adapter.setOnClickItemListener ( (ImageAdapter.OnItemClickListener) getActivity( ) );此代码生成错误，我无法解决错误
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【中文标题】adapter.setOnClickItemListener ( (ImageAdapter.OnItemClickListener) getActivity( ) );此代码生成错误，我无法解决错误【英文标题】：adapter.setOnClickItemListener ( (ImageAdapter.OnItemClickListener) getActivity( ) ); this code generates error & i am unable to solve error 【发布时间】：2020-05-10 12:19:45 【问题描述】：adapter.setOnClickItemListener ( (ImageAdapter.OnItemClickListener) getActivity( ) );这条线产生错误&我对这个错误的了解很低。两个所需的 java 文件和详细的错误在这两个 java 文件之后给出。
ImageAdapter.java
package com.example.login;
import android.content.Context;
import android.view.ContextMenu;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import com.squareup.picasso.Picasso;
import java.util.List;
public class ImageAdapter extends RecyclerView.Adapter<ImageAdapter.ImageViewHolder>
private Context Context;
private List<Upload> Uploads;
private OnItemClickListener Listener;
public ImageAdapter (Context context, List<Upload> uploads1)
Context = context;
Uploads = uploads1;
@NonNull
@Override
public ImageViewHolder onCreateViewHolder(@NonNull ViewGroup parent,int viewType)
View v= LayoutInflater.from(Context).inflate(R.layout.image_item, parent, false);
return new ImageViewHolder(v);
@Override
public void onBindViewHolder(@NonNull ImageViewHolder holder,int position)
Upload uploadCurrent= Uploads.get(position);
holder.textViewName.setText(uploadCurrent.getName());
Picasso.with(Context)
.load(uploadCurrent.getImageUrl())
.placeholder(R.drawable.logo)
.fit()
.centerInside()
.into(holder.imageView);
@Override
public int getItemCount()
return Uploads.size();
public class ImageViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener,
View.OnCreateContextMenuListener, MenuItem.OnMenuItemClickListener
public TextView textViewName;
public ImageView imageView;
public ImageViewHolder(@NonNull View itemView)
super(itemView);
textViewName = itemView.findViewById(R.id.text_product_name);
imageView = itemView.findViewById(R.id.product_image);
itemView.setOnClickListener(this);
itemView.setOnCreateContextMenuListener(this);
@Override
public void onClick(View v)
if(Listener != null)
int position = getAdapterPosition();
if (position != RecyclerView.NO_POSITION)
Listener.OnItemClick(position);
@Override
public void onCreateContextMenu(ContextMenu menu,View v,ContextMenu.ContextMenuInfo menuInfo)
menu.setHeaderTitle("Select Action");
MenuItem details = menu.add(Menu.NONE ,1,1,"Details");
MenuItem delete = menu.add(Menu.NONE ,2,2,"Delete");
details.setOnMenuItemClickListener(this);
delete.setOnMenuItemClickListener(this);
@Override
public boolean onMenuItemClick(MenuItem item)
if(Listener != null)
int position = getAdapterPosition();
if (position != RecyclerView.NO_POSITION)
switch(item.getItemId())
case 1:
Listener.OnDetailsClick(position);
return true;
case 2:
Listener.OnDeleteClick(position);
return true;
return false;
public interface OnItemClickListener
void OnItemClick(int Position);
void OnDetailsClick(int Position);
void OnDeleteClick(int Position);
public void SetOnClickItemListener(OnItemClickListener listener)
Listener = listener;
MyAddsFragment.java
package com.example.login.ui.login;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ProgressBar;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import com.example.login.ImageAdapter;
import com.example.login.R;
import com.example.login.Upload;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import java.util.ArrayList;
import java.util.List;
public class MyAddsFragment extends Fragment implements ImageAdapter.OnItemClickListener
private RecyclerView recyclerView;
private ImageAdapter adapter;
private ProgressBar progressBar;
private DatabaseReference databaseRef;
private List<Upload> Uploads;
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState)
View v = inflater.inflate(R.layout.fragment_myadds, container, false);
recyclerView = v.findViewById(R.id.Recycler_view);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
progressBar = v.findViewById(R.id.progress_bar_1);
Uploads = new ArrayList<>();
databaseRef = FirebaseDatabase.getInstance().getReference("uploads");
databaseRef.addValueEventListener(new ValueEventListener()
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot)
for (DataSnapshot postSnapshot : dataSnapshot.getChildren())
Upload upload = postSnapshot.getValue(Upload.class);
Uploads.add(upload);
adapter = new ImageAdapter(getActivity(), Uploads);
recyclerView.setAdapter(adapter);
adapter.SetOnClickItemListener((ImageAdapter.OnItemClickListener) getActivity());
progressBar.setVisibility(View.INVISIBLE);
@Override
public void onCancelled(@NonNull DatabaseError databaseError)
Toast.makeText(getActivity(),databaseError.getMessage(),Toast.LENGTH_SHORT).show();
progressBar.setVisibility(View.INVISIBLE);
);
return v;
@Override
public void OnItemClick(int Position)
Toast.makeText(getActivity(),"Normal Click Position:"+Position,Toast.LENGTH_SHORT).show();
@Override
public void OnDetailsClick(int Position)
Toast.makeText(getActivity(),"Details Click Position:"+Position,Toast.LENGTH_SHORT).show();
@Override
public void OnDeleteClick(int Position)
Toast.makeText(getActivity(),"Delete Click Position:"+Position,Toast.LENGTH_SHORT).show();
错误如下
01-24 12:33:27.072 6252-6252/com.example.login E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.login, PID: 6252
java.lang.ClassCastException: com.example.login.HomeActivity cannot be cast to com.example.login.ImageAdapter$OnItemClickListener
at com.example.login.ui.login.MyAddsFragment$1.onDataChange(MyAddsFragment.java:57)
at com.google.firebase.database.core.ValueEventRegistration.fireEvent(com.google.firebase:firebase-database@@19.2.0:75)
at com.google.firebase.database.core.view.DataEvent.fire(com.google.firebase:firebase-database@@19.2.0:63)
at com.google.firebase.database.core.view.EventRaiser$1.run(com.google.firebase:firebase-database@@19.2.0:55)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
.................................................. ..................................................... ...
【问题讨论】：
【参考方案1】：你的班级MyAddsFragment 正在实现ImageAdapter.OnItemClickListener，所以设置adapter.SetOnClickItemListener 你可以简单地使用下面的代码 -
adapter.SetOnClickItemListener(MyAddsFragment.this)
您不能将 ImageAdapter.OnItemClickListener 转换为 HomeActicity.class，因为它可能无法实现。
【讨论】：
MyAddsFragment.java 不是活动。它是一个片段。 & Fragment 不像活动。
是的，但 MyAddsFragment 正在实现接口 OnItemClickListener，因此您必须使用 adapter.SetOnClickItemListener(MyAddsFragment.this)。要在 HomeActivity 中使用 OnItemClickListener，您必须在 home Activity 中实现接口 OnItemClickListener 以便您可以像当前一样使用 - adapter.SetOnClickItemListener((HomeActivity)getActivity())
很抱歉和你争论..你是绝对正确的。错误已解决...??????
没问题很乐意帮忙:)以上是关于adapter.setOnClickItemListener ( (ImageAdapter.OnItemClickListener) getActivity( ) );此代码生成错误，我无法解决错误的主要内容，如果未能解决你的问题，请参考以下文章