Unmarshalling errors in Android app with custom pa

问题:

For my Android application, I get several unmarshalling errors although I think I've done everything that is needed to properly save and load objects via Parcelables. Can you tell me what's wrong with my code?

Error 1:

java.lang.RuntimeException: Unable to start activity ComponentInfo
Caused by: java.lang.RuntimeException: Parcel android.os.Parcel@41279860: Unmarshalling unknown type code 6619241 at offset 1372
at android.os.Parcel.readValue(Parcel.java:1922)
at android.os.Parcel.readMapInternal(Parcel.java:2094)
at android.os.Bundle.unparcel(Bundle.java:223)
at android.os.Bundle.getParcelable(Bundle.java:1158)
at android.app.Activity.onCreate(Activity.java:860)
at my.app.package.PlayComputer.onCreate(PlayComputer.java:1012)
at android.app.Activity.performCreate(Activity.java:4465)

Line 1012 in MyActivity is the call to super.onCreate(savedInstanceState); in the Activity's onCreate().

protected void onSaveInstanceState(Bundle savedInstanceState) {
    if (myObject == null) {
        savedInstanceState.putParcelable("myObject", null);
    }
    else {
        savedInstanceState.putParcelable("myObject", myObject);
    }
    savedInstanceState.putInt(...);
    savedInstanceState.putString(...);
    savedInstanceState.putBoolean(...);
    super.onSaveInstanceState(savedInstanceState);
}

myObject is of class MyObject which has the following methods:

public void writeToParcel(Parcel out, int flags) {
    out.writeIntArray(...);
    out.writeInt(...);
    out.writeStringArray(...);
    out.writeString(...);
    out.writeParcelableArray(..., flags);
}

public static final Parcelable.Creator<MyObject> CREATOR = new Parcelable.Creator<MyObject>() {
    public MyObject createFromParcel(Parcel in) {
        try {
            if (in == null) {
                return null;
            }
            else {
                return new MyObject(in);
            }
        }
        catch (Exception e) {
            return null;
        }
    }
    public MyObject[] newArray(int size) {
        return new MyObject[size];
    }
};

private MyObject(Parcel in) {
    in.readIntArray(...);
    ... = in.readInt();
    in.readStringArray(...);
    ... = in.readString();
    ... = (OtherObject[]) in.readParcelableArray(OtherObject.class.getClassLoader());
}

Error 2:

java.lang.RuntimeException: Unable to start activity ComponentInfo
Caused by: android.os.BadParcelableException: ClassNotFoundException when unmarshalling:
at android.os.Parcel.readParcelable(Parcel.java:1971)
at android.os.Parcel.readValue(Parcel.java:1859)
at android.os.Parcel.readMapInternal(Parcel.java:2099)
at android.os.Bundle.unparcel(Bundle.java:223)
at android.os.Bundle.getParcelable(Bundle.java:1158)
at android.app.Activity.onCreate(Activity.java:905)
at my.app.package.PlayComputer.onCreate(SourceFile:1012)

Same files and classes.

Error 3:

java.lang.RuntimeException: Unable to start activity ComponentInfo
Caused by: java.lang.RuntimeException: Parcel android.os.Parcel@4051aff8: Unmarshalling unknown type code 7340149 at offset 1276
at android.os.Parcel.readValue(Parcel.java:1913)
at android.os.Parcel.readMapInternal(Parcel.java:2083)
at android.os.Bundle.unparcel(Bundle.java:208)
at android.os.Bundle.getParcelable(Bundle.java:1100)
at my.app.package.PlayComputer.onCreate(SourceFile:1111)

This time, the causing line (1111) is the following one:

myObject = (MyObject) savedInstanceState.getParcelable("myObject");

回答1:

Android has two different classloaders: the framework classloader (which knows how to load Android classes) and the APK classloader (which knows how to load your code). The APK classloader has the framework classloader set as its parent, meaning it can also load Android classes.

Error #2 is likely caused by the Bundle using the framework classloader so it doesn't know of your classes. I think this can happen when Android needs to persist your Bundle and later restore it (for example when running out of memory in the background). You can fix this by setting the APK classloader on the bundle:

savedInstanceState.setClassLoader(getClass().getClassLoader());

Error #1 and #3 are more mysterious, are you perhaps writing null values in writeToParcel()? Android doesn't like that very much I'm afraid.

回答2:

By the look of it, the createFromParcel and newArray should be overridden like this:

public static final Parcelable.Creator<MyObject> CREATOR = new Parcelable.Creator<MyObject>() {
    @Override
    public MyObject createFromParcel(Parcel in) {
        MyObject myObj = new MyObject();
        myObj.intArray = in.readIntArray(...);
        myObj.intValue = in.readInt(...);
        // ....
        // IN THE SAME ORDER THAT IS WRITTEN OUT AS PER writeToParcel!
        //
        return myObj;
    }
    @Override
    public MyObject[] newArray(int size) {
        return new MyObject[size];
    }
};

Edit:

I forgot to mention that for the above to work, there should have been an empty constructor!

public MyObject(){}

回答3:

Before reading from bundle, set ClassLoader:

bundle.setClassLoader(getClass().getClassLoader());

This saved my time!