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Crashlytics: proper java stacktrace

08 Jul 2020 | hacking fix

This post continues tutorial for proper initialization of crash reporters t.
Option to track java exception was to use NSException.registerDefaultJavaUncaughtExceptionHandler(). It builds string presentation of exception creates NSException with this text as reason. At same time stack traces will be messed and will point to code where NSException is created.

FIRExceptionModel

Firebase Crashlytics provide special API FIRExceptionModel:

The Firebase Crashlytics Exception Model provides a way to report custom exceptions to Crashlytics that came from a runtime environment outside of the native platform Crashlytics is running in.

Exact case for RoboVM. To have it working its enough to setup Thread.setDefaultUncaughtExceptionHandler as bellow to convert exception stack traces into FIRExceptionModel elements:

Thread.setDefaultUncaughtExceptionHandler((thread, ex) -> {
    FIRExceptionModel model = new FIRExceptionModel(ex.getClass().getName(), ex.getMessage() != null ? ex.getMessage() : "");
    NSMutableArray<FIRStackFrame> modelFrames = new NSMutableArray<>();
    StackTraceElement[] stackTraces = ex.getStackTrace();
    if (stackTraces != null) {
        for (StackTraceElement st : stackTraces) {
            String symbol = st.getClassName() + '.' + st.getMethodName();
            String fileName;
            int lineNo = st.getLineNumber();
            if (lineNo < 0)
                lineNo = 0;
            if (st.isNativeMethod()) {
                fileName = "Native Method";
            } else {
                fileName = st.getFileName();
                if (fileName == null)
                    fileName = "Unknown Source";
            }

            FIRStackFrame frame = new FIRStackFrame(symbol, fileName, lineNo);
            modelFrames.add(frame);
        }
    }
    model.setStackTrace(modelFrames);
    FIRCrashlytics.crashlytics().recordExceptionModel(model);

    // kill app
    throw new ThreadDeath();
});

Note

Crashes will be reported as non-fatal !

Bonus

To get debug output from Crashlytics in simulator its not enought to provide -FIRDebugEnabled. Adding -FIRLoggerForceSTDERR helps.

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