Logging to a file on Android

Is there any way of retrieving log messages from an Android handset.

I'm building an application which uses the GPS of my HTC Hero. I can run and debug the application from eclipse but this isn't a good use case of GPS, sat at my desk.

When I fire the app up when I am walking around, I get an intermittent exception. Is there anyway I can output these exceptions to a text file on the SD card or output calls to Log.x("") to a text file so that I can see wh开发者_如何学Goat the exception is.

Thanks

EDIT : Solution

Here is the code I finally went with...

Thread.currentThread().setUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {
    @Override
    public void uncaughtException(Thread thread, Throwable ex) {

    PrintWriter pw;
    try {
        pw = new PrintWriter(
                new FileWriter(Environment.getExternalStorageDirectory()+"/rt.log", true));
        ex.printStackTrace(pw);
        pw.flush();
        pw.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
}
});

I had to wrap the line

pw = new PrintWriter(new FileWriter(Environment.getExternalStorageDirectory()+"/rt.log", true));

in a try/catch as Eclipse would not let me compile the app. It kept saying

Unhandled exception type IOException

1 quick fix
    Sorround with try/catch

So I did and it all works which is fine by me but it does make me wonder what Eclipse was on about...

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You could use Thread.setUncaughtExceptionHandler() to catch the Exceptions.

Writing to SD Card is as simple as retrieving the directory for the card using Environment.getExternalStorageDirectory() and creating a file there.

File f = new File(Environment.getExternalStorageDirectory(),filename);

You will need to give you app the correct permission to write to the SD Card by adding this to your Manifest:

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

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Log4j or slf4j can also be used as logging frameworks in Android together with logcat. See the project android-logging-log4j. Configuring logging to a (rotating) file(s) is very easy.

 static {
    final LogConfigurator logConfigurator = new LogConfigurator();

    logConfigurator.setFileName(Environment.getExternalStorageDirectory() + "myapp.log");
    logConfigurator.setRootLevel(Level.DEBUG);
    // Set log level of a specific logger
    logConfigurator.setLevel("org.apache", Level.ERROR);
    logConfigurator.configure();
}

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You could take a look at microlog4android. They have a solution ready to log to a file.

https://github.com/johanlkarlsson/microlog4android

---

I tried both options above (microlog4android & android-logging-log4j) and they were a struggle to try to get working. Once they compiled fine then I would get Runtime java.lang.NoClassDefFoundError.

So then I stumbled on logback-android ... also found here http://logback.qos.ch/

It has much better instructions and I got it working in a couple hours.

This appears to be the best logging solution for Android.

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Use slf4-android lib created by BrightInventions. It's simple implementation of slf4j api using android java.util.logging.*.

Features:

• logging to file out of the box
• logging to any other destination by LoggerConfiguration.configuration().addHandlerToLogger
• shake your device to send logs with screenshot via email
• really small, it tooks only ~55kB

slf4android is maintained mainly by @miensol.

Read more about slf4android on our blog:

• Introducing slf4android
• Integrate slf4android with Crashlytics

---

Based on @Greg B solution and @JPM question in the comment, I made this static method in a seperate class and each time you instanciate a new thread, call it.

package com.stackoverflow.

import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;

import android.os.Environment;

public class UnhandledExceptionHandler {

    public static void setUndhandledException(Thread thread) {
        if (thread.getUncaughtExceptionHandler() == null) {
            Thread.currentThread().setUncaughtExceptionHandler(
                    new Thread.UncaughtExceptionHandler() {
                        @Override
                        public void uncaughtException(Thread thread,
                                Throwable ex) {

                            PrintWriter pw;
                            try {
                                pw = new PrintWriter(new FileWriter(Environment
                                        .getExternalStorageDirectory()
                                        + "/rt-networkandgps"
                                        + "/gpx/"
                                        + thread.getId() + ".log", true));
                                ex.printStackTrace(pw);
                                pw.flush();
                                pw.close();
                            } catch (IOException e) {
                                e.printStackTrace();
                            }
                        }
                    });
        }

    }

}

Call it from anythread like this,

            UnhandledExceptionHandler.setUndhandledException(Thread.currentThread());