我的自定义视图不会保存它的状态

Question

我使用以下代码创建了自定义视图（为简洁起见进行了编辑）：

public class StampView extends View {

    // View State items
    private String stampText, stampTimeStamp;
    private int stampIconId;
    private boolean stamped;

    public StampView(Context context, @Nullable AttributeSet attrs) {
        // REMOVED
    }

    /**
     *
     * See: http://trickyandroid.com/saving-android-view-state-correctly/
     *
     * @return Returns a Parcelable object containing the view's current dynamic
     * state, or null if there is nothing interesting to save.
     * @see #onRestoreInstanceState(Parcelable)
     * @see #saveHierarchyState(SparseArray)
     * @see #dispatchSaveInstanceState(SparseArray)
     * @see #setSaveEnabled(boolean)
     */
    @Nullable @Override protected Parcelable onSaveInstanceState() {
        Parcelable superState = super.onSaveInstanceState();
        SavedState ss = new SavedState(superState);

        // We need to save 4 extra things to save state.
        // StampText string
        ss.stampText = stampText;
        // Icon ID int
        ss.stampIconId = stampIconId;

        // Timestamp string
        ss.stampTimestamp = stampTimeStamp;

        // Stamped boolean
        ss.stamped = stamped;

        // An example
        // ss.state = customState;
        return ss;
    }

    @Override
    public void onRestoreInstanceState(Parcelable state) {
        SavedState ss = (SavedState) state;
        super.onRestoreInstanceState(ss.getSuperState());

        // our custom saved state items
        setStampIcon(ss.stampIconId);
        setStampTitleText(ss.stampText);
        setStampTimeStampText(ss.stampTimestamp);
        setStamped(ss.stamped);
    }

    /**
     * Extending the BaseSavedState allows us to extend state saving and save our own custom state variables above.
     *
     **/
    static class SavedState extends BaseSavedState {
        int stampIconId;
        String stampText, stampTimestamp;
        boolean stamped;

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

        // Reading In from a Parcel
        private SavedState(Parcel in) {
            super(in);
            stampIconId = in.readInt();
            stampText = in.readString();
            stampTimestamp = in.readString();
            stamped = in.readByte() != 0;  //myBoolean == true if byte != 0
        }

        // Writing to a Parcel
        @Override
        public void writeToParcel(Parcel out, int flags) {
            super.writeToParcel(out, flags);
            // I assume order matters, since we don't seem to be writing the key values
            out.writeInt(stampIconId);
            out.writeString(stampText);
            out.writeString(stampTimestamp);
            out.writeByte((byte) (stamped ? 1 : 0));     //if myBoolean == true, byte == 1
        }

        public static final Parcelable.Creator<SavedState> CREATOR
                = new Parcelable.Creator<SavedState>() {
            public SavedState createFromParcel(Parcel in) {
                return new SavedState(in);
            }

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


    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        //REMOVED
    }

    @Override
    public void draw(Canvas canvas) {
        super.draw(canvas);
        Rect bounds = new Rect(0,0,mWidth,mHeight);

        if(stamped){
            // Draw the stamp

        } else {
            // Draw a placeholder instead
        }
    }

    public void constructStampViewFromPOI(POI poi){
        //removed
    }

    private void setStampTitleText (String titleString){
        this.stampText = titleString;
    }

    private void setStampTimeStampText (String tsString){
        this.stampTimeStamp = tsString;
    }



    private void setStampIcon(int collectionIconId) {
        // removed
    }

    public void setStamped(boolean bool) {
        this.stamped = bool;
        this.invalidate();
    }
}

我的自定义视图相当简单，它可以绘制出自己的 2 个版本，这取决于一个名为 'stamped' 的布尔值。您可以在 draw 方法中看到这一点。我将这个自定义视图放在一个包含 6 个项目的 RecyclerView 中的 Viewholder 中。我的 activity 应具有以下布局：

Viewholder #1 - Stamp view (#1 data) Viewholder #2 - Placeholder view Viewholder #3 - Placeholder view Viewholder #4 - Placeholder view Viewholder #5 - Placeholder view Viewholder #6 - Stamped view (#6 data)

但是如果我调试我的 activity 我看到我的自定义视图被绘制了 6 次，一次是为 recyclerview 中的每个 viewholder 绘制一次，然后由于某种原因它再次重新绘制所有 6 次。在第二遍中，它使用 Viewholder #6 的数据弄乱了 Viewholder #5 中 StampView 的状态。我最终得到了这个布局：

Viewholder #1 - Stamp view (#1 data) Viewholder #2 - Placeholder view Viewholder #3 - Placeholder view Viewholder #4 - Placeholder view Viewholder #5 - Stamped view (#6 data) Viewholder #6 - Stamped view (#6 data)

点击查看器会将我带到 DetailsActivity，如果我这样做然后 return 回到我的 RecyclerView 我看到这个布局：

Viewholder #1 - Stamp view (#1 data) Viewholder #2 - Placeholder view Viewholder #3 - Placeholder view Viewholder #4 - Stamped view (#6 data) Viewholder #5 - Stamped view (#6 data) Viewholder #6 - Stamped view (#6 data)

如果我再这样做两次，我最终会得到这个乱七八糟的布局：

Viewholder #1 - Stamp view (#1 data) Viewholder #2 - Stamped view (#6 data) Viewholder #3 - Stamped view (#6 data) Viewholder #4 - Stamped view (#6 data) Viewholder #5 - Stamped view (#6 data) Viewholder #6 - Stamped view (#6 data)

在我看来，我的自定义视图没有保存它的状态 and/or 当我在屏幕上有多个实例时会混淆它的状态。我发现 this post 提到了这类问题，并试图实现它保存状态的方式，但我无法在我的视图中触发 onSaveInstanceState 方法。我已经尝试了提到的所有内容，包括 setSaveEnabled(true); 在我的自定义视图和 viewholder 中，我已经尝试为自定义视图的每个实例设置一个自定义 id...但没有任何效果。

有人可以向我解释我做错了什么吗？
我是否正确认为这是一个状态保存问题？
我应该如何以及在何处保存我的自定义视图状态？在视图内部还是 activity 应该保存我的视图状态，因为它是视图持有者的一部分？

编辑：如果有帮助，这里是查看器代码：

@Override
public void onBindViewHolder(POI_View_Holder holder, int position) {

    //Instead lets use the viewholder bind method to assign content
    holder.bind(mPOIslist.get(position), listener);
}

static class POI_View_Holder extends RecyclerView.ViewHolder {

        // Variables for the ViewHolder
        private TextView name;
        private TextView positionText;
        private StampView stampView;

        POI_View_Holder(View itemView) {
            super(itemView);
            name = itemView.findViewById(R.id.poi_nameTV);
            positionText= itemView.findViewById(R.id.poi_positionTV);
            stampView = itemView.findViewById(R.id.poi_StampView);

//            stampView.setSaveEnabled(true); // force state saving
//            stampView.setId(getPosition());
        }

        public void bind(final POI poi, final OnPOIClickListener listener){

            // Set POI information in viewHolder
            name.setText(poi.getName());
            positionText.setText(String.valueOf(poi.getCollectionPosition()));

            if(poi.isStamped()){
                stampView.setElevation(4);
                stampView.setTranslationZ(4);
                stampView.setClipToOutline(true);
                // stampView.invalidate();
                stampView.constructStampViewFromPOI(poi);
            } else {
                stampView.setElevation(0);
                stampView.setTranslationZ(0);
            }
            Log.d("ViewHolder-", "bind: method fired");
            itemView.setOnClickListener(new View.OnClickListener() {
                @Override public void onClick(View view) {
                    listener.OnPOIClick(poi);
                }
            });
        }
    }

EDIT2：这是我的 activity 保存状态代码：

protected void onSaveInstanceState(Bundle state) {
    super.onSaveInstanceState(state);

    // Save layoutManager state
    mListState = mLayoutManager.onSaveInstanceState();
    state.putParcelable(LIST_STATE_KEY, mListState);

    mCollectionList = Parcels.wrap(mListOfPOIsInCollection);
    state.putParcelable(COLLECTION_ARRAYLIST_STATE_KEY,mCollectionList);
}

protected void onRestoreInstanceState(Bundle state) {
    super.onRestoreInstanceState(state);

    // Retrieve list state and list/item positions
    if(state != null) {
        mListState = state.getParcelable(LIST_STATE_KEY);
        //mCollectionList = state.getParcelable(COLLECTION_ARRAYLIST_STATE_KEY);
        mListOfPOIsInCollection = Parcels.unwrap(state.getParcelable(COLLECTION_ARRAYLIST_STATE_KEY));
    }
}

@Override protected void onResume() {
    super.onResume();

    if (mListState != null) {
        mLayoutManager.onRestoreInstanceState(mListState);
    }
}

Answer 1

View.onSaveInstanceState() 和 View.onRestoreInstanceState(Parcelable) 意味着当您的视图被销毁然后与 activity 一起重新创建时由系统调用，也许当您旋转 phone. RecyclerView.

没有以任何方式使用它们

我觉得你至少有一个问题，可能有两个。

首先，在适配器的 onBindViewHolder() 方法中，您需要确保始终设置每个 sub-view 的状态。人们运行经常遇到这样的问题，他们有时只设置 sub-view 的状态，这会在回收视图时导致问题。例如：

if (myItem.isStamped()) {
    holder.stampView.setStamped(true);
}

如果您的视图被回收并 re-bound 到 non-stamped 数据项，这将中断。因为您只在印记存在时设置 holder.stampView 的状态，所以当印记不存在时您不会清除它。相反，你应该写：

if (myItem.isStamped()) {
    holder.stampView.setStamped(true);
} else {
    holder.stampView.setStamped(false);
}

或者只是

holder.stampView.setStamped(myItem.isStamped());

其次，您的适配器数据听起来可能 saved/restored 不正确。我真的不能说这个，因为我没有你的任何 activity 代码，但你可以利用 Activity.onSaveInstanceState(Bundle) 和传递给 onCreate() 的 savedInstanceState 包来保存它。

我的自定义视图不会保存它的状态

My custom view will not save it's state

android

android-view

android-viewholder

android-recyclerview