ANR-WatchDog Documentation

To start monitoring for ANRs, instantiate ANRWatchDog and call .start() within the onCreate method of your Application class.

new ANRWatchDog().start();

To use ANR-WatchDog in an Android Studio project, add the following dependency to your app/build.gradle file:

implementation 'com.github.anrwatchdog:anrwatchdog:1.4.0'

To limit the number of threads reported in the ANRError stack trace, use setReportThreadNamePrefix(String prefix). Only threads whose names start with this prefix will be included in the report.

When starting your own threads, ensure you set their name to include this prefix.

new ANRWatchDog().setReportThreadNamePrefix("APP:").start();

// In your thread:
public class MyAmazingThread extends Thread {
    @Override
    public void run() {
        setName("APP: Amazing!");
        /* ... do amazing things ... */
    }
}

You can specify a custom timeout (the minimum hanging time required to trigger an ANR) in milliseconds. The default is 5000ms.

// Example: Set timeout to 10 seconds
if (BuildConfig.DEBUG == false) {
  new ANRWatchDog(10000 /*timeout*/).start();
}

By default, the watchdog ignores ANRs if a debugger is attached to avoid false positives caused by breakpoints. To force the watchdog to report ANRs even when a debugger is connected, use setIgnoreDebugger(true).

new ANRWatchDog().setIgnoreDebugger(true).start();

By default, ANR-WatchDog throws an ANRError when an ANR is detected. To prevent the application from crashing and instead handle the error manually (e.g., logging it to a crash reporting service), use setANRListener with an ANRListener implementation.

Note: This is recommended for production environments to avoid force-closing the app for the user.

new ANRWatchDog().setANRListener(new ANRWatchDog.ANRListener() {
    @Override
    public void onAppNotResponding(ANRError error) {
        // Handle the error. For example, log it to HockeyApp:
        ExceptionHandler.saveException(error, new CrashManager());
    }
}).start();

An ANRInterceptor allows you to intercept an ANR event before the error is raised. The intercept(long duration) method receives the current freeze duration. Returning a value greater than 0 will postpone the error for that many milliseconds.

This is useful if you want to detect a freeze but wait longer before officially declaring it an ANR.

new ANRWatchDog(2000).setANRInterceptor(new ANRWatchDog.ANRInterceptor() {
    @Override
    public long intercept(long duration) {
        long ret = 5000 - duration;
        if (ret > 0) {
            Log.w(TAG, "Intercepted ANR that is too short (" + duration + " ms), postponing for " + ret + " ms.");
        }
        return ret;
    }
})

The ANRError exception contains stack traces for all running threads. In the exception report, each Caused by section represents a different thread, not a nested exception.

If you are using a crash reporter like Crashlytics that already reports all thread stack traces, it is recommended to use setReportMainThreadOnly() to avoid redundant and cumbersome reports.