嵌套Parcelable通过Intent传递时出现解包错误求助

我开发Android应用时，需要通过Intent传递包含嵌套Parcelable对象的ArrayList（具体为public ArrayList<FolderModel> folderList_），但从Intent中取出数据时出现如下错误：

Parcel android.os.Parcel@9aa641d: Unmarshalling unknown type code 6881389 at offset 1696.

奇怪的是，若注释掉ExerciseModel的writeToParcel方法中的folderName_字段，就能正常运行。经测试，单独传递ExerciseModel的ArrayList无问题，推测问题出在FolderModel或其内部的ArrayList中。

核心代码 #

FolderModel类 #

public class FolderModel implements Parcelable {
    String folderName_ = "Folder";
    Boolean extended_ = false;
    ArrayList<ExerciseModel> exerciseList_;

    public FolderModel(String folderName, Boolean extended, ArrayList<ExerciseModel> exerciseList) {
        folderName_ = folderName;
        extended_ = extended;
        exerciseList_ = exerciseList;
    }

    protected FolderModel(Parcel in) {
        folderName_ = in.readString();
        byte tmpExtended_ = in.readByte();
        extended_ = tmpExtended_ == 0 ? null : tmpExtended_ == 1;
        exerciseList_ = in.createTypedArrayList(ExerciseModel.CREATOR);
    }

    public static final Creator<FolderModel> CREATOR = new Creator<FolderModel>() {
        @Override
        public FolderModel createFromParcel(Parcel in) {
            return new FolderModel(in);
        }

        @Override
        public FolderModel[] newArray(int size) {
            return new FolderModel[size];
        }
    };

    public String getFolderName_() {
        return folderName_;
    }

    public Boolean getExtended_() {
        return extended_;
    }

    public void setExtended_(boolean extended) { extended_ = extended; }

    public List<ExerciseModel> getExerciseList_() { return exerciseList_; }

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

    @Override
    public void writeToParcel(Parcel parcel, int i) {
        parcel.writeString(folderName_);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
            parcel.writeParcelableList(exerciseList_, i);
        }
    }
}

ExerciseModel类 #

public class ExerciseModel  implements Parcelable {
    String exerciseName_;
    String description_;
    String folderName_;

    public ExerciseModel(String exerciseName, String description, String folderName) {
        exerciseName_ = exerciseName;
        description_ = description;
        folderName_ = folderName;
    }

    protected ExerciseModel(Parcel in) {
        exerciseName_ = in.readString();
        description_ = in.readString();
        folderName_ = in.readString();
    }

    public static final Creator<ExerciseModel> CREATOR = new Creator<ExerciseModel>() {
        @Override
        public ExerciseModel createFromParcel(Parcel in) {
            return new ExerciseModel(in);
        }

        @Override
        public ExerciseModel[] newArray(int size) {
            return new ExerciseModel[size];
        }
    };

    public String getExerciseName_() { return exerciseName_; }

    public String getDescription_() { return description_; }

    public String getFolderName_() { return folderName_; }

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

    @Override
    public void writeToParcel(Parcel parcel, int i) {
        parcel.writeString(exerciseName_);
        parcel.writeString(description_);
        parcel.writeString(folderName_);
    }
}

问题原因与修复 #

问题根源 #

1. 字段读写不匹配：FolderModel的Parcel读取逻辑中读了extended_的byte值，但writeToParcel完全没写入该字段，导致Parcel数据顺序错位。
2. 列表读写方法不兼容+版本判断错误：读列表用createTypedArrayList，但写的时候仅在API Q+用writeParcelableList，两者不配对；低版本直接丢失exerciseList_数据，解包时却尝试读取，进一步加剧错位。ExerciseModel多写入一个字段时，错位的影响触发了未知类型码错误。

修复后的FolderModel.writeToParcel方法 #

@Override
public void writeToParcel(Parcel parcel, int i) {
    parcel.writeString(folderName_);
    // 对应读逻辑，写入extended_的byte值
    parcel.writeByte((byte) (extended_ == null ? 0 : extended_ ? 1 : 2));
    // 使用与createTypedArrayList配对的writeTypedList，全版本兼容
    parcel.writeTypedList(exerciseList_);
}

修复说明 #

• 严格保证写入字段的顺序、数量和读取逻辑完全一致，这是Parcelable实现的核心要求。
• writeTypedList和createTypedArrayList是配套方法，全版本兼容，无需API版本判断，避免低版本丢失数据。

内容的提问来源于stack exchange，提问作者Louckas