android - 保存状态自定义 RecyclerView

Question

我制作了一个自定义的 RecyclerView 以便在我的应用程序列表中启用分页。我在恢复状态时遇到了崩溃。也许这次崩溃与支持库中的一个已知错误有关，但从理论上讲，它已在支持库版本 24.0.0 中得到解决:https://code.google.com/p/android/issues/detail?id=196430 , 但它仍然崩溃。

也许我做错了什么？解码时出现 BadParcelableException ClassNotFoundException:android.support.v7.widget.RecyclerView$SavedStateHere 试图重新创建 SavedState。

这是我在 CustomRecyclerView Controller 中的 SavedState 类:

public static class SavedState extends RecyclerView.BaseSavedState {

    public boolean isLastPage;
    public boolean isLoading;
    public int maxPages;
    public int pageSize;
    public int currentPage;
    public int firstVisibleItem;
    public Parcelable layoutManagerState;

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

    public SavedState(Parcel source) {
        super(source);
        this.isLastPage = source.readByte() == 1;
        this.isLoading = source.readByte() == 1;
        this.maxPages = source.readInt();
        this.pageSize = source.readInt();
        this.currentPage = source.readInt();
        this.firstVisibleItem = source.readInt();
        this.layoutManagerState = source.readParcelable(LinearLayoutManager.SavedState.class.getClassLoader());
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        super.writeToParcel(dest, flags);
        dest.writeByte((byte) (isLastPage ? 1 : 0));
        dest.writeByte((byte) (isLoading ? 1 : 0));
        dest.writeInt(maxPages);
        dest.writeInt(pageSize);
        dest.writeInt(currentPage);
        dest.writeInt(firstVisibleItem);
        dest.writeParcelable(layoutManagerState, flags);
    }

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

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

这是我在 Controller 中保存和恢复状态的地方:

public Parcelable saveState(Parcelable superState) {
    SavedState savedState       = new SavedState(superState);
    savedState.isLastPage       = this.isLastPage;
    savedState.isLoading        = this.isLoading;
    savedState.maxPages         = this.maxPages;
    savedState.pageSize         = this.pageSize;
    savedState.currentPage      = this.currentPage;
    savedState.firstVisibleItem = this.firstVisibleItemPosition;

    if (layoutManager != null) {
        savedState.layoutManagerState = layoutManager.onSaveInstanceState();
    }

    return savedState;
}

public Parcelable restoreState(SavedState savedState) {

    this.isLastPage                 = savedState.isLastPage;
    this.isLoading                  = savedState.isLoading;
    this.maxPages                   = savedState.maxPages;
    this.pageSize                   = savedState.pageSize;
    this.currentPage                = savedState.currentPage;
    this.firstVisibleItemPosition   = savedState.firstVisibleItem;

    return savedState.layoutManagerState;
}

下面是自定义 RecyclerView 中的 onSaveInstanceState 和 onRestoreInstanceState 实现:

    @Override
    protected Parcelable onSaveInstanceState() {

        return controller.saveState(super.onSaveInstanceState());
    }

    @Override
    protected void onRestoreInstanceState(Parcelable state) {

        if (state instanceof EndlessRecyclerViewController.SavedState) {

            EndlessRecyclerViewController.SavedState savedState = (EndlessRecyclerViewController.SavedState) state;

            Parcelable layoutManagerState = controller.restoreState(savedState);

            getLayoutManager().onRestoreInstanceState(layoutManagerState);
            super.onRestoreInstanceState(savedState.getSuperState());
        }
        else
            super.onRestoreInstanceState(state);
    }

我还尝试从支持AbsSavedState 扩展SavedState，但仍然崩溃。而且我不确定是否必须调用 LinearLayoutManager 的 onSaveInstanceState...

谢谢!

Answer 1

最后，我使用支持库版本 24.2.1 中的 AbsSavedState(因此，我从中扩展了 SavedState 类)解决了问题。并更改从以下位置接收 Parcel 对象的 constructor:

public SavedState(Parcel source) {
  super(source);
  //... 
}

到:

public SavedState(Parcel source) {
  super(source, LinearLayoutManager.class.getClassLoader());
  //... 
}