好的，所以我有一个 SomeClass 类，它是 Parcelable。

它有一个名为 SuperClass 的另一个 Parcelable 类的数组。在我的 SomeClass 构造函数中，我试图将 SuperClass 对象的数组读取到 myArray 实例变量中。这很简单；然而:

SuperClass 有两个子类 FirstSubClass 和 SecondSubClass。数组 temp 应该是所有 3 个的混合，但由于某种原因它只有 SuperClass 对象(if 和 else if 语句似乎没有执行，因为 temp 的所有元素都不是子类的实例)。

public SomeClass(Parcel in) {

    myArray = new SuperClass[100];

    // this is probably where the problem is due to the classloader parameter:
    Object[] temp = in.readArray(SuperClass.class.getClassLoader());

    for(int i = 0; i < myArray.length; i++) {

        if(temp[i] instanceof FirstSubClass)
            myArray[i] = (FirstSubClass) temp[i];

        else if(temp[i] instanceof SecondSubClass)
            myArray[i] = (SecondSubClass) temp[i];

        else
            myArray[i] = (SuperClass) temp[i];
    }

}

我想弄清楚的是如何读取可打包对象数组的元素，以便该对象的子类不会自动转换为父类(super class)。

(我想我的问题措辞可能很困惑，如果是的话请告诉我)。

最佳答案

我试图重现您的问题，但我无法...我使用了 writeParcelableArray 和 NOT writeTypedArray。以下是我创建的类:

public class SuperClass implements Parcelable {
    public static final Parcelable.Creator<SuperClass> CREATOR = new Creator<SuperClass>() {

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

        @Override
        public SuperClass createFromParcel(Parcel source) {
            return new SuperClass(source);
        }
    };

    private String label;

    public SuperClass() {
    }

    protected SuperClass(Parcel source) {
        label = source.readString();
    }

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

    @Override
    public int describeContents() {
        // TODO Auto-generated method stub
        return 0;
    }
}

及其子类:

public class FirstSubClass extends SuperClass {
    public static final Parcelable.Creator<FirstSubClass> CREATOR = new Creator<FirstSubClass>() {

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

        @Override
        public FirstSubClass createFromParcel(Parcel source) {
            return new FirstSubClass(source);
        }
    };

    public FirstSubClass() {
        super();
    }

    public FirstSubClass(Parcel source) {
        super(source);
    }

}

和:

public class SecondSubClass extends SuperClass {
    public static final Parcelable.Creator<SecondSubClass> CREATOR = new Creator<SecondSubClass>() {

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

        @Override
        public SecondSubClass createFromParcel(Parcel source) {
            return new SecondSubClass(source);
        }
    };

    public SecondSubClass() {
        super();
    }

    public SecondSubClass(Parcel source) {
        super(source);
    }

}

和SomeClass:

public class SomeClass implements Parcelable {
    public static final Parcelable.Creator<SomeClass> CREATOR = new Creator<SomeClass>() {

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

        @Override
        public SomeClass createFromParcel(Parcel source) {
            return new SomeClass(source);
        }
    };

    private String name;
    private SuperClass[] array;

    public SomeClass(String name, SuperClass[] array) {
        this.name = name;
        this.array = array;
    }

    protected SomeClass(Parcel source) {
        this.name = source.readString();
        Parcelable[] temp = source.readParcelableArray(SuperClass.class.getClassLoader());
        array = new SuperClass[temp.length];
        for (int i = 0; i < temp.length; i++) {
            array[i] = (SuperClass) temp[i];
        }
    }

    public String toString() {
        StringBuilder sb = new StringBuilder(name);
        if (array == null || array.length == 0) {
            sb.append(" Array is empty");
        } else {
            sb.append(" Array:");
            for (SuperClass sc : array) {
                sb.append(sc.getClass().getSimpleName());
                sb.append(",");
            }
            sb.setLength(sb.length() - 1);
        }
        return sb.toString();
    }

    public String getName() {
        return name;
    }

    public SuperClass[] getArray() {
        return array;
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(name);
        dest.writeParcelableArray(array, flags);
    }

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

从一个 Activity 中，我点击一个按钮，创建一个 SomeClass 对象，附加到我开始一个新 Activity 的 Intent ，并从那里记录传递的值。启动 Activity 的功能:

@Override
public void onClick(View v) {
    SuperClass[] array = new SuperClass[] { new SuperClass(), new FirstSubClass(), new SecondSubClass(), new SuperClass() };
    SomeClass cl = new SomeClass("My Label", array);
    Intent intent = new Intent(this, NextActivity.class);
    intent.putExtra("PASS", cl);
    startActivity(intent);
}

来自NextActivity:

public class NextActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //set some content if you wish
        Log.d("LOG_TAG", "Passed value: " + getIntent().getParcelableExtra("PASS"));
    }
}

我可以在日志中看到:

Passed value: My Label Array:SuperClass,FirstSubClass,SecondSubClass,SuperClass

正是我从之前的 Activity 中传递的...检查与您的代码的差异，我怀疑您没有为 FirstSubClass 和 SecondSubClass 编写 CREATOR

关于java - 将对象转换为 Parcelable 父类(super class)的子类？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/21708395/