列'_id' 主键 简单光标适配器

Question

作为项目的一部分，我正在制作Android应用程序，可跟踪体育馆的用户锻炼。锻炼和锻炼各种设置，重量和代表。

我希望用户命名他们的锻炼，然后添加练习活动，当他们添加时练习时，它会填充ListView。然后，我计划添加一个完成按钮，并通过选择练习来保存锻炼。因为这将是一对一的关系。

下面的代码是我拥有的数据库助手，也是查看锻炼和锻炼的活动。但是SimpleCursoradapter给了我问题。

试图修复此错误的圈子四处走动，有人可以帮助我修复它吗？_id在主键中，所以我不知道怎么了。在我也在那里进行自动插入之前，但它也会出现错误。

日志猫如下：

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.cormac.gym12m/com.example.cormac.gym12m.ViewWorkoutsActivity}: java.lang.IllegalArgumentException: column '_id' does not exist
                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
                  at android.app.ActivityThread.access$900(ActivityThread.java:150)
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
                  at android.os.Handler.dispatchMessage(Handler.java:102)
                  at android.os.Looper.loop(Looper.java:148)
                  at android.app.ActivityThread.main(ActivityThread.java:5417)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
               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.cormac.gym12m.ViewWorkoutsActivity.onCreate(ViewWorkoutsActivity.java:42)
                  at android.app.Activity.performCreate(Activity.java:6294)
                  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108)
                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
                  at android.app.ActivityThread.access$900(ActivityThread.java:150) 
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
                  at android.os.Handler.dispatchMessage(Handler.java:102) 
                  at android.os.Looper.loop(Looper.java:148) 
                  at android.app.ActivityThread.main(ActivityThread.java:5417) 
                  at java.lang.reflect.Method.invoke(Native Method) 
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
 I/Process: Sending signal. PID: 16275 SIG: 9
  Application terminated.

dbhelper

public class DBHelper extends SQLiteOpenHelper {
public static String DATABASE_NAME = "gym_db";
private static final int DATABASE_VERSION = 1;
public static final String TABLE_WORKOUT = "workout_table";
public static final String WORKOUT_ID = "_id";
public static final String WORKOUT_NAME = "workout_name";
public static final String TABLE_EXERCISE = "exercise_table";
public static final String EXERCISE_ID = "exercise_id";
public static final String EXERCISE_NAME = "exercise_name";
public static final String EXERCISE_SET = "exercise_set";
public static final String EXERCISE_WEIGHT = "exercise_weight";
public static final String EXERCISE_REP = "exercise_rep";
public static final String createWorkoutTable = "CREATE TABLE " + TABLE_WORKOUT + "("
        + WORKOUT_ID + " _id INTEGER PRIMARY KEY, "
        + WORKOUT_NAME + " TEXT NOT NULL " +
        ")";

public static final String createExerciseTable = " CREATE TABLE " + TABLE_EXERCISE + "("
        + EXERCISE_ID + " _id INTEGER PRIMARY KEY, "
        + EXERCISE_NAME + " TEXT NOT NULL, "
        + EXERCISE_SET + " INTEGER NOT NULL, "
        + EXERCISE_WEIGHT + " INTEGER NOT NULL, "
        + EXERCISE_REP + " INTEGER NOT NULL, "
        + "FOREIGN KEY(" + EXERCISE_ID + ") REFERENCES " + TABLE_WORKOUT + "(id)" +
        ")";

public DBHelper(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL(createWorkoutTable);
    db.execSQL(createExerciseTable);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS '" + createWorkoutTable + " ' ");
    db.execSQL("DROP TABLE IF EXISTS '" + createExerciseTable + " ' ");
    onCreate(db);

}
private static void setForeignKeyConstraintEnabled(@NonNull SQLiteDatabase db){
    if (!db.isReadOnly()){
        db.execSQL("PRAGMA foreign_keys=1");
    }
}
private static void setForeignKeyConstraintDisabled(@NonNull SQLiteDatabase db){
    if (!db.isReadOnly()){
        db.execSQL("PRAGMA foreign_keys=0");
    }
}

public void addExercise(long l, String name, String set, String weight, String reps){
    SQLiteDatabase db = this.getWritableDatabase();
    //adding exercise name in exercise table
    ContentValues cv = new ContentValues();
    cv.put(EXERCISE_NAME, name);
    cv.put(EXERCISE_SET, set);
    cv.put(EXERCISE_WEIGHT,weight);
    cv.put(EXERCISE_REP,reps);
    db.insert(TABLE_EXERCISE, null, cv);
}

public long addWorkout(String name){
    SQLiteDatabase db = this.getWritableDatabase();

    //adding workout name in workout table
    ContentValues values = new ContentValues();
    values.put(WORKOUT_NAME, name);
    return this.getWritableDatabase().insert(TABLE_WORKOUT,null,values);
}
public Cursor getWorkouts(){
    return this.getWritableDatabase().query(TABLE_WORKOUT, null,null,null,null,null,null);
}
public long addExercise(String name, String set, String weight, String reps){
    SQLiteDatabase db = this.getWritableDatabase();
    //adding exercise name in exercise table
    ContentValues cv = new ContentValues();
    cv.put(EXERCISE_NAME, name);
    cv.put(EXERCISE_SET, set);
    cv.put(EXERCISE_WEIGHT,weight);
    cv.put(EXERCISE_REP,reps);
    return this.getWritableDatabase().insert(TABLE_EXERCISE,null,cv);
}
public Cursor getWorkoutExercises(long exerciseid){
    return this.getWritableDatabase().query(TABLE_EXERCISE, null,
            EXERCISE_ID+"=?",
            new String[]{Long.toString(exerciseid)},
            null,null,null);
}


public Cursor getAllWorkoutsExercises(int i){
    SQLiteDatabase db = this.getReadableDatabase();
    String SELECT_QUERY = "SELECT * FROM '" + TABLE_WORKOUT  + "'JOIN'" + TABLE_EXERCISE +  "' ON '" + EXERCISE_ID  + "' GROUP BY '" + EXERCISE_ID + "'ORDER BY'" + WORKOUT_NAME + "'";
    Cursor mCursor = db.rawQuery(SELECT_QUERY, null);
    return mCursor;
}

}

查看锻炼活动

public class ViewWorkoutsActivity extends AppCompatActivity{
ListView workoutlist;
ListView exerciselist;
Cursor workoutsCursor;
Cursor exercisesCursor;
SimpleCursorAdapter sca_workEx;
SimpleCursorAdapter sca_workouts;

DBHelper dbh = new DBHelper(this);

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_view_workouts);
    workoutlist = (ListView) findViewById(R.id.workoutlist);
    exerciselist = (ListView) findViewById(R.id.exerciselist);
    exercisesCursor = dbh.getWorkoutExercises(-1);
    workoutsCursor = dbh.getWorkouts();
    sca_workEx  = new SimpleCursorAdapter(this,
            android.R.layout.simple_list_item_1,
            exercisesCursor,
            new String[]{DBHelper.WORKOUT_NAME},
            new int[]{android.R.id.text1},0);
    sca_workouts = new SimpleCursorAdapter(this,
            android.R.layout.simple_list_item_1,
            workoutsCursor,
            new String[]{DBHelper.WORKOUT_NAME},
            new int[]{android.R.id.text1},0);

    workoutlist.setAdapter(sca_workouts);

    workoutlist.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            exercisesCursor = dbh.getAllWorkoutsExercises(1);
            sca_workouts.swapCursor(exercisesCursor);
        }
    });
}

}

Answer 1

public static final String EXERCISE_ID = "exercise_id";
        ...
        + EXERCISE_ID + " _id INTEGER PRIMARY KEY, "

此表没有名为_id的列。它确实有一个名为exercise_id的列，带有数据类型_id INTEGER PRIMARY KEY。

Answer 2

光标适应器，例如 simplcursoradapter ( cursoradapter class的一个子类(，使用的，需要一个名为 _id 的列。它使用此方法为onItemClick。

光标必须包括一个名为" _id"的列，否则此类不会 工作。

从Cursoradapter提取

这是您遇到的错误的原因。

有两个潜在的修复。

---

首先是使用 _id 用于excercise_id列名。

例如。要代码public static final String EXERCISE_ID = "_id";

这将需要删除表，也许最简单的方法，如果丢失当前数据不是问题，就是删除应用程序的数据或卸载应用程序并重新使用上述更改。另一种选择是进行更改，然后增加数据库版本，例如private static final int DATABASE_VERSION = 2;并重新启动该应用程序(这将调用您的DBHelper的onUpgrade方法，放下表和调用onCreate方法(。

---

第二种方法是将 _id 列作为光标中的列。

您可以通过以下几行更改getWorkoutExercises方法来实现这一目标： -

public Cursor getWorkoutExercises(long exerciseid){
    String[] columns = new String[]{EXERCISE_ID + " AS _id","*"}
    return this.getWritableDatabase().query(TABLE_EXERCISE, columns,
            EXERCISE_ID+"=?",
            new String[]{Long.toString(exerciseid)},
            null,null,null);
}

• 列也可能是以下
  • String columns = new String[]{"*",EXERCISE_ID + " AS _id"}
  • String columns = new String[]{"*","rowid AS _id"}
  • String columns = new String[]{"rowid AS _id","*"}

我建议重命名列名是更好的方法。