我有一个listview，它将文件夹中的所有文件作为数组列在listview中。我似乎对长时间选择listview的单个项有问题，因为当我长时间单击时，会抛出一个异常 Attempt to invoke virtual method 'void android.widget.TextView.setTextColor(int)' on a null object reference 我想实现一个选定的子视图背景颜色的变化和该视图内的文本视图的文本颜色。。。下面是我试图实现的完整代码 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;
               }
           });
    }
 }