如何从 Intent 迭代自定义对象的 ArrayList 并将它们添加到

Question

我在意图中有一个自定义 FlightData 对象的 ArrayList。我加载意图并将数组列表设置为 null，并且 foreach 循环还强制我使用Objectas 类型。将 arraylist 保存到意图中：intent.putParcelableArrayListExtra("FlightDataList", (ArrayList<? extends Parcelable>) flightDataList);加载意图：Intent intent = getIntent();LinearLayout layout_datasheet =  findViewById(R.id.layout_datasheet);List flightDataList = intent.getParcelableArrayListExtra("FlightDataList");if (flightDataList == null){    Log.d("flightDataList_size", "FlightDataList is null"); // this fires}assert flightDataList != null;for (Object data : flightDataList){    data = (FlightData) data; // items in list are of type FlightData    TextView tv = new TextView(this);    tv.setText(data.toString());    layout_datasheet.addView(tv);}我的自定义类的可分割函数（x，y，时间，有 getters-setters）：@Override    public int describeContents() {        return 0;    }    @Override    public void writeToParcel(Parcel dest, int flags) {        dest.writeDouble(x);        dest.writeDouble(y);        dest.writeDouble(time);    }    public static final Creator<FlightData> CREATOR = new Creator<FlightData>() {        @Override        public FlightData createFromParcel(Parcel in) {            return new FlightData(in);        }        @Override        public FlightData[] newArray(int size) {            return new FlightData[size];        }    };

Answer 1

我怀疑您是否在 FlightData 中实现了 Parcable https://medium.com/techmacademy/how-to-implement-and-use-a-parcelable-class-in-android-part-1-28cca73fc2d1

Answer 2

它应该有效。我在你的例子中唯一缺少的是构造函数。它可以解释null你所得到的。

尝试添加这个构造函数FlightData

  public FlightData(Parcel in) {

    x = in.readDouble();

    y = in.readDouble();

    time  = in.readDouble();

  }

Answer 3

您是否尝试创建一个实现 Parcelable 的数据结构？

public class flightDataList implements Parcelable{

    String dataThingyString;

    int dataThingyInt;

    public flightDataList(String dataThingyString, int dataThingyInt){

        this.dataThingyString = dataThingyString;

        this.dataThingyInt = dataThingyInt;

    }

    public flightDataList(Parcle in){

        this.dataThingyString = in.readString();

        this.dataThingyInt = in.readInt();

    }

    @Override

    public void writeToParcel(Parcel dest, int flags){

        dest.writeString(dataThingyString);

        dest.writeInt(dataThingyInt);

    }

    public static final Creator<flightDataList> CREATOR = new Creator<flightDataList>(){

        @Override

        public flightDataList createFromParcel(Parcel source){

            return new flightDataList(source);

        }

        @Override

        public flightDataList[] newArray(int size){

            return new flightDataList[size];

        }

    }

    public void setdataThingyString(String stringData){

        this.dataThingyString = stringData;

    }

    public void setdataThingyInt(int intData){

        this.dataThingyInt = intData;

    }

    public String getdataThingyString(){

        return dataThingyString;

    }

    public int getdataThingyInt(){

        return dataThingyInt;

    }

    @Override

    public int describeContents(){

        return 0;

    }

}

Answer 4

1.首先在FlightData对象模型/pojo/class中实现Parceable

2.val flightDataList= ArrayList<FlightData>()

3.val args = Bundle()

4.args.putParcelableArrayList("FlightDataList", flightDataList)

5.intent.putExtra(args)

然后获取列表

val flightDataList = context.getIntent().getExtras().getParcelableArrayList("FlightDataList")