重新创建活动时出现 SQLiteDatabase 错误答案

【问题标题】：SQLiteDatabase error on recreate Activity重新创建活动时出现 SQLiteDatabase 错误
【发布时间】：2021-11-25 23:41:54
【问题描述】：

重新创建意图后，每个数据库查询都会出现异常。我认为这可能是因为重新创建活动的方式，但不知道如何解决这个问题。

我在更改语言和更改暗模式后重新创建它。

重新创建活动时抛出异常：

尝试重新打开一个已经关闭的对象：SQLiteDatabase：

活动

private lateinit var db: SQLiteDatabase
private lateinit var oh: LOTDatabaseHelper
...

onCreate

...
oh = LOTDatabaseHelper(this)
db = oh.readableDatabase
...

onDestroy

...
db.close()
oh.close()
...

以及我如何重新创建意图

val intent = intent
intent.addFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION)
startActivity(intent)
finish()

编辑：

我发现 Activity 大约创建了两次，然后留下一个，其余的被销毁。 OnDestroy 似乎适用于所有活动并关闭数据库，这是不可能的。

现在我导航到启动画面，然后导航到使用数据库的活动，一切正常。那么为什么用自己替换Activity时生命周期不能正常工作呢？

【问题讨论】：

标签： android sqlite android-activity android-sqlite android-lifecycle

【解决方案1】：

打开一个已经关闭的数据库一般是由于打开和关闭不匹配造成的。

解决方法通常是不打开和关闭数据库（除非特别需要，例如从备份副本恢复数据库，或强制 WAL 检查点备份数据库），而是只打开一次数据库。

通常不需要继续打开和关闭数据库，因为当应用程序完成时数据库将被关闭（您始终可以在最顶层活动的 onDestroy 上关闭它）。此外，打开数据库需要耗费大量资源，因此多次打开会浪费资源/效率低下。

或许见Android SQLite DB When to Close

我建议删除所有关闭。您可能还希望考虑单例方法，甚至可能在 Helper 中拥有所有 DB 功能。

作为一个例子也许考虑：-

助手 DBHelper :-

class LOTDatabaseHelper(context: Context): SQLiteOpenHelper(
    context,
    DATABASE_NAME,
    null,
    DATABASE_VERSION) {

    companion object {
        const val DATABASE_NAME = "my.db"
        const val DATABASE_VERSION = 1

        @Volatile
        private var instance: SQLiteDatabase? = null

        fun getInstance(context: Context): SQLiteDatabase {
            if (instance == null) {
                instance = LOTDatabaseHelper(context).writableDatabase
            }
            return instance as SQLiteDatabase
        }

    }

    override fun onCreate(db: SQLiteDatabase?) {
        db?.execSQL(Table1.CREATE_SQL)
    }

    override fun onUpgrade(db: SQLiteDatabase?, oldVersion: Int, newVersion: Int) {
        TODO("Not yet implemented")
    }

    override fun onDowngrade(db: SQLiteDatabase?, oldVersion: Int, newVersion: Int) {
        super.onDowngrade(db, oldVersion, newVersion)
    }

    fun insert(name: String): Long {
        val cv = ContentValues()
        cv.put(Table1.COL_NAME,name)
        return instance!!.insert(Table1.TABLE_NAME,null,cv)
    }

    fun getAllFromTable1() : Cursor {
        return instance!!.query(Table1.TABLE_NAME,null,null,null,null,null,"${Table1.COL_NAME} ASC")
    }

    @SuppressLint("Range")
    fun logAll() {
        val csr = getAllFromTable1()
        var row = 1
        val nameix = csr.getColumnIndex(COL_NAME)
        while (csr.moveToNext()) {
            Log.d("CURSORINFO","Row ${row++} ${COL_NAME} is ${csr.getString(csr.getColumnIndex(
                COL_NAME))}")
            //val test = csr.getString(csr.getColumnIndex("${COL_NAME}"))

        }
        csr.close()
    }

    // Table stuff
    class Table1 {
        companion object {
            const val TABLE_NAME = "table1"
            const val COL_ID = BaseColumns._ID
            const val COL_NAME = "${TABLE_NAME}_name"
            const val CREATE_SQL = "CREATE TABLE IF NOT EXISTS $TABLE_NAME (${COL_ID} INTEGER PRIMARY KEY, $COL_NAME TEXT);"
        }
    }
}

调用第二个Activity的初始ActivityMainActivity：-

class MainActivity : AppCompatActivity() {
    val TAG = "MAINACTIVITYINFO"

    private lateinit var dbother: DBHelper
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        dbother = DBHelper.getInstance(this)!!
        dbother.insert("TESTOTHER") // Use the Insert in the DBHelper

        /* of course you can still get an SQLiteDatabase */
        /* There is very little use getting readable as it gets writable */
        /* so get writable is more accurate description */
        var sqliteDatabase = dbother.writableDatabase //<<<<<< can be used
        logCursorInfo(dbother.allAsCursor)

        // NOW Start the other Activity
        Log.d(TAG,"starting Activity2")
        intent = Intent(this,Activity2::class.java)
        startActivity(intent)
        Log.d(TAG,"after starting Activity2")

    }

    override fun onDestroy() {
        super.onDestroy()
        Log.d("ONDESTROY","On Destroy invoked.")
    }

    override fun onResume() {
        super.onResume()
        Log.d(TAG,"On Resume invoked")
        dbother = DBHelper.getInstance(this)!!
    }

    //
    @SuppressLint("Range")
    fun logCursorInfo(csr: Cursor) {
        val nameix = csr.getColumnIndex(LOTDatabaseHelper.Table1.COL_NAME)
        val idix = csr.getColumnIndex(LOTDatabaseHelper.Table1.COL_ID)
        while (csr.moveToNext()) {
            //Log.d(TAG,"${LOTDatabaseHelper.Table1.COL_ID} = ${csr.getString(idix)} ${LOTDatabaseHelper.Table1.COL_NAME} = ${csr.getString(nameix)}")
            Log.d(TAG,"${csr.getString(csr.getColumnIndex(LOTDatabaseHelper.Table1.COL_NAME))}")
        }
    }
    companion object {
        var counter: Int = 0
    }
}

这使用 DBHelper 但获取一个实例，然后添加几行，提取它们然后启动第二个 Activity。

Activity2您遇到问题的活动：-

class Activity2 : AppCompatActivity() {
    val TAG = "ACTIVITY2INFO"
    private lateinit var dbother: DBHelper
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_2)
        Log.d(TAG,"Activity 2 Started (onCreate). $this")

        dbother = DBHelper.getInstance(this)!! // Get the Database

        dbother.insert("TESTOTHER_ACTIVITY2") // Add a row
        var csr = dbother.allAsCursor // get All the rows
        DatabaseUtils.dumpCursor(csr) // dump the cursor
        csr.close() // close the cursor

        /* Start another activity (will loop so stop with counter)*/
        Log.d(TAG,"Restarting Activity. counter is ${counter++} $this")
        if (counter < 3) {
            val intent = intent
            intent.addFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION)
            startActivity(intent) //<<<<<<<<<< RUN 1 Not the Way as starts a new activity

            /* Perhaps the following???? */
            // this.intent.addFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION)
            //this.recreate() //<<<<<<<<<< RUN 2 perhaps the way but no intent
        }
        Log.d(TAG,"Finishing Activity 2 $this")
        finish()
    }

    companion object {
        var counter: Int = 0
    }

    override fun onResume() {
        super.onResume()
        Log.d(TAG,"OnResume Invoked. $this")
    }

    override fun onDestroy() {
        super.onDestroy()
        Log.d(TAG,"OnDestory (after super call - before db close and helper close. $this)")
        Log.d(TAG,"OnDestory (after all. $this)")
    }
}

这将获取一个（该）DBHelper 实例，插入一行，提取所有数据，然后启动另一个活动，注意这将无限循环，因此计数器。

希望 cmets 能提供帮助。

如您所见，我已经包含了相当多的日志记录。但是，正如建议的那样，数据库永远不会关闭。

运行应用程序

这是运行应用程序的结果，即日志（来自全新安装）：-

2021-10-06 19:52:50.715  D/DBHELPERINFO: getInstance returning instance a.a.so69454766kotlinsqlite.DBHelper@59860ab
2021-10-06 19:52:50.717  D/MAINACTIVITYINFO: TESTOTHER
2021-10-06 19:52:50.717  D/MAINACTIVITYINFO: starting Activity2
2021-10-06 19:52:50.724  D/MAINACTIVITYINFO: after starting Activity2
2021-10-06 19:52:50.734  D/MAINACTIVITYINFO: On Resume invoked
2021-10-06 19:52:50.734  D/DBHELPERINFO: getInstance returning instance a.a.so69454766kotlinsqlite.DBHelper@59860ab
2021-10-06 19:52:50.848  D/ACTIVITY2INFO: Activity 2 Started (onCreate). a.a.so69454766kotlinsqlite.Activity2@3269902
2021-10-06 19:52:50.848  D/DBHELPERINFO: getInstance returning instance a.a.so69454766kotlinsqlite.DBHelper@59860ab
2021-10-06 19:52:50.850  I/System.out: >>>>> Dumping cursor android.database.sqlite.SQLiteCursor@950aa67
2021-10-06 19:52:50.851  I/System.out: 0 {
2021-10-06 19:52:50.852  I/System.out:    _id=1
2021-10-06 19:52:50.852  I/System.out:    table1_name=TESTOTHER
2021-10-06 19:52:50.852  I/System.out: }
2021-10-06 19:52:50.852  I/System.out: 1 {
2021-10-06 19:52:50.852  I/System.out:    _id=2
2021-10-06 19:52:50.852  I/System.out:    table1_name=TESTOTHER_ACTIVITY2
2021-10-06 19:52:50.852  I/System.out: }
2021-10-06 19:52:50.852  I/System.out: <<<<<
2021-10-06 19:52:50.856  D/ACTIVITY2INFO: Restarting Activity. counter is 0 a.a.so69454766kotlinsqlite.Activity2@3269902
2021-10-06 19:52:50.864  D/ACTIVITY2INFO: Finishing Activity 2 a.a.so69454766kotlinsqlite.Activity2@3269902
2021-10-06 19:52:51.020  D/ACTIVITY2INFO: Activity 2 Started (onCreate). a.a.so69454766kotlinsqlite.Activity2@7db7a75
2021-10-06 19:52:51.020  D/DBHELPERINFO: getInstance returning instance a.a.so69454766kotlinsqlite.DBHelper@59860ab
2021-10-06 19:52:51.021  I/System.out: >>>>> Dumping cursor android.database.sqlite.SQLiteCursor@7fc80ae
2021-10-06 19:52:51.021  I/System.out: 0 {
2021-10-06 19:52:51.021  I/System.out:    _id=1
2021-10-06 19:52:51.021  I/System.out:    table1_name=TESTOTHER
2021-10-06 19:52:51.021  I/System.out: }
2021-10-06 19:52:51.021  I/System.out: 1 {
2021-10-06 19:52:51.021  I/System.out:    _id=2
2021-10-06 19:52:51.022  I/System.out:    table1_name=TESTOTHER_ACTIVITY2
2021-10-06 19:52:51.022  I/System.out: }
2021-10-06 19:52:51.022  I/System.out: 2 {
2021-10-06 19:52:51.022  I/System.out:    _id=3
2021-10-06 19:52:51.022  I/System.out:    table1_name=TESTOTHER_ACTIVITY2
2021-10-06 19:52:51.022  I/System.out: }
2021-10-06 19:52:51.022  I/System.out: <<<<<
2021-10-06 19:52:51.023  D/ACTIVITY2INFO: Restarting Activity. counter is 1 a.a.so69454766kotlinsqlite.Activity2@7db7a75
2021-10-06 19:52:51.030  D/ACTIVITY2INFO: Finishing Activity 2 a.a.so69454766kotlinsqlite.Activity2@7db7a75
2021-10-06 19:52:51.081  D/ACTIVITY2INFO: Activity 2 Started (onCreate). a.a.so69454766kotlinsqlite.Activity2@3433874
2021-10-06 19:52:51.081  D/DBHELPERINFO: getInstance returning instance a.a.so69454766kotlinsqlite.DBHelper@59860ab
2021-10-06 19:52:51.082  I/System.out: >>>>> Dumping cursor android.database.sqlite.SQLiteCursor@5c713d1
2021-10-06 19:52:51.082  I/System.out: 0 {
2021-10-06 19:52:51.082  I/System.out:    _id=1
2021-10-06 19:52:51.082  I/System.out:    table1_name=TESTOTHER
2021-10-06 19:52:51.082  I/System.out: }
2021-10-06 19:52:51.082  I/System.out: 1 {
2021-10-06 19:52:51.083  I/System.out:    _id=2
2021-10-06 19:52:51.083  I/System.out:    table1_name=TESTOTHER_ACTIVITY2
2021-10-06 19:52:51.083  I/System.out: }
2021-10-06 19:52:51.083  I/System.out: 2 {
2021-10-06 19:52:51.083  I/System.out:    _id=3
2021-10-06 19:52:51.083  I/System.out:    table1_name=TESTOTHER_ACTIVITY2
2021-10-06 19:52:51.083  I/System.out: }
2021-10-06 19:52:51.083  I/System.out: 3 {
2021-10-06 19:52:51.083  I/System.out:    _id=4
2021-10-06 19:52:51.083  I/System.out:    table1_name=TESTOTHER_ACTIVITY2
2021-10-06 19:52:51.083  I/System.out: }
2021-10-06 19:52:51.083  I/System.out: <<<<<
2021-10-06 19:52:51.084  D/ACTIVITY2INFO: Restarting Activity. counter is 2 a.a.so69454766kotlinsqlite.Activity2@3433874
2021-10-06 19:52:51.084  D/ACTIVITY2INFO: Finishing Activity 2 a.a.so69454766kotlinsqlite.Activity2@3433874
2021-10-06 19:52:51.097  D/MAINACTIVITYINFO: On Resume invoked
2021-10-06 19:52:51.097  D/DBHELPERINFO: getInstance returning instance a.a.so69454766kotlinsqlite.DBHelper@59860ab

需要注意的是，检索到的 DBHelper 实例始终是 DBHelper@59860ab（即单个实例）。

正如您所注意到的，活动发生的情况是另一个活动被启动。您不妨尝试使用注释掉的：-

        /* Perhaps the following???? */
        // this.intent.addFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION)
        //this.recreate() //<<<<<<<<<< RUN 2 perhaps the way but no intent

我不确定这是否会达到您的期望。

【讨论】：

我已经删除了 LOTDatabaseHelper 的关闭，如你所说，一切正常。谢谢