我在项目中使用Cursor时遇到1个问题。 这是我的DatabaseHelper
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1班
中打电话给Cursor res1 = db.getDataTableUser();
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);
}
}
它正常工作。我在另一个类中使用它，但是当我在这个类中使用时
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);
}
}
Cursor res = db.getDataTableUser();处出现NullPointException
你能帮我解决这个bug吗？
我的logcat
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)
答案 0 :(得分：0)
NullPointException出现在Cursor res = db.getDataTableUser();
因为您在使用之前尚未初始化db变量。
添加以下语句以初始化db变量
db = new DatabaseHelper(InsertTotalMoney.this);
Cursor res = db.getDataTableUser();
答案 1 :(得分：0)
你已经在类的顶层声明了DatabaseHelper db;变量，但你确实在任何地方分配了db变量，请先分配你的db变量然后使用db。
即。 db = DatabaseHelper.getInstance(this);
答案 2 :(得分：0)
在confirmDialog（）中，在对象db中生成DatabaseHelper参考。
db = new DatabaseHelper(this);
Cursor res = db.getDataTableUser();