java - Kotlin 数据库错误 CursorIndexOutOfBoundsException

Question

这是错误，它说索引超出范围，但我不知道如何解决它，有一些土耳其语单词但它们并不重要，我认为:

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.burhanozen.nothesaplama, PID: 26919
java.lang.RuntimeException: Unable to start activity 
ComponentInfo{com.example.burhanozen.nothesaplama/com.example.burhanozen.nothesaplama.MainActivity}: android.database.CursorIndexOutOfBoundsException: Index 1 requested, with a size of 1
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at ........

我试图存储某种学生信息。我有这些错误，我在下面分享代码。这是我的 MainActivity:

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
    val toolbar = findViewById(R.id.toolbar) as Toolbar
    setSupportActionBar(toolbar)
    val fab = findViewById(R.id.fab) as FloatingActionButton
    fab.setOnClickListener {
        val intent = Intent(this@MainActivity,NotEkrani::class.java)
        startActivity(intent) }


    val studentsArray = ArrayList<String>()

    val arrayAdapter = ArrayAdapter(this,android.R.layout.simple_list_item_1,studentsArray)
    listView.adapter= arrayAdapter

    try{

        val myDatabase = this.openOrCreateDatabase("student", Context.MODE_PRIVATE,null)
        myDatabase.execSQL("CREATE TABLE IF NOT EXISTS students (isim TEXT," +
                " dersbir TEXT, dersbirkredi TEXT, dersbirort TEXT," +
                " dersiki TEXT, dersikikredi TEXT, dersikiort TEXT) ")

        val cursor = myDatabase.rawQuery("select * from students",null)

        val nameIx = cursor.getColumnIndex("isim")
        val dersbirIx = cursor.getColumnIndex("dersbir")
        val dersbirkrediIx = cursor.getColumnIndex("dersbirkredi")
        val dersbirortIx = cursor.getColumnIndex("dersbirort")
        val dersikiIx = cursor.getColumnIndex("dersiki")
        val dersikikrediIx = cursor.getColumnIndex("dersikikredi")
        val dersikiortIx = cursor.getColumnIndex("dersikiort")

        cursor.moveToNext()

        while (cursor != null){

            studentsArray.add(cursor.getString(nameIx))
            studentsArray.add(cursor.getString(dersbirIx))
            studentsArray.add(cursor.getString(dersbirkrediIx))
            studentsArray.add(cursor.getString(dersbirortIx))
            studentsArray.add(cursor.getString(dersikiIx))
            studentsArray.add(cursor.getString(dersikikrediIx))
            studentsArray.add(cursor.getString(dersikiortIx))

            cursor.moveToNext()

            arrayAdapter.notifyDataSetChanged()


        }
        while (cursor!=null){
            cursor!!.close()
        }



    }catch (e:SQLException){

    }

这是我的第二个 Activity 页面，我在这里没有任何错误，但这可能会有所帮助。我在这里写了数据库代码。

fun kaydet(view:View){
    val isim = isim.text.toString()
    val dersbir = dersbir.text.toString()
    val dersbirkredi = dersbirkredi.text.toString()
    val dersbirort = dersbirort.text.toString()
    val dersiki = dersiki.text.toString()
    val dersikikredi = dersikikredi.text.toString()
    val dersikiort = dersikiort.text.toString()

    try {
        val myDatabase = openOrCreateDatabase("student", Context.MODE_PRIVATE,null)

        myDatabase.execSQL("CREATE TABLE IF NOT EXISTS students (isim TEXT," +
                " dersbir TEXT, dersbirkredi TEXT, dersbirort TEXT," +
                " dersiki TEXT, dersikikredi TEXT, dersikiort TEXT) ")

        val sqlString = "INSERT INTO students (isim,dersbir,dersbirkredi,dersbirort,dersiki,dersikikredi,dersikiort) VALUES(?,?,?,?,?,?,?)"
        val statement = myDatabase.compileStatement(sqlString)

        statement.bindString(1,isim)
        statement.bindString(2,dersbir)
        statement.bindString(3,dersbirkredi)
        statement.bindString(4,dersbirort)
        statement.bindString(5,dersiki)
        statement.bindString(6,dersikikredi)
        statement.bindString(7,dersikiort)
        statement.execute()


    }catch (e:SQLException){

    }
    val intent = Intent(this,MainActivity::class.java)
    startActivity(intent)

}

Answer 1

将您的 while 循环更改为如下所示:

    while (cursor.moveToNext()){

        studentsArray.add(cursor.getString(nameIx))
        ...


    }

(从您的代码中删除所有其他 cursor.moveToNext())

您正在 while 循环条件中检查 cursor != null，但在您从游标读取所有行后它不会变为 null。

在上面的代码中，如果有下一行，cursor.moveToNext 返回 true。否则返回 false 并且循环终止。

而且，刚刚注意到，您应该将其更改为

while (cursor!=null){
      cursor!!.close()
}

如果检查:

if (cursor!=null){
      cursor.close()
}

或者，作为 Todd评论中建议，您可以使用自动关闭游标的高阶函数use，这类似于 Java 7 try-with-resources。

cursor.use {
    while (cursor.moveToNext()){

            studentsArray.add(cursor.getString(nameIx))
            ...


    }
}