. You're already returning null if there's a ParseException anyway.

public static String getFormattedDate(String unformattedDate) {
    try {
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
        Date d = df.parse(unformattedDate);
        SimpleDateFormat dateFormat = new SimpleDateFormat("d MMM, yyyy");
        return dateFormat.format(d.getTime());
    } catch (Exception e) {
        Log.w("StringUtils", "getFormattedDate", e);
        return null;
    }
}

answered Sep 6, 2016 at 6:54

tynn

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1 Comment

kirtan403 Over a year ago

This is more preferable i think. Thanks!

Ravi · Accepted Answer · 2016-09-06 06:47:48Z

1

When you run it for first time user is not having any value untill you get it from Firebase database, so user.date will also be null.

Put ternary :

android:text="@{user.date==null ? `` : StringUtils.getFormattedDate(user.date)}"

answered Sep 6, 2016 at 6:47

Ravi

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1 Comment

kirtan403 Over a year ago

It is strange that it just doesn't give any specific error, and shows all my automatically generated binding classes are not found. I had this type of error when you put android:text="@{user.amount}" where amount is of type double. Putting android:text="@{String.valueOf(user.amount)}" compiles successfully. This is the case when you just don't get any specific error. I think Android Studio 2.1.3 still lakes when it comes to errors in data-binding

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