Develop Reference

How to save LogCat contents to internal memory of a file?

I have implemented a solution
try {
var process = Runtime.getRuntime().exec("logcat ${BuildConfig.APPLICATION_ID}:V *:S")
process = Runtime.getRuntime().exec("logcat -f " + "/storage/emulated/0/"+"Logging.txt")
} catch (e: Exception) {
e.printStackTrace()
}
Do we need to run this command only once or multiple times, as on Android 11 Chromebook it is working fine when run once, and on Android 10 Tablet it stops writing to file when run once, when i run it again then it writes to the same file

you have to run this snippet every time for storing all logs to file, it dumps only current logcat content. you have fixed file name so further calls are adding text to already existing file (note that this may cause duplicated lines, if only one new appeared in log, as method is storing whole output without clearing it)

Viewing logcat in tablet

Is there a way to view the log on a tablet running 4.4? I've downloaded several apps like aLogCat and none of them show what my app writes out with S.o.p or Log.d. I have an intermittent bug that gives the Unfortunately appname has stopped message.Is there any way to view the log after this event without having to connect to a PC and use the adb program?
What other ways are there to get debug output? Would trapping the System.out and System.err classes get the stack trace?
Thanks,
Norm

You're focussing on tring to read out logcat, but there are better solutions for reading crash logs. My personal preference is Crashlytics, which automatically logs fatal exceptions and provides mechanisms for logging other messages.
The way all these crash reporters work, is by defining a UncaughtExceptionHandler:
Thread.setDefaultUncaughtExceptionHandler(
new MyUncaughtExceptionHandler(this));
If you prefer to use your own solution, you may want to look into using this. See this related question for more details.

Is there a way to view the log on a tablet running 4.4?
No, sorry. An app can only see its own log messages, not those from other apps. Hence, a third-party log viewer cannot see your app's messages.
Is there any way to view the log after this event without having to connect to a PC and use the adb program?
Use any standard crash management library, like ACRA, or services like Crashlytics, BugSense, etc.

The AIDE Application (Android Integrated Development Environment) allows one to develop android Apps directly on android device.
One particular feature is to read the logcat.
You can get it here https://play.google.com/store/apps/details?id=com.aide.ui

Here's the code I've put in the program. It seems to work:
// Define inner class to handle exceptions
class MyExceptionHandler implements Thread.UncaughtExceptionHandler {
public void uncaughtException(Thread t, Throwable e){
java.util.Date dt = new java.util.Date();
String fn = LogFilePathPfx + "exception_" + sdf.format(dt) + ".txt";
try{
PrintStream ps = new PrintStream( fn );
e.printStackTrace(ps);
ps.close();
System.out.println("wrote trace to " + fn);
e.printStackTrace(); // capture here also???
SaveStdOutput.stop(); // close here vs calling flush() in class
}catch(Exception x){
x.printStackTrace();
}
lastUEH.uncaughtException(t, e); // call last one Gives: "Unfortunately ... stopped" message
return; //???? what to do here
}
}
lastUEH = Thread.getDefaultUncaughtExceptionHandler(); // save previous one
Thread.setDefaultUncaughtExceptionHandler(new MyExceptionHandler());

Keep Logcat from deleting entries

In Eclipse, I notice that Logcat only retains a few dozen entries and deletes the older ones as soon as a new one come in. Is there a way to prevent this? I need my app to run for a long time and not lose any entries because my app eventually hangs or crashes after a few days, and I want to see if something in Logcat has been recorded.

I am not sure if this is the most elegant solution to the problem, but you can always increase the LogCat message size in Eclipse.
Window -> Preferences -> Android -> LogCat -> Maximum number of LogCat messages to buffer
The default is 5000, I believe. You can set it to be very high if you are planning to run your application for a long time.

i think you need to increase this show image

Here's a better solution:
Set the Default Uncaught Exception Handler. Whenever the app crashes, this will be called with the exception. Simply write a log entry saying it crashed then dump the logcat to a file. Finally, make sure you re-throw the exception to make sure the app crashes and funky things don't happen. Note: This is per thread, keep that in mind.
Thread.setDefaultUncaughtExceptionHandler(new UncaughtExceptionHandler() {
#Override
public void uncaughtException(Thread thread, Throwable ex) {
Log.e("TAG", "---My app crashed just now---", ex);
//TODO: Dump logcat to file
throw new RuntimeException(ex);
}
});

if you want to keep your app running for days.. its better you capture your logs from adb shell.
the common shell command would be :
logcat -c \\ to clear previous logs
logcat -v time>yourLogs.txt & \\ to capture fresh logs

How to install apps in phone which contains sqlite database in android

I want to install my app which contains regestration form whose username and password is stored im sqlite database. after copyiny .apk file my apps does not contains any database table for that work.
So my question is how to import this database in my app which is installed on android device it is working fine on emulator.

Have you initialized database class object
EditDatabase db=new EditDatabase(this);
onCreate or onResume activity?
if not then initialize it.

Update from logcat output
Based on the logcat output, it shows that this is an unhandled exception. i.e. it happens outside the try{} ... catch{} block of the onClick(View) method.
This means that it is a problem in one of these 2 lines:
unname = username1.getText().toString();
storePassword1 = db.getdata(unname);
My feeling is that username1 is null because it is not referenced in your layout XML file.
Here's how you should check - replace those 2 lines with these null checks:
if (unname != null)
{
unname = username1.getText().toString();
}
else
{
Log.d("MyTag", "unname is null");
}
if (storePassword1 != null)
{
storePassword1 = db.getdata(unname);
}
else
{
Log.d("MyTag", "storePassword1 is null");
}
if (unname == null || storePassword1 == null)
{
return;
}
Run the code again, check the logcat output again, and see if it tells you about the problem.
Also try not to use System.out(String) - rather use the Log.d(String, String) methods. These are more useful on Android.
Original
Firstly, please provide a stack trace - it will show where the null pointer error happened.
For Android, the most useful way of doing that will be to use the adb logcat terminal command. This outputs the internal log of your Android device/emulator to the screen, so you can view what went wrong.
In your catch{} block, I would put the following line:
Log.d("MyTag", "Stack Trace of exception...", e);
This will output the text, and information about the error e to this log - I think it will include the stack trace.
Copy the lines starting with "MyTag" and paste them into your question.
Secondly, without the stack trace, confirm that these 3 variables are not null typically:
username1
db
password (if the app actually crashed with the NullPointerException then this one is not the problem, because the exception would be handled by the catch{} block)
i.e. confirm that you have initialised all of them before the click event.

Unauthorized Caller Error

I am stuck writing some code that uses reflection that calls IConnectivityManager.startLegacyVpn
The error I get is java.lang.SecurityException: Unauthorized Caller
Looking through the android source I see this is the code hanging me up:
if (Binder.getCallingUid() != Process.SYSTEM_UID) { raise the above exception }
My question is if I root my AVD and install my app in system/app will this be sufficient to get around this error?
If so, any tips on how to do this (every time I try to move my apk to the system/app folder it says the app is not installed when I click on the app icon.
Thanks!

I have the same problem, following android 4.01 open source, i see somethings like this:
public synchronized LegacyVpnInfo getLegacyVpnInfo() {
// Only system user can call this method.
if (Binder.getCallingUid() != Process.SYSTEM_UID) {
throw new SecurityException("Unauthorized Caller");
}
return (mLegacyVpnRunner == null) ? null : mLegacyVpnRunner.getInfo();
}
Or,
// Only system user can revoke a package.
if (Binder.getCallingUid() != Process.SYSTEM_UID) {
throw new SecurityException("Unauthorized Caller");
}
Or,
public void protect(ParcelFileDescriptor socket, String interfaze) throws Exception {
PackageManager pm = mContext.getPackageManager();
ApplicationInfo app = pm.getApplicationInfo(mPackage, 0);
if (Binder.getCallingUid() != app.uid) {
throw new SecurityException("Unauthorized Caller");
}
jniProtect(socket.getFd(), interfaze);
}
However, these block of code above is belongs to com.android.server.connectivity.Vpn
(class Vpn), which is not defined in interface IConnectivityManager.
I also find in startLegacyVpnInfo() function but i can't see anything involve exception
"Unauthorized Caller", so i wonder why startLegacyVpnInfo() function throws this exception?
Any solutions for this?

I am trying to make the same calls. So far I can confirm that rooting the device and copying the apk to /system/app does not work, it does not start under the system uid.
Also, this does not work:
Field uidField = Process.class.getDeclaredField("SYSTEM_UID");
uidField.setAccessible(true);
uidField.set(null, Process.myUid());
Those calls succeed, but they don't seem to affect the SYSTEM_UID field, the field is probably optimized out at compile time.

If you include android: sharedUserId="android.uid.system" into your manifest tag (not just the manifest), this should then run the application as system. This should now let you run the code.
As for pushing to /system/app, you need to run adb root followed by adb remount. This will now let you push to /system/app.