ListView item long click listener throwing a null pointer exception

Question

I have a ListView that lists all the files in a folder into the ListView as an array. I seem to have a problem with long selection of the ListView's single item in that, when i long click an exception is thrown that Attempt to invoke virtual method 'void android.widget.TextView.setTextColor(int)' on a null object reference I want to achieve a change of color for the selected child view Background and the Text color of the TextView inside that View... Here is the complete code i tried to implement my AdapterView.OnLongItemClickListener

public class video_player extends AppCompatActivity implements GestureDetector.OnGestureListener {
    ListView filelist;
    List files;
  @RequiresApi(api = Build.VERSION_CODES.Q)
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.medias_combine);
         filelist = (ListView) findViewById(R.id.filelist);
        files=new ArrayList<>();
        //Defining folder to read files from
        File store = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
          File[] myfiles=store.listFiles();
         //Adding filenames to the ArrayList
        for(int i=0;i<myfiles.length;i++){
         //Adding a file filter
            if(myfiles[i].isFile()&& myfiles[i].getName().contains(".mp4")){
                files.add(myfiles[i].getName());
            }
           //Build the ListView
              ListAdapter myadapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, files);
                filelist.setAdapter(myadapter);
            //ListView Item long item click listener
             filelist.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
                   @Override
                   public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
                       for(int i=0;i<filelist.getCount();i++){
                         //Problem is in this loop
                           if(position==id){
                               view.setBackgroundColor(Color.WHITE);
                               TextView mytext=(TextView)filelist.getChildAt(position);
                               mytext.setTextColor(Color.parseColor("#6600cc"));
                           }else{
                               view.setBackgroundColor(Color.parseColor("#6600cc"));
                               TextView mytext=(TextView)filelist.getItemAtPosition(position);
                             //  TextView text=(TextView)parent.getItemAtPosition(position);
                               mytext.setTextColor(Color.WHITE);
                           }
                       }

                       return true;
                   }
               });
        }
     }

score 0 · Answer 1 · answered Dec 03 '20 at 08:58

0

I think the problem with this line TextView mytext=(TextView)filelist.getChildAt(position); mytext is null because when code tries to get the view from the viewList the assigned value is null so try to find the reason for this.

answered Dec 03 '20 at 08:58

Mahmoud Sallam

19
3

Kalai · Accepted Answer · 2020-12-03T09:24:29.240

0

Your getItemAtPosition gets the data associated with the specified position in the list, not a View. Instead of TextView mytext=(TextView)filelist.getChildAt(position); use the view provided, which is actually the item being clicked within your ListView. Try this instead:

  public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
            if(position==id){
                view.setBackgroundColor(Color.WHITE);
                TextView mytext=(TextView)view;
                mytext.setTextColor(Color.parseColor("#6600cc"));
            }else{
                view.setBackgroundColor(Color.parseColor("#6600cc"));
                TextView mytext=(TextView)view;
                mytext.setTextColor(Color.WHITE);
            }
        

        return true;
    }

Since,you use android.R.layout.simple_list_item_1 to inflate the view item within the ListView, you can type cast it as a TextView and call setText() on it.

Note: android.R.layout.simple_list_item_1 consist of just a TextView. Refer to this Q&A.

edited Dec 03 '20 at 09:24

answered Dec 03 '20 at 09:02

Kalai

503
1
3
12

View has no method to fetch text unfortunately – Dec 03 '20 at 09:14
Typecast it as a TextView – Kalai Dec 03 '20 at 09:14
1

Post the code, that way it will be easier – Dec 03 '20 at 09:17
Please check the answer again. I have edited it. – Kalai Dec 03 '20 at 09:21
1

It worked, am accepting your answer and i hope to see you more often here at SO – Dec 03 '20 at 09:26

ListView item long click listener throwing a null pointer exception

2 Answers2