Crash report for Android App

To err is human and to crash is the software created by human (even if it is made for Android ;)

So when your app crashes on your users' phones, it's a good idea to collect the details of the crash and prompt the user to send them to you. I recently wrote one such scheme for ReaderScope and it has been very helpful. Here is how I am doing it.

I found the code snippets after googling around. Mainly from this stackoverflow article. This morning however, I added few more bits to work well with exceptions that take place in background threads.

The way to do this is to implement the Thread.UncaughtExceptionHandler interface and pass it to Thread.setDefaultUncaughtExceptionHandler() at the beginning of your Activity's onCreate(). Here is the implementation class TopExceptionHandler.

package com.altcanvas.readerscope;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Context;
import java.io.*;

public class TopExceptionHandler implements Thread.UncaughtExceptionHandler {

private Thread.UncaughtExceptionHandler defaultUEH;

private Activity app = null;

public TopExceptionHandler(Activity app) {
this.defaultUEH = Thread.getDefaultUncaughtExceptionHandler();
this.app = app;
}

public void uncaughtException(Thread t, Throwable e)
{
StackTraceElement[] arr = e.getStackTrace();
String report = e.toString()+"\n\n";
report += "--------- Stack trace ---------\n\n";
for (int i=0; i<arr.length; i++)
{
report += "    "+arr[i].toString()+"\n";
}
report += "-------------------------------\n\n";

// If the exception was thrown in a background thread inside
// AsyncTask, then the actual exception can be found with getCause
report += "--------- Cause ---------\n\n";
Throwable cause = e.getCause();
if(cause != null) {
report += cause.toString() + "\n\n";
arr = cause.getStackTrace();
for (int i=0; i<arr.length; i++)
{
report += "    "+arr[i].toString()+"\n";
}
}
report += "-------------------------------\n\n";

try {
FileOutputStream trace = app.openFileOutput(
"stack.trace", Context.MODE_PRIVATE);
trace.write(report.getBytes());
trace.close();
} catch(IOException ioe) {
// ...
}

defaultUEH.uncaughtException(t, e);
}
}

Note that we are not consuming the exception. We let the Android framework's defaultUEH to handle it. If you don't do this, bad things may happen.

At the top of your Activity register an instance of above class like this:

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

Thread.setDefaultUncaughtExceptionHandler(new TopExceptionHandler(this));

...

This exception handler saves the trace in a file. When ReaderScope restarts next time, it detects the file and prompts the user if he/she wants to email it to the developer.

Emailing the stack trace with user's consent is so much easier on Android, than setting up a crash report server. Somewhere near the beginning of your activity just check if stack.trace file is present. If so, execute following code to pack it in an email.

try {
BufferedReader reader = new BufferedReader(
new InputStreamReader(ReaderScopeActivity.this
.openFileInput("stack.trace")));
while((line = reader.readLine()) != null) {
trace += line+"\n";
}
} catch(FileNotFoundException fnfe) {
// ...
} catch(IOException ioe) {
// ...
}

Intent sendIntent = new Intent(Intent.ACTION_SEND);
String subject = "Error report";
String body =
"Mail this to readerscope@altcanvas.com: "+
"\n\n"+
trace+
"\n\n";

sendIntent.putExtra(Intent.EXTRA_EMAIL,
new String[] {"readerscope@altcanvas.com"});
sendIntent.putExtra(Intent.EXTRA_TEXT, body);
sendIntent.putExtra(Intent.EXTRA_SUBJECT, subject);
sendIntent.setType("message/rfc822");

ReaderScopeActivity.this.startActivity(
Intent.createChooser(sendIntent, "Title:"));

ReaderScopeActivity.this.deleteFile("stack.trace");

Hope this helps! If you have suggestions for improvements, please do let me know in comments.

code syntax highlighting by GVIM, using the "delek" theme.


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