从数据库中删除一行以创建一个新列表答案

【问题标题】：Remove a row from database to create a new list从数据库中删除一行以创建一个新列表
【发布时间】：2017-01-23 22:38:45
【问题描述】：

在循环通过解析的 xml Web 服务响应后第一次创建数据库时，我能够看到数据库正在正确保存。问题是，我试图从该表中删除一行，并且有两行具有相同的员工编号。我有一种方法，我试图删除其中一条记录，这样我就可以使用另一个来制作新的列表来填充列表视图。

public class MainActivity extends AppCompatActivity {

    private ListView mTopList, directReportListView;
    private ProgressBar mProgressBar;
    private ArrayList<Employee> mEmployees = new ArrayList<>();
    private BottomListViewAdapter mBottomListViewAdapter;
    EmployeeDBHandler dbHandler;
    SQLiteDatabase db;
    SimpleCursorAdapter simpleCursorAdapter;
    private String startingEmployeeID = employeeNumberWishToDelete;
    private String table = "employees";


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        dbHandler = new EmployeeDBHandler(getApplicationContext());

        directReportListView = (ListView) findViewById(R.id.mDirectReportList);
        mProgressBar = (ProgressBar) findViewById(R.id.progressBar);
        mProgressBar.setVisibility(View.VISIBLE);
        mBottomListViewAdapter = new BottomListViewAdapter(this, mEmployees);
        directReportListView.setAdapter(mBottomListViewAdapter);
        getBottomViewXMLData();

        displayTopList(startingEmployeeID);

        //displayTopList();


        //GUI for seeing android SQLite Database in Chrome Dev Tools
        Stetho.InitializerBuilder inBuilder = Stetho.newInitializerBuilder(this);
        inBuilder.enableWebKitInspector(Stetho.defaultInspectorModulesProvider(this));
        Stetho.Initializer in = inBuilder.build();
        Stetho.initialize(in);


    }

    public void getBottomViewXMLData() {
        OkHttpClient client = getUnsafeOkHttpClient();
        Request request = new Request.Builder()
                .url(getString(R.string.API_FULL_URL))
                .build();
        client.newCall(request).enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {
                e.printStackTrace();
            }

            @Override
            public void onResponse(Call call, final Response response) throws IOException {
                final String responseData = response.body().string();
                final InputStream stream = new ByteArrayInputStream(responseData.getBytes());
                final XMLPullParserHandler parserHandler = new XMLPullParserHandler();
                final ArrayList<Employee> employees = (ArrayList<Employee>) parserHandler.parse(stream);

                for (Employee e : employees) {
                    dbHandler.addEmployee(e);
                }

                mEmployees.clear();
                mEmployees.addAll(employees);

                //tell adapter on the UI thread its data changed
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        mBottomListViewAdapter.notifyDataSetChanged();
                        directReportListView.setVisibility(View.VISIBLE);
                        mProgressBar.setVisibility(View.GONE);
                    }
                });
            }
        });
    }

    public void displayTopList(String employeeNumber) {
        String table = "employees";
        String whereClause = "Employee_number=?";
        String[] whereArgs  = new String[] {String.valueOf(employeeNumber)};
        db = dbHandler.getWritableDatabase();
        db.delete(table, whereClause, whereArgs);
      //  Cursor cursor = (Cursor) dbHandler.getEmployee(startingEmployeeID);
     //   Log.i("ADAM", cursor.toString());
    }
}

当我运行它时，我得到了

错误代码：1555 (SQLITE_CONSTRAINT_PRIMARYKEY) 原因：由于违反约束而中止。（UNIQUE 约束失败：employees.Employee_number（代码 1555））。

我知道这是因为没有删除具有相同员工编号的第二条记录。不知道为什么上面的代码没有删除记录。是否可以删除 1 行并在另一个列表中使用它？

public class EmployeeDBHandler extends SQLiteOpenHelper {
    private static final int DATABASE_VERSION = 1;
    private static final String DATABASE_NAME = "OneTeam";
    private static final String TABLE_EMPLOYEE = "employees";

    //Employee table columns names
    private static final String KEY_ID = "Employee_number";
    private static final String KEY_FIRST_NAME = "First_name";
    private static final String KEY_LAST_NAME = "Last_name";
    private static final String KEY_PHONE_NUMBER_MOBILE = "Phone_mobile";
    private static final String KEY_PHONE_NUMBER_OFFICE = "Phone_office";
    private static final String KEY_PAYROLL_TITLE = "Payroll_title";
    private static final String KEY_HAS_DIRECT_REPORTS = "Has_direct_reports";
    private static final String KEY_EMAIL = "Email";
    private static final String KEY_COST_CENTER = "Cost_center_id";
    private static final String KEY_THUMBNAIL_IMAGE = "ThumbnailData";


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

    @Override
    public void onCreate(SQLiteDatabase db) {
        String CREATE_EMPLOYEE_TABLE = "CREATE TABLE IF NOT EXISTS " + TABLE_EMPLOYEE + "("
                + KEY_ID + " STRING PRIMARY KEY,"
                + KEY_FIRST_NAME + " TEXT,"
                + KEY_LAST_NAME + " TEXT,"
                + KEY_PHONE_NUMBER_MOBILE + " TEXT,"
                + KEY_PHONE_NUMBER_OFFICE + " TEXT,"
                + KEY_PAYROLL_TITLE + " TEXT,"
                + KEY_HAS_DIRECT_REPORTS + " TEXT,"
                + KEY_EMAIL + " TEXT,"
                + KEY_THUMBNAIL_IMAGE + " TEXT,"
                + KEY_COST_CENTER + " TEXT" + ")";
        db.execSQL(CREATE_EMPLOYEE_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        //drop old table if existence
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_EMPLOYEE);

        //Create table again
        onCreate(db);
    }

    //Add new employee
    public boolean addEmployee(Employee employee) {
        SQLiteDatabase database = this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(KEY_ID, employee.getEmployee_number());
        values.put(KEY_FIRST_NAME, employee.getFirst_name());
        values.put(KEY_LAST_NAME, employee.getLast_name());
        values.put(KEY_PHONE_NUMBER_MOBILE, employee.getPhone_mobile());
        values.put(KEY_PHONE_NUMBER_OFFICE, employee.getPhone_office());
        values.put(KEY_HAS_DIRECT_REPORTS, employee.getHas_direct_reports());
        values.put(KEY_EMAIL, employee.getEmail());
        values.put(KEY_COST_CENTER, employee.getCost_center_id());
        values.put(KEY_PAYROLL_TITLE, employee.getPayroll_title());
        values.put(KEY_THUMBNAIL_IMAGE, employee.getThumbnailData());


        //Inserting Row
        database.insert(TABLE_EMPLOYEE, null, values);
        database.close();
        return true;
    }

    //Get single employee
    public Employee getEmployee(int employeeNumber) {
        SQLiteDatabase database = this.getReadableDatabase();
        Employee employee = null;

        Cursor cursor = database.query(TABLE_EMPLOYEE, new String[] {
                KEY_ID, KEY_FIRST_NAME, KEY_LAST_NAME, KEY_PHONE_NUMBER_OFFICE, KEY_PHONE_NUMBER_MOBILE,
                KEY_HAS_DIRECT_REPORTS, KEY_EMAIL, KEY_COST_CENTER, KEY_PAYROLL_TITLE, KEY_THUMBNAIL_IMAGE}, KEY_ID + "=?",
                new String[]{ String.valueOf(employeeNumber)}, null, null, null, null);
        if(cursor != null) {
            if(cursor.moveToFirst()) {
                employee = new Employee(cursor.getString(0),
                        cursor.getString(1), cursor.getString(2), cursor.getString(3), cursor.getString(4),
                        cursor.getString(5), cursor.getString(6), cursor.getString(7), cursor.getString(8),
                        cursor.getString(9), cursor.getString(10), cursor.getString(11), cursor.getString(12),
                        cursor.getString(12), cursor.getString(14), cursor.getString(15), cursor.getString(16),
                        cursor.getString(17), cursor.getString(18), cursor.getString(19), cursor.getString(20),
                        cursor.getString(21), cursor.getString(22), cursor.getString(23), cursor.getString(24),
                        cursor.getString(24), cursor.getString(25), cursor.getString(26));
            }
        }
            cursor.close();
            database.close();
            return employee;

    }

    //Get All Employees
    public ArrayList<Employee> getAllEmployees() {
        ArrayList<Employee> employeeList = new ArrayList<>();
        //Select all query
        String selectQuery = "SELECT * FROM " + TABLE_EMPLOYEE;

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

        //looping through all rows and adding to list
        if (cursor.moveToFirst()) {
            do {
                Employee employee = new Employee();
                employee.setEmployee_number(cursor.getString(cursor.getColumnIndex(KEY_ID)));
                employee.setFirst_name(cursor.getString(cursor.getColumnIndex(KEY_FIRST_NAME)));
                employee.setLast_name(cursor.getString(cursor.getColumnIndex(KEY_LAST_NAME)));
                employee.setPhone_office(cursor.getString(cursor.getColumnIndex(KEY_PHONE_NUMBER_MOBILE)));
                employee.setPhone_mobile(cursor.getString(cursor.getColumnIndex(KEY_PHONE_NUMBER_OFFICE)));
                employee.setHas_direct_reports(cursor.getString(cursor.getColumnIndex(KEY_HAS_DIRECT_REPORTS)));
                employee.setEmail(cursor.getString(cursor.getColumnIndex(KEY_EMAIL)));
                employee.setCost_center_id(cursor.getString(cursor.getColumnIndex(KEY_COST_CENTER)));
                employee.setPayroll_title(cursor.getString(cursor.getColumnIndex(KEY_PAYROLL_TITLE)));
                employee.setThumbnailData(cursor.getString(cursor.getColumnIndex(KEY_THUMBNAIL_IMAGE)));
            } while (cursor.moveToNext());
        }

        //return employees list
        return employeeList;
    }

    //Get Employee Count
    public int getEmployeeCount() {
        String countQuery = "SELECT * FROM " + TABLE_EMPLOYEE;
        SQLiteDatabase database = this.getReadableDatabase();
        Cursor cursor = database.rawQuery(countQuery, null);
        cursor.close();

        return cursor.getCount();
    }

    //Updating single employee
    public int updateEmployee(Employee employee){
        SQLiteDatabase database = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(KEY_FIRST_NAME, employee.getFirst_name());
        values.put(KEY_LAST_NAME, employee.getLast_name());
        values.put(KEY_PHONE_NUMBER_MOBILE, employee.getPhone_mobile());
        values.put(KEY_PHONE_NUMBER_OFFICE, employee.getPhone_office());
        values.put(KEY_HAS_DIRECT_REPORTS, employee.getHas_direct_reports());
        values.put(KEY_EMAIL, employee.getEmail());
        values.put(KEY_COST_CENTER, employee.getCost_center_id());
        values.put(KEY_PAYROLL_TITLE, employee.getPayroll_title());
        values.put(KEY_THUMBNAIL_IMAGE, employee.getThumbnailData());

        return database.update(TABLE_EMPLOYEE, values, KEY_ID + " = ?",
                new String[] {String.valueOf(employee.getEmployee_number())});
    }

    //Delete single employee
    public void deleteEmployee(Employee employee) {
        SQLiteDatabase database = this.getWritableDatabase();
        database.delete(TABLE_EMPLOYEE, KEY_ID + " = ?",
                new String[] {String.valueOf(employee.getEmployee_number())});
        database.close();
    }
}

【问题讨论】：

“我用游标和简单适配器尝试了几件事，但我似乎没有做任何事情来删除记录并填充另一个列表视图。”这是正确的做法。您应该准确地展示您尝试过的内容。
我已经用我用来尝试删除重复记录的方法更新了我的代码
记住Java代码必须有一个类。请在此处发布的代码中显示这一点。
另外，在将 ListView 与数据库连接时，应该使用 CursorAdapter 而不是 ArrayAdapter。
我很困惑如何首先允许具有相同主键的两条记录。

标签： android listview android-sqlite

【解决方案1】：

是否存在具有重复 Employee_number 的其他记录？这些也会导致您报告的问题。您违反了不能有多个记录具有相同 Employee_number 的约束。如果您需要多个具有相同 Employee_number 的记录，请设置另一个主键（可能是自动递增）。然后您的删除命令将删除两条记录。

编辑：您不能违反您创建的约束，因此您需要确保在添加记录时不违反它（在添加之前检查预先存在的 Employee_number）或更改您的主键按照建议。

编辑 2：以下是具有自动主键的表的语法：添加到此表将自动为您填充“id”，确保它是唯一的。

 String CREATE_EMPLOYEE_TABLE = "CREATE TABLE IF NOT EXISTS " + TABLE_EMPLOYEE + "("
                + "id INT NOT NULL AUTO_INCREMENT PRIMARY KEY, "
                + KEY_ID + " STRING,"
                + KEY_FIRST_NAME + " TEXT, "
                + KEY_LAST_NAME + " TEXT, "
                ...

【讨论】：

不，Web 服务中只有 1 条重复记录，我无法让他们删除该重复记录，因此我在解析并存储响应后尝试在 SQLite 中执行此操作。跨度>
是否可以创建一个不与响应或 POJO 绑定的唯一 ID？只需为添加的每一行创建一个 1、2、3 等？也许这样我可以获得特定的新唯一 ID 并删除它？考虑过使用 Sugar ORM 之类的东西，但这无济于事，因为我有两次将相同的员工编号添加到数据库中。
是的，这就是我所指的 auto_increment 列 - 示例见编辑 2