我正在尝试对我的第一个 Realm 数据库进行简单的查询。我在尝试访问查询方法返回的对象的属性时遇到错误。
我有两个问题:
1.这个错误是什么意思?我很难理解它......
2. 我是否以正确的方式进行查询?如果不是,我做错了什么?
错误日志:
[mono-rt] Stacktrace:
[mono-rt] at <unknown> <0xffffffff>
[mono-rt] at (wrapper managed-to-native) Realms.NativeTable.get_string >(Realms.TableHandle,intptr,intptr,intptr,intptr,bool&) <0x00057>
[mono-rt] at Realms.RealmObject.GetStringValue (string) <IL 0x0009d, >0x00323>
[mono-rt] at EasyVending.RCreditCard.get_holderName () <IL 0x0000e, 0x0006f>
[mono-rt] at EasyVending.RealmManager.getCreditCard () [0x0001c] in /Users/Bernardo/Projects/EasyVending/EasyVending/DataBase/RealmManager.cs:75
[mono-rt] at EasyVending.Android.CreditCartManagement.OnCreate (Android.OS.Bundle) [0x00111] in /Users/Bernardo/Projects/EasyVending/EasyVending.Android/Activities/CreditCartManagement.cs:89
[mono-rt] at Android.Support.V4.App.FragmentActivity.n_OnCreate_Landroid_os_Bundle_ (intptr,intptr,intptr) <IL 0x00013, 0x000ff>
[mono-rt] at (wrapper dynamic-method) object.13add723-97a5-4397-9c8a-e6fc23d98c3c (intptr,intptr,intptr) <IL 0x00017, 0x00043>
[mono-rt] at (wrapper native-to-managed) object.13add723-97a5-4397-9c8a-e6fc23d98c3c (intptr,intptr,intptr) <IL 0x0001f, 0x00097>
[mono-rt] Attempting native Android stacktrace:
[mono-rt] at ???+1 [0xbe903ac0]
[mono-rt] at ???+1 [0x98f50ffc]
=================================================================
Got a SIGSEGV while executing native code. This usually indicates
[mono-rt] a fatal error in the mono runtime or one of the native libraries
[mono-rt] used by your application.
[mono-rt]
[libc] Fatal signal 11 (SIGSEGV), code 1, fault addr 0x97b77168 in tid 9849 (vending_android)
========================================
public class RCreditCard : RealmObject {
public string holderName { get; set; }
public string bandeira { get; set; }
public string digitos { get; set; }
public string token { get; set; }
}
public class RealmManager {
private string databaseName {
get {
return "PayBluDatabase.db";
}
}
private string androidPath {
get {
return Path.Combine (Environment.GetFolderPath (Environment.SpecialFolder.Personal), databaseName);
}
}
public Realm getRealm() {
return Realm.GetInstance(androidPath);
}
public void closeRealm(Realm realm) {
realm.Close();
}
public Transaction insertCreditCard(EasyVending.CreditCard creditCard) {
var realm = getRealm();
using(var transaction = realm.BeginWrite()) {
var insertedCreditCard = realm.CreateObject<RCreditCard>();
insertedCreditCard.holderName = creditCard.HolderName;
insertedCreditCard.bandeira = creditCard.CreditCardBrand;
insertedCreditCard.digitos = creditCard.MaskedCreditCardNumber;
insertedCreditCard.token = creditCard.InstantBuyKey;
transaction.Commit();
closeRealm(realm);
return transaction;
}
}
public Transaction removeCreditCard() {
var realm = getRealm();
using(var transaction = realm.BeginWrite()) {
realm.RemoveAll<RCreditCard>();
transaction.Commit();
closeRealm(realm);
return transaction;
}
}
public CreditCard getCreditCard() {
var realm = getRealm();
var rCreditCard = realm.All<RCreditCard>().First();
closeRealm(realm);
var creditCard = new CreditCard() {
CreditCardBrand = rCreditCard.bandeira,
MaskedCreditCardNumber = rCreditCard.digitos,
HolderName = rCreditCard.holderName
};
return creditCard;
}
public bool hasCreditCard() {
bool answer = false;
var realm = getRealm();
if(realm.All<RCreditCard>().Count() > 0) {
answer = true;
}
closeRealm(realm);
return answer;
}
}
当我尝试访问查询返回的 RCreditCard 对象的任何属性时,会发生错误:
CreditCardBrand = rCreditCard.bandeira,
来自
var rCreditCard = realm.All<RCreditCard>().First();
如果问题不够清楚,请告诉我。
最佳答案
问题是您在尝试读取 getCreditCard()
中的 rCreditCard
属性之前关闭了 Realm 。 Realm 对象中的属性是零拷贝的,它们直接访问数据库,因此一旦关闭 Realm,该对象就会失效。我们应该更好地处理这种情况,目前还不清楚。感谢您向我们指出!
一般来说,您可能不想像以前那样频繁地打开和关闭 Realm ,除非这些调用发生在不同的线程上。如果您坚持这样做,则应将 Realm.Close()
调用移至事务 using
范围之外。就像现在一样,如果在事务期间发生异常,它将被回滚,但您的 Realm 不会像您预期的那样关闭。
最后,通常不需要有一个镜像您的 RealmObject 类的“普通”类。当然,在您的情况下可能有一些原因并不明显。通常,您可以直接使用 RealmObject
类。
关于c# - (包装器托管到 native )Realms.NativeTable.get_string 中的 Realm 查询出错,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/38468403/