catch only ENOSPC on Android - android

This might be a basic question but I cannot find an answer. When you want to catch only FileNotFound in Android, then you write
} catch (FileNotFoundException e) {
But what do you write if you want to catch exactly ENOSPC (No space left on device) errors? I can't use "catch (Exception e)" because I want to explicitly deal with this one error.


You cannot do so directly as enospc is signaled as a java.io.IOException which will catch many other io related issues as well. But by looking up the cause and the error it's signalling you can zoom in and handle enospc exceptions but rethrow all others, like this:
} catch (IOException ex) {
boolean itsanenospcex = false;
// make sure the cause is an ErrnoException
if (ex.getCause() instanceof android.system.ErrnoException) {
// if so, we can get to the causing errno
int errno = ((android.system.ErrnoException) ex.getCause()).errno;
// and check for the appropriate value
itsanenospcex = errno == OsConstants.ENOSPC;
}
if (itsanenospcex) {
// handle it
} else {
// if it's any other ioexception, rethrow it
throw ex;
}
}
Sidenote: } catch (Exception e) { is generally considered bad practice.

Related

How to handle errors in BlockingObservable without subscribe()?

for various reasons I have to block on observable like this
Foo foo = fooBarNetworkRequestObservable()
.toBlocking()
.single();
return foo;
But how do I handle errors now? Is is possible without subscribe(new Subscriber .. onError()?. I tried wrapping the code in try-catch but compiler complains that IOException is never thrown in coresponding try-catch block. Any solutions? Thanks

You are in blocking world so you need try-catch. Since the API can't throw checked exceptions, we wrap them into RuntimeException for you:
try {
source.toBlocking.single();
} catch (RuntimeException ex) {
if (ex.getCause() instanceof IOException) {
// handle IOException
} else {
throw ex; // something other happened
}
}

Cannot catch exception, catch block is never reached

I have code structurred in this way
public void generalMethod(){
try{
methodThatStartAsyncWebTask();
catch(Exception e){
offlineDataAlternativeMethod();
}
}
the method
public void offlineDataAlternativeMethod(){
try(
loadArchivedFile();
}
catch(Exception e){
reInitializeeData();
}
}
The App crashes at line loadArchivedFile(); that fails because doesn't found the file, but the strange thing is that catch block that invokes reInitializeeData(); isn't reached.
Why cannot reach catch block in anyway? Any idea?
This is the first time that see a similar issue. Any solution?

Try this
getting file not found exception

How to prevent android app from crashing when a file has not been found using openFileInput

I want to react to a situation that no file has been found using FileInputStream. When i ran an app that loads a file that doesn't exist it opens an android popup with force close. I would like to react to the situation by changing a text in a text view and saying that the file has not been found. i tried changing the exceptions to change a text view and show that a file has not been found and the app still crashes.
Here is the piece of code:
FileInputStream fis = null;
String collected = null;
try {
fis = openFileInput("test");
byte[] dataArray = new byte[fis.available()];
while (fis.read(dataArray) != -1){
collected = new String(dataArray);
}
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
try {
fis.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
tv.setText(collected);

To ensure that an Android application does not force-close, your options are: a) do not do anything that will cause an exception, b) catch your exception with your own try/catch block, c) install an application level uncaught exception handler. Option a is not too feasible, c is not very helpful, and based on your code snippet you seem to be trying b -- however there appears to be another exception that you're not catching with this. The contents of logcat will tell you what exception, and the stack trace will lead to a point in your code which needs the try/catch.

setPin() shows error in eclipse that "setPin() is undefined for BluetoothDevice"

I don't find many BluetoothDevice methodes such as , setPasskey(), setPin(), setPairingConfirmation(), setRemoteOutOfBandData().
I searched on Android site as well but I don't find it. When I use these methods in my program in eclipse it shows me an error: its undefined for the type BluetoothDevice.
Are these obsolete now? If yes then what are the new methods of same type.

It is assumed that paring process is performed only by applications delivered with a platform!
This means that this application have access to hidden API. For example you can find hidden API for Bluetooth here.
It is strongly recommended to not use hidden API since it can change without warning in next Android release.
If you are still planning to use this API safest way is to use reflection:
try {
Class<? extends BluetoothDevice> c = device.getClass(); // BluetoothDevice.class
Method createBond = c.getMethod("createBond");
Object result = createBond.invoke(device);
Boolean castedResult = (Boolean)result;
Log.d(TAG, "Result: " + castedResult.toString());
} catch (SecurityException e) {
e.printStackTrace();
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
There is also alternative way to easy use hidden API, but I didn't try it.

Android - print full exception backtrace to log

I have a try/catch block that throws an exception and I would like to see information about the exception in the Android device log.
I read the log of the mobile device with this command from my development computer:
/home/dan/android-sdk-linux_x86/tools/adb shell logcat
I tried this first:
try {
// code buggy code
} catch (Exception e)
{
e.printStackTrace();
}
but that doesn't print anything to the log. That's a pity because it would have helped a lot.
The best I have achieved is:
try {
// code buggy code
} catch (Exception e)
{
Log.e("MYAPP", "exception: " + e.getMessage());
Log.e("MYAPP", "exception: " + e.toString());
}
Better than nothing but not very satisfying.
Do you know how to print the full backtrace to the log?
Thanks.

try {
// code that might throw an exception
} catch (Exception e) {
Log.e("MYAPP", "exception", e);
}
More Explicitly with Further Info
(Since this is the oldest question about this.)
The three-argument Android log methods will print the stack trace for an Exception that is provided as the third parameter. For example
Log.d(String tag, String msg, Throwable tr)
where tr is the Exception.
According to this comment those Log methods "use the getStackTraceString() method ... behind the scenes" to do that.

This helper function also works nice since Exception is also a Throwable.
try{
//bugtastic code here
}
catch (Exception e)
{
Log.e(TAG, "Exception: "+Log.getStackTraceString(e));
}

catch (Exception e) {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
PrintStream stream = new PrintStream( baos );
e.printStackTrace(stream);
stream.flush();
Log.e("MYAPP", new String( baos.toByteArray() );
}
Or... ya know... what EboMike said.

public String getStackTrace(Exception e){
StringWriter sw = new StringWriter();
PrintWriter pw = new PrintWriter(sw);
e.printStackTrace(pw);
return sw.toString();
}

e.printStackTrace() prints it to me. I don't think you're running the logcat correctly. Don't run it in a shell, just run
/home/dan/android-sdk-linux_x86/tools/adb logcat

The standard output and error output are directed to /dev/null by default so it is all lost. If you want to log this output then you need to follow the instructions "Viewing stdout and stderr" shown here

try{
...
} catch (Exception e) {
Log.e(e.getClass().getName(), e.getMessage(), e.getCause());
}

if you want to print out stack trace without exception, you can create it by following command
(new Throwable()).printStackTrace();

In the context of Android, I had to cast the Exception to a String:
try {
url = new URL(REGISTRATION_PATH);
urlConnection = (HttpURLConnection) url.openConnection();
} catch(MalformedURLException e) {
Log.i("MALFORMED URL", String.valueOf(e));
} catch(IOException e) {
Log.i("IOException", String.valueOf(e));
}

KOTLIN SOLUTION:
You can make use of the helper function getStackTraceString() belonging to the android.util.Log class to print the entire error message on console.
Example:
try {
// your code here
} catch (e: Exception) {
Log.e("TAG", "Exception occurred, stack trace: " + e.getStackTraceString());
}

Kotlin extension. Returns the detailed description of this throwable with its stack trace.
e.stackTraceToString()

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