android - 当编译器没有给出任何错误时，为什么 RecyclerView 不工作？

Question

通常，我不会问这样的问题；我做了我的研究，至少能够在 StackOverflow 上提问之前找出问题所在。但这一次，即使经过彻底研究和一遍又一遍地查看我的代码，我什至无法确定问题所在。因此，对于提出如此广泛的问题，我深表歉意。
我的应用程序中有一些 RecyclerViews(准确地说是 9 个)。其中一个正在工作，八个没有。我一遍又一遍地查看我的代码，但我似乎无法确定问题所在。我将粘贴一个回收器 View 及其适配器的代码。这是我对单个元素的布局:

这是我的单个元素布局的代码(我只是发布它让人们知道ID):

    <?xml version="1.0" encoding="utf-8"?>
    <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:background="#0099ff">

        <androidx.constraintlayout.widget.Guideline
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/left_guideline_view"
            app:layout_constraintGuide_percent=".12077"
            android:orientation="vertical"/>

        <androidx.constraintlayout.widget.Guideline
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/right_guideline_view"
            app:layout_constraintGuide_percent=".87923"
            android:orientation="vertical"/>

        <androidx.constraintlayout.widget.Guideline
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/left_guideline_image_view"
            app:layout_constraintGuide_percent=".16908"
            android:orientation="vertical"/>

        <androidx.constraintlayout.widget.Guideline
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/top_guideline_image_view"
            app:layout_constraintGuide_percent=".14706"
            android:orientation="horizontal"/>

        <androidx.constraintlayout.widget.Guideline
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/left_guideline_text_view"
            app:layout_constraintGuide_percent=".37198"
            android:orientation="vertical"/>

        <androidx.constraintlayout.widget.Guideline
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/right_guideline_text_view"
            app:layout_constraintGuide_percent=".83"
            android:orientation="vertical"/>

        <androidx.constraintlayout.widget.Guideline
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/top_guideline_text_view_order"
            app:layout_constraintGuide_percent=".13235"
            android:orientation="horizontal"/>

        <androidx.constraintlayout.widget.Guideline
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/bottom_guideline_text_view_order"
            app:layout_constraintGuide_percent=".38235"
            android:orientation="horizontal"/>

        <androidx.constraintlayout.widget.Guideline
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/bottom_guideline_text_view_planter"
            app:layout_constraintGuide_percent=".61765"
            android:orientation="horizontal"/>

        <androidx.constraintlayout.widget.Guideline
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/left_guideline_mark_fulfilled_icon"
            app:layout_constraintGuide_percent=".32367"
            android:orientation="vertical"/>

        <androidx.constraintlayout.widget.Guideline
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/right_guideline_mark_fulfilled_icon"
            app:layout_constraintGuide_percent=".43961"
            android:orientation="vertical"/>

        <androidx.constraintlayout.widget.Guideline
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/top_guideline_icon"
            app:layout_constraintGuide_percent=".74265"
            android:orientation="horizontal"/>

        <androidx.constraintlayout.widget.Guideline
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/bottom_guideline_icon"
            app:layout_constraintGuide_percent=".96324"
            android:orientation="horizontal"/>

        <androidx.constraintlayout.widget.Guideline
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/left_guideline_message_icon"
            app:layout_constraintGuide_percent=".58696"
            android:orientation="vertical"/>

        <androidx.constraintlayout.widget.Guideline
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/right_guideline_message_icon"
            app:layout_constraintGuide_percent=".70290"
            android:orientation="vertical"/>

        <FrameLayout
            android:layout_width="0dp"
            android:layout_height="0dp"
            android:id="@+id/left_border"
            android:background="#0099ff"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="@id/left_guideline_view"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintBottom_toBottomOf="parent">

            <Button
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:background="#0099ff" />

        </FrameLayout>

        <FrameLayout
            android:layout_width="0dp"
            android:layout_height="0dp"
            android:id="@+id/right_border"
            android:background="#0099ff"
            app:layout_constraintLeft_toLeftOf="@id/right_guideline_view"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintBottom_toBottomOf="parent">

            <Button
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:background="#0099ff" />

        </FrameLayout>

        <FrameLayout
            android:layout_width="0dp"
            android:layout_height="0dp"
            android:id="@+id/middle"
            android:paddingTop="8dp"
            android:paddingBottom="8dp"
            app:layout_constraintLeft_toLeftOf="@+id/left_guideline_view"
            app:layout_constraintRight_toRightOf="@id/right_guideline_view"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintBottom_toBottomOf="parent">

            <Button
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:background="@drawable/order_planter_message_shape" />

        </FrameLayout>

        <com.mikhaellopez.circularimageview.CircularImageView
            android:layout_width="64dp"
            android:layout_height="64dp"
            android:id="@+id/image_view"
            app:civ_border_color="#ffffff"
            app:civ_border_width="1dp"
            app:civ_shadow="false"
            app:layout_constraintLeft_toLeftOf="@+id/left_guideline_image_view"
            app:layout_constraintTop_toTopOf="@+id/top_guideline_image_view" />

        <TextView
            android:layout_width="0dp"
            android:layout_height="0dp"
            android:id="@+id/text_view_order"
            android:text="# Trees"
            android:fontFamily="@font/inter_semibold"
            android:textSize="24sp"
            android:textColor="#ffffff"
            android:textAllCaps="false"
            android:gravity="bottom|start"
            app:layout_constraintLeft_toLeftOf="@+id/left_guideline_text_view"
            app:layout_constraintRight_toRightOf="@+id/right_guideline_text_view"
            app:layout_constraintTop_toTopOf="@+id/top_guideline_text_view_order"
            app:layout_constraintBottom_toBottomOf="@+id/bottom_guideline_text_view_order"/>

        <TextView
            android:layout_width="0dp"
            android:layout_height="0dp"
            android:id="@+id/text_view_planter"
            android:text="David Malan, $20"
            android:fontFamily="@font/inter_regular"
            android:textSize="18sp"
            android:textColor="#ffffff"
            android:textAllCaps="false"
            android:gravity="bottom|start"
            app:layout_constraintLeft_toLeftOf="@+id/left_guideline_text_view"
            app:layout_constraintRight_toRightOf="@+id/right_guideline_text_view"
            app:layout_constraintTop_toTopOf="@+id/bottom_guideline_text_view_order"
            app:layout_constraintBottom_toBottomOf="@+id/bottom_guideline_text_view_planter"/>

        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/mark_fulfilled_icon"
            android:src="@drawable/ic_check_mark"
            app:layout_constraintLeft_toLeftOf="@+id/left_guideline_mark_fulfilled_icon"
            app:layout_constraintRight_toRightOf="@+id/right_guideline_mark_fulfilled_icon"
            app:layout_constraintTop_toTopOf="@+id/top_guideline_icon"
            app:layout_constraintBottom_toBottomOf="@+id/bottom_guideline_icon"/>

        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/message_icon"
            android:src="@drawable/ic_check_mark"
            app:layout_constraintLeft_toLeftOf="@+id/left_guideline_message_icon"
            app:layout_constraintRight_toRightOf="@+id/right_guideline_message_icon"
            app:layout_constraintTop_toTopOf="@+id/top_guideline_icon"
            app:layout_constraintBottom_toBottomOf="@+id/bottom_guideline_icon"/>

    </androidx.constraintlayout.widget.ConstraintLayout>

这是我的 RecyclerView 适配器代码:

    package com.example.treeapp;

    import android.content.Intent;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.ImageView;
    import android.widget.TextView;

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

    import com.mikhaellopez.circularimageview.CircularImageView;

    import java.util.List;

    public class DonorOrdersAdapter extends RecyclerView.Adapter<DonorOrdersAdapter.DonorOrdersViewHolder> {
        public String email;
        public static DownloadImageTask downloadImageTask;

        public static class DonorOrdersViewHolder extends RecyclerView.ViewHolder {
            public CircularImageView imageView;
            public TextView orderTextView;
            public TextView planterTextView;
            public ImageView markFulfilledIcon;
            public ImageView messageIcon;

            DonorOrdersViewHolder(View view) {
                super(view);

                imageView = view.findViewById(R.id.image_view);
                orderTextView = view.findViewById(R.id.text_view_order);
                planterTextView = view.findViewById(R.id.text_view_planter);
                markFulfilledIcon = view.findViewById(R.id.mark_fulfilled_icon);
                messageIcon = view.findViewById(R.id.message_icon);
                downloadImageTask = new DownloadImageTask(imageView);
            }
        }

        DonorOrdersAdapter(String email) {
            this.email = email;
        }

        List<Integer> orders = MainActivity.database.ordersDao().getOrdersByDonor(email);

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

            return new DonorOrdersViewHolder(view);
        }

        @Override
        public void onBindViewHolder(@NonNull DonorOrdersViewHolder holder, int position) {
            final int current = orders.get(position);
            final String planterEmail = MainActivity.database.ordersDao().getPlanter(current);

            if (MainActivity.database.plantersDao().getImageUrl(planterEmail) != null) {
                downloadImageTask.execute(MainActivity.database.plantersDao().getImageUrl(planterEmail));
            }

            holder.orderTextView.setText(MainActivity.database.ordersDao(  ).getTrees(current) + " trees");
            holder.planterTextView.setText(MainActivity.database.plantersDao().getName(planterEmail) + ", $" +
                                           MainActivity.database.ordersDao().getPayment(current));

            holder.markFulfilledIcon.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    Intent fulfillIntent = new Intent(view.getContext(), ConfirmPaymentActivity.class);
                    fulfillIntent.putExtra("email", email);
                    fulfillIntent.putExtra("orderId", current);

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

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

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

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

我正在使用使用房间库的 SQLite 表。这是表格行的代码:

    package com.example.treeapp;

    import androidx.room.ColumnInfo;
    import androidx.room.Entity;
    import androidx.room.PrimaryKey;

    @Entity(tableName = "Orders")
    public class Order {
        @PrimaryKey(autoGenerate = true)
        public int id;

        @ColumnInfo(name = "Donor")
        public String donorEmail;

        @ColumnInfo(name = "Planter")
        public String planterEmail;

        @ColumnInfo(name = "Trees")
        public int trees;

        @ColumnInfo(name = "Payment")
        public int payment;

        @ColumnInfo(name = "Fulfilled")
        public int fulfilled;
    }

这是数据访问对象的代码:

    package com.example.treeapp;

    import androidx.room.Dao;
    import androidx.room.Query;

    import java.util.List;

    @Dao
    public interface OrdersDao {
        @Query("INSERT INTO Orders (Donor, Planter, Trees, Payment, Fulfilled) VALUES (:donorEmail, :planterEmail, :trees, :payment, 0)")
        void create(String donorEmail, String planterEmail, int trees, int payment);

        @Query("SELECT Donor FROM Orders WHERE id = :id")
        String getDonor(int id);

        @Query("SELECT Planter FROM Orders WHERE id = :id")
        String getPlanter(int id);

        @Query("SELECT Trees FROM Orders WHERE id = :id")
        int getTrees(int id);

        @Query("SELECT Payment FROM Orders WHERE id = :id")
        int getPayment(int id);

        @Query("SELECT Fulfilled FROM Orders WHERE id = :id")
        int getFulfilled(int id);

        @Query("UPDATE Orders SET Fulfilled = 1 WHERE id = :id")
        void markFulfilled(int id);

        @Query("SELECT id FROM Orders WHERE Donor = :donorEmail AND Fulfilled = 0")
        List<Integer> getOrdersByDonor(String donorEmail);

        @Query("SELECT id FROM Orders WHERE Planter = :planterEmail AND Fulfilled = 0")
        List<Integer> getOrdersToPlanter(String planterEmail);

        @Query("SELECT id FROM Orders WHERE Fulfilled = 0")
        List<Integer> getUnfulfilledOrders();
    }

这是我使用回收器 View 的 Activity 的代码:

    package com.example.treeapp;

    import androidx.appcompat.app.AppCompatActivity;
    import androidx.recyclerview.widget.LinearLayoutManager;
    import androidx.recyclerview.widget.RecyclerView;

    import android.os.Bundle;

    public class DonorOrdersActivity extends AppCompatActivity {
        private String email;
        private RecyclerView recyclerView;
        private RecyclerView.Adapter adapter;
        private RecyclerView.LayoutManager layoutManager;

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_donor_orders);

            email = getIntent().getStringExtra("email");
            recyclerView = findViewById(R.id.recycler_view);
            adapter = new DonorOrdersAdapter(email);
            layoutManager = new LinearLayoutManager(this);

            recyclerView.setAdapter(adapter);
            recyclerView.setLayoutManager(layoutManager);
        }
    }

如果有人能够弄清楚我的 RecyclerViews 出了什么问题，请告诉我。
**编辑:** 我已经通过记录订单表中的数据测试了我的数据库实际上包含订单。

Answer 1

如果你看到你的 logcat，你可以看到 E/RecyclerView: No adapter attached; skipping layout .所以解决方案是改变这个:

recyclerView.setAdapter(adapter);
recyclerView.setLayoutManager(layoutManager);

对此:

recyclerView.setLayoutManager(layoutManager);
recyclerView.setAdapter(adapter);