Android application crashes when trying to get string length

-4

Those who invented Android and Java didn't invented for themselves. Since I started developing application with Java in Android I get the most ridiculous errors and I am really going crazy (and if I do, Google and Sun Microsystems will make "booooom")

I have this simple code that is supposed to get the length of a string passed as an argument. The application just crashes, making me spend some minutes swearing and torturing the keyboard.

My code:

@Override
protected void onPostExecute(String result) {
    if (result.length() == 0) {
        txtStatus.setText("Ready");
    }
}

If I remove the condition it works (the text "Ready" is shown on my TextView). This is something weird and I know that I might be missing some little something.

Give me some clues and thanks for everything!

P.S. If you hear a gun shoot coming from your neighbor it might be me.

2012-04-04 19:41
by ali

Save yourself a lot of stress and learn about the logcat utility - available through Eclipse or from the command line. When something crashes the logcat output will include a stack trace which has useful hints such as null pointer exception. In the worst case copy/paste the exception message into a Google search to find others who have seen the same problem and gain from the wisdom of others who have already solved the problem - Colin 2012-04-05 03:05

Its because your string is perhaps null. Do it like this:

@Override
protected void onPostExecute(String result) {
    if (!TextUtils.isEmpty(result)) {
        txtStatus.setText("Ready");
    }
}

2012-04-04 19:43
by waqaslam

Yeah! I initiated result as null but I thought that it would become an empty string after getting an empty content from a web page. Anyway, your answer was my solution. Thanks - ali 2012-04-04 19:52

Try this:

@Override
protected void onPostExecute(String result) {
    if (result != null && result.length() == 0) {
        txtStatus.setText("Ready");
    }
}

2012-04-04 19:44
by Rui Gaspar

Check if result is null first, Handle it appropriately, then check it's length. My best guess is you have an unhandled NullPointerException.

@Override
protected void onPostExecute(String result) {
    if (result == null) {
        result = ""; // change this line if null is an error.
    }
    if (result.length() == 0) {
        txtStatus.setText("Ready");
    }
}

A debugging technique to figure out what is wrong and making your program crash would be to wrap the condition in a try/catch block.

    @Override
protected void onPostExecute(String result) {
    try {
        if (result.length() == 0) {
            txtStatus.setText("Ready");
        }
    catch (Throwable t) { // both error and exception inherit from Throwable.
        // print or inspect 't' here to determine the reason for the crash.
    }
}

2012-04-04 19:51
by Colin D

As said by Waqas the problem is because your string maybe null. If the string is null the method length is not defined.So add an additional condition checking for null i.e

if(result ==NULL)
// do something else
else
//your code here

2012-04-04 20:06
by Desert Ice