CardView 不显示披萨片段中的图片

问题描述

我正在从书本上学习 android studio。我想要带有 RecyclerView 的 CardView。 我有我的代码，但 cardView 不显示图片。它只显示带有文本的 empy CardView。 就像这里 -> https://feedbackassistant.apple.com/ 谁能告诉我出了什么问题？

我的适配器

public class CaptionedImagesAdapter extends
        RecyclerView.Adapter<CaptionedImagesAdapter.ViewHolder> {

    private String[] captions;
    private int[] imageIds;




        public CaptionedImagesAdapter(String [] captions,int [] imageIds){
        this.captions = captions;
        this.imageIds = imageIds;
    }

    public int getItemCount(){
        return captions.length;
    }

    public CaptionedImagesAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,int viewType){
        CardView cv =  (CardView)LayoutInflater.from(parent.getContext())
                .inflate(R.layout.card_captioned_image,parent,false);
        return new ViewHolder(cv);
    }

    public void onBindViewHolder(CaptionedImagesAdapter.ViewHolder holder,int position){
        final CardView cardView = holder.cardView;
        ImageView imageView = (ImageView)cardView.findViewById(R.id.info_image);
        Drawable drawable =
                ContextCompat.getDrawable(cardView.getContext(),imageIds[position]);
        imageView.setimageDrawable(drawable);
        imageView.setContentDescription(captions[position]);
        TextView textView = (TextView)cardView.findViewById(R.id.info_text);
        textView.setText(captions[position]);
    }

    public static class ViewHolder extends RecyclerView.ViewHolder{
        private CardView cardView;

        public ViewHolder(CardView v){
            super(v);
            cardView = v;
        }
    }
}

包含在 mainActivity 中的片段

public class PizzaFragment extends Fragment {





    @Override
    public View onCreateView(LayoutInflater inflater,ViewGroup container,Bundle savedInstanceState) {

        RecyclerView pizzaRecycler = (RecyclerView)inflater.inflate(
                R.layout.fragment_pizza,container,false);

        String[] pizzaNames = new String[Pizza.pizzas.length];
        for(int i =0; i < pizzaNames.length; i++){
            pizzaNames[i] = Pizza.pizzas[i].getName();
        }

        int[] pizzaimages = new int[Pizza.pizzas.length];
        for(int i=0; i< pizzaimages.length; i++){
            pizzaimages[i] = Pizza.pizzas[i].getimageResourceId();
        }

        CaptionedImagesAdapter adapter =
                new CaptionedImagesAdapter(pizzaNames,pizzaimages);

        GridLayoutManager layoutManager = new GridLayoutManager(getActivity(),2);
        pizzaRecycler.setLayoutManager(layoutManager);
        pizzaRecycler.setAdapter(adapter);



                return pizzaRecycler;
    }
}

片段的xml

<?xml version="1.0" encoding="utf-8"?>
    <androidx.recyclerview.widget.RecyclerView
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/pizza_recycler"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scrollbars="vertical"/>

我的主要活动

public class MainActivity extends AppCompatActivity {



    private ViewPager2 viewPager;
    private FragmentStateAdapter pagerAdapter;
    private ShareActionProvider shareActionProvider;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar)findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        viewPager = findViewById(R.id.pager);
        pagerAdapter = new ScreenSlidePagerAdapter(this);
        viewPager.setAdapter(pagerAdapter);

        CharSequence hoMetab0 = getResources().getText(R.string.home_tab);
        CharSequence hoMetab1 = getResources().getText(R.string.pizza_tab);
        CharSequence hoMetab2 = getResources().getText(R.string.psata_tab);
        CharSequence hoMetab3 = getResources().getText(R.string.store_tab);

        String [] titles = new String[]{
                String.valueOf(hoMetab0),String.valueOf(hoMetab1),String.valueOf(hoMetab2),String.valueOf(hoMetab3)
        };

        TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
        new TabLayoutMediator(tabLayout,viewPager,(tab,position) ->
            tab.setText(titles[position])).attach();


    }



    public boolean onCreateOptionsMenu(Menu menu){

        getMenuInflater().inflate(R.menu.menu_main,menu);
        MenuItem menuItem = menu.findItem(R.id.action_share);
        shareActionProvider = (ShareActionProvider) MenuItemCompat.getActionProvider(menuItem);
        setShareActionIntent("Umowimy sie na pizze?");
        return super.onCreateOptionsMenu(menu);
    }

    private void setShareActionIntent(String text){
        Intent intent = new Intent(Intent.ACTION_SEND);
        intent.setType("text/plain");
        intent.putExtra(Intent.EXTRA_TEXT,text);
        shareActionProvider.setShareIntent(intent);
    }

    public boolean onoptionsItemSelected(MenuItem item){
        switch(item.getItemId()){
            case R.id.action_create_order:
                Intent intent = new Intent(this,OrderActivity.class);
                startActivity(intent);
                return true;
            default:
                return super.onoptionsItemSelected(item);
        }
    }

    private class ScreenSlidePagerAdapter extends FragmentStateAdapter {
        public ScreenSlidePagerAdapter(FragmentActivity fm) {
            super(fm);
        }



        public int getItemCount(){
            return 4;
        }

        public Fragment createFragment(int position){
            switch (position){
                case 0:
                    return new TopFragment();
                case 1:
                    return  new PizzaFragment();
                case 2:
                    return new StoresFragment();

                case 3:
                    return new PastaFragment();

            }
            return null;
        }


    }

    public void onBackpressed() {
        if (viewPager.getCurrentItem() == 0) {
// If the user is currently looking at the first step,allow the system to handle the
            // Back button. This calls finish() on this activity and pops the back stack.d
            super.onBackpressed();
        } else {
// Otherwise,select the prevIoUs step.
            viewPager.setCurrentItem(viewPager.getCurrentItem() - 1);
        }
    }

MainActivity的xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout 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">



    <com.google.android.material.appbar.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

        <androidx.appcompat.widget.Toolbar
            android:id="@+id/toolbar"
            app:layout_scrollFlags="scroll|enteralways"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"

            />
        <com.google.android.material.tabs.TabLayout
            android:id="@+id/tabs"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>

    </com.google.android.material.appbar.AppBarLayout>



    <androidx.viewpager2.widget.ViewPager2
        android:id="@+id/pager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"

        />

</androidx.coordinatorlayout.widget.CoordinatorLayout>

我的数据类

public class Pizza {
    private String name;
    private int imageResourceId;

    public static final Pizza[] pizzas ={
            new Pizza("Diavolo9999",R.drawable.diavolo),new Pizza("Fungi",R.drawable.funghi)
    };

    public  Pizza(String name,int imageResourceId){
        this.name = name;
        this.imageResourceId = imageResourceId;
    }

    public String getName(){
        return name;
    }

    public int getimageResourceId(){
        return imageResourceId;
    }
}

卡片xml

<?xml version="1.0" encoding="utf-8"?>
    <androidx.cardview.widget.CardView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    android:id="@+id/card_view"
    android:layout_width="match_parent"
    android:layout_height="200dp"
    android:layout_margin="4dp"
    card_view:cardElevation="2dp"
    card_view:cardCornerRadius="4dp">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <ImageView
            android:id="@+id/info_image"
            android:layout_height="0dp"
            android:layout_width="match_parent"
            android:layout_weight="1.0"
            android:scaleType="centerCrop"/>

        <TextView
            android:id="@+id/info_text"
            android:layout_marginLeft="4dp"
            android:layout_marginBottom="4dp"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"/>

    </LinearLayout>

</androidx.cardview.widget.CardView>

解决方法

您的 ImageView 高度为零！如果你想使用LinearLayout，那么你可以将你的卡片xml更改为：

<?xml version="1.0" encoding="utf-8"?>
<androidx.cardview.widget.CardView 
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:card_view="http://schemas.android.com/apk/res-auto"
android:id="@+id/card_view"
android:layout_width="match_parent"
android:layout_height="200dp"
android:layout_margin="4dp"
card_view:cardCornerRadius="4dp"
card_view:cardElevation="2dp">

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <ImageView
        android:id="@+id/info_image"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1.0"
        android:scaleType="centerCrop" />

    <TextView
        android:id="@+id/info_text"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_marginLeft="4dp"
        android:layout_marginBottom="4dp"
        android:layout_weight="1.0" />
</LinearLayout>
</androidx.cardview.widget.CardView>