Firebase Realtime Database Workshop

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    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="match_parent"
    android:paddingBottom="16dp"
    android:paddingTop="16dp"
    android:paddingLeft="16dp"
    android:paddingRight="16dp"
    tools:context="com.sckim.fbtodoapp.MainActivity">

    <android.support.v7.widget.RecyclerView
    android:id="@+id/task_list"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentTop="true"
        android:layout_above="@+id/add_task_wrapper"
        android:layout_marginBottom="12dp"
        android:orientation="vertical"
        android:scrollbars="none"
    />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:id="@+id/add_task_wrapper"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true">

        <EditText
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="7"
            android:inputType="text"
            android:id="@+id/add_task_box"
            />
        <Button
            android:id="@+id/add_task_button"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="@string/add_task_button"
            android:layout_weight="3"/>
    </LinearLayout>


</RelativeLayout>

MainActivity.java

package com.sckim.fbtodoapp;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

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 java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private static final String TAG = MainActivity.class.getSimpleName();
    private RecyclerView recyclerView;
    private LinearLayoutManager linearLayoutManager;
    private RecyclerViewAdapter recyclerViewAdapter;
    private EditText addTaskBox;
    private List<Task> allTask;
    private DatabaseReference databaseReference;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        databaseReference = FirebaseDatabase.getInstance().getReference();
        allTask = new ArrayList<Task>();
        recyclerView = (RecyclerView)findViewById(R.id.task_list);
        linearLayoutManager = new LinearLayoutManager(getApplicationContext());
        recyclerView.setLayoutManager(linearLayoutManager);
        addTaskBox = (EditText)findViewById(R.id.add_task_box);
        Button addTaskButton = (Button)findViewById(R.id.add_task_button);
        addTaskButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String enteredTask = addTaskBox.getText().toString();
                if (TextUtils.isEmpty(enteredTask)){
                    Toast.makeText(MainActivity.this, "You need input something !", Toast.LENGTH_LONG).show();
                    return;
                }
                if (enteredTask.length() < 6){
                    Toast.makeText(MainActivity.this, "Task count must be more than 6", Toast.LENGTH_LONG).show();
                }
                Task taskObject = new Task(enteredTask);
                databaseReference.push().setValue(taskObject);
                addTaskBox.setText("");
            }
        });
        databaseReference.addChildEventListener(new ChildEventListener() {
            @Override
            public void onChildAdded(DataSnapshot dataSnapshot, String s) {
                getAllTask(dataSnapshot);
            }

            @Override
            public void onChildChanged(DataSnapshot dataSnapshot, String s) {
                getAllTask(dataSnapshot);
            }

            @Override
            public void onChildRemoved(DataSnapshot dataSnapshot) {
                taskDeletion(dataSnapshot);
            }

            @Override
            public void onChildMoved(DataSnapshot dataSnapshot, String s) {

            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });
    }
    private void getAllTask(DataSnapshot dataSnapshot){
        for(DataSnapshot singleSnapshot : dataSnapshot.getChildren()){
            String taskTitle = singleSnapshot.getValue(String.class);
            allTask.add(new Task(taskTitle));
            recyclerViewAdapter = new RecyclerViewAdapter(MainActivity.this, allTask);
            recyclerView.setAdapter(recyclerViewAdapter);
        }
    }
    private void taskDeletion(DataSnapshot dataSnapshot){
        for(DataSnapshot singleSnapshot : dataSnapshot.getChildren()){
            String taskTitle = singleSnapshot.getValue(String.class);
            for (int i = 0; i< allTask.size(); i++){
                if(allTask.get(i).getTask().equals(taskTitle)){
                    allTask.remove(i);
                }
            }
            Log.d(TAG,"Task title" + taskTitle);
            recyclerViewAdapter.notifyDataSetChanged();
            recyclerViewAdapter = new RecyclerViewAdapter(MainActivity.this, allTask);
            recyclerView.setAdapter(recyclerViewAdapter);
        }
    }
}

RecyclerViewAdapter.java

package com.sckim.fbtodoapp;

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import java.util.List;

/**
 * Created by SC Kim on 10/19/2017.
 */

public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewHolders>{

    private List<Task> task;
    protected Context context;
    public RecyclerViewAdapter (Context context, List<Task> task){
        this.task = task;
        this.context = context;
    }

    @Override
    public RecyclerViewHolders onCreateViewHolder(ViewGroup parent, int viewType) {
        RecyclerViewHolders viewHolder = null;
        View layoutView = LayoutInflater.from(parent.getContext()).inflate(R.layout.to_do_list, parent, false);
        viewHolder = new RecyclerViewHolders(layoutView, task);
        return viewHolder;
    }

    @Override
    public void onBindViewHolder(RecyclerViewHolders holder, int position) {
        holder.categoryTitle.setText(task.get(position).getTask());
    }

    @Override
    public int getItemCount() {
        return this.task.size();
    }
}

RecyclerViewHolders.java

package com.sckim.fbtodoapp;

import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

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 java.util.List;

/**
 * Created by SC Kim on 10/19/2017.
 */

public class RecyclerViewHolders extends RecyclerView.ViewHolder{
    private static final String TAG = RecyclerViewHolders.class.getSimpleName();
    public ImageView deleteIcon;
    public TextView categoryTitle;
    public List<Task> taskObject;

    public RecyclerViewHolders(final View itemView, final List<Task> taskObject) {
        super(itemView);
        this.taskObject = taskObject;
        categoryTitle = (TextView)itemView.findViewById(R.id.task_title);
        deleteIcon = (ImageView)itemView.findViewById(R.id.task_delete);
        deleteIcon.setOnClickListener(new View.OnClickListener(){
        @Override
            public void onClick(View v) {
            //What happens when X is clicked.
            Toast.makeText(v.getContext(), "Delete icon is triggered",Toast.LENGTH_LONG).show();
            String taskTitle = taskObject.get(getAdapterPosition()).getTask();
            DatabaseReference ref = FirebaseDatabase.getInstance().getReference();
            final Query applesQuery = ref.orderByChild("task").equalTo(taskTitle);
            applesQuery.addListenerForSingleValueEvent(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {
                    for (DataSnapshot appleSnapshot: dataSnapshot.getChildren()){
                        appleSnapshot.getRef().removeValue();
                    }
                }

                @Override
                public void onCancelled(DatabaseError databaseError) {
                    Log.e(TAG, "onCanceled", databaseError.toException());
                }
            });


                  }
              }

            );
    }
}

Task.java

package com.sckim.fbtodoapp;

/**
 * Created by SC Kim on 10/19/2017.
 */

public class Task {
    private String task;
    public Task() {}
    public Task (String task){
        this.task = task;

    }
    public String getTask(){
        return task;
    }
}

to_do_list.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:paddingTop="16dp"
    android:paddingBottom="16dp">
    <TextView
        android:id="@+id/task_title"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="80"
        android:layout_marginLeft="16dp"
        android:text="@string/app_name"
        android:textSize="16sp"
        android:textColor="#000000"/>

    <ImageView
        android:id="@+id/task_delete"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="20"
        android:layout_marginRight="16dp"
        android:contentDescription="@string/app_name"
        android:src="@drawable/ic_clear_black_24dp" />
</LinearLayout>