如何解决CardView 不显示披萨片段中的图片
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>
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