如何在社交媒体Android应用程序的主页上检索博客？

这是6的“建立一个社会化媒体应用Android Studio中”教程中的一部分，我们将要在本文中介绍了以下功能：

• 我们将检索用户在HomeFragment上编写的博客。
• 在这里，我们仅显示了用户数据以及博客的标题，描述和图像，但是我们还将在即将到来的博客中实现点赞和评论功能。
• 然后，我们将显示“发布详细信息活动”，用户可以在其中发表评论。
• 我们还实现了“赞博客”功能。

分步实施

步骤1：创建一个新的布局资源文件

转到应用程序> res>布局>新建>布局资源文件，并将文件命名为row_posts 。下面是代码 row_posts.xml文件。

步骤2：建立新的Java类别

请参阅本文在Android Studio中创建类并将该类命名为ModelPost。下面是ModelPost的代码。 Java文件。创建了此类以初始化密钥，以便我们以后可以检索密钥的值。

Java

package com.example.socialmediaapp;
  
public class ModelPost {
    public ModelPost() {
    }
  
    String description;
  
    public String getDescription() {
        return description;
    }
  
    public void setDescription(String description) {
        this.description = description;
    }
  
    public String getPid() {
        return pid;
    }
  
    public void setPid(String pid) {
        this.pid = pid;
    }
  
    public String getPtime() {
        return ptime;
    }
  
    public void setPtime(String ptime) {
        this.ptime = ptime;
    }
  
    public String getTitle() {
        return title;
    }
  
    public void setTitle(String title) {
        this.title = title;
    }
  
    public String getUdp() {
        return udp;
    }
  
    public void setUdp(String udp) {
        this.udp = udp;
    }
  
    public String getUemail() {
        return uemail;
    }
  
    public void setUemail(String uemail) {
        this.uemail = uemail;
    }
  
    public String getUid() {
        return uid;
    }
  
    public void setUid(String uid) {
        this.uid = uid;
    }
  
    public String getUimage() {
        return uimage;
    }
  
    public void setUimage(String uimage) {
        this.uimage = uimage;
    }
  
    public String getUname() {
        return uname;
    }
  
    public void setUname(String uname) {
        this.uname = uname;
    }
  
    public String getPlike() {
        return plike;
    }
  
    public void setPlike(String plike) {
        this.plike = plike;
    }
  
    String pid;
  
    public String getPcomments() {
        return pcomments;
    }
  
    public void setPcomments(String pcomments) {
        this.pcomments = pcomments;
    }
  
    public ModelPost(String description, String pid, String ptime, String pcomments, String title, String udp, String uemail, String uid, String uimage, String uname, String plike) {
        this.description = description;
        this.pid = pid;
        this.ptime = ptime;
        this.pcomments = pcomments;
        this.title = title;
        this.udp = udp;
        this.uemail = uemail;
        this.uid = uid;
        this.uimage = uimage;
        this.uname = uname;
        this.plike = plike;
    }
  
    String ptime, pcomments;
      
    String title;
  
    String udp;
    String uemail;
    String uid;
    String uimage;
  
    String uname, plike;
      
}

同样，创建另一个Java类并将该类命名为AdapterPosts。下面是AdapterPosts的代码。 Java文件。

Java

package com.example.socialmediaapp;
  
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.text.format.DateFormat;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.PopupMenu;
import android.widget.TextView;
import android.widget.Toast;
  
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
  
import com.bumptech.glide.Glide;
import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.firebase.auth.FirebaseAuth;
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.Query;
import com.google.firebase.database.ValueEventListener;
import com.google.firebase.storage.FirebaseStorage;
import com.google.firebase.storage.StorageReference;
  
import java.util.Calendar;
import java.util.List;
import java.util.Locale;
  
public class AdapterPosts extends RecyclerView.Adapter {
      
    Context context;
    String myuid;
    private DatabaseReference liekeref, postref;
    boolean mprocesslike = false;
  
    public AdapterPosts(Context context, List modelPosts) {
        this.context = context;
        this.modelPosts = modelPosts;
        myuid = FirebaseAuth.getInstance().getCurrentUser().getUid();
        liekeref = FirebaseDatabase.getInstance().getReference().child("Likes");
        postref = FirebaseDatabase.getInstance().getReference().child("Posts");
    }
  
    List modelPosts;
  
    @NonNull
    @Override
    public MyHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(context).inflate(R.layout.row_posts, parent, false);
        return new MyHolder(view);
    }
  
    @Override
    public void onBindViewHolder(@NonNull final MyHolder holder, final int position) {
        final String uid = modelPosts.get(position).getUid();
        String nameh = modelPosts.get(position).getUname();
        final String titlee = modelPosts.get(position).getTitle();
        final String descri = modelPosts.get(position).getDescription();
        final String ptime = modelPosts.get(position).getPtime();
        String dp = modelPosts.get(position).getUdp();
        String plike = modelPosts.get(position).getPlike();
        final String image = modelPosts.get(position).getUimage();
        String email = modelPosts.get(position).getUemail();
        String comm = modelPosts.get(position).getPcomments();
        final String pid = modelPosts.get(position).getPtime();
        Calendar calendar = Calendar.getInstance(Locale.ENGLISH);
        calendar.setTimeInMillis(Long.parseLong(ptime));
        String timedate = DateFormat.format("dd/MM/yyyy hh:mm aa", calendar).toString();
        holder.name.setText(nameh);
        holder.title.setText(titlee);
        holder.description.setText(descri);
        holder.time.setText(timedate);
        holder.like.setText(plike + " Likes");
        holder.comments.setText(comm + " Comments");
        setLikes(holder, ptime);
        try {
            Glide.with(context).load(dp).into(holder.picture);
        } catch (Exception e) {
  
        }
        holder.image.setVisibility(View.VISIBLE);
        try {
            Glide.with(context).load(image).into(holder.image);
        } catch (Exception e) {
  
        }
        holder.like.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(holder.itemView.getContext(), PostLikedByActivity.class);
                intent.putExtra("pid", pid);
                holder.itemView.getContext().startActivity(intent);
            }
        });
        holder.likebtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                final int plike = Integer.parseInt(modelPosts.get(position).getPlike());
                mprocesslike = true;
                final String postid = modelPosts.get(position).getPtime();
                liekeref.addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                        if (mprocesslike) {
                            if (dataSnapshot.child(postid).hasChild(myuid)) {
                                postref.child(postid).child("plike").setValue("" + (plike - 1));
                                liekeref.child(postid).child(myuid).removeValue();
                                mprocesslike = false;
                            } else {
                                postref.child(postid).child("plike").setValue("" + (plike + 1));
                                liekeref.child(postid).child(myuid).setValue("Liked");
                                mprocesslike = false;
                            }
                        }
                    }
  
                    @Override
                    public void onCancelled(@NonNull DatabaseError databaseError) {
  
                    }
                });
            }
        });
        holder.more.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                showMoreOptions(holder.more, uid, myuid, ptime, image);
            }
        });
        holder.comment.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(context, PostDetailsActivity.class);
                intent.putExtra("pid", ptime);
                context.startActivity(intent);
            }
        });
    }
  
    private void showMoreOptions(ImageButton more, String uid, String myuid, final String pid, final String image) {
        PopupMenu popupMenu = new PopupMenu(context, more, Gravity.END);
        if (uid.equals(myuid)) {
            popupMenu.getMenu().add(Menu.NONE, 0, 0, "DELETE");
        }
        popupMenu.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
            @Override
            public boolean onMenuItemClick(MenuItem item) {
                if (item.getItemId() == 0) {
                    deltewithImage(pid, image);
                }
  
                return false;
            }
        });
        popupMenu.show();
    }
  
    private void deltewithImage(final String pid, String image) {
        final ProgressDialog pd = new ProgressDialog(context);
        pd.setMessage("Deleting");
        StorageReference picref = FirebaseStorage.getInstance().getReferenceFromUrl(image);
        picref.delete().addOnSuccessListener(new OnSuccessListener() {
            @Override
            public void onSuccess(Void aVoid) {
                Query query = FirebaseDatabase.getInstance().getReference("Posts").orderByChild("ptime").equalTo(pid);
                query.addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                        for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
                            dataSnapshot1.getRef().removeValue();
                        }
                        pd.dismiss();
                        Toast.makeText(context, "Deleted Sucessfully", Toast.LENGTH_LONG).show();
                    }
                    @Override
                    public void onCancelled(@NonNull DatabaseError databaseError) {
  
                    }
                });
            }
        }).addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
  
            }
        });
    }
      
    private void setLikes(final MyHolder holder, final String pid) {
        liekeref.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                if (dataSnapshot.child(pid).hasChild(myuid)) {
                    holder.likebtn.setCompoundDrawablesWithIntrinsicBounds(R.drawable.ic_liked, 0, 0, 0);
                    holder.likebtn.setText("Liked");
                } else {
                    holder.likebtn.setCompoundDrawablesWithIntrinsicBounds(R.drawable.ic_like, 0, 0, 0);
                    holder.likebtn.setText("Like");
                }
            }
  
            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
  
            }
        });
    }
  
    @Override
    public int getItemCount() {
        return modelPosts.size();
    }
      
    class MyHolder extends RecyclerView.ViewHolder {
        ImageView picture, image;
        TextView name, time, title, description, like, comments;
        ImageButton more;
        Button likebtn, comment;
        LinearLayout profile;
  
        public MyHolder(@NonNull View itemView) {
            super(itemView);
            picture = itemView.findViewById(R.id.picturetv);
            image = itemView.findViewById(R.id.pimagetv);
            name = itemView.findViewById(R.id.unametv);
            time = itemView.findViewById(R.id.utimetv);
            more = itemView.findViewById(R.id.morebtn);
            title = itemView.findViewById(R.id.ptitletv);
            description = itemView.findViewById(R.id.descript);
            like = itemView.findViewById(R.id.plikeb);
            comments = itemView.findViewById(R.id.pcommentco);
            likebtn = itemView.findViewById(R.id.like);
            comment = itemView.findViewById(R.id.comment);
            profile = itemView.findViewById(R.id.profilelayout);
        }
    }
}

步骤3：使用fragment_home.xml文件

导航到应用程序> res>布局> fragment_home.xml，然后将以下代码添加到该文件中。以下是fragment_home.xml文件的代码。

步骤4：使用HomeFragment。 Java文件

这就是我们将如何从Firebase检索博客的方法。每次数据更改时，值也会相应更改。

DatabaseReference databaseReference= FirebaseDatabase.getInstance().getReference("Posts");
        databaseReference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                posts.clear();
               for (DataSnapshot dataSnapshot1:dataSnapshot.getChildren()){
               }
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            Toast.makeText(getActivity(),databaseError.getMessage(),Toast.LENGTH_LONG).show();
       }
 });

Java

package com.example.socialmediaapp;
  
import android.content.Intent;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
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.google.firebase.auth.FirebaseAuth;
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;
  
/**
 * A simple {@link Fragment} subclass.
 */
public class HomeFragment extends Fragment {
  
    FirebaseAuth firebaseAuth;
    String myuid;
    RecyclerView recyclerView;
    List posts;
    AdapterPosts adapterPosts;
  
    public HomeFragment() {
        // Required empty public constructor
    }
  
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_home, container, false);
        firebaseAuth = FirebaseAuth.getInstance();
        recyclerView = view.findViewById(R.id.postrecyclerview);
        recyclerView.setHasFixedSize(true);
        LinearLayoutManager layoutManager = new LinearLayoutManager(getActivity());
        layoutManager.setReverseLayout(true);
        layoutManager.setStackFromEnd(true);
        recyclerView.setLayoutManager(layoutManager);
        posts = new ArrayList<>();
        loadPosts();
        return view;
    }
  
    private void loadPosts() {
        DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference("Posts");
        databaseReference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                posts.clear();
                for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
                    ModelPost modelPost = dataSnapshot1.getValue(ModelPost.class);
                    posts.add(modelPost);
                    adapterPosts = new AdapterPosts(getActivity(), posts);
                    recyclerView.setAdapter(adapterPosts);
                }
            }
  
            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
  
                Toast.makeText(getActivity(), databaseError.getMessage(), Toast.LENGTH_LONG).show();
            }
        });
    }
  
    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        setHasOptionsMenu(true);
        super.onCreate(savedInstanceState);
    }
      
}

步骤5：创建2个新的空活动，并将活动命名为PostLikedByActivity和PostDetailsActivity 。保持文件原样。

输出：

对于本文中使用的所有可绘制文件，请参考以下链接： https://drive.google.com/drive/folders/1M_knOH_ugCuwSP5nkYzeD4dRp-Honzbe?usp=sharing

下面是执行这些操作后的文件结构：