Question

我正在使用Firebase通过博客帖子填充我的BlogRecycleadapter并从Like Buttons获取Likes但是当设备离线并且用户按下Like Button时，应用程序崩溃...所以我试图实现isNetworkavailaible的第二个条件if声明如下......

if (!task.getResult().exists() && isNetworkStatusAvialable(getApplicationContext())){

                        Map<String, Object> likesMap = new HashMap<>();
                        likesMap.put("timestamp", FieldValue.serverTimestamp());


                        firebaseFirestore.collection("Posts/" + blogPostId + "/Likes").document(currentUserId).set(likesMap);

                    } else {
                        firebaseFirestore.collection("Posts/" + blogPostId + "/Likes").document(currentUserId).delete();

                    }

但是我在getApplicationContext()中得到了错误，从少数谷歌搜索中，我发现getApplicationContext()不适用于Class，但只适用于活动。

那么如何在这里实现getApplicationContext？

我的整个回收适配器代码是

＆＃13;

package com.nepalpolice.cdp;

import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Build;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.text.format.DateFormat;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import com.bumptech.glide.Glide;
import com.bumptech.glide.request.RequestOptions;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.firestore.DocumentSnapshot;
import com.google.firebase.firestore.EventListener;
import com.google.firebase.firestore.FieldValue;
import com.google.firebase.firestore.FirebaseFirestore;
import com.google.firebase.firestore.FirebaseFirestoreException;
import com.google.firebase.firestore.QuerySnapshot;

import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import de.hdodenhof.circleimageview.CircleImageView;

public class BlogRecyclerAdapter extends RecyclerView.Adapter<BlogRecyclerAdapter.ViewHolder> {

    public List<BlogPost> blog_list;
    public Context context;

    private FirebaseFirestore firebaseFirestore;
private FirebaseAuth firebaseAuth;


    public BlogRecyclerAdapter(List<BlogPost> blog_list,Context context){

        this.blog_list = blog_list;
        this.context=context;

    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.blog_list_item, parent, false);
        context = parent.getContext();
        firebaseFirestore = FirebaseFirestore.getInstance();
        firebaseAuth = FirebaseAuth.getInstance();
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(final ViewHolder holder, int position) {

        holder.setIsRecyclable(false);

        final String blogPostId = blog_list.get(position).BlogPostId;
        final String currentUserId = firebaseAuth.getCurrentUser().getUid();

        String desc_data = blog_list.get(position).getDesc();
        holder.setDescText(desc_data);

        String image_url = blog_list.get(position).getImage_url();
        holder.setBlogImage(image_url);

        String user_id = blog_list.get(position).getUser_id();
        //User Data will be retrieved here...
        firebaseFirestore.collection("Users").document(user_id).get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
            @Override
            public void onComplete(@NonNull Task<DocumentSnapshot> task) {

                if(task.isSuccessful()){

                    String userName = task.getResult().getString("name");
                    String userImage = task.getResult().getString("image");

                    holder.setUserData(userName, userImage);


                } else {

                    //Firebase Exception

                }

            }
        });

        long millisecond = blog_list.get(position).getTimestamp().getTime();
        String dateString = DateFormat.format("MM/dd/yyyy", new Date(millisecond)).toString();
        holder.setTime(dateString);

        //Get Likes Count
        firebaseFirestore.collection("Posts/" + blogPostId + "/Likes").addSnapshotListener(((Main2Activity) context),new EventListener<QuerySnapshot>() {
            @Override
            public void onEvent(QuerySnapshot documentSnapshots, FirebaseFirestoreException e) {

                if (!documentSnapshots.isEmpty()){

int count = documentSnapshots.size();
holder.updateLikesCount(count);

                }else{
holder.updateLikesCount(0);

                }

            }
        });



        //Get Likes

        firebaseFirestore.collection("Posts/" + blogPostId + "/Likes").document(currentUserId).addSnapshotListener(((Main2Activity) context),new EventListener<DocumentSnapshot>() {
            @Override
            public void onEvent(DocumentSnapshot documentSnapshot, FirebaseFirestoreException e) {

                if (documentSnapshot.exists()){

                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
                        holder.blogLikeBtn.setImageDrawable(context.getDrawable(R.mipmap.action_like_accent));
                    }
                    else {
                        holder.blogLikeBtn.setImageDrawable(context.getResources().getDrawable(R.mipmap.action_like_accent));
                    }
                } else {

                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
                        holder.blogLikeBtn.setImageDrawable(context.getDrawable(R.mipmap.action_like_gray));
                    }else{
                        holder.blogLikeBtn.setImageDrawable(context.getResources().getDrawable(R.mipmap.action_like_gray));
                    }
                }

            }
        });

        //like Feature



        holder.blogLikeBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {



                firebaseFirestore.collection("Posts/" + blogPostId + "/Likes").document(currentUserId).get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
                    @Override
                    public void onComplete(@NonNull Task<DocumentSnapshot> task) {
                        if (!task.getResult().exists() && isNetworkStatusAvialable(getApplicationContext())){

                            Map<String, Object> likesMap = new HashMap<>();
                            likesMap.put("timestamp", FieldValue.serverTimestamp());


                            firebaseFirestore.collection("Posts/" + blogPostId + "/Likes").document(currentUserId).set(likesMap);

                        } else {
                            firebaseFirestore.collection("Posts/" + blogPostId + "/Likes").document(currentUserId).delete();

                        }

                    }
                });



            }
        });

    }

    @Override
    public int getItemCount() {

        return blog_list.size();
    }

    public class ViewHolder extends RecyclerView.ViewHolder {

        private View mView;

        private TextView descView;
        private ImageView blogImageView;
        private TextView blogDate;

        private TextView blogUserName;
        private CircleImageView blogUserImage;
        private ImageView blogLikeBtn;
        private  TextView blogLikeCount;

        public ViewHolder(View itemView) {
            super(itemView);
            mView = itemView;



        }

        public void setDescText(String descText){

            descView = mView.findViewById(R.id.blog_desc);
            descView.setText(descText);

            blogLikeBtn = mView.findViewById(R.id.blog_like_btn);
        }

        public void setBlogImage(String downloadUri){

            blogImageView = mView.findViewById(R.id.blog_image);
            RequestOptions requestOptions = new RequestOptions();
            requestOptions.placeholder(R.drawable.image_placeholder);
            Glide.with(context).applyDefaultRequestOptions(requestOptions).load(downloadUri).into(blogImageView);

        }

        public void setTime(String date) {

            blogDate = mView.findViewById(R.id.blog_date);
            blogDate.setText(date);

        }

        public void setUserData(String name, String image){

            blogUserImage = mView.findViewById(R.id.blog_user_image);
            blogUserName = mView.findViewById(R.id.blog_user_name);

            blogUserName.setText(name);

            RequestOptions placeholderOption = new RequestOptions();
            placeholderOption.placeholder(R.drawable.profile_placeholder);

            Glide.with(context).applyDefaultRequestOptions(placeholderOption).load(image).into(blogUserImage);

        }

public void  updateLikesCount (int count){

            blogLikeCount = mView.findViewById(R.id.blog_like_count);
            blogLikeCount.setText(count + "Likes");
}

    }
    public static boolean isNetworkStatusAvialable (Context context) {
        ConnectivityManager cm =
                (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);

        NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
        return activeNetwork != null &&
                activeNetwork.isConnectedOrConnecting();

    }
}

＆＃13;

我的HOmeFragment来自我调用适配器类的地方

＆＃13;

package com.nepalpolice.cdp;


import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;

import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.firestore.DocumentChange;
import com.google.firebase.firestore.DocumentSnapshot;
import com.google.firebase.firestore.EventListener;
import com.google.firebase.firestore.FirebaseFirestore;
import com.google.firebase.firestore.FirebaseFirestoreException;
import com.google.firebase.firestore.Query;
import com.google.firebase.firestore.QuerySnapshot;

import java.util.ArrayList;
import java.util.List;


/**
 * A simple {@link Fragment} subclass.
 */
public class HomeFragment extends Fragment {

    private RecyclerView blog_list_view;
    private List<BlogPost> blog_list;

    private FirebaseFirestore firebaseFirestore;
    private FirebaseAuth firebaseAuth;
    private BlogRecyclerAdapter blogRecyclerAdapter;

    private DocumentSnapshot lastVisible;
    private Boolean isFirstPageFirstLoad = true;

    public HomeFragment() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, final ViewGroup container,
                             Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.fragment_home, container, false);

        blog_list = new ArrayList<>();
        blog_list_view = view.findViewById(R.id.blog_list_view);

        firebaseAuth = FirebaseAuth.getInstance();

        blogRecyclerAdapter = new BlogRecyclerAdapter(blog_list);
        blog_list_view.setLayoutManager(new LinearLayoutManager(container.getContext()));
        blog_list_view.setAdapter(blogRecyclerAdapter);

        if(firebaseAuth.getCurrentUser() != null) {

            firebaseFirestore = FirebaseFirestore.getInstance();

            blog_list_view.addOnScrollListener(new RecyclerView.OnScrollListener() {
                @Override
                public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                    super.onScrolled(recyclerView, dx, dy);

                    Boolean reachedBottom = !recyclerView.canScrollVertically(1);

                    if(reachedBottom){

                        String desc = lastVisible.getString("desc");
                        Toast.makeText(container.getContext(), "Reached : " + desc, Toast.LENGTH_SHORT).show();

                        loadMorePost();

                    }

                }
            });

            Query firstQuery = firebaseFirestore.collection("Posts").orderBy("timestamp", Query.Direction.DESCENDING).limit(3);
            firstQuery.addSnapshotListener(getActivity(), new EventListener<QuerySnapshot>() {
                @Override
                public void onEvent(QuerySnapshot documentSnapshots, FirebaseFirestoreException e) {
                    if (isFirstPageFirstLoad){

                        lastVisible = documentSnapshots.getDocuments().get(documentSnapshots.size() - 1);

                    }
                    for (DocumentChange doc : documentSnapshots.getDocumentChanges()){
                        if (doc.getType() == DocumentChange.Type.ADDED) {

                            String blogPostId = doc.getDocument().getId();
                            BlogPost blogPost = doc.getDocument().toObject(BlogPost.class).withId(blogPostId);

                            if (isFirstPageFirstLoad){
                                blog_list.add(blogPost);

                            }else {
                                blog_list.add(0,blogPost);

                            }
                           blogRecyclerAdapter.notifyDataSetChanged();;
                        }
                    }
isFirstPageFirstLoad = false;
                }
            });

        }

        // Inflate the layout for this fragment
        return view;
    }

    public void loadMorePost(){

        Query nextQuery = firebaseFirestore.collection("Posts")
                .orderBy("timestamp", Query.Direction.DESCENDING)
                .startAfter(lastVisible)
                .limit(3);

        nextQuery.addSnapshotListener(getActivity(), new EventListener<QuerySnapshot>() {
            @Override
            public void onEvent(QuerySnapshot documentSnapshots, FirebaseFirestoreException e) {

                    if (!documentSnapshots.isEmpty()){


                        lastVisible = documentSnapshots.getDocuments().get(documentSnapshots.size() - 1);
                    for (DocumentChange doc : documentSnapshots.getDocumentChanges()) {
                        if (doc.getType() == DocumentChange.Type.ADDED) {
                            String blogPostId = doc.getDocument().getId();
                            BlogPost blogPost = doc.getDocument().toObject(BlogPost.class).withId(blogPostId);
                            blog_list.add(blogPost);

                            blogRecyclerAdapter.notifyDataSetChanged();

                        }
                    }

                }

            }
        });

    }

}

＆＃13;

提前致谢。

Answer 1

试试这个

您可以在 Context
的构造函数中传递 BlogRecyclerAdapter

public BlogRecyclerAdapter(List < BlogPost > blog_list, Context context) {

    this.blog_list = blog_list;
    this.context = context;

 }

像这样使用

firebaseFirestore = FirebaseFirestore.getInstance(context);
firebaseAuth = FirebaseAuth.getInstance(context);



Glide.with(context).applyDefaultRequestOptions(placeholderOption).load(image).into(blogUserImage);

像这样打电话给 BlogRecyclerAdapter

BlogRecyclerAdapter adapter= new BlogRecyclerAdapter( blog_list, YourActivity.this );

Answer 2

创建一个Adapter构造函数，并在发送列表数据时从主类发送另一个参数上下文。

这在Fragment中

 blogRecyclerAdapter = new BlogRecyclerAdapter(blog_list,getContext());
        blog_list_view.setLayoutManager(new LinearLayoutManager(container.getContext()));
        blog_list_view.setAdapter(blogRecyclerAdapter);

这是适配器

public BlogRecyclerAdapter(List<BlogPost> blog_list,Context context){
  this.blog_list = blog_list;
  this.context=context;
}

然后，您可以在适配器类

中将此上下文用作getApplicationContext();

在没有互联网时禁用按钮。

if(!isNetworkAvailable()){
like_btn.setClickable(false); }

private boolean isNetworkAvailable() {
    ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
    return activeNetworkInfo != null && activeNetworkInfo.isConnected();
}

Answer 3

如果没有发送参数，当您调用网络检查方法时，您可以使用下面的方法来执行相同的操作

isNetworkStatusAvialable( holder.blogLikeBtn.getContext())

您可以从任何视图中获取上下文，而不是传递 getApplicationContext（）方法。

通过使用上述方法，我传递了被单击的相同按钮的上下文。希望对你有所帮助。

如何在Adapter Class中使用get getApplicationContext（）

3 个答案: