Java Kotlin数据库错误CursorIndexOutOfBoundsException
这是一个错误,它说索引超出范围,但我无法解决它,有一些土耳其语单词,但它们并不重要,我认为:Java Kotlin数据库错误CursorIndexOutOfBoundsException,java,android,sql,sqlite,kotlin,Java,Android,Sql,Sqlite,Kotlin,这是一个错误,它说索引超出范围,但我无法解决它,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/co
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 ........
我试图储存一些学生信息。我有这些错误,我在下面分享代码。
这是我的主要活动:
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){
}
将while循环更改为如下所示:
while (cursor.moveToNext()){
studentsArray.add(cursor.getString(nameIx))
...
}
(从代码中删除所有其他光标.moveToNext()
)
您正在检查光标!=null
在while循环条件下,但从游标读取所有行后,它不会变为null
在上面的代码中,cursor.moveToNext
如果下一行存在,则返回true。否则返回false,循环终止
刚才注意到,你应该从
while (cursor!=null){
cursor!!.close()
}
要进行if检查,请执行以下操作:
if (cursor!=null){
cursor.close()
}
或者,正如注释中所建议的,您可以使用更高阶的函数use
,它会自动关闭光标,这与Java 7 try with resources类似
cursor.use {
while (cursor.moveToNext()){
studentsArray.add(cursor.getString(nameIx))
...
}
}
出现此错误是因为光标大小为1。数据库中只有一条记录。但您要查询数据库不止一次。这就是你犯错误的原因 首先,您的完整执行代码是错误的 您正在活动中创建数据库。如果您这样做,您就无法正确有效地管理数据库 首先,必须在单独的类中创建SqliteOpenHelper数据库。然后你必须在那里创建一个表。然后在那里编写helper方法,从中获取和插入值 您的数据库类应该如下面的示例所示
class DbHelper(context: Context) : SQLiteOpenHelper(context, "example.db", null, 4) {
val TAG = javaClass<DbHelper>().getSimpleName()
val TABLE = "logs"
companion object {
public val ID: String = "_id"
public val TIMESTAMP: String = "TIMESTAMP"
public val TEXT: String = "TEXT"
}
val DATABASE_CREATE =
"CREATE TABLE if not exists " + TABLE + " (" +
"${ID} integer PRIMARY KEY autoincrement," +
"${TIMESTAMP} integer," +
"${TEXT} text"+
")"
fun log(text: String) {
val values = ContentValues()
values.put(TEXT, text)
values.put(TIMESTAMP, System.currentTimeMillis())
getWritableDatabase().insert(TABLE, null, values);
}
fun getLogs() : Cursor {
return getReadableDatabase()
.query(TABLE, arrayOf(ID, TIMESTAMP, TEXT), null, null, null, null, null);
}
override fun onCreate(db: SQLiteDatabase) {
Log.d(TAG, "Creating: " + DATABASE_CREATE);
db.execSQL(DATABASE_CREATE)
}
override fun onUpgrade(p0: SQLiteDatabase, p1: Int, p2: Int) {
}
}
classdbhelper(context:context):SQLiteOpenHelper(context,“example.db”,null,4){
val TAG=javaClass().getSimpleName()
val TABLE=“日志”
伴星{
public val ID:String=“\u ID”
public val TIMESTAMP:String=“TIMESTAMP”
public val TEXT:String=“TEXT”
}
创建val数据库=
“如果不存在,则创建表”+表+”(“+
${ID}整数主键自动递增+
“${TIMESTAMP}整数,”+
“${TEXT}TEXT”+
")"
趣味日志(文本:字符串){
val values=ContentValues()
value.put(文本,文本)
value.put(时间戳,System.currentTimeMillis())
getWritableDatabase().insert(表,null,值);
}
fun getLogs():游标{
返回getReadableDatabase()
.query(表、数组(ID、时间戳、文本)、null、null、null、null、null);
}
重写onCreate(db:SQLiteDatabase){
Log.d(标记“创建:”+数据库创建);
db.execSQL(数据库创建)
}
重写优先级(p0:SQLiteDatabase,p1:Int,p2:Int){
}
}
由于您使用的是Kotin数据库,因此使用Anko Sqlite非常简单。通过这个库,从数据库存储和检索数据非常容易。你可以在这里查一下。
class DbHelper(context: Context) : SQLiteOpenHelper(context, "example.db", null, 4) {
val TAG = javaClass<DbHelper>().getSimpleName()
val TABLE = "logs"
companion object {
public val ID: String = "_id"
public val TIMESTAMP: String = "TIMESTAMP"
public val TEXT: String = "TEXT"
}
val DATABASE_CREATE =
"CREATE TABLE if not exists " + TABLE + " (" +
"${ID} integer PRIMARY KEY autoincrement," +
"${TIMESTAMP} integer," +
"${TEXT} text"+
")"
fun log(text: String) {
val values = ContentValues()
values.put(TEXT, text)
values.put(TIMESTAMP, System.currentTimeMillis())
getWritableDatabase().insert(TABLE, null, values);
}
fun getLogs() : Cursor {
return getReadableDatabase()
.query(TABLE, arrayOf(ID, TIMESTAMP, TEXT), null, null, null, null, null);
}
override fun onCreate(db: SQLiteDatabase) {
Log.d(TAG, "Creating: " + DATABASE_CREATE);
db.execSQL(DATABASE_CREATE)
}
override fun onUpgrade(p0: SQLiteDatabase, p1: Int, p2: Int) {
}
}