Android SQLite 值必须 ≥ 0 getColumnIndex Kotlin

Question

我在 Android Studio 中遇到与我的光标有关的错误。

我的代码中有以下行

val dataText = cursor.getString(cursor.getColumnIndex(MyDbNameClass.COLUMN_NAME_TITLE))

我尝试使用cursor.getColumnIndexOrThrow()，但没有帮助 我是安卓新手，希望你能帮助我。这是我的代码。

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/tvTest"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/edTitle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:ems="10"
        android:inputType="textPersonName"
        android:text="Name"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.437"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.071" />

    <EditText
        android:id="@+id/edDesc"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:ems="10"
        android:inputType="textPersonName"
        android:text="Name"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.437"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.166" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="onClickSave"
        android:text="Button"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.498"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.796" />

</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity.kt

package com.example.todo

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.widget.EditText
import android.widget.TextView
import com.example.todo.db.MyDbManager

class MainActivity : AppCompatActivity() {

    val myDbManager = MyDbManager(this)

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
    }
    fun onClickSave(view: View) {
        val edTitle = findViewById<EditText>(R.id.edTitle)
        val edDesc = findViewById<EditText>(R.id.edDesc)
        val tvTest = findViewById<TextView>(R.id.tvTest)
        tvTest.text = ""
        myDbManager.openDb()
        myDbManager.insertToDb(edTitle.text.toString(), edDesc.text.toString())
        val dataList = myDbManager.readDbData()
        for (item in dataList) {
            tvTest.append(item)
            tvTest.append("\n")
        }
    }
    override fun onDestroy() { //при выходе с активити
        super.onDestroy()
        myDbManager.closeDb()
    }
}

MyDbNameClass.kt

package com.example.todo.db

import android.provider.BaseColumns

object MyDbNameClass: BaseColumns {
    const val TABLE_NAME = "info"
    const val COLUMN_NAME_TITLE = "title"
    const val COLUMN_NAME_DESC = "desc"

    const val DATABASE_VERSION = 1
    const val DATABASE_NAME = "ToDoDb.db"

    const val CREATE_TABLE = "CREATE TABLE $TABLE_NAME (" +
            "${BaseColumns._ID} INTEGER PRIMARY KEY, $COLUMN_NAME_TITLE TEXT, $COLUMN_NAME_DESC TEXT)"
    const val SQL_DELETE_TABLE = "DROP TABLE IF EXISTS $TABLE_NAME"
}

MyDbHelper.kt

package com.example.todo.db

import android.content.ContentValues
import android.content.Context
import android.database.Cursor
import android.database.sqlite.SQLiteDatabase
import android.database.sqlite.SQLiteOpenHelper
import android.provider.BaseColumns

class MyDbHelper(context: Context) : SQLiteOpenHelper(context, MyDbNameClass.DATABASE_NAME, null, MyDbNameClass.DATABASE_VERSION) {
    override fun onCreate(db: SQLiteDatabase?) {
        db?.execSQL(MyDbNameClass.CREATE_TABLE)
    }

    override fun onUpgrade(db: SQLiteDatabase?, oldVersion: Int, newVersion: Int) {
        db?.execSQL(MyDbNameClass.SQL_DELETE_TABLE)
        onCreate(db)
    }
}

MyDbManager.kt（此处错误）

package com.example.todo.db

import android.content.ContentValues
import android.content.Context
import android.database.sqlite.SQLiteDatabase

class MyDbManager(context: Context) {
    private val myDbHelper = MyDbHelper(context)
    private var db: SQLiteDatabase? = null

    fun openDb(){
        db = myDbHelper.writableDatabase
    }
    fun insertToDb(title: String, desc: String){
        val values = ContentValues().apply {
            put(MyDbNameClass.COLUMN_NAME_TITLE, title)
            put(MyDbNameClass.COLUMN_NAME_DESC, desc)
        }
        db?.insert(MyDbNameClass.TABLE_NAME, null, values)
    }

    fun readDbData() : ArrayList<String> {
        val dataList = ArrayList<String>()
        val cursor = db?.query(MyDbNameClass.TABLE_NAME, null, null,
            null, null, null, null)
        db?.rawQuery(MyDbNameClass.TABLE_NAME, null)
        var k = 1
        while (cursor?.moveToNext()!!){
            val dataText = cursor.getString(cursor.getColumnIndex(MyDbNameClass.COLUMN_NAME_TITLE))
            dataList.add(dataText.toString())
        }
        cursor.close()
        return dataList
    }
    fun closeDb(){
        myDbHelper.close()
    }
}

Answer 1

这是一个警告

表示在该方法中，

getColumnIndex(..)

的值必须是

≥ 0

， 但它会是

-1

getColumnIndex()

返回给定列的从零开始的索引 名称，如果该列不存在，则为 -1。如果您希望该列 存在使用 getColumnIndexOrThrow(String) 代替，这将使 错误更清楚。

---

您有两个选择：

使用

getColumnIndexOrThrow()

代替

getColumnIndex()

getColumnIndexOrThrow()

返回给定的从零开始的索引 列名，或者如果列不存在则抛出 IllegalArgumentException 存在。

或添加注释

    @SuppressLint("Range")

要禁用此警告，请添加注释

@SuppressLint("Range")

，因为方法

getColumnIndex()

需要特定数值范围内的值 (

≥ 0

)。

@SuppressLint("Range")
fun readDbData() : ArrayList<String> {
        val dataList = ArrayList<String>()
        val cursor = db?.query(MyDbNameClass.TABLE_NAME, null, null,
            null, null, null, null)
        db?.rawQuery(MyDbNameClass.TABLE_NAME, null)
        var k = 1
        while (cursor?.moveToNext()!!){
            val dataText = cursor.getString(cursor.getColumnIndex(MyDbNameClass.COLUMN_NAME_TITLE))
            dataList.add(dataText.toString())
        }
        cursor.close()
        return dataList
    }