NullPointException與光標

我有1個問題，當我在我的項目中使用光標。這是我DatabaseHelperNullPointException與光標

package com.example.khuatduytan.quanlytaichinh; 

import android.content.ContentValues; 
import android.content.Context; 
import android.database.Cursor; 
import android.database.sqlite.SQLiteDatabase; 
import android.database.sqlite.SQLiteOpenHelper; 

/** 
* Created by Khuat Duy Tan on 1/17/2016. 
*/ 
public class DatabaseHelper extends SQLiteOpenHelper { 
    private static String DATABASE_NAME = "QuanLyTaiChinh"; 
    private static String TABLE_USER = "User"; 
    private static String TABLE_FAMILY_MEMBER = "Family_Member"; 
    private static String TABLE_TYPE_NOTE = "Type_Note"; 
    private static String TABLE_NOTE = "Note"; 
    //Common column name 
    public static String KEY_ID = "_id"; 

    //User table 
    private static String KEY_USERNAME = "Username"; 
    private static String KEY_PASSWORD = "Password"; 
    private static String KEY_QUESTION = "Question"; 
    private static String KEY_ANSWER = "Answer"; 
    private static String KEY_TOTAL_MONEY ="Total_Money"; 
    private static String KEY_INSERT_FAMILYMEMBER_STATUS = "InsertMember_Status"; 
    private static String KEY_INSERT_TYPENOTES_STATUS = "Insert_TypeNotes_Status"; 
    private static String KEY_INSERT_TOTALMONEY_STATUS = "Insert_Money_Status"; 

    //Family Member table 
    public static String KEY_NAME = "Name"; 
    public static String KEY_AGE = "Age"; 
    public static String KEY_ID_FAMILY = "Id_Family"; 

    //Type Notes table 
    private static String KEY_NAME_TYPE_NOTES = "Type_Note"; 

    //Note table 
    private static String KEY_CONTENT_NOTE = "Content"; 
    private static String KEY_DATE_NOTE = "Date_Created"; 
    private static String KEY_ID_MEMBER_IN_NOTE = "ID_Family_Member"; 
    private static String KEY_ID_TYPE_NOTE = "ID_Type_Note"; 
    private static String KEY_MONEY = "Money"; 

    //User table create statement 
    private static String CREATE_USER_TABLE = "CREATE TABLE " + TABLE_USER + " (" + KEY_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + KEY_USERNAME + 
      " TEXT, " + KEY_PASSWORD + " TEXT, " + KEY_QUESTION + " TEXT, " + KEY_ANSWER + " TEXT, " + KEY_TOTAL_MONEY + " TEXT, " + KEY_INSERT_FAMILYMEMBER_STATUS + 
      " TEXT, " + KEY_INSERT_TYPENOTES_STATUS + " TEXT, " + KEY_INSERT_TOTALMONEY_STATUS + " TEXT" + ")"; 

    //Family Member table create statement 
    private static String CREATE_FAMILY_MEMBER_TABLE = "CREATE TABLE " + TABLE_FAMILY_MEMBER + " (" + KEY_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + KEY_ID_FAMILY + 
      " TEXT, " + KEY_NAME + " TEXT, " + KEY_AGE + " TEXT" + ")"; 

    //Type Note table create statement 
    private static String CREATE_TYPE_NOTE_TABLE = "CREATE TABLE " + TABLE_TYPE_NOTE + " (" + KEY_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + KEY_NAME_TYPE_NOTES + " TEXT" + ")"; 

    //Note table create statement 
    private static String CREATE_NOTE_TABLE = "CREATE TABLE " + TABLE_NOTE + " (" + KEY_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "+ KEY_CONTENT_NOTE + " TEXT, " + KEY_DATE_NOTE + " TEXT, " + 
      KEY_ID_MEMBER_IN_NOTE + " TEXT, " + KEY_ID_TYPE_NOTE + " TEXT, " + KEY_MONEY + " TEXT" + ")"; 

// private static String[] ALL_KEY_FAMILY_MEMBER_TABLE = new String[]{KEY_ID, KEY_ID_FAMILY, KEY_NAME, KEY_AGE}; 

    public DatabaseHelper(Context context) { 
     super(context, DATABASE_NAME, null, 1); 
    } 


    @Override 
    public void onCreate(SQLiteDatabase db) { 
     db.execSQL(CREATE_USER_TABLE); 
     db.execSQL(CREATE_FAMILY_MEMBER_TABLE); 
     db.execSQL(CREATE_TYPE_NOTE_TABLE); 
     db.execSQL(CREATE_NOTE_TABLE); 
    } 

    public Cursor getDataTableUser(){ 
     SQLiteDatabase db = this.getWritableDatabase(); 
     Cursor res = db.rawQuery("SELECT * FROM " + TABLE_USER, null); 
     return res; 
    } 

    public Cursor getDataTableMemberFamily(){ 
     SQLiteDatabase db = this.getWritableDatabase(); 
     Cursor res = db.rawQuery("SELECT * FROM " + TABLE_FAMILY_MEMBER, null); 
     return res; 
    } 

    public long insertUserTable(String username, String password, String question, String answer, String totalMoney, String insertMemberStatus, String insertTypeNoteStatus, String insertTotalMoneyStatus){ 
     SQLiteDatabase db = this.getWritableDatabase(); 
     ContentValues contentValues = new ContentValues(); 
     contentValues.put(KEY_USERNAME,username); 
     contentValues.put(KEY_PASSWORD,password); 
     contentValues.put(KEY_QUESTION,question); 
     contentValues.put(KEY_ANSWER,answer); 
     contentValues.put(KEY_TOTAL_MONEY, totalMoney); 
     contentValues.put(KEY_INSERT_FAMILYMEMBER_STATUS, insertMemberStatus); 
     contentValues.put(KEY_INSERT_TYPENOTES_STATUS, insertTypeNoteStatus); 
     contentValues.put(KEY_INSERT_TOTALMONEY_STATUS, insertTotalMoneyStatus); 

     long result = db.insert(TABLE_USER, null, contentValues); 
     return result; 
    } 

    public long insertMemberFamilyTable(String idFamily, String name, String age){ 
     SQLiteDatabase db = this.getWritableDatabase(); 
     ContentValues contentValues = new ContentValues(); 
     contentValues.put(KEY_ID_FAMILY, idFamily); 
     contentValues.put(KEY_NAME, name); 
     contentValues.put(KEY_AGE, age); 
     long result = db.insert(TABLE_FAMILY_MEMBER, null, contentValues); 
     return result; 
    } 

    public long updateUserTable(long id, String username, String password, String question, String answer, String totalMoney, String insertMemberStatus, String insertTypeNoteStatus, String insertTotalMoneyStatus){ 
     SQLiteDatabase db = this.getWritableDatabase(); 
     ContentValues contentValues = new ContentValues(); 
     contentValues.put(KEY_USERNAME,username); 
     contentValues.put(KEY_PASSWORD,password); 
     contentValues.put(KEY_QUESTION,question); 
     contentValues.put(KEY_ANSWER,answer); 
     contentValues.put(KEY_TOTAL_MONEY, totalMoney); 
     contentValues.put(KEY_INSERT_FAMILYMEMBER_STATUS, insertMemberStatus); 
     contentValues.put(KEY_INSERT_TYPENOTES_STATUS, insertTypeNoteStatus); 
     contentValues.put(KEY_INSERT_TOTALMONEY_STATUS, insertTotalMoneyStatus); 
     long result = db.update(TABLE_USER, contentValues, KEY_ID + "=" + id, null); 
     return result; 
    } 

    @Override 
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
     db.execSQL("DROP TABLE IF EXIST " + TABLE_USER); 
     db.execSQL("DROP TABLE IF EXIST " + TABLE_FAMILY_MEMBER); 
     db.execSQL("DROP TABLE IF EXIST " + TABLE_TYPE_NOTE); 
     db.execSQL("DROP TABLE IF EXIST " + TABLE_NOTE); 
     onCreate(db); 
    } 
}

我在第1類

package com.example.khuatduytan.quanlytaichinh; 

import android.app.AlertDialog; 
import android.content.DialogInterface; 
import android.content.Intent; 
import android.database.Cursor; 
import android.graphics.Color; 
import android.graphics.Typeface; 
import android.os.Bundle; 
import android.support.design.widget.FloatingActionButton; 
import android.support.design.widget.Snackbar; 
import android.support.v7.app.AppCompatActivity; 
import android.support.v7.widget.Toolbar; 
import android.view.View; 
import android.widget.Button; 
import android.widget.LinearLayout; 
import android.widget.ListView; 
import android.widget.SimpleCursorAdapter; 
import android.widget.TableLayout; 
import android.widget.TableRow; 
import android.widget.TextView; 
import android.widget.TableRow.LayoutParams; 
import android.widget.Toast; 

public class InsertFamilyMember extends AppCompatActivity { 
    Button btnResetInsertFamilyMember, btnSubmitInsertFamilyMember, btnCancelInsertFamilyMember, btnCompleteInsertFamilyMember; 
    TextView editTextNameInsertFamilyMember, editTextAgeInsertFamilyMember; 
    DatabaseHelper db; 
    SimpleCursorAdapter dataAdapter; 
    private static final int REQUEST_CODE = 10; 
    Intent data; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_insert_family_member); 
     Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
     setSupportActionBar(toolbar); 
     getSupportActionBar().setTitle("Insert Family Member"); 

     btnSubmitInsertFamilyMember = (Button) findViewById(R.id.button_submitInsertFamilyMember); 
     btnResetInsertFamilyMember = (Button) findViewById(R.id.button_resetInsertFamilyMember); 
     btnCancelInsertFamilyMember = (Button) findViewById(R.id.button_cancelInsertFamilyMember); 
     btnCompleteInsertFamilyMember = (Button) findViewById(R.id.button_completeInsertFamilyMember); 
     editTextNameInsertFamilyMember = (TextView) findViewById(R.id.editText_nameInsertFamilyMember); 
     editTextAgeInsertFamilyMember = (TextView) findViewById(R.id.editText_ageInsertFamilyMember); 

     db = new DatabaseHelper(this); 
     FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab); 
     fab.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG) 
         .setAction("Action", null).show(); 
      } 
     }); 

     Bundle extras = getIntent().getExtras(); 
     final String idUser = extras.getString("IdUser"); 
     addDataListView(); 
     addFamilyMember(idUser); 
     completeFamilyMember(); 
     cancelFamilyMember(); 
     resetFamilyMember(); 
    } 

    public void addDataListView(){ 
     Cursor cursor = db.getDataTableMemberFamily(); 
     String form[] = new String []{db.KEY_NAME, db.KEY_AGE}; 
     int to[] = new int[] {R.id.textView_itemNameInsertFamilyMember, R.id.textView_itemAgeInsertFamilyMember}; 
     dataAdapter = new SimpleCursorAdapter(this, R.layout.item_memberfamily, cursor, form, to, 0); 
     ListView listViewMemberFamily = (ListView) findViewById(R.id.listView_FamilyMember); 
     listViewMemberFamily.setAdapter(dataAdapter); 
    } 

    public void completeFamilyMember(){ 
     btnCompleteInsertFamilyMember.setOnClickListener(
       new View.OnClickListener() { 

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

    public void resetFamilyMember(){ 
     btnResetInsertFamilyMember.setOnClickListener(
       new View.OnClickListener(){ 

        @Override 
        public void onClick(View v) { 
         editTextNameInsertFamilyMember.setText(""); 
         editTextAgeInsertFamilyMember.setText(""); 
        } 
       } 
     ); 
    } 

    public void cancelFamilyMember(){ 
     btnCancelInsertFamilyMember.setOnClickListener(
       new View.OnClickListener(){ 

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

    public void addFamilyMember(final String idFamily){ 
     btnSubmitInsertFamilyMember.setOnClickListener(
       new View.OnClickListener() { 

        @Override 
        public void onClick(View v) { 
         String name, age; 
         int temp = 0; 
         name = editTextNameInsertFamilyMember.getText().toString(); 
         age = editTextAgeInsertFamilyMember.getText().toString(); 
         Cursor res = db.getDataTableMemberFamily(); 
         while (res.moveToNext()) { 
          if (res.getString(2).equals(name)) { 
           temp = 1; 
          } 
         } 

         if (temp == 1) { 
          Toast.makeText(InsertFamilyMember.this, "This member is available", Toast.LENGTH_LONG).show(); 
          editTextNameInsertFamilyMember.setText(""); 
          editTextAgeInsertFamilyMember.setText(""); 
         } else { 
          long isInserted = db.insertMemberFamilyTable(idFamily, name, age); 
          if (isInserted == -1) { 
           Toast.makeText(InsertFamilyMember.this, "Insert Unsuccessful", Toast.LENGTH_LONG).show(); 
          } else { 
           Toast.makeText(InsertFamilyMember.this, "Insert Successful", Toast.LENGTH_LONG).show(); 
          } 
         } 
         addDataListView(); 
        } 
       } 
     ); 
    } 

    private void confirmDialog() { 
     AlertDialog.Builder builder = new AlertDialog.Builder(this); 

     builder 
       .setMessage("Are you sure?") 
       .setPositiveButton("Yes", new DialogInterface.OnClickListener() { 
        @Override 
        public void onClick(DialogInterface dialog, int id) { 
         Cursor res = db.getDataTableMemberFamily(); 
         Cursor res1 = db.getDataTableUser(); 

         Bundle extras = getIntent().getExtras(); 
         String idFamily = extras.getString("IdUser"); 
         long id_User = 0; 
         String idUserSend = null; 
         String username = null; 
         String password = null; 
         String question = null; 
         String answer = null; 
         String totalMoney = null; 
         String insertMemberStatus = null; 
         String insertTypeNoteStatus = null; 
         String insertTotalMoneyStatus = null; 
         while (res1.moveToNext()){ 
          String idUser = res1.getString(0); 
          if(idUser.equals(idFamily)){ 
           id_User = Long.parseLong(idUser); 
           username = res1.getString(1); 
           password = res1.getString(2); 
           question = res1.getString(3); 
           answer = res1.getString(4); 
           totalMoney = res1.getString(5); 
           insertMemberStatus = "Complete"; 
           insertTypeNoteStatus = res1.getString(7); 
           insertTotalMoneyStatus = res1.getString(8); 
           idUserSend = idUser; 
           break; 
          } 
         } 
         long isUpdated = db.updateUserTable(id_User, username, password, question, answer, totalMoney, insertMemberStatus, insertTypeNoteStatus, insertTotalMoneyStatus); 
         if (isUpdated == -1) { 
          Toast.makeText(InsertFamilyMember.this, "Update Unsuccessful", Toast.LENGTH_LONG).show(); 
         } else { 
          Toast.makeText(InsertFamilyMember.this, "Update Successful", Toast.LENGTH_LONG).show(); 
         } 
//      Bundle bundle = data.getExtras(); 
//      User user = bundle.getParcelable("User"); 
         doOpenInsertTotalMoney(idUserSend); 
        } 
       }) 
       .setNegativeButton("No", new DialogInterface.OnClickListener() { 
        @Override 
        public void onClick(DialogInterface dialog, int id) { 
         dialog.cancel(); 
        } 
       }) 
       .show(); 
    } 

    public void doOpenLogin(){ 
     Intent intent = new Intent(this, MainActivity.class); 
     startActivity(intent); 
    } 

    public void doOpenInsertTotalMoney(String id){ 
     Intent intent = new Intent(this, InsertTotalMoney.class); 
     intent.putExtra("idUser", id); 
     startActivityForResult(intent, REQUEST_CODE); 
//  Bundle b = new Bundle(); 
//  b.putParcelable("User", user); 
//  intent.putExtras(b); 
//  startActivityForResult(intent, REQUEST_CODE); 
    } 
}

稱爲Cursor res1 = db.getDataTableUser();和它的作品一般。我用在另一個班，但當我在這個類中使用

package com.example.khuatduytan.quanlytaichinh;

import android.app.AlertDialog; 
import android.content.DialogInterface; 
import android.content.Intent; 
import android.database.Cursor; 
import android.os.Bundle; 
import android.provider.ContactsContract; 
import android.support.design.widget.FloatingActionButton; 
import android.support.design.widget.Snackbar; 
import android.support.v7.app.AppCompatActivity; 
import android.support.v7.widget.Toolbar; 
import android.view.View; 
import android.widget.Button; 
import android.widget.EditText; 
import android.widget.Toast; 

public class InsertTotalMoney extends AppCompatActivity { 

    Button btnSubmitInsertTotalMoney, btnCancelInsertTotalMoney; 
    EditText editTextInsertTotalMoney; 
    DatabaseHelper db; 
    private static final int REQUEST_CODE = 10; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_insert_total_money); 
     Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
     setSupportActionBar(toolbar); 

     FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab); 
     fab.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG) 
         .setAction("Action", null).show(); 
      } 
     }); 

     btnSubmitInsertTotalMoney = (Button) findViewById(R.id.btn_submitInsertTotalMoney); 
     btnCancelInsertTotalMoney = (Button) findViewById(R.id.btn_cancelInsertTotalMoney); 
     editTextInsertTotalMoney = (EditText) findViewById(R.id.editText_insertTotalMoney); 
     doOpenInsertFamilyMember(); 
     addTotalMoney(); 
    } 

    public void doOpenInsertFamilyMember(){ 
     btnCancelInsertTotalMoney.setOnClickListener(
       new View.OnClickListener(){ 

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

    public void addTotalMoney(){ 
     btnSubmitInsertTotalMoney.setOnClickListener(
       new View.OnClickListener(){ 

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

    private void confirmDialog() { 
     AlertDialog.Builder builder = new AlertDialog.Builder(this); 

     builder 
       .setMessage("Are you sure?") 
       .setPositiveButton("Yes", new DialogInterface.OnClickListener() { 
        @Override 
        public void onClick(DialogInterface dialog, int id) { 

         long id_User = 0; 
         String idUserSend = null; 
         String username = null; 
         String password = null; 
         String question = null; 
         String answer = null; 
         String totalMoney = null; 
         String insertMemberStatus = null; 
         String insertTypeNoteStatus = null; 
         String insertTotalMoneyStatus = null; 

         Cursor res = db.getDataTableUser(); 
         Bundle extras = getIntent().getExtras(); 
         String idUser = extras.getString("idUser"); 

         while (res.moveToNext()){ 
          if(idUser.equals(res.getString(0))){ 
           id_User = Long.parseLong(idUser); 
           username = res.getString(1); 
           password = res.getString(2); 
           question = res.getString(3); 
           answer = res.getString(4); 
           totalMoney = editTextInsertTotalMoney.getText().toString(); 
           insertMemberStatus = res.getString(6); 
           insertTypeNoteStatus = res.getString(7); 
           insertTotalMoneyStatus = "Complete"; 
           idUserSend = idUser; 
           break; 
          } 
         } 
         long isUpdated = db.updateUserTable(id_User, username, password, question, answer, totalMoney, insertMemberStatus, insertTypeNoteStatus, insertTotalMoneyStatus); 
         if (isUpdated == -1) { 
          Toast.makeText(InsertTotalMoney.this, "Update Unsuccessful", Toast.LENGTH_LONG).show(); 
         } else { 
          Toast.makeText(InsertTotalMoney.this, "Update Successful", Toast.LENGTH_LONG).show(); 
         } 
         doOpenInsertTypeNotes(idUserSend); 
        } 
       }) 
       .setNegativeButton("No", new DialogInterface.OnClickListener() { 
        @Override 
        public void onClick(DialogInterface dialog, int id) { 
         dialog.cancel(); 
        } 
       }) 
       .show(); 
    } 

    public void openInsertFamilyMember(){ 
     Intent intent = new Intent(this, InsertFamilyMember.class); 
     startActivity(intent); 
    } 

    public void doOpenInsertTypeNotes(String s){ 
     Intent intent = new Intent(this, InsertTypeNotes.class); 
     intent.putExtra("idUser", s); 
     startActivityForResult(intent, REQUEST_CODE); 
    } 

}

一個NullPointException出現在Cursor res = db.getDataTableUser(); 你能幫我解決這個錯誤？我logcat的

01-22 01:38:31.679 1331-1331/? E/AndroidRuntime: FATAL EXCEPTION: main 
               Process: com.example.khuatduytan.quanlytaichinh, PID: 1331 
               java.lang.NullPointerException 
                at com.example.khuatduytan.quanlytaichinh.InsertTotalMoney$5.onClick(InsertTotalMoney.java:92) 
                at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:166) 
                at android.os.Handler.dispatchMessage(Handler.java:102) 
                at android.os.Looper.loop(Looper.java:136) 
                at android.app.ActivityThread.main(ActivityThread.java:5001) 
                at java.lang.reflect.Method.invokeNative(Native Method) 
                at java.lang.reflect.Method.invoke(Method.java:515) 
                at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785) 
                at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601) 
                at dalvik.system.NativeStart.main(Native Method)

來源

2016-01-22 Khuất Duy Tân

Ok'String idUser = extras.getString（「idUser」）;'line cause issue。因爲臨時演員是'空' –

我發送「idUser從另一個類，我沒有發佈在這裏 –

可能重複[什麼是空指針異常，以及如何解決它？]（http://stackoverflow.com/questions/218384/what-is-null-pointer-exception-and-how-do-i-fix-it） – Henry

NullPointException因爲你還沒有使用它之前初始化的變量db出現在Cursor res = db.getDataTableUser();

。

添加以下語句來初始化數據庫變量，

db = new DatabaseHelper(InsertTotalMoney.this); 
Cursor res = db.getDataTableUser();

來源

2016-01-22 06:48:32

非常感謝你。 –

@KhuấtDuyTân你的問題解決了嗎？ –

你對類的頂部聲明DatabaseHelper db;可變的，但你沒有指定DB變量的任何地方，請第一分配你的數據庫變量，然後使用D b。

即db = DatabaseHelper.getInstance(this);

來源

2016-01-22 06:52:36

在confirmDialog

（）使在對象分貝DatabaseHelper refrence。

db = new DatabaseHelper(this); 
Cursor res = db.getDataTableUser();

來源

2016-01-22 06:58:40

NullPointException與光標

回答

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