Question

我正在尝试删除给定特定ID的行，并查看我的listview中反映的更新，但该行未被删除。同一过程适用于update，但不适用于删除。这是代码：

MainActivity.java

...

@Override
    public void onPositiveClick(DialogFragment dialog, int which) {

            //Shared Preferences
            SharedPreferences pref = getSharedPreferences(EditLog.PREF_FILENAME, 0);
            long id = 0;
            String date = "";
            String hours = "";
            String lessonType = "";
            String weatherCondition = "";
            if (!(pref == null)) {
                id = pref.getLong("rowId", 0);
                date = pref.getString("date", "");
                hours = pref.getString("hours", "");
                lessonType = pref.getString("lessonType", "");
                weatherCondition = pref.getString("weatherCondition", "");
            }

            if (which == 2) {
                LessonLogDBHelper dbhelp = new LessonLogDBHelper(getApplicationContext());
                final SQLiteDatabase db = dbhelp.getWritableDatabase();
                db.delete(LessonLogContract.LogEntry.TABLE_NAME, "_id=?", new String[]{Long.toString(id)});
            } else {
                LessonLogDBHelper dbhelp = new LessonLogDBHelper(getApplicationContext());
                final SQLiteDatabase db = dbhelp.getWritableDatabase();
                final ContentValues values = new ContentValues();
                values.put(LessonLogContract.LogEntry.CN_DATE, date);
                values.put(LessonLogContract.LogEntry.CN_HOURS, hours);
                values.put(LessonLogContract.LogEntry.CN_LESSON_TYPE, lessonType);
                values.put(LessonLogContract.LogEntry.CN_WEATHER, weatherCondition);
                db.update(LessonLogContract.LogEntry.TABLE_NAME, values, "_id=" + id, null);

            }

            FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
            transaction.replace(R.id.content_main, new DrivingLog());
            transaction.commit();

    }

...

如果= = 2，这意味着用户点击了delete按钮，则点击了项目的id（在数据库中），并且我呼叫delete。此过程适用于更新，但不能删除。

编辑：整洁的事情

我发现奇怪的是，如果我尝试update一个条目，那么我将从db中删除任何单个条目。如果我不先尝试更新，那么我就不能。

这是我的表格def：

LessonLogContract

package com.example.name.drivinglessona3;

import android.provider.BaseColumns;
import android.util.StringBuilderPrinter;

public class LessonLogContract {
    private LessonLogContract() {}

    public static class LogEntry implements BaseColumns {
        public static final String TABLE_NAME = "lesson";
        public static final String CN_DATE = "date";
        public static final String CN_HOURS = "hours";
        public static final String CN_LESSON_TYPE = "lesson_type";
        public static final String CN_WEATHER = "weather";
    }
}

LessonLogDBHelper

package com.example.name.drivinglessona3;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;



public class LessonLogDBHelper extends SQLiteOpenHelper {
    // If you change the database schema, you must increment the database version.
    private static final String SQL_CREATE_ENTRIES =
            "CREATE TABLE " + LessonLogContract.LogEntry.TABLE_NAME + " (" +
                    LessonLogContract.LogEntry._ID + " INTEGER PRIMARY KEY," +
                    LessonLogContract.LogEntry.CN_DATE+ " TEXT," +
                    LessonLogContract.LogEntry.CN_HOURS+ " TEXT," +
                    LessonLogContract.LogEntry.CN_LESSON_TYPE+ " TEXT," +
                    LessonLogContract.LogEntry.CN_WEATHER + " TEXT)";

    private static final String SQL_DELETE_ENTRIES =
            "DROP TABLE IF EXISTS " + LessonLogContract.LogEntry.TABLE_NAME;

    public static final int DATABASE_VERSION = 1;
    public static final String DATABASE_NAME = "LogEntry.db";

    public LessonLogDBHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(SQL_CREATE_ENTRIES);
    }
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // This database is only a cache for online data, so its upgrade policy is
        // to simply to discard the data and start over
        db.execSQL(SQL_DELETE_ENTRIES);
        onCreate(db);
    }
    public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        onUpgrade(db, oldVersion, newVersion);
    }
}

解决

当我点击我的删除按钮时，我没有将_id保存到SharedPreferences，因此在MainActivity中我得到了错误的id值。

Answer 1

试试这个：

public void delete(int id) {
        SQLiteDatabase db = getWritableDatabase();
        db.delete("MST_Item", "ItemID=" + id, null);
        db.close();
}

Answer 2

只需在删除行中更改 String.valueOf（）而不是Long.toString（）。这意味着用以下代码替换db.delete（）行：

subscribe()

我希望这种方法适用于你。

Android SQLite不按ID删除行

2 个答案: