在 C# 中的 Android 活动之间传递自定义对象 [英] Passing custom object between Android activities in C#

问题描述

我正在使用 Xamarin.Android 在 VS2012 中创建一个 android 应用程序.我在主屏幕中显示自定义列表.当用户单击列表项时，我需要将一个自定义对象(带有 ID、字符串、字符串、字符串属性)从这个 Main 活动传递给另一个.

谁能帮我举个例子?

我已经尝试过在其他问题中提到的解决方案

但问题是我遇到了以下异常:

这就是我在第二个活动中提取

InsuranceReminderBO i = (InsuranceReminderBO)Intent.GetSerializableExtra("SelectedItemID");

i 为空

并且在第一个活动设置中是这样的:

Intent intent = new Intent(this, typeof(ReminderDetails));intent.PutExtra("SelectedItemID", selectedInsurance);StartActivity(typeof(ReminderDetails));

其中 class InsuranceReminderBO 定义为

public class InsuranceReminderBO : Java.Lang.Object, Java.IO.ISerializable

我也尝试过使用 IParcelable 但我得到了错误 Creator is not defined在 ICreator 或 Creator 中

遵循 Iparcelable 在 CustomObject 上的实现

'public class InsuranceReminderBO : Java.Lang.Object, IParcelable{公共保险ReminderBO(){}#region 对象和属性私有整数 ID；私人字符串 strCompanyName;私人字符串 strPremiumAmount;私人字符串标准日期；公共整数 ID{得到 { 返回 this.id;}设置 { this.id = 值；}}公共字符串 Company_Name{得到 { 返回 this.strCompanyName;}set { this.strCompanyName = value;}}公共字符串 Premium_Amount{得到 { 返回 this.strPremiumAmount;}设置 { this.strPremiumAmount = value;}}公共字符串 Due_Date{得到 { 返回 this.stDueDate;}设置 { this.stDueDate = 值；}}#endregion#region IParcelable 实现//创建者创建指定对象的实例私有静态只读 GenericParcelableCreator_创作者= new GenericParcelableCreator((parcel) => new InsuranceReminderBO(parcel));[导出字段(创建者")]public static GenericParcelableCreator获取创建者(){返回_creator;}//创建一个新的 SelectListItem，其中填充了 Parcel 中的值私人保险ReminderBO(包裹包裹){ID = Parcel.ReadInt();Company_Name = parcel.ReadString();Premium_Amount = parcel.ReadString();Due_Date = parcel.ReadString();}public int DescribeContents(){返回0；}//将此实例的值保存到parcel公共无效WriteToParcel(Parcel dest，ParcelableWriteFlags标志){dest.WriteInt(ID);dest.WriteString(Company_Name);dest.WriteString(Premium_Amount);dest.WriteString(Due_Date);}//最接近实现创建者的Java"方式/* 公共密封类 SelectListItemCreator : Java.Lang.Object, IParcelableCreator{public Java.Lang.Object CreateFromParcel(Parcel source){返回新的 SelectListItem(source);}public Java.Lang.Object[] NewArray(int size){返回新的 SelectListItem[size];}}*/#endregion}#region GenericParcelableCreator///<总结>///通用 Parcelable 创建器，可用于从包裹创建对象///</总结>公共密封类 GenericParcelableCreator: Java.Lang.Object, IParcelableCreator其中 T : Java.Lang.Object, new(){private readonly Func<Parcel, T>_createFunc;///<总结>///初始化 <see cref="ParcelableDemo.GenericParcelableCreator`1"/> 的新实例班级.///</总结>//////创建 T 实例的 Func，填充来自parcel 参数的值///</param>公共 GenericParcelableCreator(Func createFromParcelFunc){_createFunc = createFromParcelFunc;}#region IParcelableCreator 实现public Java.Lang.Object CreateFromParcel(Parcel source){返回 _createFunc(source);}public Java.Lang.Object[] NewArray(int size){返回新的 T[size];}#endregion}#endregion'

我把对象放在意图中

InsuranceReminderBO selectedInsurance = listOfInsurance[e.Position];Intent intent = new Intent(this, typeof(ReminderDetails));intent.PutExtra("SelectedItem", selectedInsurance);

在第二个活动中阅读

InsuranceReminderBO i = (InsuranceReminderBO)Intent.GetParcelableExtra("SelectedItem");

但让 i 为空.

解决方案

在 Google 上做了大量搜索后，我终于找到了解决方案 此处.

基本上我使用了 StartActivity(intent);

I am creating an android app in VS2012 using Xamarin.Android. I am displaying a custom list in Main screen. I need to pass a custom object(with ID,String,String,String properties) from this Main activity to another when user clicks on list item.

Can anyone please help me with some example?

edit:

I have already tried solution mention in other question

but the problem is I am getting below exception:

This is how I am extracting in second activity

InsuranceReminderBO i = (InsuranceReminderBO)Intent.GetSerializableExtra("SelectedItemID");

i is null

and in first activity setting it like this:

Intent intent = new Intent(this, typeof(ReminderDetails));

intent.PutExtra("SelectedItemID", selectedInsurance);

StartActivity(typeof(ReminderDetails));

where class InsuranceReminderBO is defined as

public class InsuranceReminderBO : Java.Lang.Object, Java.IO.ISerializable

I have also tried using IParcelable but in that I got error Creator is not defined in ICreator or Creator

Following the implementation of Iparcelable on CustomObject

'public class InsuranceReminderBO : Java.Lang.Object, IParcelable
    {
        public InsuranceReminderBO()
        {
        }

        #region Objects and Properties
        private int id;
        private String strCompanyName;
        private String strPremiumAmount;
        private String stDueDate;

        public int ID
        {
            get { return this.id; }
            set { this.id = value; }
        }

        public String Company_Name
        {
            get { return this.strCompanyName; }
            set { this.strCompanyName = value; }
        }

        public String Premium_Amount
        {
            get { return this.strPremiumAmount; }
            set { this.strPremiumAmount = value; }
        }

        public String Due_Date
        {
            get { return this.stDueDate; }
            set { this.stDueDate = value; }
        }
        #endregion

        #region IParcelable implementation

        // The creator creates an instance of the specified object
        private static readonly GenericParcelableCreator<InsuranceReminderBO> _creator 
            = new GenericParcelableCreator<InsuranceReminderBO>((parcel) => new InsuranceReminderBO(parcel));

        [ExportField("CREATOR")]
        public static GenericParcelableCreator<InsuranceReminderBO> GetCreator()
        {
            return _creator;
        }

        // Create a new SelectListItem populated with the values in parcel
        private InsuranceReminderBO(Parcel parcel)
        {
            ID = parcel.ReadInt();
            Company_Name = parcel.ReadString();
            Premium_Amount = parcel.ReadString();
            Due_Date = parcel.ReadString();
        }

        public int DescribeContents()
        {
            return 0;
        }

        // Save this instance's values to the parcel
        public void WriteToParcel(Parcel dest, ParcelableWriteFlags flags)
        {
            dest.WriteInt(ID);
            dest.WriteString(Company_Name);
            dest.WriteString(Premium_Amount);
            dest.WriteString(Due_Date);
        }

        // Closest to the 'Java' way of implementing the creator
        /*public sealed class SelectListItemCreator : Java.Lang.Object, IParcelableCreator
        {
            public Java.Lang.Object CreateFromParcel(Parcel source)
            {
                return new SelectListItem(source);
            }

            public Java.Lang.Object[] NewArray(int size)
            {
                return new SelectListItem[size];
            }
        }*/

        #endregion
    }

#region GenericParcelableCreator
    /// <summary>
    /// Generic Parcelable creator that can be used to create objects from parcels
    /// </summary>
    public sealed class GenericParcelableCreator<T> : Java.Lang.Object, IParcelableCreator
        where T : Java.Lang.Object, new()
    {
        private readonly Func<Parcel, T> _createFunc;

        /// <summary>
        /// Initializes a new instance of the <see cref="ParcelableDemo.GenericParcelableCreator`1"/> class.
        /// </summary>
        /// <param name='createFromParcelFunc'>
        /// Func that creates an instance of T, populated with the values from the parcel parameter
        /// </param>
        public GenericParcelableCreator(Func<Parcel, T> createFromParcelFunc)
        {
            _createFunc = createFromParcelFunc;
        }

        #region IParcelableCreator Implementation

        public Java.Lang.Object CreateFromParcel(Parcel source)
        {
            return _createFunc(source);
        }

        public Java.Lang.Object[] NewArray(int size)
        {
            return new T[size];
        }
        #endregion
    }
#endregion'

I am putting object in intent as

InsuranceReminderBO selectedInsurance = listOfInsurance[e.Position];
Intent intent = new Intent(this, typeof(ReminderDetails));
            intent.PutExtra("SelectedItem", selectedInsurance);

And reading in second activity as

InsuranceReminderBO i = (InsuranceReminderBO)Intent.GetParcelableExtra("SelectedItem");

but getting i as null.

解决方案

After doing a lot of search on Google finally i found a solution here.

Basically I used StartActivity(intent);

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