Androidは最後のリストビューをフラグメント変更後に更新します

Question

私は2つの異なるフラグメントを持っています。最初のフラグメントでは、私はカスタムのStudent ArrayListに新しい学生エントリを追加しています。私はまた、私の2番目の断片に学生リストを示すListViewを持っています。しかし、2番目のFragmentに行くと、最新のListViewは更新されません。だから私の質問は、どのように私のフラグメントタブを変更した後、私のリストビューを更新することができますか？

registerBtnはstudentsのArrayListに新しいエントリを追加するだけです。

まず、「取得」ボタンを使用してListViewを更新しようとしましたが、動作しませんでした。私がしたいことは、StudentsFragmentに渡すたびにListViewをリフレッシュすることです。

RegisterFragment.java：

package com.rawsly.android.schoolprogram; 

import android.os.Bundle; 
import android.support.annotation.Nullable; 
import android.support.v4.app.Fragment; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.Button; 
import android.widget.EditText; 
import android.widget.TextView; 
import android.widget.Toast; 

import java.util.ArrayList; 
import java.util.Random; 

public class RegisterFragment extends Fragment { 
    private static final String TAG = "RegisterFragment"; 
    public ArrayList<Students> studentsArrayList = new ArrayList<>(); 
    private ArrayList<Long> idList = new ArrayList<>(); 
    private TextView studentID; 
    private Button registerBtn, clearBtn, exitBtn; 
    private EditText editName, editLastName, editGender, editFaculty, editDepartment, editAdvisor; 

    @Nullable 
    @Override 
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { 
     View view = inflater.inflate(R.layout.register_fragment, container, false); 

     studentID = (TextView) view.findViewById(R.id.studentID); 
     studentID.setText(String.valueOf(generateID())); 
     editName = (EditText) view.findViewById(R.id.editName); 
     editLastName = (EditText) view.findViewById(R.id.editLastName); 
     editGender = (EditText) view.findViewById(R.id.editGender); 
     editFaculty = (EditText) view.findViewById(R.id.editFaculty); 
     editDepartment = (EditText) view.findViewById(R.id.editDepartment); 
     editAdvisor = (EditText) view.findViewById(R.id.editAdvisor); 

     registerBtn = (Button) view.findViewById(R.id.registerBtn); 
     registerBtn.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       String id = studentID.getText().toString(); 
       String name = editName.getText().toString(); 
       String lastName = editLastName.getText().toString(); 
       String gender = editGender.getText().toString(); 
       String faculty = editFaculty.getText().toString(); 
       String department = editDepartment.getText().toString(); 
       String advisor = editAdvisor.getText().toString(); 

       studentsArrayList.add(new Students(id, name, lastName, gender, faculty, department, advisor)); 
       Toast.makeText(getContext(), "New entry added.", Toast.LENGTH_SHORT).show(); 
      } 
     }); 

     clearBtn = (Button) view.findViewById(R.id.clearBtn); 
     clearBtn.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       editName.setText(null); 
       editLastName.setText(null); 
       editGender.setText(null); 
       editFaculty.setText(null); 
       editDepartment.setText(null); 
       editAdvisor.setText(null); 
       studentID.setText(String.valueOf(generateID())); 
      } 
     }); 

     exitBtn = (Button) view.findViewById(R.id.exitBtn); 
     exitBtn.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       System.exit(1); 
      } 
     }); 

     return view; 
    } 

    // Generates a random ID. 
    public long generateID() { 
     Random rnd = new Random(); 
     char [] digits = new char[11]; 
     digits[0] = (char) (rnd.nextInt(9) + '1'); 
     for(int i=1; i<digits.length; i++) { 
      digits[i] = (char) (rnd.nextInt(10) + '0'); 
     } 
     long result = Long.parseLong(new String(digits)); 
     if(idList.contains(result)) { 
      return generateID(); 
     } else { 
      return result; 
     } 
    } 
} 

StudentsFragment.java：

package com.rawsly.android.schoolprogram; 

import android.app.Dialog; 
import android.os.Bundle; 
import android.support.annotation.Nullable; 
import android.support.v4.app.Fragment; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.AdapterView; 
import android.widget.Button; 
import android.widget.EditText; 
import android.widget.ListView; 
import android.widget.TextView; 
import android.widget.Toast; 

import java.util.ArrayList; 

public class StudentsFragment extends Fragment { 
    private static final String TAG = "StudentsFragment"; 
    private EditText txtSearch; 
    private ListView studentsListView; 
    private Button getStudents, updateStudent, deleteStudent, exitBtn; 
    public StudentsAdapter adapter; 
    public ArrayList<Students> studentsArrayList = new ArrayList<>();; 
    public int selectedItem = -1; // to update or delete the data 

    @Nullable 
    @Override 
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { 
     View view = inflater.inflate(R.layout.students_fragment, container, false); 


     // Dummy Data 
     studentsArrayList.add(new Students("1122334455", "Ahmet", "Özdemir", "Male", "Mühendislik ve Doğa Bilimleri", "Bilgisayar Mühendisliği", "Tuğba Yıldız")); 
     studentsArrayList.add(new Students("1234567890", "Ezgi", "İmamoğlu", "Female", "Mühendislik ve Doğa Bilimleri", "Bilgisayar Mühendisliği", "Tuğba Yıldız")); 
     studentsArrayList.add(new Students("", "Enise", "Usta", "Female", "Sosyal ve Beşeri Bilimler Fakültesi", "Uluslararası İlişkiler", "Murat Orhun")); 
     studentsArrayList.add(new Students("1122445588", "Sinem", "Ünver", "Female", "Mühendislik ve Doğa Bilimleri", "Endüstri Mühendisliği", "Zehra Yılmaz")); 
     studentsArrayList.add(new Students("2546882547", "Zehra", "Gürçay", "Female", "Mühendislik ve Doğa Bilimleri", "Endüstri Mühendisliği", "Şule Gündüz")); 


     adapter = new StudentsAdapter(getContext(), studentsArrayList); 

     studentsListView = (ListView) view.findViewById(R.id.studentsListView); 
     studentsListView.setAdapter(adapter); 

     studentsListView.setOnItemClickListener(new AdapterView.OnItemClickListener() { 
      @Override 
      public void onItemClick(AdapterView<?> adapterView, View view, int position, long id) { 
       selectedItem = position; 
       Toast.makeText(getContext(), "Selected entry: " + (selectedItem+1), Toast.LENGTH_LONG).show(); 
      } 
     }); 

     // Opens a dialog window 
     getStudents = (Button) view.findViewById(R.id.getStudents); 
     getStudents.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       adapter.notifyDataSetChanged(); 
       studentsListView.invalidate(); 
      } 
     }); // end of the add action 

     // To delete the selected School object 
     deleteStudent = (Button) view.findViewById(R.id.deleteStudent); 
     deleteStudent.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       if(selectedItem == -1) { 
        Toast.makeText(getContext(), "Please, select an entry first.", Toast.LENGTH_SHORT).show(); 
       } else { 
        studentsArrayList.remove(selectedItem); 
        selectedItem = -1; 
        adapter.notifyDataSetChanged(); 
        Toast.makeText(getContext(), "Selected entry is deleted.", Toast.LENGTH_SHORT).show(); 
       } 
      } 
     }); // end of the delete action 

     // To exit the program 
     exitBtn = (Button) view.findViewById(R.id.exitBtn); 
     exitBtn.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       System.exit(1); 
      } 
     }); // end of the exit action 

     // To update the selected School object 
     updateStudent = (Button) view.findViewById(R.id.updateStudent); 
     updateStudent.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       if(selectedItem == -1) { 
        Toast.makeText(getContext(), "Please, select an entry first.", Toast.LENGTH_SHORT).show(); 
       } else { 
        final Dialog dialog = new Dialog(getContext()); 
        dialog.setContentView(R.layout.update_student); 
        dialog.setTitle("Update An Entry"); 
        // Dialog components - EditText, Button 
        String id = studentsArrayList.get(selectedItem).id; 
        String name = studentsArrayList.get(selectedItem).name; 
        String lastName = studentsArrayList.get(selectedItem).lastName; 
        String gender = studentsArrayList.get(selectedItem).gender; 
        String faculty = studentsArrayList.get(selectedItem).faculty; 
        String department = studentsArrayList.get(selectedItem).department; 
        String advisor = studentsArrayList.get(selectedItem).advisor; 

        final TextView studentID = (TextView) dialog.findViewById(R.id.studentID); 
        final EditText editName = (EditText) dialog.findViewById(R.id.editName); 
        final EditText editLastName = (EditText) dialog.findViewById(R.id.editLastName); 
        final EditText editGender = (EditText) dialog.findViewById(R.id.editGender); 
        final EditText editFaculty = (EditText) dialog.findViewById(R.id.editFaculty); 
        final EditText editDepartment = (EditText) dialog.findViewById(R.id.editDepartment); 
        final EditText editAdvisor = (EditText) dialog.findViewById(R.id.editAdvisor); 

        studentID.setText(id); 
        editName.setText(name); 
        editLastName.setText(lastName); 
        editGender.setText(gender); 
        editFaculty.setText(faculty); 
        editDepartment.setText(department); 
        editAdvisor.setText(advisor); 

        Button updateStudent = (Button) dialog.findViewById(R.id.updateStudent); 
        Button clearStudent = (Button) dialog.findViewById(R.id.clearStudent); 
        Button cancelStudent = (Button) dialog.findViewById(R.id.cancelStudent); 

        // Updates the selected School object 
        updateStudent.setOnClickListener(new View.OnClickListener() { 
         @Override 
         public void onClick(View view) { 
          String id = studentID.getText().toString(); 
          String name = editName.getText().toString(); 
          String lastName = editLastName.getText().toString(); 
          String gender = editGender.getText().toString(); 
          String faculty = editFaculty.getText().toString(); 
          String department = editDepartment.getText().toString(); 
          String advisor = editAdvisor.getText().toString(); 
          studentsArrayList.get(selectedItem).setId(id); 
          studentsArrayList.get(selectedItem).setName(name); 
          studentsArrayList.get(selectedItem).setLastName(lastName); 
          studentsArrayList.get(selectedItem).setGender(gender); 
          studentsArrayList.get(selectedItem).setFaculty(faculty); 
          studentsArrayList.get(selectedItem).setDepartment(department); 
          studentsArrayList.get(selectedItem).setAdvisor(advisor); 

          adapter.notifyDataSetChanged(); 
          Toast.makeText(getContext(), "An entry is updated.", Toast.LENGTH_SHORT).show(); 
          dialog.dismiss(); 
         } 
        }); 

        // Clears all fields 
        clearStudent.setOnClickListener(new View.OnClickListener() { 
         @Override 
         public void onClick(View view) { 
          editName.setText(null); 
          editLastName.setText(null); 
          editGender.setText(null); 
          editFaculty.setText(null); 
          editDepartment.setText(null); 
          editAdvisor.setText(null); 
         } 
        }); 

        // Dismisses the dialog 
        cancelStudent.setOnClickListener(new View.OnClickListener() { 
         @Override 
         public void onClick(View view) { 
          dialog.dismiss(); 
         } 
        }); 

        dialog.show(); 
        adapter.notifyDataSetChanged(); // notifying adapter about changes 
       } 
      } 
     }); // end of the update action 

     return view; 
    } 
} 

Answer 1

「（）notifyDataSetChangedを呼び出すと、獲得したすべてのレイアウト方法を動作しない場合は

のトラブルシューティングリストビューが正しく更新されたと信じてください。彼はあなたのアダプターのデータがどこから来るのかを確認する必要があります。

これはメモリに残っているコレクションの場合、notifyDataSetChanged（）を呼び出す前に実際にアイテムをコレクションから削除したり、コレクションに追加したことを確認します。

データベースまたはサービスバックエンドで作業している場合は、notifyDataSetChanged（）を呼び出す前に、情報を再度取得する（またはメモリ内のデータを操作する）メソッドを呼び出す必要があります。

このnotifyDataSetChangedは、データセットが変更された場合にのみ機能します。だからこそ、あなたは変化が見られないかどうかを見る場所です。デバッグに必要な場合は、「

重複：あなたがインターフェイスを定義することができHow to refresh Android listview?