Android 正确覆盖RecyclerView动画

我有一个RecycleView，其中显示一个项目列表。我为RecyclerView指定默认的动画设置，如下所示：

recyclerView.setItemAnimator( new DefaultItemAnimator() );

    public class MyAnimator extends RecyclerView.ItemAnimator {

    @Override
    public  boolean animateDisappearance(@NonNull RecyclerView.ViewHolder viewHolder, @NonNull ItemHolderInfo preLayoutInfo, @Nullable ItemHolderInfo postLayoutInfo) {
        return false;
    }

    @Override
    public  boolean animateAppearance(@NonNull RecyclerView.ViewHolder viewHolder, @Nullable ItemHolderInfo preLayoutInfo, @NonNull ItemHolderInfo postLayoutInfo) {
        return false;
    }

    @Override
    public  boolean animatePersistence(@NonNull RecyclerView.ViewHolder viewHolder, @NonNull ItemHolderInfo preLayoutInfo, @NonNull ItemHolderInfo postLayoutInfo) {
        return false;
    }

    @Override
    public  boolean animateChange(@NonNull RecyclerView.ViewHolder oldHolder, @NonNull RecyclerView.ViewHolder newHolder, @NonNull ItemHolderInfo preLayoutInfo, @NonNull ItemHolderInfo postLayoutInfo) {
        return false;
    }

    @Override
    public  void runPendingAnimations() {

    }

    @Override
    public  void endAnimation(RecyclerView.ViewHolder item) {

    }

    @Override
    public  void endAnimations() {

    }

    @Override
    public  boolean isRunning() {
        return false;
    }
}

一切都很好，但我想使用自己的自定义动画来添加/删除/更新列表中的元素

我定义了一个自定义animator类，如下所示：

recyclerView.setItemAnimator( new DefaultItemAnimator() );

    public class MyAnimator extends RecyclerView.ItemAnimator {

    @Override
    public  boolean animateDisappearance(@NonNull RecyclerView.ViewHolder viewHolder, @NonNull ItemHolderInfo preLayoutInfo, @Nullable ItemHolderInfo postLayoutInfo) {
        return false;
    }

    @Override
    public  boolean animateAppearance(@NonNull RecyclerView.ViewHolder viewHolder, @Nullable ItemHolderInfo preLayoutInfo, @NonNull ItemHolderInfo postLayoutInfo) {
        return false;
    }

    @Override
    public  boolean animatePersistence(@NonNull RecyclerView.ViewHolder viewHolder, @NonNull ItemHolderInfo preLayoutInfo, @NonNull ItemHolderInfo postLayoutInfo) {
        return false;
    }

    @Override
    public  boolean animateChange(@NonNull RecyclerView.ViewHolder oldHolder, @NonNull RecyclerView.ViewHolder newHolder, @NonNull ItemHolderInfo preLayoutInfo, @NonNull ItemHolderInfo postLayoutInfo) {
        return false;
    }

    @Override
    public  void runPendingAnimations() {

    }

    @Override
    public  void endAnimation(RecyclerView.ViewHolder item) {

    }

    @Override
    public  void endAnimations() {

    }

    @Override
    public  boolean isRunning() {
        return false;
    }
}

并将其设置为与我为DefaultItemAnimator所做的相同的方式。动画不再播放了，所以我想它起作用了，但问题是有时项目会堆叠在一起，当我移除所有项目时，有些项目仍然保留，所以我想我遗漏了一些东西

据我所知，animateDisappearance是一个在从列表中删除项时被调用的方法。如果我返回false，就我所知，它应该跳过动画，对吗

我走对了吗？当我在github上寻找这方面的例子时，结果很少，总的来说，我似乎找不到任何基本的代码示例如何做到这一点，我找到的都是数千行代码

在不使用任何外部库的情况下，如何用自己的动画覆盖默认的添加/删除动画？谢谢

编辑：

我可以通过以下方式覆盖默认动画：

        recyclerView.setItemAnimator(new DefaultItemAnimator() {
            @Override
            public boolean animateRemove(RecyclerView.ViewHolder holder) {
                holder.itemView.clearAnimation();
                final RecyclerView.ViewHolder h = holder;
                holder.itemView.animate()
                        .alpha(0)
                        .setInterpolator(new AccelerateInterpolator(2.f))
                        .setDuration(1350)
                        .setListener(new AnimatorListenerAdapter() {
                            @Override
                            public void onAnimationEnd(Animator animation) {
                                dispatchRemoveFinished(h);
                            }
                        })
                        .start();
                //
                return false;
            }
        } );

---

动画工作得非常完美，但由于某些原因，似乎“dispatchRemoveFinished”会立即触发，因此，它们不会在动画之后调整其余元素，而是在移除视图后立即执行此操作。有什么方法可以解决这个问题吗？

在实现您的

RecyclerView.ItemAnimator

时，您必须遵循一些规则，否则RecyclerView状态将变得混乱：

所有返回false的空方法必须至少调用

dispatchAnimationFinished（viewHolder）

，以清除动画状态

如果这些方法要启动动画，您应该

dispatchAnimationStarted（viewHolder）

，存储动画请求并返回true以调用

runPendingAnimations（）

您需要跟踪正在进行的动画，以便能够正确地取消它们，您将获得对已设置动画的项目的请求

下面是一个示例

itemaniator

，它仅为移除和移动设置动画。请注意，充当动画数据持有者和动画状态侦听器的内部类：

public class RecAnimator extends RecyclerView.ItemAnimator {

private final static String TAG = "RecAnimator";

private final static int ANIMATION_TYPE_DISAPPEAR = 1;
private final static int ANIMATION_TYPE_MOVE = 2;

// must keep track of all pending/ongoing animations.
private final ArrayList<AnimInfo> pending = new ArrayList<>();
private final HashMap<RecyclerView.ViewHolder, AnimInfo> disappearances = new HashMap<>();
private final HashMap<RecyclerView.ViewHolder, AnimInfo> persistences = new HashMap<>();

@Override
public boolean animateDisappearance(@NonNull RecyclerView.ViewHolder viewHolder, @NonNull ItemHolderInfo preLayoutInfo, @Nullable ItemHolderInfo postLayoutInfo) {
    pending.add(new AnimInfo(viewHolder, ANIMATION_TYPE_DISAPPEAR, 0));
    dispatchAnimationStarted(viewHolder);
    // new pending animation added, return true to indicate we want a call to runPendingAnimations()
    return true;
}

@Override
public boolean animateAppearance(@NonNull RecyclerView.ViewHolder viewHolder, @Nullable ItemHolderInfo preLayoutInfo, @NonNull ItemHolderInfo postLayoutInfo) {
    dispatchAnimationFinished(viewHolder);
    return false;
}

@Override
public boolean animatePersistence(@NonNull RecyclerView.ViewHolder viewHolder, @NonNull ItemHolderInfo preLayoutInfo, @NonNull ItemHolderInfo postLayoutInfo) {
    if (preLayoutInfo.top != postLayoutInfo.top) {
        // required movement
        int topDiff = preLayoutInfo.top - postLayoutInfo.top;
        AnimInfo per = persistences.get(viewHolder);
        if(per != null && per.isRunning) {
            // there is already an ongoing animation - update it instead
            per.top = per.holder.itemView.getTranslationY() + topDiff;
            per.start();
            // discard this animatePersistence call
            dispatchAnimationFinished(viewHolder);
            return false;
        }
        pending.add(new AnimInfo(viewHolder, ANIMATION_TYPE_MOVE, topDiff));
        dispatchAnimationStarted(viewHolder);
        // new pending animation added, return true to indicate we want a call to runPendingAnimations()
        return true;
    }
    dispatchAnimationFinished(viewHolder);
    return false;
}

@Override
public boolean animateChange(@NonNull RecyclerView.ViewHolder oldHolder, @NonNull RecyclerView.ViewHolder newHolder, @NonNull ItemHolderInfo preLayoutInfo, @NonNull ItemHolderInfo postLayoutInfo) {
    dispatchAnimationFinished(oldHolder);
    dispatchAnimationFinished(newHolder);
    return false;
}

@Override
public void runPendingAnimations() {
    for (AnimInfo ai: pending) {
        ai.start();
    }
    pending.clear();
}

@Override
public void endAnimation(RecyclerView.ViewHolder item) {
    AnimInfo ai = disappearances.get(item);
    if (ai != null && ai.isRunning) {
        ai.holder.itemView.animate().cancel();
    }
    ai = persistences.get(item);
    if (ai != null && ai.isRunning) {
        ai.holder.itemView.animate().cancel();
    }
}

@Override
public void endAnimations() {
    for (AnimInfo ai: disappearances.values())
        if (ai.isRunning)
            ai.holder.itemView.animate().cancel();

    for (AnimInfo ai: persistences.values())
        if (ai.isRunning)
            ai.holder.itemView.animate().cancel();
}

@Override
public boolean isRunning() {
    return !pending.isEmpty() &&
            !disappearances.isEmpty() &&
            !persistences.isEmpty();
}

/** 
 * This is container for each animation. It's also cancel/end listener for them.
 * */
private final class AnimInfo implements Animator.AnimatorListener {
    private final RecyclerView.ViewHolder holder;
    private final int animationType;
    private float top;
    private boolean isRunning = false;

    private AnimInfo(RecyclerView.ViewHolder holder, int animationType, float top) {
        this.holder = holder;
        this.animationType = animationType;
        this.top = top;
    }

    void start(){
        View itemView = holder.itemView;
        itemView.animate().setListener(this);
        switch (animationType) {
            case ANIMATION_TYPE_DISAPPEAR:
                itemView.setPivotY(0f);
                itemView.animate().scaleX(0f).scaleY(0f).setDuration(getRemoveDuration());
                disappearances.put(holder, this);   // must keep track of all animations
                break;
            case ANIMATION_TYPE_MOVE:
                itemView.setTranslationY(top);
                itemView.animate().translationY(0f).setDuration(getMoveDuration());
                persistences.put(holder, this);     // must keep track of all animations
                break;
        }
        isRunning = true;
    }

    private void resetViewHolderState(){
        // reset state as if no animation was ran
        switch (animationType) {
            case ANIMATION_TYPE_DISAPPEAR:
                holder.itemView.setScaleX(1f);
                holder.itemView.setScaleY(1f);
                break;
            case ANIMATION_TYPE_MOVE:
                holder.itemView.setTranslationY(0f);
                break;
        }
    }

    @Override
    public void onAnimationEnd(Animator animation) {
        switch (animationType) {
            case ANIMATION_TYPE_DISAPPEAR:
                disappearances.remove(holder);
                break;
            case ANIMATION_TYPE_MOVE:
                persistences.remove(holder);
                break;
        }
        resetViewHolderState();
        holder.itemView.animate().setListener(null); // clear listener
        dispatchAnimationFinished(holder);
        if (!isRunning())
            dispatchAnimationsFinished();
        isRunning = false;
    }

    @Override
    public void onAnimationCancel(Animator animation) {
        // jump to end state
        switch (animationType) {
            case ANIMATION_TYPE_DISAPPEAR:
                holder.itemView.setScaleX(0f);
                holder.itemView.setScaleY(0f);
                break;
            case ANIMATION_TYPE_MOVE:
                holder.itemView.setTranslationY(0f);
                break;
        }
    }

    @Override
    public void onAnimationStart(Animator animation) {

    }

    @Override
    public void onAnimationRepeat(Animator animation) {

    }
}
}

public类RecAnimator扩展了RecyclerView.ItemAnimator{
私有最终静态字符串TAG=“RecAnimator”；
私有最终静态int动画类型=1；
私有最终静态int动画类型移动=2；
//必须跟踪所有挂起/正在进行的动画。
私有的最终ArrayList类，为您将
animate…
方法解析为
animateMove
，
animateMove
等。
…有一些例子。要使用其中任何一个，我需要使用BaseItemAnimator类，它几乎有1k行代码：这是覆盖默认动画的唯一方法吗？似乎有应该是一个较短的方法，是吗？这是
DefaultItemAnimator
：-您可以跳过实现一些接口方法，只需调用
super.methodName（）
在它们内部…除非调用
super
类，只返回
false
，否则不会成功。对不起，我不确定我是否完全理解。你的意思是覆盖DefaultItemAnimator方法（就像我在编辑的问题中所做的那样）最后调用super？您需要实现
animatePersistence
，以便在移除项目时设置移动动画。