如何在Adapter Class中使用get getApplicationContext（）

我正在使用Firebase通过博客文章填充我的BlogRecycleadapter并从Like Buttons获取Likes但是当设备离线并且用户按下Like按钮时，应用程序崩溃…所以我试图在if语句中实现isNetworkavailaible的第二个条件。 。如下

if (!task.getResult().exists() && isNetworkStatusAvialable(getApplicationContext())){ Map 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() ，从几个谷歌搜索，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Recycle适配器代码是

 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 { public List blog_list; public Context context; private FirebaseFirestore firebaseFirestore; private FirebaseAuth firebaseAuth; public BlogRecyclerAdapter(List 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() { @Override public void onComplete(@NonNull Task 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() { @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() { @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() { @Override public void onComplete(@NonNull Task task) { if (!task.getResult().exists() && isNetworkStatusAvialable(getApplicationContext())){ Map 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(); } } 

我的HOmeFragment来自我调用适配器类的地方

 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 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() { @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() { @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(); } } } } }); } } 

提前致谢。

Answer 1

尝试这个

您可以在BlogRecyclerAdapter构造函数中传递Context

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

像这样用

 firebaseFirestore = FirebaseFirestore.getInstance(context); firebaseAuth = FirebaseAuth.getInstance(context); Glide.with(context).applyDefaultRequestOptions(placeholderOption).load(image).into(blogUserImage); 

像这样调用你的BlogRecyclerAdapter

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

Answer 2

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。

Answer 3

创建适配器构造函数，并在发送列表数据时从主类发送另一个参数上下文。

在片段中

  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 blog_list,Context context){ this.blog_list = blog_list; this.context=context; } 

然后你可以使用这个上下文作为getApplicationContext(); 在适配器类中

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(); }