如何从自定义列表视图获取所有edittext值

Question

我在自定义列表视图中有20行，但我可以从ListView的屏幕可见性部分获取值。无法从自定义列表视图中获取所有20行值。在运行时，我得到如下错误：

java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference 

这是我的BaseAdapter类。在这个类中，我打电话给我自己的ArrayList，它从AddClassTestMarkActivity类中获取值。

public class StudentListClassTestMarkBaseAdapter extends BaseAdapter { 

ArrayList<StudentsClassTestMarks> myList = new ArrayList<StudentsClassTestMarks>(); 
LayoutInflater inflater; 
Context context; 

public StudentListClassTestMarkBaseAdapter(Context context, ArrayList<StudentsClassTestMarks> myList) { 
    this.myList = myList; 
    this.context = context; 
    inflater = LayoutInflater.from(this.context); 
} 

@Override 
public int getCount() { 
    return myList.size(); 
} 

@Override 
public StudentsClassTestMarks getItem(int position) { 
    return myList.get(position); 
} 

@Override 
public long getItemId(int position) { 
    if (myList != null) { 
     return myList.get(position).id; 
    } 
    return 0; 
} 

@Override 
public View getView(int position, View convertView, ViewGroup parent) { 
    MyViewHolder mViewHolder; 

    if (convertView == null) { 
     convertView = inflater.inflate(R.layout.students_class_test_mark_list_item, parent, false); 
     mViewHolder = new MyViewHolder(convertView); 
     mViewHolder.edtStudentMarks = (EditText) convertView.findViewById(R.id.class_test_marks); 
     mViewHolder.edtStudentMarks.setText("" + mViewHolder.defaultNumber); 

     convertView.setTag(mViewHolder); 
    } else { 
     mViewHolder = (MyViewHolder) convertView.getTag(); 
    } 

    StudentsClassTestMarks currentListData = getItem(position); 

    mViewHolder.txtStudentId.setText(currentListData.getEnrollId()); 
    mViewHolder.txtStudentName.setText(currentListData.getStudentName()); 

    return convertView; 
} 

private class MyViewHolder { 

    TextView txtStudentId; 
    TextView txtStudentName; 
    EditText edtStudentMarks; 
    int defaultNumber = 0; 

    public MyViewHolder(View item) { 
     txtStudentId = (TextView) item.findViewById(R.id.txt_studentId); 
     txtStudentName = (TextView) item.findViewById(R.id.txt_studentName); 
    } 
} 
} 

我的活动类

public class AddClassTestMarkActivity extends AppCompatActivity { 

ListView lvStudent; 
ArrayList<StudentsClassTestMarks> myList = new ArrayList<StudentsClassTestMarks>(); 

@Override 
protected void onCreate(@Nullable Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_add_class_test_mark); 

    lvStudent = (ListView) findViewById(R.id.listView_students); 

    btnSave = (ImageView) findViewById(R.id.btnSave); 
    btnSave.setOnClickListener(this);   

    GetStudentsList(classId); 

    lvStudent.setItemsCanFocus(true); 

    StudentListClassTestMarkBaseAdapter cadapter = new StudentListClassTestMarkBaseAdapter(AddClassTestMarkActivity.this, myList); 
    lvStudent.setAdapter(cadapter); 

} 

private void GetStudentsList(String classSectionId) { 

    myList.clear(); 

    try { 
     Cursor c = db.getStudentsOfClassBasedOnClassId(classSectionId); 
     if (c.getCount() > 0) { 
      if (c.moveToFirst()) { 
       int i = 0; 
       do { 
        StudentsClassTestMarks lde = new StudentsClassTestMarks(); 
        lde.setId(Integer.parseInt(c.getString(0))); 
        lde.setEnrollId(c.getString(1)); 
        lde.setAdmissionId(c.getString(2)); 
        lde.setClassId(c.getString(3)); 
        storeClassId = c.getString(3); 
        lde.setStudentName(c.getString(4)); 
        lde.setClassSection(c.getString(5)); 

        // Add this object into the ArrayList myList 
        myList.add(lde); 

       } while (c.moveToNext()); 
      } 
     } 


     db.close(); 

    } catch (Exception e) { 
     Toast.makeText(getApplicationContext(), "Error", Toast.LENGTH_LONG) 
       .show(); 
     e.printStackTrace(); 
    } 
}  

@Override 
public void onClick(View v) { 
    SaveStudentsClasstestMarks(); 
}  

private void SaveStudentsClasstestMarks() { 


     ArrayList<String> mannschaftsnamen = new ArrayList<String>(); 

      for (int i = 0; i < lvStudent.getAdapter().getCount(); i++) { 
       View viewTelefone = lvStudent.getChildAt(i); 
       TextView et = (TextView) viewTelefone.findViewById(R.id.txt_studentId); 
       TextView et1 = (TextView) viewTelefone.findViewById(R.id.txt_studentName); 
       EditText edtMarks = (EditText) viewTelefone.findViewById(R.id.class_test_marks); 

       if (et != null) { 
        mannschaftsnamen.add(String.valueOf(et.getText().toString())); 
        String enrollId = String.valueOf(et.getText().toString()); 
        String studentName = String.valueOf(et1.getText().toString()); 
        String marks = edtMarks.getText().toString(); 
        String remarks = ""; 
        if (marks.isEmpty()) { 
         marks = "0"; 
        } 

        long c = db.class_test_mark_insert(enrollId, homeWorkId, serverHomeWorkId, marks, remarks, "Active", PreferenceStorage.getUserId(getApplicationContext()), formattedServerDate, PreferenceStorage.getUserId(getApplicationContext()), formattedServerDate, "NS"); 
        if (c == -1) { 
         Toast.makeText(getApplicationContext(), "Error while marks add...", 
           Toast.LENGTH_LONG).show(); 
        } 
        Log.v("ypgs", String.valueOf(et.getText())); 
       } 
      } 

      db.updateClassTestHomeWorkMarkStatus(homeWorkId); 
      Toast.makeText(getApplicationContext(), "Class Test - " + title + ".\n Marks Updated Successfully...", 
        Toast.LENGTH_LONG).show(); 

      finish(); 
}  
} 

是否有任何的ListView替代？

Answer 1

public MyViewHolder(View item) { 
    txtStudentId = (TextView) item.findViewById(R.id.txt_studentId); 
    txtStudentName = (TextView) item.findViewById(R.id.txt_studentName); 
    edtStudentMarks = (EditText) item.findViewById(R.id.class_test_marks); 
} 

删除此行从getview

mViewHolder.edtStudentMarks = (EditText) convertView.findViewById(R.id.class_test_marks);