我正在做一个项目，我遵循了RecycleView上的Youtube教程，但是当我编译我的项目并在Android Studio上启动应用程序时，我的应用程序崩溃了。我完全遵循了视频显示的内容，但此后某些组件的工作方式可能不同。
这是我得到的输出：
java.lang.ClassCastException: android.support.constraint.ConstraintLayout cannot be cast to android.support.v7.widget.CardView
at e.user.popcorn.RecyclerViewAdapter$MyViewHolder.<init>(RecyclerViewAdapter.java:78)
at e.user.popcorn.RecyclerViewAdapter.onCreateViewHolder(RecyclerViewAdapter.java:33)
at e.user.popcorn.RecyclerViewAdapter.onCreateViewHolder(RecyclerViewAdapter.java:16)
这是代码回收器视图适配器.java
package e.user.popcorn;
import android.content.Context;
import android.content.Intent;
import android.media.Image;
import android.support.v7.widget.CardView;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import java.util.List;
public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.MyViewHolder> {
private Context mContext ;
private List<movie_page> mData ;
public RecyclerViewAdapter(Context mContext, List<movie_page> mData) {
this.mContext = mContext;
this.mData = mData;
}
@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view ;
LayoutInflater mInflater = LayoutInflater.from(mContext);
view = mInflater.inflate(R.layout.layout_boxoffice_movie,parent,false);
return new MyViewHolder(view);
}
@Override
public void onBindViewHolder(MyViewHolder holder, final int position) {
holder.tv_movie_title.setText(mData.get(position).getTitle());
holder.img_movie_thumbnail.setImageResource(mData.get(position).getThumbnail());
holder.cardView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(mContext,SelectedMovie.class);
// passing data to the book activity
intent.putExtra("Title",mData.get(position).getTitle());
intent.putExtra("Description",mData.get(position).getDescription());
intent.putExtra("Thumbnail",mData.get(position).getThumbnail());
intent.putExtra("Categorie",mData.get(position).getCategory());
// start the activity
mContext.startActivity(intent);
}
});
}
@Override
public int getItemCount() {
return mData.size();
}
public static class MyViewHolder extends RecyclerView.ViewHolder {
TextView tv_movie_title;
ImageView img_movie_thumbnail;
CardView cardView ;
public MyViewHolder(View itemView) {
super(itemView);
tv_movie_title = (TextView) itemView.findViewById(R.id.movie_title) ;
img_movie_thumbnail = (ImageView) itemView.findViewById(R.id.movie_poster);
cardView = (CardView) itemView.findViewById(R.id.movie_id);
}
}
}
还有movie_page.java
package e.user.popcorn;
public class movie_page {
private String Title;
private String Category ;
private String Description ;
private int Thumbnail ;
public movie_page() {
}
public movie_page(String title, String category, String description, int thumbnail) {
Title = title;
Category = category;
Description = description;
Thumbnail = thumbnail;
}
public String getTitle() {
return Title;
}
public String getCategory() {
return Category;
}
public String getDescription() {
return Description;
}
public int getThumbnail() {
return Thumbnail;
}
public void setTitle(String title) {
Title = title;
}
public void setCategory(String category) {
Category = category;
}
public void setDescription(String description) {
Description = description;
}
public void setThumbnail(int thumbnail) {
Thumbnail = thumbnail;
}
}
这是Layout_boxoffice_movie.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/movie_id"
android:clickable="true"
android:foreground="?android:attr/selectableItemBackground"
android:layout_width="120dp"
android:layout_height="200dp"
android:layout_margin="5dp"
xmlns:cardview="http://schemas.android.com/apk/res-auto">
<LinearLayout
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/colorWhite">
<ImageView
android:id="@+id/movie_poster"
android:layout_width="match_parent"
android:layout_height="170dp"
android:scaleType="centerCrop"
android:background="@color/colorNavBackground"/>
<TextView
android:id="@+id/movie_title"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="Movie Title"
android:gravity="center"
android:textColor="@color/colorNavBackground"/>
</LinearLayout>
您需要将
ConstraintLayout替换为CardView。
这将是您更正的代码。
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/movie_id"
android:clickable="true"
android:foreground="?android:attr/selectableItemBackground"
android:layout_width="120dp"
android:layout_height="200dp"
android:layout_margin="5dp"
xmlns:cardview="http://schemas.android.com/apk/res-auto">
<LinearLayout
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/colorWhite">
<ImageView
android:id="@+id/movie_poster"
android:layout_width="match_parent"
android:layout_height="170dp"
android:scaleType="centerCrop"
android:background="@color/colorNavBackground"/>
<TextView
android:id="@+id/movie_title"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="Movie Title"
android:gravity="center"
android:textColor="@color/colorNavBackground"/>
</LinearLayout>
</android.support.v7.widget.CardView>
你关心ConstraintLayout投CardView .更改此行
<android.support.constraint.ConstraintLayout
跟
android.support.v7.widget.CardView
下行的问题
cardView = (CardView) itemView.findViewById(R.id.movie_id);
根据布局 xml 文件，您使用的是 ConstraintLayout，而您在 Java 文件中使用的是 CardView。这才是真正的问题。您需要使用 CardView 而不是 ConstraintLayout。
取代
<android.support.constraint.ConstraintLayout
跟
<android.support.v7.widget.CardView
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