Fatal Exception: AsyncTask #1 - exception

Question

I have a Fatal Exception: AsyncTask #1 in the following part, but dont know why.
/**
* getting Charts from URL
* */
protected String doInBackground(String... args) {
// Building Parameters
ArrayList<NameValuePair> params = new ArrayList<NameValuePair>();
// getting JSON string from URL
JSONObject json = jParser.makeHttpRequest(url_read, "POST", params);
// Check your log cat for JSON response
Log.d("Charts: ", json.toString());
try {
// Checking for SUCCESS TAG
int success = json.getInt(TAG_SUCCESS);
if (success == 1) {
// products found
// Getting Array of Products
JSONArray charts = json.getJSONArray(TAG_CHARTS);
// looping through All Products
for(int i=0;i<charts.length();i++) {
JSONObject json_data = charts.getJSONObject(i);
String id = json_data.getString("id");
String interpret = json_data.getString("interpret");
String titel = json_data.getString("titel");
String album = json_data.getString("album");
String albumcover = json_data.getString("albumcover");
String likes = json_data.getString("likes");
HashMap<String, String> map = new HashMap<String, String>();
map.put(TAG_ID, id);
map.put(TAG_INTERPRET, interpret);
map.put(TAG_TITEL, titel);
map.put(TAG_ALBUM, album);
map.put(TAG_ALBUMCOVER, albumcover);
map.put(TAG_LIKES, likes);
songslist.add(map);
}
} else {
// no products found
// Launch Add New product Activity
Intent i = new Intent(getApplicationContext(),
CreateSong.class);
// Closing all previous activities
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(i);
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
This is my first question. Hope you know what to do. I get the data from a Database and put them into a JSON Array and then into a Hashmap, but it seems that the error comes by the JSON.
EDIT: LOG CAT
07-11 23:20:48.320: D/CLIPBOARD(13241): Hide Clipboard dialog at Starting input: finished by someone else... !
07-11 23:20:52.510: D/dalvikvm(13241): GC_FOR_ALLOC freed 139K, 3% free 9004K/9223K, paused 13ms
07-11 23:20:52.650: E/JSON Parser(13241): Error parsing data org.json.JSONException: Value <!DOCTYPE of type java.lang.String cannot be converted to JSONObject
07-11 23:20:52.650: W/dalvikvm(13241): threadid=11: thread exiting with uncaught exception (group=0x40c331f8)
07-11 23:20:52.675: E/AndroidRuntime(13241): FATAL EXCEPTION: AsyncTask #1
07-11 23:20:52.675: E/AndroidRuntime(13241): java.lang.RuntimeException: An error occured while executing doInBackground()
07-11 23:20:52.675: E/AndroidRuntime(13241): at android.os.AsyncTask$3.done(AsyncTask.java:278)
07-11 23:20:52.675: E/AndroidRuntime(13241): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
07-11 23:20:52.675: E/AndroidRuntime(13241): at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
07-11 23:20:52.675: E/AndroidRuntime(13241): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
07-11 23:20:52.675: E/AndroidRuntime(13241): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
07-11 23:20:52.675: E/AndroidRuntime(13241): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
07-11 23:20:52.675: E/AndroidRuntime(13241): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
07-11 23:20:52.675: E/AndroidRuntime(13241): at java.lang.Thread.run(Thread.java:856)
07-11 23:20:52.675: E/AndroidRuntime(13241): Caused by: java.lang.NullPointerException
07-11 23:20:52.675: E/AndroidRuntime(13241): at de.andreasgloeckner.ShowCharts$LoadAllProducts.doInBackground(ShowCharts.java:172)
07-11 23:20:52.675: E/AndroidRuntime(13241): at de.andreasgloeckner.ShowCharts$LoadAllProducts.doInBackground(ShowCharts.java:1)
07-11 23:20:52.675: E/AndroidRuntime(13241): at android.os.AsyncTask$2.call(AsyncTask.java:264)
07-11 23:20:52.675: E/AndroidRuntime(13241): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
07-11 23:20:52.675: E/AndroidRuntime(13241): ... 4 more

Answer 1

You have a NullPointerException in your code (ShowCharts.java, line 172). Now figure out which line is that . You are accessing on a null object obviously or just share line 172 here. It could be songslist object. I don't see initialization in the code block you shared.
Caused by: java.lang.NullPointerException
07-11 23:20:52.675: E/AndroidRuntime(13241): at de.andreasgloeckner.ShowCharts$LoadAllProducts.doInBackground(ShowCharts.java:172)

Answer 2

from inside the doInBackground method , you cant change or touch any UI element , so you cant call another activity , what you have to do is to call the another activity from inside the onPostExecute method from your Asynctask