I am trying to develop small application for reset Logging on Phone.
Can some one throw some Lights on how to achieve logging in AndriodRunTimeInit whenever there is exception? I want to write into file whenever there is RunTime exception.
It is recommended that you use Android's built in logging via Log. You can access the log via adb logcat and don't have to worry about anything else.
Related
I am trying to diagnose an issue in an app I have written. The issue is a sporadic one, and occurs only under real-world conditions: in the field, away from my PC, and when I’m in the middle of something else, with no resources to spare for immediate debugging. Therefore, my best bet is collecting and analyzing log data.
Unfortunately, by the time I realize the issue has struck again and get around to debugging it, any log data has already rotated out of the Android log as I frequently have other chatty apps running at the same time. Increasing the size of the log buffer has not helped (either Android does not honor it or other apps are still too chatty) so I have abandoned this route.
For this reason, I am now considering having my app log to a separate text file in addition to the regular log.
Now I could easily double every call like
Log.i(TAG, "something happened");
adding another call that writes the same thing to the log file—but that does not seem very elegant to me.
Another option would be to replace all calls to Log with a wrapper that writes the event both to the Android log and the log file.
Question: Does the Android API provide a built-in mechanism for this, i.e. telling Log to write its data to the default log and a text file at the same time? Or do I need to code this by myself?
Edit:
Assumptions:
I know where in my code I need to generate log output (which can happen anywhere, which may or may not involve an exception) and what I want to be written to the log.
Getting log data from the device to my PC is also not a concern (one-man show, I just plug my phone into my PC and transfer the log file).
If you know the current Android API has no built-in mechanism to achieve what I want, then ”no, Android does not support this” is a perfectly acceptable answer. In that case the solution is clear—I would fall back to the wrapper function. I am specifically not looking for a different approach to the problem.
After doing some more research, it seems the Android API does not provide a standard way to do this. There are two possible workarounds:
Mirror output at the source
System.out and System.err output, which is written to the console in desktop systems, writes to the log on Android. These two can be redirected into any PrintStream of your choice, which would give you all Java console output. You can subclass PrintStream to duplicate its input, feeding it into the default stream as well as into a file of your choice.
Create a class which exposes the same methods as android.util.Log. In each method, call through to the respective android.util.Log method and additionally log the data to a file. If you call your class Log (but with a different package name, e.g. org.example.Log), then all you need to do is replace imports of android.util.Log with an import of your class, and any Log method calls will go to your class.
Caveats: This will only give you data explicitly logged by your code (i.e. for which you have the source files), as well as anything that goes to System.out or System.err. It will not include log output from JAR libraries (if you cannot modify their source code), nor any output generated by the system (such as stack traces from default exception handlers) or by other processes (some of which may be system processes and report conditions related to your process).
Read the logs from the command line
This article explains how to read the logs from within Android. In a nutshell:
Android includes a command line utility called logcat on the device, which will give you a continuous feed of log messages until stopped. (Try it by adb shelling into your device and running it. It has a bunch of command-line options to control its behavior. Not sure if it is present on all distributions, though.)
Launch this command via Runtime.getRuntime().exec("logcat"), then obtain the input stream of the process returned. This will give you an input stream of log messages.
According to the article, your app needs the android.permission.READ_LOGS permission to read logs.
I have read statements that certain versions of Android (4.2 was mentioned) do not allow this permission to be granted to non-system apps, though. According to my own tests, behavior without this permissions differ: Anbox will return the full logcat, while LineageOS (tested on 15.1) will only show log entries from the app which called it (including previous instances, presumably everything associated with the same Linux user). This can be a limitation or a welcome filter feature. YMMV.
logcat conveniently has a command line option, -f, to specify an output file. I tried
Runtime.getRuntime().exec("logcat -f " + absolutePathToLogFile);
and logcat keeps logging as long as the app’s process runs. Killing the app (by clicking the X in the title bar on Anbox) apparently also terminated the child process.
Now you can either run this code when your app starts up, or you can turn this functionality into a separate app which starts on boot and continuously collects logs for all apps.
Caveats: This may fill up your storage space quickly if you have some chatty apps running (which is why entries rotate out of the logcat so quickly in the first place). It is recommended to make log mirroring configurable (e.g. via Preferences) and/or ensure old files are deleted regularly. Also, if you keep the logcat process running until your app terminates, you will not be able to access the file over MTP as there is no easy way to run the media scanner (if you scan the file while it is still written to, it will appear truncated over MTP until another media scan runs).
You have not specified if some exception are thrown but you don't handle.
In case, take a look at this answer:
Android Handling Unhandled Exception
If you must look at a bunch of variables and objects, I'd suggest two choices:
Write a copy of your logs on a file. When your problem occurs, just ask the user to send the file to you. This is ideal during tests with self-aware users.
Obtain statistics about usage, like commercial software do. Just log user operations and send the data to your server (you would need one for this). This is the most transparent way to do remote logging.
In the case of writing log to a file, you can read and write what you want in internal memory (inside the app's sandbox) or external memory (in this case, write permission is required and explicit permission must have been granted at runtime if you are targeting Android 6 and above).
I am trying understand some concepts about android device startup ,I want to know that is there any way that I can get a log of applications that get started on device Boot-up ? How can we get that ?
I also want to know that, Is it possible to write an application that gets started at first after boot-up and stop certain apps from getting started on boot-up ?
Is there any IntentService that we have to write ? or this is not feasible unless we have root access ? Please help me in understanding this concepts.
The device log is kept in a buffer, so the most recent entries will be there. If you are early enough before the buffer gets overwritten you will get it since the device booted.
You can access it using
$ adb logcat
I have an android application that I have recently finished. So I have successfully finished each function and ensured that no errors are encountered.
When I have exported it to an apk file. It runs smoothly. It uses httpRequests to communicate with a remote mySQL server. But there are times that it spontaneously crashes?
For example, I have an activity that would receive input from the user then communicate with the server. It runs smoothly and quickly. But on next run it would crash. And when I restart the application it would run smoothly again even on the second run. I'm just going crazy from this. Are there any explanations for these?
Use ACRA to collect crash reports from your app. You don't need your own server, just a Google Docs form. The integration is described here:
https://github.com/ACRA/acra/wiki/BasicSetup#wiki-Setting-up_your_project
The advantage of using a crash report tool vs. logcat is that you don't need physical access to the device. There are also chances that you see crashes that you or your testers didn't even notice.
The first step to debugging your problem is to get a stack trace. If you can reproduce this on your own device, then right after you see a crash, connect it to your dev pc and run this command:
adb logcat > crash.log
Open the log file, copy and paste its contents on http://pastebin.com/ or similar and add the link to your question. Once we have that, we can try to figure out what's going on.
On Android I am using the android.util.Log to log within my application and during development I am using the adb logcat or Eclipse to see the logs - I use it even more then debugging...
On device I can save the logfile from my code or use some application form Android Market to save the logs - e.g. aLogCat.
Now can I do the same on the iPhone? I can use the NSLog(#"message");, but can I easily save the log file from my application and access it? Are there any ways for that?
Regards,
STeN
This is from NSFoundation reference
NSLog:
Simply calls NSLogv, passing it a variable number of arguments.
NSLogv:
Logs an error message to the Apple System Log facility (see man 3 asl). If the STDERR_FILENO file descriptor has been redirected away from the default or is going to a tty, it will also be written there. If you want to direct output elsewhere, you need to use a custom logging facility.
Thus, it is only a matter of redirecting the file-descriptor "stderr" (2) to a custom file, and you will get everything that you print using NSLog in that file.
This seems to be exactly what you want.
Note that if you want to get logs on console when you are connected to the debugger, you can wrap your code around this to avoid redirection in this case:
if (!isatty(STDERR_FILENO)) { // Not connected to any terminal
// your redirection code
}
You can access the console log from Organizer->Device->Your device->console.
If that is not powerful enough, consider using utilities like NSLogger.
The previous answers are good; also see this if you're inclined to making system calls.
In my application I have written code to make a call to helpline just by clicking on button. When I copy this application to my Android device, if the network is not available it exits the application. I want to display a error message rather than exiting.
One more issue,I have written code to add a helpline number to contactbook when the application is loaded into device. When i check it on emulator it works, but on device it's not working :(
Use logcat to see why your application is exiting.
For example if its due to an error or uncaught exception, detect it (make sure an object isn't null before calling its methods) or catch and handle the exception.