Loading Data from the Firebase Database

app/build.gradle

@@ -29,6 +29,7 @@ dependencies {
     implementation 'com.firebaseui:firebase-ui-auth:3.3.1'
     implementation 'com.google.firebase:firebase-storage:15.0.0'
     implementation 'com.google.firebase:firebase-database:15.0.0'
+    implementation 'com.squareup.picasso:picasso:2.71828'
 }
 
 apply plugin: 'com.google.gms.google-services'

app/src/main/java/com/dragosholban/myinstagramapp/FeedActivity.java

@@ -9,26 +9,38 @@
 import android.support.v4.content.ContextCompat;
 import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
+import android.support.v7.widget.LinearLayoutManager;
+import android.support.v7.widget.RecyclerView;
 import android.view.View;
 import android.widget.Toast;
 
 import com.google.android.gms.tasks.OnFailureListener;
 import com.google.android.gms.tasks.OnSuccessListener;
 import com.google.firebase.auth.FirebaseAuth;
 import com.google.firebase.auth.FirebaseUser;
+import com.google.firebase.database.ChildEventListener;
+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 com.google.firebase.storage.UploadTask;
 
 import java.text.SimpleDateFormat;
+import java.util.ArrayList;
 import java.util.Date;
 
 public class FeedActivity extends AppCompatActivity {
 
     FirebaseUser fbUser;
     DatabaseReference database;
+    RecyclerView recyclerView;
+    RecyclerView.LayoutManager mLayoutManager;
+    ImageAdapter mAdapter;
+    ArrayList<Image> images = new ArrayList<>();
 
     static final int RC_PERMISSION_READ_EXTERNAL_STORAGE = 1;
     static final int RC_IMAGE_GALLERY = 2;
@@ -44,6 +56,61 @@ protected void onCreate(Bundle savedInstanceState) {
         }
 
         database = FirebaseDatabase.getInstance().getReference();
+
+        // Setup the RecyclerView
+        recyclerView = findViewById(R.id.recyclerView);
+        mLayoutManager = new LinearLayoutManager(this);
+        recyclerView.setLayoutManager(mLayoutManager);
+        mAdapter = new ImageAdapter(images, this);
+        recyclerView.setAdapter(mAdapter);
+
+        // Get the latest 100 images
+        Query imagesQuery = database.child("images").orderByKey().limitToFirst(100);
+        imagesQuery.addChildEventListener(new ChildEventListener() {
+            @Override
+            public void onChildAdded(DataSnapshot dataSnapshot, String s) {
+
+                // A new image has been added, add it to the displayed list
+                final Image image = dataSnapshot.getValue(Image.class);
+
+                // get the image user
+                database.child("users/" + image.userId).addListenerForSingleValueEvent(new ValueEventListener() {
+                    @Override
+                    public void onDataChange(DataSnapshot dataSnapshot) {
+                        User user = dataSnapshot.getValue(User.class);
+                        image.user = user;
+                        mAdapter.notifyDataSetChanged();
+                    }
+
+                    @Override
+                    public void onCancelled(DatabaseError databaseError) {
+
+                    }
+                });
+
+                mAdapter.addImage(image);
+            }
+
+            @Override
+            public void onChildChanged(DataSnapshot dataSnapshot, String s) {
+
+            }
+
+            @Override
+            public void onChildRemoved(DataSnapshot dataSnapshot) {
+
+            }
+
+            @Override
+            public void onChildMoved(DataSnapshot dataSnapshot, String s) {
+
+            }
+
+            @Override
+            public void onCancelled(DatabaseError databaseError) {
+
+            }
+        });
     }
 
     public void uploadImage(View view) {

app/src/main/java/com/dragosholban/myinstagramapp/ImageAdapter.java

@@ -0,0 +1,68 @@
+package com.dragosholban.myinstagramapp;
+
+import android.support.v7.widget.RecyclerView;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.Button;
+import android.widget.ImageView;
+import android.widget.TextView;
+
+import com.squareup.picasso.Picasso;
+
+import java.util.ArrayList;
+
+public class ImageAdapter extends RecyclerView.Adapter<ImageAdapter.ViewHolder> {
+    private ArrayList<Image> mDataset;
+    private FeedActivity mActivity;
+
+    public static class ViewHolder extends RecyclerView.ViewHolder {
+        public TextView mTextView;
+        public ImageView mImageView;
+        public Button mLikeButton;
+
+        public ViewHolder(View v) {
+            super(v);
+            mTextView = v.findViewById(R.id.textView2);
+            mImageView = v.findViewById(R.id.imageView);
+            mLikeButton = v.findViewById(R.id.likeButton);
+        }
+    }
+
+    public ImageAdapter(ArrayList<Image> myDataset, FeedActivity activity) {
+        mDataset = myDataset;
+        mActivity = activity;
+    }
+
+    // Create new views (invoked by the layout manager)
+    @Override
+    public ImageAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
+        // create a new view
+        View v = LayoutInflater.from(parent.getContext())
+                .inflate(R.layout.image_view, parent, false);
+
+        ViewHolder vh = new ViewHolder(v);
+        return vh;
+    }
+
+    // Replace the contents of a view (invoked by the layout manager)
+    @Override
+    public void onBindViewHolder(ViewHolder holder, final int position) {
+        final Image image = (Image) mDataset.get(position);
+        if (image.user != null) {
+            holder.mTextView.setText(image.user.displayName);
+        }
+        Picasso.get().load(image.downloadUrl).into(holder.mImageView);
+    }
+
+    // Return the size of your dataset (invoked by the layout manager)
+    @Override
+    public int getItemCount() {
+        return mDataset.size();
+    }
+
+    public void addImage(Image image) {
+        mDataset.add(0, image);
+        notifyDataSetChanged();
+    }
+}

app/src/main/res/layout/activity_feed.xml

@@ -21,4 +21,19 @@
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintStart_toStartOf="parent" />
 
+    <android.support.v7.widget.RecyclerView
+        android:id="@+id/recyclerView"
+        android:layout_width="0dp"
+        android:layout_height="0dp"
+        android:layout_marginBottom="8dp"
+        android:layout_marginEnd="8dp"
+        android:layout_marginLeft="8dp"
+        android:layout_marginRight="8dp"
+        android:layout_marginStart="8dp"
+        android:layout_marginTop="8dp"
+        app:layout_constraintBottom_toTopOf="@+id/uploadButton"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent" />
+
 </android.support.constraint.ConstraintLayout>

app/src/main/res/layout/image_view.xml

@@ -0,0 +1,52 @@
+<?xml version="1.0" encoding="utf-8"?>
+<android.support.constraint.ConstraintLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content">
+
+    <ImageView
+        android:id="@+id/imageView"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_marginBottom="8dp"
+        android:layout_marginEnd="8dp"
+        android:layout_marginLeft="8dp"
+        android:layout_marginRight="8dp"
+        android:layout_marginStart="8dp"
+        android:layout_marginTop="8dp"
+        app:layout_constraintBottom_toTopOf="@+id/textView2"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent"
+        android:adjustViewBounds="true" />
+
+    <TextView
+        android:id="@+id/textView2"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_marginBottom="8dp"
+        android:layout_marginEnd="8dp"
+        android:layout_marginLeft="8dp"
+        android:layout_marginRight="8dp"
+        android:layout_marginStart="8dp"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toStartOf="@id/likeButton"
+        app:layout_constraintStart_toStartOf="parent" />
+
+    <Button
+        android:id="@+id/likeButton"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginBottom="8dp"
+        android:layout_marginEnd="8dp"
+        android:layout_marginLeft="8dp"
+        android:layout_marginRight="8dp"
+        android:layout_marginStart="8dp"
+        android:text="Like"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toEndOf="@id/textView2" />
+
+</android.support.constraint.ConstraintLayout>