当ProgressDialog dismiss方法被称为android时发生NullPointerException

Question

I am getting random crash while dismissing progress dialog. My code is:

if(progressdialog != null && progressdialog.isShowing())
{
   progressdialog.dismiss();
}

I am getting NullPointerException on progressdialog.dismiss(). How it is possible after passing null check?

Here is crash log

java.lang.NullPointerException
at com.ebooks.android.Category_Author_Listing$1.handleMessage(Author_Listing.java:1325)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5103)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)

Answer 1

This might be because android UI components are not Thread safe , I guess you have declared variable before oncreate and then used .show inside oncreate or any method called after oncreate initialised .

Solution is to just use

progressDialog =ProgressDialog.show(MainActivity.this,"title","message");

Now you can dismiss it will not show null pointer.