CustomViewWithStateRestoration.java

/**
 * Custom view that handles view state restoration properly.
 * This process is to be used when using non-unique ids which causes the state restoration to lose its reference.
 * It basically handles the state restoration by creating a SparseArray for each children views thus avoiding the non-unique id issue.
 * @see <a href="http://trickyandroid.com/saving-android-view-state-correctly/">http://trickyandroid.com/saving-android-view-state-correctly/</a>
 * Created by StephenVinouze on 05/02/2016.
 */
public class CustomViewWithStateRestoration extends ViewGroup {

    public CustomViewWithStateRestoration(Context context) {
        super(context);
    }

    public CustomViewWithStateRestoration(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    public Parcelable onSaveInstanceState() {
        Parcelable superState = super.onSaveInstanceState();
        SavedState ss = new SavedState(superState);
        ss.childrenStates = new SparseArray();
        for (int i = 0; i < getChildCount(); i++) {
            getChildAt(i).saveHierarchyState(ss.childrenStates);
        }
        return ss;
    }

    @Override
    public void onRestoreInstanceState(Parcelable state) {
        SavedState ss = (SavedState) state;
        super.onRestoreInstanceState(ss.getSuperState());
        for (int i = 0; i < getChildCount(); i++) {
            getChildAt(i).restoreHierarchyState(ss.childrenStates);
        }
    }

    @Override
    protected void dispatchSaveInstanceState(SparseArray<Parcelable> container) {
        dispatchFreezeSelfOnly(container);
    }

    @Override
    protected void dispatchRestoreInstanceState(SparseArray<Parcelable> container) {
        dispatchThawSelfOnly(container);
    }

    static class SavedState extends BaseSavedState {
        SparseArray childrenStates;

        SavedState(Parcelable superState) {
            super(superState);
        }

        private SavedState(Parcel in, ClassLoader classLoader) {
            super(in);
            childrenStates = in.readSparseArray(classLoader);
        }

        @Override
        public void writeToParcel(Parcel out, int flags) {
            super.writeToParcel(out, flags);
            out.writeSparseArray(childrenStates);
        }

        public static final ClassLoaderCreator<SavedState> CREATOR
                = new ClassLoaderCreator<SavedState>() {
            @Override
            public SavedState createFromParcel(Parcel source, ClassLoader loader) {
                return new SavedState(source, loader);
            }

            @Override
            public SavedState createFromParcel(Parcel source) {
                return createFromParcel(null);
            }

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

}