RecyclerView 項目未顯示

Question

活動_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <RelativeLayout
        android:id="@+id/relativeLayout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toTopOf="@+id/addNotificationPanel"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.498"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.207">

        <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/notificationPanelRecView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="5dp"
            android:visibility="visible" />

    </RelativeLayout>
    
</androidx.constraintlayout.widget.ConstraintLayout>

notification_panel_cardview.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/notificationPanelParent"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_margin="5dp"
    app:cardCornerRadius="7dp"
    app:cardElevation="4dp">

    <RelativeLayout
        android:layout_width="335dp"
        android:layout_height="130dp">

        <EditText
            android:id="@+id/notificationName"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="5dp"
            android:maxLength="29"
            android:text="Notification"
            android:textSize="14sp"
            tools:ignore="TouchTargetSizeCheck" />

        <CheckBox
            android:id="@+id/enableNotificationCheckbox"
            android:layout_width="34dp"
            android:layout_height="34dp"
            android:layout_marginRight="4dp"
            android:layout_toLeftOf="@+id/deleteNotificationPanel"
            android:gravity="fill"
            tools:ignore="TouchTargetSizeCheck" />

        <ImageButton
            android:id="@+id/deleteNotificationPanel"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentRight="true"
            android:layout_gravity="right|center_vertical"
            android:layout_marginRight="6dp"
            android:background="@null"
            android:src="@android:drawable/ic_delete"
            tools:ignore="TouchTargetSizeCheck,SpeakableTextPresentCheck" />

        <TextView
            android:id="@+id/notifyEvery"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@+id/notificationName"
            android:layout_marginLeft="6dp"
            android:layout_marginTop="1dp"
            android:text="Notify me every :"
            android:textSize="17sp" />

        <Spinner
            android:id="@+id/hoursSpinner"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@+id/notificationName"
            android:layout_toRightOf="@+id/notifyEvery"
            tools:ignore="TouchTargetSizeCheck,SpeakableTextPresentCheck" />

        <RelativeLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@+id/notifyEvery"
            android:layout_marginTop="5dp">

            <CheckBox
                android:id="@+id/mondayCheckBox"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:button="@null"
                android:drawableBottom="?android:attr/listChoiceIndicatorMultiple"
                android:gravity="center"
                android:text="Mon"
                android:textSize="13sp" />

            <CheckBox
                android:id="@+id/tuesdayCheckBox"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_toRightOf="@+id/mondayCheckBox"
                android:button="@null"
                android:drawableBottom="?android:attr/listChoiceIndicatorMultiple"
                android:gravity="center"
                android:text="Tue"
                android:textSize="13sp" />

            <CheckBox
                android:id="@+id/wednesdayCheckBox"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_toRightOf="@+id/tuesdayCheckBox"
                android:button="@null"
                android:drawableBottom="?android:attr/listChoiceIndicatorMultiple"
                android:gravity="center"
                android:text="Wed"
                android:textSize="13sp" />

            <CheckBox
                android:id="@+id/thursdayCheckBox"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_toRightOf="@id/wednesdayCheckBox"
                android:button="@null"
                android:drawableBottom="?android:attr/listChoiceIndicatorMultiple"
                android:gravity="center"
                android:text="Thu"
                android:textSize="13sp" />

            <CheckBox
                android:id="@+id/fridayCheckBox"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_toRightOf="@+id/thursdayCheckBox"
                android:button="@null"
                android:drawableBottom="?android:attr/listChoiceIndicatorMultiple"
                android:gravity="center"
                android:text="Fri"
                android:textSize="13sp" />

            <CheckBox
                android:id="@+id/saturdayCheckBox"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_toRightOf="@+id/fridayCheckBox"
                android:button="@null"
                android:drawableBottom="?android:attr/listChoiceIndicatorMultiple"
                android:gravity="center"
                android:text="Sat"
                android:textSize="13sp" />

            <CheckBox
                android:id="@+id/sundayCheckBox"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_toRightOf="@id/saturdayCheckBox"
                android:button="@null"
                android:drawableBottom="?android:attr/listChoiceIndicatorMultiple"
                android:gravity="center"
                android:text="Sun"
                android:textSize="13sp"
                tools:ignore="TouchTargetSizeCheck" />
        </RelativeLayout>

    </RelativeLayout>

</androidx.cardview.widget.CardView>

通知面板.java

public class NotificationPanel {
    private int id;
    private String notificationName ;

    public NotificationPanel(int id, String notificationName) {
        this.id = id;
        this.notificationName = notificationName;

    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getNotificationName() {
        return notificationName;
    }

    public void setNotificationName(String notificationName) {
        this.notificationName = notificationName;
    }

    @Override
    public String toString() {
        return "NotificationPanel{" +
                "id=" + id +
                ", notificationName='" + notificationName + '\'' +
                '}';
    }
}

NotificationPanelRecViewAdapter.java

public class NotificationPanelRecViewAdapter extends RecyclerView.Adapter<NotificationPanelRecViewAdapter.ViewHolder> {
    private String TAG = "NotificationPanelRecViewAdapter";

    private ArrayList<NotificationPanel> notificationPanel = new ArrayList<>();
    private Context mContext;

    public NotificationPanelRecViewAdapter(Context mContext) {
        this.mContext = mContext;
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        LayoutInflater inflater = LayoutInflater.from(mContext);
        View view = inflater.inflate(R.layout.notification_panel_cardview,null,false);
        ViewHolder holder = new ViewHolder(view);
        return holder;
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder,final int position) {
        Log.d(TAG,"onBindViewHolder: Called");
        holder.notificationName.setText(notificationPanel.get(position).getNotificationName());

    }

    @Override
    public int getItemCount() {
        return 0;
    }

    public void setNotificationPanel(ArrayList<NotificationPanel> notificationPanel) {
        this.notificationPanel = notificationPanel;
        notifyDataSetChanged();
    }

    public class ViewHolder extends RecyclerView.ViewHolder{
        private CardView parent;
        private EditText notificationName ;
        private CheckBox monCheckBox ,tueCheckBox,wedCheckBox,thuCheckBox,friCheckBox,satCheckBox,sunCheckBox,enableNotifCheckbox;
        private TextView notifyEvery;
        private Spinner hoursSpinner;
        private ImageButton deleteNotificationPanel;

        public ViewHolder(@NonNull View itemView) {
            super(itemView);
            parent = itemView.findViewById(R.id.notificationPanelParent);
            notificationName = itemView.findViewById(R.id.notificationName);
            monCheckBox = itemView.findViewById(R.id.mondayCheckBox);
            tueCheckBox = itemView.findViewById(R.id.tuesdayCheckBox);
            wedCheckBox = itemView.findViewById(R.id.wednesdayCheckBox);
            thuCheckBox = itemView.findViewById(R.id.thursdayCheckBox);
            friCheckBox = itemView.findViewById(R.id.fridayCheckBox);
            satCheckBox = itemView.findViewById(R.id.saturdayCheckBox);
            sunCheckBox = itemView.findViewById(R.id.sundayCheckBox);
            enableNotifCheckbox = itemView.findViewById(R.id.enableNotificationCheckbox);
            notifyEvery = itemView.findViewById(R.id.notifyEvery);
            hoursSpinner = (Spinner) itemView.findViewById(R.id.hoursSpinner);
            deleteNotificationPanel = itemView.findViewById(R.id.deleteNotificationPanel);

            ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(mContext,R.array.hoursSpinnerValues,R.layout.notification_panel_cardview);
        }
    }
}

主活動.java

公共類 MainActivity 擴展 AppCompatActivity {

private RecyclerView notificationPanelRecView;
private NotificationPanelRecViewAdapter adapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO);

    notificationPanelRecView = findViewById(R.id.notificationPanelRecView);

    ArrayList<NotificationPanel> notificationPanel = new ArrayList<>();
    notificationPanel.add(new NotificationPanel(1, "Pills"));

    NotificationPanelRecViewAdapter adapter = new NotificationPanelRecViewAdapter(this);
    adapter.setNotificationPanel(notificationPanel);

    notificationPanelRecView.setLayoutManager(new LinearLayoutManager(this));
    notificationPanelRecView.setAdapter(adapter);

}

我在 MainActivity 中添加了一個項目的 ArrayList 只是為了測試布局，我的問題是它根本沒有顯示。 關於為什么會發生這種情況的任何提示都會有所幫助。 --------------------------------------- -------------------------------------------------- ---------------

Answer 1

如果適配器認為沒有要綁定的東西，它就不會綁定任何東西。

@Override
public int getItemCount() {
     return 0;
}

需要是

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