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ben reitman
ben reitman

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Posted on    June-08-2015 7:20 AM

 Android Android 
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How can I get crash data (stack traces at least) from my Android application? At least when working on my own device being retrieved by cable, but ideally from any instance of my application running on the wild so that I can improve it and make it more solid.


Mayank Tripathi
Mayank Tripathi

Total Post:397

Points:3117
Posted on    June-08-2015 7:42 AM

It is possible to handle these exceptions with Thread.setDefaultUncaughtExceptionHandler(), however this appears to mess with Android's method of handling exceptions. I attempted to use a handler of this nature:
private class ExceptionHandler implements Thread.UncaughtExceptionHandler {
    @Override
    public void uncaughtException(Thread thread, Throwable ex){
        Log.e(Constants.TAG, "uncaught_exception_handler: uncaught exception in thread " + thread.getName(), ex);
        //hack to rethrow unchecked exceptions
        if(ex instanceof RuntimeException)
            throw (RuntimeException)ex;
        if(ex instanceof Error)
            throw (Error)ex;
        //this should really never happen
        Log.e(Constants.TAG, "uncaught_exception handler: unable to rethrow checked exception");
    }
}
However, even with rethrowing the exceptions, I was unable to get the desired behavior, ie logging the exception while still allowing Android to shutdown the component it had happened it, so I gave up on it after a while.

Mayank Tripathi
Mayank Tripathi

Total Post:397

Points:3117
Posted on    June-08-2015 7:49 AM

For sample applications and debugging purposes, I use a simple solution that allows me to write the stacktrace to the sd card of the device and/or upload it to a server. This solution has been inspired by http://code.google.com/p/android-remote-stacktrace (specifically, the save-to-device and upload-to-server parts) and I think it solves the problem mentioned by Soonil. It's not optimal, but it works and you can improve it if you want to use it in a production application. If you decide to upload the stacktraces to the server, you can use a php script (index.php) to view them. If you're interested, you can find all the sources below - one java class for your application and two optional php scrips for the server hosting the uploaded stacktraces.

In a Context (e.g. the main Activity), call

if(!(Thread.getDefaultUncaughtExceptionHandler() instanceof CustomExceptionHandler)) {
    Thread.setDefaultUncaughtExceptionHandler(new CustomExceptionHandler(
            "/sdcard/<desired_local_path>", "http://<desired_url>/upload.php"));
}

CustomExceptionHandler

public class CustomExceptionHandler implements UncaughtExceptionHandler {
    private UncaughtExceptionHandler defaultUEH;
    private String localPath;
    private String url;
    /* 
     * if any of the parameters is null, the respective functionality 
     * will not be used 
     */
    public CustomExceptionHandler(String localPath, String url) {
        this.localPath = localPath;
        this.url = url;
        this.defaultUEH = Thread.getDefaultUncaughtExceptionHandler();
    }
    public void uncaughtException(Thread t, Throwable e) {
        String timestamp = TimestampFormatter.getInstance().getTimestamp();
        final Writer result = new StringWriter();
        final PrintWriter printWriter = new PrintWriter(result);
        e.printStackTrace(printWriter);
        String stacktrace = result.toString();
        printWriter.close();
        String filename = timestamp + ".stacktrace";
        if (localPath != null) {
            writeToFile(stacktrace, filename);
        }
        if (url != null) {
            sendToServer(stacktrace, filename);
        }
        defaultUEH.uncaughtException(t, e);
    }
    private void writeToFile(String stacktrace, String filename) {
        try {
            BufferedWriter bos = new BufferedWriter(new FileWriter(
                    localPath + "/" + filename));
            bos.write(stacktrace);
            bos.flush();
            bos.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    private void sendToServer(String stacktrace, String filename) {
        DefaultHttpClient httpClient = new DefaultHttpClient();
        HttpPost httpPost = new HttpPost(url);
        List<NameValuePair> nvps = new ArrayList<NameValuePair>();
        nvps.add(new BasicNameValuePair("filename", filename));
        nvps.add(new BasicNameValuePair("stacktrace", stacktrace));
        try {
            httpPost.setEntity(
                    new UrlEncodedFormEntity(nvps, HTTP.UTF_8));
            httpClient.execute(httpPost);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

upload.php

<?php
    $filename = isset($_POST['filename']) ? $_POST['filename'] : "";
    $message = isset($_POST['stacktrace']) ? $_POST['stacktrace'] : "";
    if (!ereg('^[-a-zA-Z0-9_. ]+$', $filename) || $message == ""){
        die("This script is used to log debug data. Please send the "
                . "logging message and a filename as POST variables.");
    }
    file_put_contents($filename, $message . "\n", FILE_APPEND);
?>

index.php

<?php
    $myDirectory = opendir(".");
    while($entryName = readdir($myDirectory)) {
        $dirArray[] = $entryName;
    }
    closedir($myDirectory);
    $indexCount = count($dirArray);
    sort($dirArray);
    print("<TABLE border=1 cellpadding=5 cellspacing=0 \n");
    print("<TR><TH>Filename</TH><TH>Filetype</th><th>Filesize</TH></TR>\n");
    for($index=0; $index < $indexCount; $index++) {
        if ((substr("$dirArray[$index]", 0, 1) != ".") 
                && (strrpos("$dirArray[$index]", ".stacktrace") != false)){ 
            print("<TR><TD>");
            print("<a href=\"$dirArray[$index]\">$dirArray[$index]</a>");
            print("</TD><TD>");
            print(filetype($dirArray[$index]));
            print("</TD><TD>");
            print(filesize($dirArray[$index]));
            print("</TD></TR>\n");
        }
    }
    print("</TABLE>\n");
?>

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