AsyncTask: ClassCastException: java.lang.Object[] cannot be cast to java.lang.String[]
android, android-asynctask, java
Solution
How is your `sendTask` declared? I suppose its simply `AsyncTask sendTask;`, if so then change it to:
AsyncTask<String, String, String> sendTask;
The cause of this exception is similar to the one that occurs in below code:
Object arr1[] = new Object[] {null,null,null};
String arr2[] = (String[])arr1; // here java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ljava.lang.String;
VarArgs in java are implemented as arrays, so when you declare sendTask as `AsyncTask<String, String, String>` then compiler will call your `doInBackground` with `new String[]{null,null,null}`, but when you declare it as `AsyncTask` then `doInBackground` is called with `new Object[]{null,null,null}`.
Because of type erasure, compiler will add hidden implicit cast from `Object[]` to `String[]`. This is to allow code as below to work correctly:
AsyncTask sendTask = ...;
Object[] arg = new String[]{null,null,null};
sendTask.execute(arg);
Problem
In my application I run these code for gcm ccs(xmpp) and the code shows following error An error occurred while executing `doinbackground.excute()` This is the code: ``` sendTask = new AsyncTask<String, String, String>() { protected String doInBackground(String... title) { Bundle data = new Bundle(); data.putString("ACTION", action); data.putString("CLIENT_MESSAGE", "Hello GCM CCS XMPP!"); String id = Integer.toString(ccsMsgId.incrementAndGet()); try { Log.d("RegisterActivity", "messageid: " + id); gcm.send(SENDER_ID + "@gcm.googleapis.com", id, data); Log.d("RegisterActivity", "After gcm.send successful."); } catch (IOException e) { Log.d("RegisterActivity", "Exception: " + e); e.printStackTrace(); } return "Sent message."; } protected void onPostExecute(String result) { sendTask = null; // tosat about the success in return } }; sendTask.execute(null, null, null); ```