列'_id'主键SimpleCursorAdapter

Question

作为项目的一部分，我正在制作一款可跟踪用户在健身房锻炼的Android应用。 进行各种设定，重量和次数的锻炼。

我希望用户命名他们的锻炼，然后采取添加锻炼活动的方式，在他们添加锻炼时将其填充到列表视图中。 然后，我计划添加一个完成按钮，并通过选择练习保存锻炼。 因为这将是一对多的关系。

下面的代码是我拥有的数据库助手以及查看锻炼和练习的活动。 但是SimpleCursorAdapter给我问题。

绕圈子尝试修复此错误，有人可以帮助我修复此错误吗？ _id在主键中，所以我不知道出了什么问题。 在我也有AUTOINCREMENT之前，但是它也给出了一个错误。

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, "

该表没有名为_id的列。 它确实有一个名为exercise_id的列，其数据类型为_id INTEGER PRIMARY KEY 。

Answer 2

您使用过的游标适配器，例如SimplCursorAdapter （ CursorAdapter类的子类） ，需要一列_id 。 它使用它为诸如onItemClick方法提供ID 。

游标必须包含一个名为“ _id”的列，否则此类将无法使用。

从CursorAdapter中提取

这就是您得到错误的原因。

有两个潜在的修复程序。

---

第一种是使用_id作为EXCERCISE_ID列名。

例如，对public static final String EXERCISE_ID = "_id";进行编码public static final String EXERCISE_ID = "_id";

这将需要删除表，如果丢失当前数据不是问题，那么最简单的方法可能就是删除应用程序的数据或卸载应用程序并通过上述更改重新运行。 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; 并重新运行该应用程序（这将调用DBHelper的onUpgrade方法，删除表并调用onCreate方法）。

---

第二种方法是在游标中提供_id列作为派生列。

您可以通过按照getWorkoutExercises方式更改getWorkoutExercises方法来实现：

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);

}

• 列也可以是以下之一
  • 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。