sqlite的光标列返回错误的值 [英] sqlite cursor returning wrong value for a column

问题描述

为什么我从数据库中获取空从列网​​址？

我在源码这样添加数据

 无效addObjects（对象对象）{
        SQLiteDatabase DB = this.getWritableDatabase（）;

        ContentValues​​值=新ContentValues​​（）;

        values​​.put（OBJECT_ID，10）; //对象名称
        values​​.put（OBJECT_NAME，H）; //对象名称
        values​​.put（OBJECT_URLhttp://api.androidhive.info/images/sample.jpg）; // URL对象
        values​​.put（OBJECT_TYPE，图像）; //接触式
        的System.out.println（值）;

        //插入行
        db.insert（TABLE_OBJECTS，空，价值观）;
        db.close（）; //闭幕数据库连接
    }
 

日志值 www.i我/的System.out的结果是：TYPE =图片名称= H ID = 10 URL = HTTP：//api.androidhive.info/images/sample.jpg

然而，当我得到的所有结果我的url = NULL

 公开名单＆LT;对象＆GT; getAllObjects（）{
    名单＆LT;对象＆GT; Objectslist =新的ArrayList＆LT;对象＆GT;（）;
    //选择所有查询
    字符串selectQuery =SELECT * FROM+ TABLE_OBJECTS;

    SQLiteDatabase DB = this.getWritableDatabase（）;
    光标光标= db.rawQuery（selectQuery，NULL）;

    //遍历所有行和添加到列表
    如果（cursor.moveToFirst（））{
        做 {
            对象对象=新的对象（）;
            Log.d（OBJECT_URL，OBJECT_URL）;

            object.setId（cursor.getInt（cursor.getColumnIndex（OBJECT_ID）））;
            object.setName（cursor.getString（cursor.getColumnIndex（对象）））;
            object.setUrl（cursor.getString（cursor.getColumnIndex（OBJECT_URL）））;
            //添加联系人列出
            Objectslist.add（对象）;
        }而（cursor.moveToNext（））;
    }
 

这是主要的活动我得到的sqlite的结果

 名单，其中，对象和GT;对象= db.getAllObjects（）;
    Log.d（他，TTTTTT）;
    的System.out.println（对象）;
    DBadapter适配器=新DBadapter（getApplicationContext（），R.layout.grid_item_layout，对象）;
 

这是系统outprint的结果

  [对象{n = 10，名称=HTTP：//api.androidhive.info/images/sample.jpg，URL ='空'，类型='空' ，类='空'}，{对象ID = 10，名称=HTTP：//api.androidhive.info/images/sample.jpg，URL ='空'，类型='空'，类别='空}
 

这是完整的源码级

 公共类数据库处理器扩展SQLiteOpenHelper {

//所有静态变量
//数据库版本
私有静态最终诠释DATABASE_VERSION = 1;



    //联系方式表名
    私有静态最后弦乐TABLE_OBJECTS =物;
    私有静态最后弦乐OBJECT_ID =ID;
    私有静态最后弦乐OBJECT_NAME =NAME;
    私有静态最后弦乐OBJECT_TYPE =类型;
    私有静态最后弦乐OBJECT_URL =URL;
    私有静态最后弦乐OBJECT_CATEGORY =类别;
    私有静态最后弦乐OBJECT_DATE_ADDED =DATE_ADDED;
    私有静态最后弦乐OBJECT_USERS_ID =USERS_ID;
    私有静态最后弦乐OBJECT_HIDE_YN =HIDE_YN;


    公共数据库处理器（上下文的背景下）{
        超（背景下，DATABASE_NAME，空，DATABASE_VERSION）;
    }

    //创建表
    @覆盖
    公共无效的onCreate（SQLiteDatabase DB）{
        db.execSQL（DROP TABLE IF EXISTS+ TABLE_OBJECTS）;

        字符串CREATE_OBJECTS_TABLE =CREATE TABLE+ TABLE_OBJECTS +（
       + OBJECT_ID +INTEGER PRIMARY KEY AUTOINCREMENT，
       + OBJECT_NAME +VARCHAR（100）NULL，
        + OBJECT_TYPE +VARCHAR（10）NULL，
        + OBJECT_URL +VARCHAR（1000）NULL，
        + OBJECT_CATEGORY +VARCHAR（50）NULL，
        + OBJECT_DATE_ADDED +DATETIME NULL，
        + OBJECT_USERS_ID +NUMERIC（10）NULL，
        + OBJECT_HIDE_YN +VARCHAR（1）NULL）;
        db.execSQL（CREATE_OBJECTS_TABLE）;
    }
    //升级数据库
    @覆盖
    公共无效onUpgrade（SQLiteDatabase分贝，INT oldVersion，诠释静态网页）{
        如果存在//删除旧的表
        db.execSQL（DROP TABLE IF EXISTS+ TABLE_OBJECTS）;

        //再次创建表
        的onCreate（DB）;
    }

    / **
     *所有CRUD（创建，读取，更新，删除）操作
     * /

    //添加新联系人
    无效addObjects（对象对象）{
        SQLiteDatabase DB = this.getWritableDatabase（）;

        ContentValues​​值=新ContentValues​​（）;

        values​​.put（OBJECT_ID，10）; //对象名称
        values​​.put（OBJECT_NAME，H）; //对象名称
        values​​.put（OBJECT_URLhttp://api.androidhive.info/images/sample.jpg）; // URL对象
        values​​.put（OBJECT_TYPE，图像）; //接触式
        的System.out.println（值）;

        //插入行
        长ID = db.insert（TABLE_OBJECTS，空，价值观）;
        的System.out.println（ID：+ ID）;
        db.insert（TABLE_OBJECTS，空，价值观）;
        db.close（）; //闭幕数据库连接
    }
  //对象对象=新的对象（字符串）;

    //获取单触点
    对象的getURL（字符串名称）{
        SQLiteDatabase DB = this.getReadableDatabase（）;
        光标光标= db.query（TABLE_OBJECTS，新的String [] {OBJECT_URL，
                        OBJECT_NAME，OBJECT_CATEGORY，OBJECT_TYPE}，OBJECT_NAME +=？，
                新的String [] {将String.valueOf（名称）}，NULL，NULL，NULL，NULL）;
        如果（光标！= NULL）
            cursor.moveToFirst（）;

        对象对象=新的对象（cursor.getString（0），cursor.getString（1）
                cursor.getString（2），cursor.getString（3））;

        返回对象;
    }

    //获取所有联系人
    公开名单＆LT;对象＆GT; getAllObjects（）{
        名单＆LT;对象＆GT; Objectslist =新的ArrayList＆LT;对象＆GT;（）;
        //选择所有查询
        字符串selectQuery =SELECT * FROM+ TABLE_OBJECTS;

        SQLiteDatabase DB = this.getWritableDatabase（）;
        光标光标= db.rawQuery（selectQuery，NULL）;

        //遍历所有行和添加到列表
        如果（cursor.moveToFirst（））{
            做 {
                对象对象=新的对象（）;
                Log.d（OBJECT_URL，OBJECT_URL）;

                object.setId（cursor.getInt（cursor.getColumnIndex（OBJECT_ID）））;
                object.setName（cursor.getString（cursor.getColumnIndex（对象）））;
                object.setUrl（cursor.getString（cursor.getColumnIndex（OBJECT_URL）））;
                //添加联系人列出
                Objectslist.add（对象）;
            }而（cursor.moveToNext（））;
        }

        //返回联系人列表
        返回Objectslist;
    }

    //更新单触点
    公众诠释updateContact（对​​象对象）{
        SQLiteDatabase DB = this.getWritableDatabase（）;

        ContentValues​​值=新ContentValues​​（）;
        values​​.put（OBJECT_NAME，object.getName（））; //对象名称
        values​​.put（OBJECT_URL，object.getUrl（））; // URL对象
        values​​.put（OBJECT_TYPE，object.getType（））; //接触式
        values​​.put（OBJECT_CATEGORY，object.getCategory（））; //联系范畴

        //更新行
        返回db.update（TABLE_OBJECTS，价值观，OBJECT_ID +=？，
                新的String [] {将String.valueOf（object.getId（））}）;
    }

    //删除单个联系人
    公共无效deleteContact（对​​象对象）{
        SQLiteDatabase DB = this.getWritableDatabase（）;
        db.delete（TABLE_OBJECTS，OBJECT_ID +=？，
                新的String [] {将String.valueOf（objects.getId（））}）;
        db.close（）;
    }


    //获取联系人计数
    公众诠释getObjectsCount（）{
        字符串countQuery =SELECT * FROM+ TABLE_OBJECTS;
        SQLiteDatabase DB = this.getReadableDatabase（）;
        光标光标= db.rawQuery（countQuery，NULL）;
        cursor.close（）;

        //返回计数
        返回cursor.getCount（）;
    }

}
 

解决方案

在你的对象的getURL（字符串名称）的方法，改变

 光标光标= db.query（TABLE_OBJECTS，新的String [] {OBJECT_URL，
                OBJECT_NAME，OBJECT_CATEGORY，OBJECT_TYPE}，OBJECT_NAME +=？，
                新的String [] {将String.valueOf（名称）}，NULL，NULL，NULL，NULL）;
 

到

 光标光标= db.query（TABLE_OBJECTS，新的String [] {OBJECT_ID，
                OBJECT_NAME，OBJECT_URL，OBJECT_TYPE}，OBJECT_NAME +=？，
                新的String [] {将String.valueOf（名称）}，NULL，NULL，NULL，NULL）;
 

假设您的对象类的结构如下：

 公共类对象{
    私人字符串ID;
    私人字符串名称;
    私人字符串URL;
    私人字符串类型;

    //方法
}
 

在 TableColumn来参数（新的String [] {OBJECT_ID，OBJECT_NAME，OBJECT_URL，OBJECT_TYPE} ），您传递到 db.query（）方法有尊重顺序相同的对象类（第 ID ，第二届名称，第三网​​址 4 键入）

why I am getting from the database null from column url ?

I am adding data in sqlite like this

  void addObjects(Objects object) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();

        values.put(OBJECT_ID,"10" ); // OBJECT Name
        values.put(OBJECT_NAME, "H"); // OBJECT Name
        values.put(OBJECT_URL, "http://api.androidhive.info/images/sample.jpg"); // OBJECT URL
        values.put(OBJECT_TYPE, "image"); // Contact type
        System.out.println(values);

        // Inserting Row
        db.insert(TABLE_OBJECTS, null, values);
        db.close(); // Closing database connection
    }

the result of log values www.i I/System.out﹕ TYPE=image NAME=H ID=10 URL=http://api.androidhive.info/images/sample.jpg

however when I get all the result I have url = null

public List<Objects> getAllObjects() {
    List<Objects> Objectslist = new ArrayList<Objects>();
    // Select All Query
    String selectQuery = "SELECT  * FROM " + TABLE_OBJECTS;

    SQLiteDatabase db = this.getWritableDatabase();
    Cursor cursor = db.rawQuery(selectQuery, null);

    // looping through all rows and adding to list
    if (cursor.moveToFirst()) {
        do {
            Objects object = new Objects();
            Log.d("OBJECT_URL", OBJECT_URL);

            object.setId(cursor.getInt(cursor.getColumnIndex(OBJECT_ID)));
            object.setName(cursor.getString(cursor.getColumnIndex(OBJECT_NAME)));
            object.setUrl(cursor.getString(cursor.getColumnIndex(OBJECT_URL)));
            // Adding contact to list
            Objectslist.add(object);
        } while (cursor.moveToNext());
    }

This is main activity I am getting the result of sqlite

List<Objects> Objects = db.getAllObjects();
    Log.d("he","tttttt");
    System.out.println(Objects);
    DBadapter adapter = new DBadapter(getApplicationContext(), R.layout.grid_item_layout, Objects);

this is the result of system outprint

[Objects{id=10, name='http://api.androidhive.info/images/sample.jpg', url='null', type='null', category='null'}, Objects{id=10, name='http://api.androidhive.info/images/sample.jpg', url='null', type='null', category='null'}

this is full sqlite class

     public class DatabaseHandler extends SQLiteOpenHelper {

// All Static variables
// Database Version
private static final int DATABASE_VERSION = 1;



    // Contacts table name
    private static final String TABLE_OBJECTS = "OBJECTS";
    private static final String OBJECT_ID="ID";
    private static final String OBJECT_NAME="NAME";
    private static final String OBJECT_TYPE ="TYPE";
    private static final String OBJECT_URL ="URL";
    private static final String OBJECT_CATEGORY ="CATEGORY";
    private static final String OBJECT_DATE_ADDED ="DATE_ADDED";
    private static final String OBJECT_USERS_ID ="USERS_ID";
    private static final String OBJECT_HIDE_YN ="HIDE_YN";


    public DatabaseHandler(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    // Creating Tables
    @Override
    public void onCreate(SQLiteDatabase db){
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_OBJECTS);

        String CREATE_OBJECTS_TABLE ="CREATE TABLE " +TABLE_OBJECTS+"("
       + OBJECT_ID +" INTEGER PRIMARY KEY AUTOINCREMENT,"
       + OBJECT_NAME +" VARCHAR(100) NULL,"
        + OBJECT_TYPE +" VARCHAR(10) NULL,"
        + OBJECT_URL +" VARCHAR(1000) NULL,"
        +OBJECT_CATEGORY +" VARCHAR(50) NULL,"
        +OBJECT_DATE_ADDED +" DATETIME NULL,"
        +OBJECT_USERS_ID +" NUMERIC(10) NULL,"
        +OBJECT_HIDE_YN +" VARCHAR(1) NULL) ";
        db.execSQL(CREATE_OBJECTS_TABLE);
    }
    // Upgrading database
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // Drop older table if existed
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_OBJECTS);

        // Create tables again
        onCreate(db);
    }

    /**
     * All CRUD(Create, Read, Update, Delete) Operations
     */

    // Adding new contact
    void addObjects(Objects object) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();

        values.put(OBJECT_ID,"10" ); // OBJECT Name
        values.put(OBJECT_NAME, "H"); // OBJECT Name
        values.put(OBJECT_URL, "http://api.androidhive.info/images/sample.jpg"); // OBJECT URL
        values.put(OBJECT_TYPE, "image"); // Contact type
        System.out.println(values);

        // Inserting Row
        long id = db.insert(TABLE_OBJECTS, null, values);
        System.out.println( "id:"+id);
        db.insert(TABLE_OBJECTS, null, values);
        db.close(); // Closing database connection
    }
  //  Objects object=new Objects(String );

    // Getting single contact
    Objects geturl(String name) {
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.query(TABLE_OBJECTS, new String[] {OBJECT_URL,
                        OBJECT_NAME , OBJECT_CATEGORY, OBJECT_TYPE }, OBJECT_NAME + "=?",
                new String[] { String.valueOf(name) }, null, null, null, null);
        if (cursor != null)
            cursor.moveToFirst();

        Objects object = new Objects(cursor.getString(0),cursor.getString(1),
                cursor.getString(2),cursor.getString(3));

        return object;
    }

    // Getting All Contacts
    public List<Objects> getAllObjects() {
        List<Objects> Objectslist = new ArrayList<Objects>();
        // Select All Query
        String selectQuery = "SELECT  * FROM " + TABLE_OBJECTS;

        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);

        // looping through all rows and adding to list
        if (cursor.moveToFirst()) {
            do {
                Objects object = new Objects();
                Log.d("OBJECT_URL", OBJECT_URL);

                object.setId(cursor.getInt(cursor.getColumnIndex(OBJECT_ID)));
                object.setName(cursor.getString(cursor.getColumnIndex(OBJECT_NAME)));
                object.setUrl(cursor.getString(cursor.getColumnIndex(OBJECT_URL)));
                // Adding contact to list
                Objectslist.add(object);
            } while (cursor.moveToNext());
        }

        // return contact list
        return Objectslist;
    }

    // Updating single contact
    public int updateContact(Objects object) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(OBJECT_NAME, object.getName()); // OBJECT Name
        values.put(OBJECT_URL, object.getUrl()); // OBJECT URL
        values.put(OBJECT_TYPE, object.getType()); // Contact type
        values.put(OBJECT_CATEGORY, object.getCategory()); // Contact category

        // updating row
        return db.update(TABLE_OBJECTS, values, OBJECT_ID + " = ?",
                new String[] { String.valueOf(object.getId()) });
    }

    // Deleting single contact
    public void deleteContact(Objects objects) {
        SQLiteDatabase db = this.getWritableDatabase();
        db.delete(TABLE_OBJECTS, OBJECT_ID + " = ?",
                new String[] { String.valueOf(objects.getId()) });
        db.close();
    }


    // Getting contacts Count
    public int getObjectsCount() {
        String countQuery = "SELECT  * FROM " + TABLE_OBJECTS;
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery(countQuery, null);
        cursor.close();

        // return count
        return cursor.getCount();
    }

}

解决方案

In your Objects geturl(String name) method , change

Cursor cursor = db.query(TABLE_OBJECTS, new String[] {OBJECT_URL,
                OBJECT_NAME , OBJECT_CATEGORY, OBJECT_TYPE }, OBJECT_NAME + "=?",
                new String[] { String.valueOf(name) }, null, null, null, null);

to

Cursor cursor = db.query(TABLE_OBJECTS, new String[] {OBJECT_ID,
                OBJECT_NAME , OBJECT_URL, OBJECT_TYPE }, OBJECT_NAME + "=?",
                new String[] { String.valueOf(name) }, null, null, null, null);

Supposing that your Objects class has the following structure:

public class Objects {
    private String id;
    private String name;
    private String url;
    private String type;

    // methods
}

the tableColumns argument (new String[] {OBJECT_ID,OBJECT_NAME , OBJECT_URL, OBJECT_TYPE }) that you pass to the db.query() method has to respect the same order as in your Objects class (first the id, 2nd name, 3rd url, 4th type)

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