如何将自定义对象的数组列表从一个Java类传递到另一个Java类? [英] How do I pass arraylist of a custom object from one java class to another?

问题描述

我有一个Arraylist自定义对象.我试图将其从一个Java文件传递到另一个.我尝试了putExtra方法和Parcelable选项；但我听不懂Parcelable.

I have an Arraylist of custom objects. I am trying to pass it from one java file to another. I tried the putExtra method and the Parcelable option; but I'm unable to understand Parcelable.

这是我的自定义对象:

public class AddValues implements Serializable{
    public int id;
    String value;

    public AddValues(int id, String value)
    {
        this.id = id;
        this.value = value;
    }

    @Override
    public String toString() {
        String result = "id = "+id+","+" value = "+value;
        return result;
    }

    public  int getid()
    {
        return  this.id;
    }

    public String getvalue()
    {
        return this.value;
    }
}

这是我发送ArrayList的代码:

Intent intent = new Intent(BluetoothLeService.this,HomePageFragment.class);
intent.putExtra("id", data_id);
intent.putExtra("value", list);

此处的列表"指的是ArrayList.

Here "list" refers to the ArrayList.

推荐答案

Serializable和Parcelable虽然用途相同，但它们并不相同.这篇帖子包含了一个可打包对象的示例.

Serializable and Parcelable are not the same thing, although they serve the same purpose. This post contains an example of the Parcelable object.

要创建的所有Parcelable对象均应遵循采用的模式，仅更改writeToParcel和AddValues(Parcel in)方法.这两个方法应该互相镜像，如果writeToParcel编写int然后是string，则构造函数应先读取int然后是string

The pattern employed should be followed for all Parcelable objects you want to create, changing only the writeToParcel and AddValues(Parcel in) methods. These two methods should mirror eachother, if writeToParcel writes an int then a string, the constructor should read an int then a string

可拆分

public class AddValues implements Parcelable{
    private int id;
    private String value;

    // Constructor
    public AddValues (int id, String value){
        this.id = id;
        this.value= value;
   }

   // Parcelling part
   public AddValues (Parcel in){
       this.id = in.readInt();
       this.value= in.readString();
   }

   @Override
    public int describeContents() {
        return 0;
    }

   @Override
   public void writeToParcel(Parcel dest, int flags) {
       dest.writeInt(id);
       dest.writeString(value);
   }

   public final Parcelable.Creator CREATOR = new Parcelable.Creator() {
       public AddValues createFromParcel(Parcel in) {
           return new AddValues(in); 
       }

       public AddValues[] newArray(int size) {
           return new AddValues[size];
       }
   };

}

现在将列表添加到Intent Extra中应该很简单

Adding the list to an Intent extra should be simple now

额外添加列表

ArrayList<AddValue> list = new ArrayList<>();
Intent intent = new Intent(BluetoothLeService.this,HomePageFragment.class);
intent.putExtra("arg_key", list);

额外获取列表

ArrayList<AddValues> list = (ArrayList<AddValues>) intent.getSerializableExtra("arg_key");

顺便说一句，您可以使用Pair<Integer, String>对象而不是创建AddValues对象.这不会影响答案，但是很高兴知道.

As an aside, you can use the Pair<Integer, String> object instead of creating an AddValues object. This doesn't affect the answer, but might be nice to know.

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