java - 为什么这个 RecyclerView + CardView 示例不起作用？

Question

我正在尝试创建一个应用程序，其中包含主要 Activity 的食物列表以及每种食物的复选框。

我按照本教程完成了整个文本和复选框的操作:http://android-pratap.blogspot.co.il/2015/01/recyclerview-with-checkbox-example.html

但是每当我运行应用程序时，它都不会在主屏幕上显示 RecyclerView...(应用程序将运行，但 RecyclerView 不存在)

如果有人可以解释我如何更改我的代码，这样就不需要卡片，那就太棒了。这是我的代码:

MainAcitivity.java:(只是将RecyclerView与FoodAdapter结合起来)

package com.gregskl.foodreminder;

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private RecyclerView recycler;
    private RecyclerView.Adapter adapter;

    private List<Food> foods;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        foods = new ArrayList<>();
        foods.add(new Food("Grapes", true));
        foods.add(new Food("Oranges", true));

        recycler = (RecyclerView) findViewById(R.id.recycler);
        recycler.setLayoutManager(new LinearLayoutManager(this));
        adapter = new FoodAdapater(foods);
        recycler.setAdapter(adapter);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

FoodAdapter.java:

package com.gregskl.foodreminder;

import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.CheckBox;
import android.widget.TextView;
import android.widget.Toast;

import java.util.List;

/**
 * Created by Gregory on 11-Sep-16.
 */
public class FoodAdapater extends RecyclerView.Adapter<FoodAdapater.ViewHolder> {

    private List<Food> foods;

    public FoodAdapater(List<Food> foods) {
        this.foods = foods;
    }

    @Override
    public FoodAdapater.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View itemLayoutView = LayoutInflater.from(parent.getContext()).inflate(R.layout.list, null);
        return new ViewHolder(itemLayoutView);
    }

    @Override
    public void onBindViewHolder(FoodAdapater.ViewHolder holder, int position) {
        ViewHolder h = (ViewHolder) holder;
        h.text.setText(foods.get(position).getText());
        h.checkbox.setChecked(foods.get(position).isAvailable());
        h.checkbox.setTag(foods.get(position));
        h.checkbox.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                Toast.makeText(v.getContext(), "Hey", Toast.LENGTH_LONG).show();
            }
        });
    }

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

    public static class ViewHolder extends RecyclerView.ViewHolder {

        public TextView text;
        public CheckBox checkbox;

        public ViewHolder(View itemView) {
            super(itemView);
            text = (TextView) itemView.findViewById(R.id.text);
            checkbox = (CheckBox) itemView.findViewById(R.id.checkbox);
        }
    }
}

Food.java:(食物的数据模型)

package com.gregskl.foodreminder;

/**
 * Created by Gregory on 11-Sep-16.
 */
public class Food {

    private String text;
    private boolean available;

    public Food(String text, boolean available) {
        this.text = text;
        this.available = available;
    }

    public String getText() {
        return text;
    }

    public boolean isAvailable() {
        return available;
    }

    public void setText(String text) {
        this.text = text;
    }

    public void setAvailable(boolean available) {
        this.available = available;
    }
}

content_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.gregskl.foodreminder.MainActivity"
    tools:showIn="@layout/activity_main">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recycler"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_margin="5dp"
        android:layout_weight="1"
        android:scrollbars="vertical" />

</RelativeLayout>

列表.xml:

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    card_view:cardCornerRadius="5dp"

    card_view:cardUseCompatPadding="true" >

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="5dp" >

        <TextView
            android:id="@+id/text"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_alignParentTop="true"
            android:text="name"
            android:textColor="@android:color/black"
            android:textSize="18sp" />
        <CheckBox
            android:id="@+id/checkbox"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentRight="true"
            android:layout_centerVertical="true"
            />
    </RelativeLayout>

</android.support.v7.widget.CardView>

Answer 1

尝试在 RecyclerView 中将高度从 android:layout_height="0dp" 设置为 android:layout_height="match_parent"。

0dp高度用于LinearLayout，你的是RelativeLayout。