Question

我已将ID重命名为_id，但仍然获得column '_id' does not exist ...我错过了什么吗？

MyDatabaseelper.java

public class MyDatabaseHelper extends SQLiteOpenHelper {
    public static final int DATABASE_VERSION=1;
    public static final String DATABASE_NAME="alm.db";
    public static final String TABLE_INFO="Information";
    public static final String TABLE_WORKFORCE="WorkForce";
    public static final  String TABLE_WORKDETAILS="WorkDetails";
    public static final String Subcontractors="Subcontractors";
    public static final String NumberOfPerson="NumberOfPerson";
    public static final String NumberOfHours="NumberOfHours";
    public static final String ID="_id";
    public static final String TimeIn_Info="timeIn_Info";
    public static final String TimeOut_Info="timeOut_Info";

  public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table " + TABLE_INFO + "(ID INTEGER PRIMARY KEY ,Name TEXT,Weather TEXT, Date DATETIME, Status Text, TimeIn_Info DATE TIME, TimeOut_Info DATETIME)");
        db.execSQL("create table " + TABLE_WORKFORCE + "(ID INTEGER PRIMARY KEY  ,Subcontractors TEXT,NumberOfPerson INTEGER,NumberOfHours TEXT, TInfo_id INTEGER, FOREIGN KEY(TInfo_id) REFERENCES "+TABLE_INFO+"(ID))");

}

ListDisplay.java

public class ListDisplay extends AppCompatActivity {
    InfoAPI sqlcon;
    private SimpleCursorAdapter dataAdapter;


    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.listdisplay1);
        sqlcon = new InfoAPI(this);
        final String name1 = getIntent().getExtras().getString("name");
        BuildList(name1);
    }

    public void BuildList(String name) {
        final String name1 = name;
        sqlcon.open();
        Cursor cursor=sqlcon.readEntry(name1);

       String[] columns=new String[]{
               MyDatabaseHelper.Weather,MyDatabaseHelper.Date,MyDatabaseHelper.Status,MyDatabaseHelper.TimeIn,MyDatabaseHelper.TimeOut
       };

        int[] to=new int[]{
                R.id.weather,R.id.date,R.id.status,R.id.in,R.id.out
        };

        // create the adapter using the cursor pointing to the desired data
        //as well as the layout information
        dataAdapter = new SimpleCursorAdapter(
                this, R.layout.listdispaly,
                cursor,
                columns,
                to,
                0);

        ListView listView = (ListView) findViewById(R.id.listView1);
        // Assign adapter to ListView
        listView.setAdapter(dataAdapter);






    }

}

InfoAPI.java

  public Cursor readEntry(String name)
    {
        Cursor c=database.rawQuery("SELECT  Weather, Date, Status, TimeIn_Info, TimeOut_Info FROM " + MyDatabaseHelper.TABLE_INFO + " WHERE Name = ?", new String[]{String.valueOf(name)}, null);

        if (c != null) {
            c.moveToFirst();
        }
        return c;
    }
}

LogCat错误

  Caused by: java.lang.IllegalArgumentException: column '_id' does not exist
            at android.database.AbstractCursor.getColumnIndexOrThrow(AbstractCursor.java:333)
            at android.widget.CursorAdapter.init(CursorAdapter.java:180)
            at android.widget.CursorAdapter.<init>(CursorAdapter.java:157)
            at android.widget.ResourceCursorAdapter.<init>(ResourceCursorAdapter.java:96)
            at android.widget.SimpleCursorAdapter.<init>(SimpleCursorAdapter.java:104)
            at com.example.project.project.ListDisplay.BuildList(ListDisplay.java:49)
            at com.example.project.project.ListDisplay.onCreate(ListDisplay.java:31)
            at android.app.Activity.performCreate(Activity.java:6237)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
            at android.app.ActivityThread.-wrap11(ActivityThread.java)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)

Answer 1

您创建的表查询仍然使用“ID”（硬编码字符串）

public void onCreate(SQLiteDatabase db) {
   db.execSQL("create table " + TABLE_INFO + " ( " + ID + " INTEGER PRIMARY KEY ,Name TEXT,Weather TEXT, Date DATETIME, Status Text, TimeIn_Info DATE TIME, TimeOut_Info DATETIME)");
   db.execSQL("create table " + TABLE_WORKFORCE + " ( " + ID + " INTEGER PRIMARY KEY  ,Subcontractors TEXT,NumberOfPerson INTEGER,NumberOfHours TEXT, TInfo_id INTEGER, FOREIGN KEY(TInfo_id) REFERENCES "+TABLE_INFO+"(ID))");
}

您必须强制升级数据库，或者从设备中完全卸载应用程序并重新安装或增加版本。

SimpleCursorAdapter想要光标中的_id。将其添加到查询中，例如

 Cursor c=database.rawQuery("SELECT _id,  Weather, Date, Status, TimeIn_Info, TimeOut_Info FROM " + MyDatabaseHelper.TABLE_INFO + " WHERE Name = ?", new String[]{String.valueOf(name)}, null);

Answer 2

在将ID更改为_id之后，您需要卸载应用程序以重新安装。您还可以覆盖在SQLiteOpenHelper类下的辅助方法OnUpgrade方法，通过为数据库提供不同的版本号来升级数据库，然后删除旧的数据库版本。这可以确保您每次数据库发生更改时都不必重新安装应用程序。

您可以使用以下代码sinnipet。

@Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
                    + newVersion + ", which will destroy all old data");
            db.execSQL("DROP TABLE IF EXISTS donotes");
            //Create the data base with the New Data
            onCreate(db);
        }

像这样使用：

public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table " + TABLE_INFO + "(ID INTEGER PRIMARY KEY ,Name TEXT,Weather TEXT, Date DATETIME, Status Text, TimeIn_Info DATE TIME, TimeOut_Info DATETIME);");
        db.execSQL("create table " + TABLE_WORKFORCE + "(ID INTEGER PRIMARY KEY  ,Subcontractors TEXT,NumberOfPerson INTEGER,NumberOfHours TEXT, TInfo_id INTEGER, FOREIGN KEY(TInfo_id) REFERENCES "+TABLE_INFO+"(ID));");

}

专栏＆＃39; _id＆＃39;虽然ID已更改为_id，但不存在

2 个答案: