huanghaibin-dev/CalendarView · error

e.printStackTrace()

Error message

e.printStackTrace()

What it means

In the CalendarViewDelegate constructor, Class.forName resolves the custom WeekBar class from app:calendar_week_bar_view. If the class path string names a class not on the classpath, Class.forName throws and printStackTrace hides it, leaving mWeekBarClass as the assignment result of the ternary chain rather than the intended custom class.

Solutions

1. Fix app:calendar_week_bar_view in XML to the exact fully-qualified class name (package + class).
2. Confirm the class exists and is public in a module included as a dependency.
3. Add a keep rule so shrinking tools don't remove/rename the class.
4. Check logcat for the ClassNotFoundException stack trace to confirm.
5. If no custom week bar is needed, remove the attribute so the default WeekBar is used.

Example fix

// before
app:calendar_week_bar_view="com.example.views.WeekBarView"
// after (class moved to com.example.ui)
app:calendar_week_bar_view="com.example.ui.WeekBarView"

// Validate the XML attribute value before inflating the CalendarView:
String path = "com.example.MyWeekBar";
Class<?> cls = Class.forName(path); // will throw ClassNotFoundException early if wrong
if (!WeekBar.class.isAssignableFrom(cls)) throw new IllegalStateException("Not a WeekBar");

static boolean isLoadableWeekBar(String path) {
    try { return WeekBar.class.isAssignableFrom(Class.forName(path)); }
    catch (Throwable t) { return false; }
}

// Library swallows the exception; wrap your own initialization to detect it:
try {
    setContentView(R.layout.activity_calendar);
} finally {
    if (calendarView.getWeekBar() == null) {
        Log.e("Calendar", "Custom week bar failed to load; check calendar_week_bar_view");
    }
}

When it happens

Trigger: app:calendar_week_bar_view set to a misspelled or renamed fully-qualified class name; the class exists in a different module/dependency not included; class removed by shrinking tools.

Common situations: Copy-pasting a config from a tutorial with a package name that doesn't match the project; refactoring a package without updating XML attributes; release builds with ProGuard stripping the view class.

Related errors

• e.printStackTrace()
• e.printStackTrace()
• e.printStackTrace()
• e.printStackTrace()

AI-assisted analysis of huanghaibin-dev/CalendarView@f5479ea3ba (2026-09-11). Data as JSON: /api/errors/1fffa5dd3dfed044. Report an issue: GitHub.

Appendix: source

Thrown at calendarview/src/main/java/com/haibin/calendarview/CalendarViewDelegate.java:560

        array.recycle();
        init();
    }

    private void init() {
        mCurrentDate = new Calendar();
        Date d = new Date();
        mCurrentDate.setYear(CalendarUtil.getDate("yyyy", d));
        mCurrentDate.setMonth(CalendarUtil.getDate("MM", d));
        mCurrentDate.setDay(CalendarUtil.getDate("dd", d));
        mCurrentDate.setCurrentDay(true);
        LunarCalendar.setupLunarCalendar(mCurrentDate);
        setRange(mMinYear, mMinYearMonth, mMaxYear, mMaxYearMonth);

        try {
            mWeekBarClass = TextUtils.isEmpty(mWeekBarClassPath) ?
                    mWeekBarClass = WeekBar.class : Class.forName(mWeekBarClassPath);
        } catch (Exception e) {
            e.printStackTrace();
        }

        try {
            mYearViewClass = TextUtils.isEmpty(mYearViewClassPath) ?
                    mYearViewClass = DefaultYearView.class : Class.forName(mYearViewClassPath);
        } catch (Exception e) {
            e.printStackTrace();
        }
        try {
            mMonthViewClass = TextUtils.isEmpty(mMonthViewClassPath) ?
                    DefaultMonthView.class : Class.forName(mMonthViewClassPath);
        } catch (Exception e) {
            e.printStackTrace();
        }
        try {
            mWeekViewClass = TextUtils.isEmpty(mWeekViewClassPath) ?
                    DefaultWeekView.class : Class.forName(mWeekViewClassPath);
        } catch (Exception e) {

View on GitHub (pinned to f5479ea3ba)