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POCant understand reason for Null pointer
 

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  1. POCant understand reason for Null pointer
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    <p>I am trying to run a thread in the following code but it is crashing by some unknown reason. This is the code -></p> <pre><code>public class StaticRef extends Activity implements Runnable { Cursor cursor; Thread tSearchSongs=new Thread(this,"SearchSongs"); WritingXML wxml; public void searchforsongs() { tSearchSongs.start(); } @Override public void run() { Looper.prepare(); try { wxml=new WritingXML(); String[] STAR = { "*" }; Uri allsongsuri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI; String selection = MediaStore.Audio.Media.IS_MUSIC + " != 0"; cursor = managedQuery(allsongsuri, STAR, selection, null, null); if (cursor != null) { if (cursor.moveToFirst()) { do { //SongName String song_name = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.DISPLAY_NAME)); //SongID int song_id = cursor.getInt(cursor.getColumnIndex(MediaStore.Audio.Media._ID)); //SongPath String fullpath = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.DATA)); //Song's album name String album_name = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.ALBUM)); //Song's album ID int album_id = cursor.getInt(cursor.getColumnIndex(MediaStore.Audio.Media.ALBUM_ID)); //Song's artist name String artist_name = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.ARTIST)); //Song's artist ID int artist_id = cursor.getInt(cursor.getColumnIndex(MediaStore.Audio.Media.ARTIST_ID)); try { wxml.AddDatatoXML(Integer.toString(song_id) , song_name, fullpath); } catch(Exception exp) { Log.e("~~Exception Occurred in StaticRef~~", exp.toString()); } } while (cursor.moveToNext()); } cursor.close(); } } catch(NullPointerException exp) { Log.e("~~Null Pointer Exception~~",exp.toString()); android.util.Log.e("-&gt;&gt;" , "~~stacktrace~~", exp); } catch(Exception exp) { Log.e("~~Exception~~",exp.toString()); } } </code></pre> <p>}</p> <p>The following is its LOGCAT</p> <pre><code>08-29 13:54:03.149: E/~~Null Pointer Exception~~(13899): java.lang.NullPointerException 08-29 13:54:03.159: E/-&gt;&gt;(13899): ~~stacktrace~~ 08-29 13:54:03.159: E/-&gt;&gt;(13899): java.lang.NullPointerException 08-29 13:54:03.159: E/-&gt;&gt;(13899): at android.content.ContextWrapper.getContentResolver(ContextWrapper.java:91) 08-29 13:54:03.159: E/-&gt;&gt;(13899): at android.app.Activity.managedQuery(Activity.java:1708) 08-29 13:54:03.159: E/-&gt;&gt;(13899): at com.example.boombastic.StaticRef.run(StaticRef.java:53) 08-29 13:54:03.159: E/-&gt;&gt;(13899): at java.lang.Thread.run(Thread.java:856) </code></pre> <p>I would also like to know what is looper and its significant importance in a thread execution?</p>
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    1. COwhat is line 53?
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      1. USMohit
    2. COLine 53 is cursor = managedQuery(allsongsuri, STAR, selection, null, null);
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    3. COIt doesn't seem like a good idea for your `Activity` to implement `Runnable`. You should create a local variable / member `Runnable` that performs the actions you want.
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      1. USItai Hanski
 

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