Android AsyncTask崩溃

Question

Hi i have problem with AsyncTask, im parsing some data from web, but when i want to use this class my app crashes:

10-31 12:29:29.941: E/AndroidRuntime(3741): FATAL EXCEPTION: AsyncTask #2
10-31 12:29:29.941: E/AndroidRuntime(3741): java.lang.RuntimeException: An error occured while executing doInBackground()
10-31 12:29:29.941: E/AndroidRuntime(3741):     at android.os.AsyncTask$3.done(AsyncTask.java:299)
10-31 12:29:29.941: E/AndroidRuntime(3741):     at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
10-31 12:29:29.941: E/AndroidRuntime(3741):     at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
10-31 12:29:29.941: E/AndroidRuntime(3741):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
10-31 12:29:29.941: E/AndroidRuntime(3741):     at java.util.concurrent.FutureTask.run(FutureTask.java:137)
10-31 12:29:29.941: E/AndroidRuntime(3741):     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
10-31 12:29:29.941: E/AndroidRuntime(3741):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
10-31 12:29:29.941: E/AndroidRuntime(3741):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
10-31 12:29:29.941: E/AndroidRuntime(3741):     at java.lang.Thread.run(Thread.java:856)
10-31 12:29:29.941: E/AndroidRuntime(3741): Caused by: java.lang.IndexOutOfBoundsException: Invalid index 0, size is 0
10-31 12:29:29.941: E/AndroidRuntime(3741):     at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:251)
10-31 12:29:29.941: E/AndroidRuntime(3741):     at java.util.ArrayList.get(ArrayList.java:304)
10-31 12:29:29.941: E/AndroidRuntime(3741):     at morisson.Notowaniagieldowe.MainActivity$Cena.doInBackground(MainActivity.java:169)
10-31 12:29:29.941: E/AndroidRuntime(3741):     at morisson.Notowaniagieldowe.MainActivity$Cena.doInBackground(MainActivity.java:1)
10-31 12:29:29.941: E/AndroidRuntime(3741):     at android.os.AsyncTask$2.call(AsyncTask.java:287)
10-31 12:29:29.941: E/AndroidRuntime(3741):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
10-31 12:29:29.941: E/AndroidRuntime(3741):     ... 5 more

and code is:

public class Cena extends AsyncTask<Integer,Void,String>{
ProgressDialog dialog;

@Override
protected String doInBackground(Integer... params) {

    int a = params[0];
    try {

        Document doc = Jsoup.connect("http://www.money.pl/gielda/gpw/akcje/").get();

        Elements elements = doc.select("td.ar");

        System.out.println("test2:" + elements.get(a).text());
        return elements.get(a).text();


    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

return null;
}
}

I use also 2 others class which use AsyncTask but i don't have any problems with them. crash appear when im trying to print "test2", and ofcourse when im trying to return a value. Any suggestions?

Answer 1

If you closely inspect the error log you will find that the actual error here is ArrayIndexOutOfBound exception. Meaning either elements.get(a) or int a = params[0]; is likely to be returning null.

Since the exception has not been caught (which led to your crash), I highly suspect int a = params[0]; to be the cause of issue because it is the only code that is not in the try catch block.

Answer 2

try {
    Document doc = Joup.connect("http://www.money.pl/gielda/gpw/akcje/").get();
    Elements elements = doc.select("td.ar");
    if(elemetns!=null&&a!=null){
        System.out.println("test2:" + elements.get(a).text());
        return elements.get(a).text();
    }
} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}