在 RecyclerView 中配置 ItemTouchHelper 以使 Snackbar 被显示的另一个 Snackbar 解散答案

【问题标题】：Configure ItemTouchHelper in RecyclerView to work for Snackbar being dismissed by another Snackbar being displayed在 RecyclerView 中配置 ItemTouchHelper 以使 Snackbar 被显示的另一个 Snackbar 解散
【发布时间】：2020-09-12 14:38:59
【问题描述】：

我的应用中有一个包含消息的 RecyclerView。在向右滑动时，我将其配置为删除消息，在向左滑动时，将其存档。下面是删除和归档相关的ItemTouchHelper部分的代码：

if (direction == ItemTouchHelper.LEFT) {
    donorMessagesAdapter.deleteMessages(position);
} else if (direction == ItemTouchHelper.RIGHT) {
    donorMessagesAdapter.archiveMessages(position);
}

这里是 deleteMessages() 和 archiveMessages() 函数（它们几乎相同）：

public void deleteMessages(final int position) {
    recentlyDeletedPeer = sortedPeers.get(position);
    recentlyDeletedPeerPosition = position;

    sortedPeers.remove(position);
    notifyItemRemoved(position);

    Snackbar snackbar = Snackbar.make(activity.findViewById(R.id.constraint_layout),
            "Messages Deleted", Snackbar.LENGTH_LONG);
    snackbar.setAction("UNDO", new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            sortedPeers.add(recentlyDeletedPeerPosition, recentlyDeletedPeer);
            notifyItemInserted(recentlyDeletedPeerPosition);
        }
    });
    snackbar.setActionTextColor(0xff0099ff);

    snackbar.addCallback(new Snackbar.Callback() {
        @Override
        public void onDismissed(Snackbar snackbar, int event) {
            if (event == Snackbar.Callback.DISMISS_EVENT_TIMEOUT || event == Snackbar.Callback.DISMISS_EVENT_CONSECUTIVE) {
                MainActivity.database.receivedMessagesDao().deleteAllReceivedMessagesFromSender(email, recentlyDeletedPeer);
                MainActivity.database.sentMessagesDao().deleteAllSentMessagesFromReceiver(email, recentlyDeletedPeer);
            }
        }
    });

    snackbar.show();
}

public void archiveMessages(final int position) {
    recentlyArchivedPeer = sortedPeers.get(position);
    recentlyArchivedPeerPosition = position;

    sortedPeers.remove(position);
    notifyItemRemoved(position);

    Snackbar snackbar = Snackbar.make(activity.findViewById(R.id.constraint_layout),
            "Messages archived", Snackbar.LENGTH_LONG);
    snackbar.setAction("UNDO", new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            sortedPeers.add(recentlyArchivedPeerPosition, recentlyArchivedPeer);
            notifyItemInserted(recentlyArchivedPeerPosition);
        }
    });
    snackbar.setActionTextColor(0xff0099ff);

    snackbar.addCallback(new Snackbar.Callback() {
        @Override
        public void onDismissed(Snackbar snackbar, int event) {
            if (event == Snackbar.Callback.DISMISS_EVENT_TIMEOUT || event == Snackbar.Callback.DISMISS_EVENT_CONSECUTIVE) {
                MainActivity.database.receivedMessagesDao().archive(email, recentlyArchivedPeer);
                MainActivity.database.sentMessagesDao().archive(email, recentlyArchivedPeer);
            }
        }
    });

    snackbar.show();
}

删除/归档一条消息时一切正常。在 Snackbar 消失后，滑动会删除或存档消息，当我单击撤消时，删除/存档会反转。删除/归档多条消息时会出现问题。

问题 1： 当我删除/归档多条消息而不等待每条消息的 Snackbar 消失时，除了第一条消息之外的所有消息都被删除/归档。让我感到奇怪的是，并不是只有最后一条消息被删除/归档，除了第一条消息之外的所有消息都被删除/归档。

问题2：当我删除/归档多条消息而不等待每条消息的Snackbar消失时，如果我按UNDO，即在Snackbar上删除最后一条消息/存档，应用程序崩溃。

顺便说一句，我正在使用 Room Library 将消息存储在数据库中（由 MainActivity.database 引用）。

我认为问题出在 Snackbar 的 addCallback() 函数中。我应该为event == Snackbar.Callback.DISMISS_EVENT_CONSECUTIVE 和event == Snackbar.Callback.DISMISS_EVENT_TIMEOUT 做一些不同的事情，但我不知道我应该做些什么不同的事情，以及究竟是什么导致了问题。

这是我的整个适配器类供参考（错误消息行旁边标有注释）：

package com.example.treeapp;

import android.app.Activity;
import android.content.Intent;
import android.os.Handler;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import com.google.android.material.snackbar.Snackbar;
import com.mikhaellopez.circularimageview.CircularImageView;

import java.time.LocalDateTime;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;

public class DonorMessagesAdapter extends RecyclerView.Adapter<DonorMessagesAdapter.DonorMessagesViewHolder> { // line 24 in error message
    private Activity activity;
    public String email;
    public List<String> sortedPeers;
    public static CircularImageView imageView;
    private String recentlyDeletedPeer;
    private int recentlyDeletedPeerPosition;
    private String recentlyArchivedPeer;
    private int recentlyArchivedPeerPosition;

    public static class DonorMessagesViewHolder extends RecyclerView.ViewHolder {
        public Button middleButton;
        public TextView nameTextView;
        public TextView messageTextView;

        DonorMessagesViewHolder(View view) {
            super(view);

            middleButton = view.findViewById(R.id.middle_button);
            imageView = view.findViewById(R.id.image_view);
            nameTextView = view.findViewById(R.id.text_view_name);
            messageTextView = view.findViewById(R.id.text_view_message);
        }
    }

    DonorMessagesAdapter(Activity activity, String email) {
        this.activity = activity;
        this.email = email;
        this.sortedPeers = getSortedPeers(email);
    }

    @NonNull
    @Override
    public DonorMessagesViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.message, parent, false);

        return new DonorMessagesViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull DonorMessagesViewHolder holder, int position) {
        final String current = sortedPeers.get(position);

        // Start of getting last message
        String lastMessage;
        String lastMessageType;
        List<Integer> receivedMessages = MainActivity.database.receivedMessagesDao().getMessagesToReceiverFromSender(email, current, 0);
        List<Integer> sentMessages = MainActivity.database.sentMessagesDao().getMessagesBySenderToReceiver(email, current, 0);

        if (sentMessages.size() == 0) {
            lastMessage = MainActivity.database.receivedMessagesDao().getMessage(receivedMessages.get(receivedMessages.size() - 1));  // line 74 in error message
            lastMessageType = "received";
            if (MainActivity.database.receivedMessagesDao().getImage(receivedMessages.get(receivedMessages.size() - 1)) == 1) {
                lastMessageType = "receivedImage";
            }
        } else if (receivedMessages.size() == 0) {
            lastMessage = MainActivity.database.sentMessagesDao().getMessage(sentMessages.get(sentMessages.size() - 1));
            lastMessageType = "sent";
            if (MainActivity.database.sentMessagesDao().getImage(sentMessages.get(sentMessages.size() - 1)) == 1) {
                lastMessageType = "sentImage";
            }
        } else {
            LocalDateTime lastReceivedMessageTime = LocalDateTime.parse(MainActivity.database.receivedMessagesDao().getTime(receivedMessages.get(receivedMessages.size() - 1)));
            LocalDateTime lastSentMessageTime = LocalDateTime.parse(MainActivity.database.sentMessagesDao().getTime(sentMessages.get(sentMessages.size() - 1)));

            if (lastReceivedMessageTime.isAfter(lastSentMessageTime)) {
                lastMessage = MainActivity.database.receivedMessagesDao().getMessage(receivedMessages.get(receivedMessages.size() - 1));
                lastMessageType = "received";
                if (MainActivity.database.receivedMessagesDao().getImage(receivedMessages.get(receivedMessages.size() - 1)) == 1) {
                    lastMessageType = "receivedImage";
                }
            } else {
                lastMessage = MainActivity.database.sentMessagesDao().getMessage(sentMessages.get(sentMessages.size() - 1));
                lastMessageType = "sent";
                if (MainActivity.database.sentMessagesDao().getImage(sentMessages.get(sentMessages.size() - 1)) == 1) {
                    lastMessageType = "sentImage";
                }
            }
        }
        // End of getting last message

        if (MainActivity.database.plantersDao().checkEmail(current) == 1) {
            if (MainActivity.database.plantersDao().getImageUrl(current) != null) {
                new DownloadImageTask(imageView).execute(MainActivity.database.plantersDao().getImageUrl(current));
            }
        } else if (MainActivity.database.donorsDao().checkEmail(current) == 1) {
            if (MainActivity.database.donorsDao().getImageUrl(current) != null) {
                new DownloadImageTask(imageView).execute(MainActivity.database.donorsDao().getImageUrl(current));
            }
        }

        if (MainActivity.database.plantersDao().checkEmail(current) == 1) {
            holder.nameTextView.setText(MainActivity.database.plantersDao().getName(current));
        } else if (MainActivity.database.donorsDao().checkEmail(current) == 1) {
            holder.nameTextView.setText(MainActivity.database.donorsDao().getName(current));
        }

        if (lastMessageType.equals("received")) {
            if (lastMessage.length() > 17) {
                holder.messageTextView.setText(lastMessage.substring(0, 16) + "...");
            } else {
                holder.messageTextView.setText(lastMessage);
            }
        } else if (lastMessageType.equals("sent")) {
            if (lastMessage.length() > 12) {
                holder.messageTextView.setText("You: " + lastMessage.substring(0, 11) + "...");
            } else {
                holder.messageTextView.setText("You: " + lastMessage);
            }
        } else if (lastMessageType.equals("receivedImage")) {
            holder.messageTextView.setText("Image");
        } else if (lastMessageType.equals("sentImage")) {
            holder.messageTextView.setText("You: " + "Image");
        }

        holder.middleButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(view.getContext(), MessageActivity.class);
                intent.putExtra("email", email);
                intent.putExtra("peerEmail", current);
                intent.putExtra("archived", 0);

                view.getContext().startActivity(intent);
            }
        });
    }

    @Override
    public int getItemCount() {
        return sortedPeers.size();
    }

    public void reload() {
        sortedPeers = getSortedPeers(email);
        notifyDataSetChanged();
    }

    private List<String> getSortedPeers(String email) {
        List<String> senders = MainActivity.database.receivedMessagesDao().getSendersForReceiver(email, 0);
        List<String> receivers = MainActivity.database.sentMessagesDao().getReceiversForSender(email, 0);

        List<String> peers = new ArrayList<>();
        peers.addAll(senders);
        peers.addAll(receivers);
        peers = new ArrayList<>(new HashSet<>(peers));

        List<String> sortedPeers = new ArrayList<>();
        while (peers.size() > 0) {
            LocalDateTime latestMessageTime = null;
            String latestPeer = null;

            for (String peer : peers) {
                List<Integer> receivedMessages = MainActivity.database.receivedMessagesDao().getMessagesToReceiverFromSender(email, peer, 0);
                List<Integer> sentMessages = MainActivity.database.sentMessagesDao().getMessagesBySenderToReceiver(email, peer, 0);

                LocalDateTime lastMessageTime;
                if (sentMessages.size() == 0) {
                    lastMessageTime = LocalDateTime.parse(MainActivity.database.receivedMessagesDao().getTime(receivedMessages.get(receivedMessages.size() - 1)));
                } else if (receivedMessages.size() == 0) {
                    lastMessageTime = LocalDateTime.parse(MainActivity.database.sentMessagesDao().getTime(sentMessages.get(sentMessages.size() - 1)));
                } else {
                    LocalDateTime lastReceivedMessageTime = LocalDateTime.parse(MainActivity.database.receivedMessagesDao().getTime(receivedMessages.get(receivedMessages.size() - 1)));
                    LocalDateTime lastSentMessageTime = LocalDateTime.parse(MainActivity.database.sentMessagesDao().getTime(sentMessages.get(sentMessages.size() - 1)));

                    if (lastReceivedMessageTime.isAfter(lastSentMessageTime)) {
                        lastMessageTime = lastReceivedMessageTime;
                    } else {
                        lastMessageTime = lastSentMessageTime;
                    }
                }

                if (latestMessageTime != null) {
                    if (lastMessageTime.isAfter(latestMessageTime)) {
                        latestMessageTime = lastMessageTime;
                        latestPeer = peer;
                    }
                } else {
                    latestMessageTime = lastMessageTime;
                    latestPeer = peer;
                }
            }

            sortedPeers.add(latestPeer);
            peers.remove(latestPeer);
        }

        return sortedPeers;
    }

    public void deleteMessages(final int position) {
        recentlyDeletedPeer = sortedPeers.get(position);
        recentlyDeletedPeerPosition = position;

        sortedPeers.remove(position);
        notifyItemRemoved(position);

        Snackbar snackbar = Snackbar.make(activity.findViewById(R.id.constraint_layout),
                "Messages Deleted", Snackbar.LENGTH_LONG);
        snackbar.setAction("UNDO", new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                sortedPeers.add(recentlyDeletedPeerPosition, recentlyDeletedPeer);
                notifyItemInserted(recentlyDeletedPeerPosition);
            }
        });
        snackbar.setActionTextColor(0xff0099ff);

        snackbar.addCallback(new Snackbar.Callback() {
            @Override
            public void onDismissed(Snackbar snackbar, int event) {
                if (event == Snackbar.Callback.DISMISS_EVENT_TIMEOUT || event == Snackbar.Callback.DISMISS_EVENT_CONSECUTIVE) {
                    MainActivity.database.receivedMessagesDao().deleteAllReceivedMessagesFromSender(email, recentlyDeletedPeer);
                    MainActivity.database.sentMessagesDao().deleteAllSentMessagesFromReceiver(email, recentlyDeletedPeer);
                }
            }
        });

        snackbar.show();
    }

    public void archiveMessages(final int position) {
        recentlyArchivedPeer = sortedPeers.get(position);
        recentlyArchivedPeerPosition = position;

        sortedPeers.remove(position);
        notifyItemRemoved(position);

        Snackbar snackbar = Snackbar.make(activity.findViewById(R.id.constraint_layout),
                "Messages archived", Snackbar.LENGTH_LONG);
        snackbar.setAction("UNDO", new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                sortedPeers.add(recentlyArchivedPeerPosition, recentlyArchivedPeer);
                notifyItemInserted(recentlyArchivedPeerPosition);
            }
        });
        snackbar.setActionTextColor(0xff0099ff);

        snackbar.addCallback(new Snackbar.Callback() {
            @Override
            public void onDismissed(Snackbar snackbar, int event) {
                if (event == Snackbar.Callback.DISMISS_EVENT_TIMEOUT || event == Snackbar.Callback.DISMISS_EVENT_CONSECUTIVE) {
                    MainActivity.database.receivedMessagesDao().archive(email, recentlyArchivedPeer);
                    MainActivity.database.sentMessagesDao().archive(email, recentlyArchivedPeer);
                    reload();
                }
            }
        });

        snackbar.show();
    }
}

这是我得到的错误（我的类标有**）：

2020-09-12 19:24:11.547 689-689/com.example.treeapp E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.treeapp, PID: 689
    java.lang.ArrayIndexOutOfBoundsException: length=0; index=-1
        at java.util.ArrayList.get(ArrayList.java:439)
        **at com.example.treeapp.DonorMessagesAdapter.onBindViewHolder(DonorMessagesAdapter.java:74)
        at com.example.treeapp.DonorMessagesAdapter.onBindViewHolder(DonorMessagesAdapter.java:24)**
        at androidx.recyclerview.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:7065)
        at androidx.recyclerview.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:7107)
        at androidx.recyclerview.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:6012)
        at androidx.recyclerview.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:6279)
        at androidx.recyclerview.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:6118)
        at androidx.recyclerview.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:6114)
        at androidx.recyclerview.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2303)
        at androidx.recyclerview.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1627)
        at androidx.recyclerview.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1587)
        at androidx.recyclerview.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:665)
        at androidx.recyclerview.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:4134)
        at androidx.recyclerview.widget.RecyclerView.dispatchLayout(RecyclerView.java:3851)
        at androidx.recyclerview.widget.RecyclerView.onLayout(RecyclerView.java:4404)
        at android.view.View.layout(View.java:20967)
        at android.view.ViewGroup.layout(ViewGroup.java:6440)
        at androidx.constraintlayout.widget.ConstraintLayout.onLayout(ConstraintLayout.java:1762)
        at android.view.View.layout(View.java:20967)
        at android.view.ViewGroup.layout(ViewGroup.java:6440)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
        at android.view.View.layout(View.java:20967)
        at android.view.ViewGroup.layout(ViewGroup.java:6440)
        at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1791)
        at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1635)
        at android.widget.LinearLayout.onLayout(LinearLayout.java:1544)
        at android.view.View.layout(View.java:20967)
        at android.view.ViewGroup.layout(ViewGroup.java:6440)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
        at android.view.View.layout(View.java:20967)
        at android.view.ViewGroup.layout(ViewGroup.java:6440)
        at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1791)
        at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1635)
        at android.widget.LinearLayout.onLayout(LinearLayout.java:1544)
        at android.view.View.layout(View.java:20967)
        at android.view.ViewGroup.layout(ViewGroup.java:6440)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
        at com.android.internal.policy.DecorView.onLayout(DecorView.java:955)
        at android.view.View.layout(View.java:20967)
        at android.view.ViewGroup.layout(ViewGroup.java:6440)
        at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:3092)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2779)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1863)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:8072)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:911)
        at android.view.Choreographer.doCallbacks(Choreographer.java:723)
        at android.view.Choreographer.doFrame(Choreographer.java:658)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:897)
        at android.os.Handler.handleCallback(Handler.java:790)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:164)

【问题讨论】：

标签： android android-recyclerview

【解决方案1】：

要解决您的问题 1，您可以尝试仅检查关闭是否是由点击引起的，例如：

snackbar.addCallback(new Snackbar.Callback() {
    @Override
    public void onDismissed(Snackbar snackbar, int event) {
        if (event != Snackbar.Callback.DISMISS_EVENT_ACTION) {
            MainActivity.database.receivedMessagesDao().deleteAllReceivedMessagesFromSender(email, recentlyDeletedPeer);
            MainActivity.database.sentMessagesDao().deleteAllSentMessagesFromReceiver(email, recentlyDeletedPeer);
        }
    }
});

至于您的第二个问题，发生崩溃是因为您只检查 sentMessages 列表是否为空

if (sentMessages.size() == 0) {
        lastMessage = MainActivity.database.receivedMessagesDao().getMessage(receivedMessages.get(receivedMessages.size() - 1));  // line 74 in error message
        lastMessageType = "received";
        if (MainActivity.database.receivedMessagesDao().getImage(receivedMessages.get(receivedMessages.size() - 1)) == 1) {
            lastMessageType = "receivedImage";
        }
    }

你在这里忘记做的是检查 reveivedMessages 是否也是空的。例如：

if (sentMessages.size() == 0) {
    if(receivedMessages.size() != 0) {
        lastMessage = MainActivity.database.receivedMessagesDao().getMessage(receivedMessages.get(receivedMessages.size() - 1));  // line 74 in error message
        lastMessageType = "received";
        if (MainActivity.database.receivedMessagesDao().getImage(receivedMessages.get(receivedMessages.size() - 1)) == 1) {
            lastMessageType = "receivedImage";
        }
    }
}

发生的情况是您的 receivedMessages 列表也是空的，这意味着您尝试在位置 -1 获取项目，这显然不起作用。

即使这些技巧解决了您的问题，您也应该认真考虑如何访问数据库中的数据，因为您似乎在 UI 线程上执行所有调用，这是不可取的，因为它会阻塞 UI 线程。

【讨论】：

我实施了您的第一个建议，但没有任何影响。至于第二个，我已经实现了 getSortedPeers() 并且数据库是 sortedPeers 只有在它有接收消息或发送消息时才应该有一个对等点。换句话说，如果 sentMessages.size() = 0 和 receivedMessages.size() = 0，则变量不应位于 sortedPeers 中。感谢您的帮助。
好的，但是关于你的第二个问题，这肯定是发生了什么，因为 receivedMessages.size() 必须为 0 才能获得这个 OutOfBoundException。它在堆栈跟踪中说长度为 0，您尝试访问的索引为 -1