Registering own Handler for unexpected exceptions

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This is how you can react to exceptions which have not been catched, similar to the system’s standard “Application XYZ has crashed”

import android.app.Application;
import android.util.Log;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;

/**
 * Application class writing unexpected exceptions to a crash file before crashing.
 */
public class MyApplication extends Application {

private static final String TAG = “ExceptionHandler”;

@Override public void onCreate() { super.onCreate();

// Setup handler for uncaught exceptions.
final Thread.UncaughtExceptionHandler defaultHandler = Thread.getDefaultUncaughtExceptionHandler();
Thread.setDefaultUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {
    @Override
    public void uncaughtException(Thread thread, Throwable e) {
        try {
            handleUncaughtException(e);
            System.exit(1);
        } catch (Throwable e2) {
            Log.e(TAG, "Exception in custom exception handler", e2);
            defaultHandler.uncaughtException(thread, e);
        }
    }
});

}

private void handleUncaughtException(Throwable e) throws IOException { Log.e(TAG, “Uncaught exception logged to local file”, e);

// Create a new unique file
final DateFormat dateFormat =  new SimpleDateFormat("yyyy-MM-dd_HH-mm-ss", Locale.US);
String timestamp;
File file = null;
while (file == null || file.exists()) {
    timestamp = dateFormat.format(new Date());
    file = new File(getFilesDir(), "crashLog_" + timestamp + ".txt");
}
Log.i(TAG, "Trying to create log file " + file.getPath());
file.createNewFile();

// Write the stacktrace to the file
FileWriter writer = null;
try {
    writer = new FileWriter(file, true);
    for (StackTraceElement element : e.getStackTrace()) {
        writer.write(element.toString());
    }
} finally {
    if (writer != null) writer.close();
}

// You can (and probably should) also display a dialog to notify the user

}

Then register this Application class in your AndroidManifest.xml:

<application android:name="de.ioxp.arkmobile.MyApplication" >

Found a mistake? Have a question or improvement idea? Let me know.

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