我有一個(gè)我的SQLiteOpenHelper班級，它被寫成單身人士。我應(yīng)該注意，我不是在 Java 中執(zhí)行此操作，而是使用 Xamarin.Android C# 編寫此程序。這是該課程的一個(gè)片段：public class DatabaseHelper : SQLiteOpenHelper{ private static readonly string TAG = typeof(DatabaseHelper).FullName; private static readonly string _databaseName = "istockdb"; private static readonly int _databaseVersion = 32; private static DatabaseHelper _instance; private Context _context; private DatabaseHelper(Context context) : base(context, _databaseName, null, _databaseVersion) { _context = context; } [MethodImpl(MethodImplOptions.Synchronized)] public static DatabaseHelper Instance(Context context) { // *** Use the application context, which will ensure that *** // *** the Activity's context is not accidentally leaked *** return _instance ?? (_instance = new DatabaseHelper(context.ApplicationContext)); }}所以我有DatabaseHelper一個(gè)單身人士，在活動(dòng)和服務(wù)中這樣使用：服務(wù)：[Service(Name=Text.MobileBackgroundHbService, Enabled = true, Exported = true), IntentFilter(new []{Intents.SyncHeartbeats})]public class BGHeartbeatService : BaseIntentService{ public BGHeartbeatService() { this._database = DatabaseHelper.Instance(Application.Context); } protected override void OnHandleIntent(Intent intent) { if (this._database == null) this._database = DatabaseHelper.Instance(Application.Context); if (intent.Action.Equals(Intents.SyncHeartbeats)) SyncHeartbeatRecords(); var broadcastIntent = new Intent(Intents.MobileRefresh); SendBroadcast(broadcastIntent); }}
1 回答
隔江千里
TA貢獻(xiàn)1906條經(jīng)驗(yàn) 獲得超10個(gè)贊
事實(shí)證明，我的單例實(shí)例DatbaseHelper沒有被處理掉。
實(shí)際上發(fā)生的事情是我正在處理由輔助方法中SQLiteDatabase的 from 使用的對象。DatbaseHelper
要真正解決這個(gè)問題，我所要做的就是改變：
/// <summary>
/// Inserts a Heartbeat record into local DB.
/// </summary>
/// <param name="heartbeat"></param>
/// <returns></returns>
public long InsertHeartbeat(Heartbeat heartbeat)
{
if (heartbeat == null) return -2L;
// This using() statement is causing the disposal
using (var db = this.WritableDatabase)
{
var id = -3L;
db.BeginTransactionNonExclusive();
try
{
var cv = GetContentValues(heartbeat);
id = db.Insert(DatabaseSchema.Heartbeat.TableName, null, cv);
db.SetTransactionSuccessful();
}
catch (Exception e)
{
// TODO: Document Exception
Util.Tools.Bark(e);
}
finally
{
db.EndTransaction();
}
return id;
}
}
到：
/// <summary>
/// Inserts a Heartbeat record into local DB.
/// </summary>
/// <param name="heartbeat"></param>
/// <returns></returns>
public long InsertHeartbeat(Heartbeat heartbeat)
{
if (heartbeat == null) return -2L;
// This is no longer initialized in a using() statement
var db = this.WritableDatabase;
var id = -3L;
db.BeginTransactionNonExclusive();
try
{
var cv = GetContentValues(heartbeat);
id = db.Insert(DatabaseSchema.Heartbeat.TableName, null, cv);
db.SetTransactionSuccessful();
}
catch (Exception e)
{
// TODO: Document Exception
Util.Tools.Bark(e);
}
finally
{
db.EndTransaction();
}
return id;
}
概括：
通過在輔助方法內(nèi)的語句內(nèi)初始化我的SQLiteDatabase db對象，我處理了我需要的對象。using()SQLiteDatabaseDatabaseHelper
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