Android RecyclerView add remove item example

activity_main.xml


<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/rl"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="10dp"
    tools:context=".MainActivity"
    android:background="#ecb0dd"
    >
    <Button
        android:id="@+id/btn_add"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:padding="0dp"
        android:background="@android:color/transparent"
        android:drawableLeft="@drawable/ic_add_circle_black_24dp"
        android:drawableStart="@drawable/ic_add_circle_black_24dp"
        android:text="Add an item"
        />
    <android.support.v7.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scrollbars="vertical"
        android:layout_below="@id/btn_add"
        >
    </android.support.v7.widget.RecyclerView>
</RelativeLayout>

custom_view.xml


<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    android:id="@+id/card_view"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    card_view:cardCornerRadius="4dp"
    card_view:cardMaxElevation="4dp"
    card_view:cardElevation="2dp"
    card_view:contentPadding="5dp"
    >
    <RelativeLayout
        android:id="@+id/rl"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:padding="3dp"
        >
        <TextView
            android:id="@+id/tv"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:textColor="#000"
            android:textSize="25dp"
            android:textStyle="bold"
            android:layout_margin="2dp"
            android:padding="10dp"
            android:layout_gravity="center"
            android:gravity="center"
            />
        <ImageButton
            android:id="@+id/ib_remove"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@drawable/ic_close_circle_outline_white_18dp"
            android:layout_alignParentRight="true"
            android:layout_alignParentEnd="true"
            android:background="@android:color/transparent"
            android:padding="0dp"
            />
    </RelativeLayout>
</android.support.v7.widget.CardView>

MainActivity.java


package com.cfsuman.me.androidcode;

import android.content.Context;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.view.Window;
import android.widget.Button;
import android.widget.RelativeLayout;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Random;


public class MainActivity extends AppCompatActivity {
    private Context mContext;

    RelativeLayout mRelativeLayout;
    private RecyclerView mRecyclerView;
    private Button mButtonAdd;

    private RecyclerView.Adapter mAdapter;
    private RecyclerView.LayoutManager mLayoutManager;
    private Random mRandom = new Random();


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // Request window feature action bar
        requestWindowFeature(Window.FEATURE_ACTION_BAR);
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Get the application context
        mContext = getApplicationContext();

        // Change the action bar color
        getSupportActionBar().setBackgroundDrawable(
                new ColorDrawable(Color.parseColor("#FFFF00BF"))
        );

        // Get the widgets reference from XML layout
        mRelativeLayout = (RelativeLayout) findViewById(R.id.rl);
        mButtonAdd = (Button) findViewById(R.id.btn_add);
        mRecyclerView = (RecyclerView) findViewById(R.id.recycler_view);

        // Initialize a new String array
        final String[] animals = {
                "Aardvark",
                "Albatross",
                "Alligator",
                "Alpaca",
                "Ant",
                "Anteater",
                "Antelope",
                "Ape",
                "Armadillo",
                "Donkey",
                "Baboon",
                "Badger",
                "Barracuda",
                "Bear",
                "Beaver",
                "Bee"
        };

        // Intilize an array list from array
        final List<String> animalsList = new ArrayList(Arrays.asList(animals));

        // Define a layout for RecyclerView
        mLayoutManager = new GridLayoutManager(mContext,3);
        mRecyclerView.setLayoutManager(mLayoutManager);

        // Initialize a new instance of RecyclerView Adapter instance
        mAdapter = new AnimalsAdapter(mContext,animalsList);

        // Set the adapter for RecyclerView
        mRecyclerView.setAdapter(mAdapter);

        // Set a click listener for add item button
        mButtonAdd.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                // Specify the position
                int position = 0;
                String itemLabel = "" + mRandom.nextInt(100);

                // Add an item to animals list
                animalsList.add(position,"" + itemLabel);

                /*
                    public final void notifyItemInserted (int position)
                        Notify any registered observers that the item reflected at position has been
                        newly inserted. The item previously at position is now at position position + 1.

                        This is a structural change event. Representations of other existing items
                        in the data set are still considered up to date and will not be rebound,
                        though their positions may be altered.

                    Parameters
                    position : Position of the newly inserted item in the data set

                */

                // Notify the adapter that an item inserted
                mAdapter.notifyItemInserted(position);

                /*
                    public void scrollToPosition (int position)
                        Convenience method to scroll to a certain position. RecyclerView does not
                        implement scrolling logic, rather forwards the call to scrollToPosition(int)

                    Parameters
                    position : Scroll to this adapter position

                */
                // Scroll to newly added item position
                mRecyclerView.scrollToPosition(position);

                // Show the added item label
                Toast.makeText(mContext,"Added : " + itemLabel,Toast.LENGTH_SHORT).show();
            }
        });
   }
}

AnimalsAdapter.java


package com.cfsuman.me.androidcode;

import android.content.Context;
import android.graphics.Color;
import android.graphics.EmbossMaskFilter;
import android.graphics.drawable.GradientDrawable;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageButton;
import android.widget.RelativeLayout;
import android.widget.TextView;
import android.widget.Toast;

import java.util.List;
import java.util.Random;


public class AnimalsAdapter extends RecyclerView.Adapter<AnimalsAdapter.ViewHolder>{
    private List<String> mDataSet;
    private Context mContext;
    private Random mRandom = new Random();

    public AnimalsAdapter(Context context,List<String> list){
        mDataSet = list;
        mContext = context;
    }

    public static class ViewHolder extends RecyclerView.ViewHolder{
        public TextView mTextView;
        public ImageButton mRemoveButton;
        public RelativeLayout mRelativeLayout;
        public ViewHolder(View v){
            super(v);
            mTextView = (TextView) v.findViewById(R.id.tv);
            mRemoveButton = (ImageButton) v.findViewById(R.id.ib_remove);
            mRelativeLayout = (RelativeLayout) v.findViewById(R.id.rl);
        }
    }

    @Override
    public AnimalsAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType){
        // Create a new View
        View v = LayoutInflater.from(mContext).inflate(R.layout.custom_view,parent,false);
        ViewHolder vh = new ViewHolder(v);
        return vh;
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, final int position){
        holder.mTextView.setText((String)mDataSet.get(position));
        // Generate a random color
        int color = getRandomHSVColor();

        // Set a random color for TextView background
        holder.mTextView.setBackgroundColor(getLighterColor(color));

        // Set a text color for TextView
        holder.mTextView.setTextColor(getReverseColor(color));

        // Set a gradient background for RelativeLayout
        holder.mRelativeLayout.setBackground(getGradientDrawable());

        // Emboss the TextView text
        applyEmbossMaskFilter(holder.mTextView);

        // Set a click listener for TextView
        holder.mTextView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String animal = mDataSet.get(position);
                Toast.makeText(mContext,animal,Toast.LENGTH_SHORT).show();
            }
        });

        // Set a click listener for item remove button
        holder.mRemoveButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                // Get the clicked item label
                String itemLabel = mDataSet.get(position);

                // Remove the item on remove/button click
                mDataSet.remove(position);

                /*
                    public final void notifyItemRemoved (int position)
                        Notify any registered observers that the item previously located at position
                        has been removed from the data set. The items previously located at and
                        after position may now be found at oldPosition - 1.

                        This is a structural change event. Representations of other existing items
                        in the data set are still considered up to date and will not be rebound,
                        though their positions may be altered.

                    Parameters
                        position : Position of the item that has now been removed
                */
                notifyItemRemoved(position);

                /*
                    public final void notifyItemRangeChanged (int positionStart, int itemCount)
                        Notify any registered observers that the itemCount items starting at
                        position positionStart have changed. Equivalent to calling
                        notifyItemRangeChanged(position, itemCount, null);.

                        This is an item change event, not a structural change event. It indicates
                        that any reflection of the data in the given position range is out of date
                        and should be updated. The items in the given range retain the same identity.

                    Parameters
                        positionStart : Position of the first item that has changed
                        itemCount : Number of items that have changed
                */
                notifyItemRangeChanged(position,mDataSet.size());

                // Show the removed item label
                Toast.makeText(mContext,"Removed : " + itemLabel,Toast.LENGTH_SHORT).show();
            }
        });
    }

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

    // Custom method to apply emboss mask filter to TextView
    protected void applyEmbossMaskFilter(TextView tv){
        EmbossMaskFilter embossFilter = new EmbossMaskFilter(
                new float[]{1f, 5f, 1f}, // direction of the light source
                0.8f, // ambient light between 0 to 1
                8, // specular highlights
                7f // blur before applying lighting
        );
        tv.setLayerType(View.LAYER_TYPE_SOFTWARE,null);
        tv.getPaint().setMaskFilter(embossFilter);
    }

    // Custom method to generate random HSV color
    protected int getRandomHSVColor(){
        // Generate a random hue value between 0 to 360
        int hue = mRandom.nextInt(361);
        // We make the color depth full
        float saturation = 1.0f;
        // We make a full bright color
        float value = 1.0f;
        // We avoid color transparency
        int alpha = 255;
        // Finally, generate the color
        int color = Color.HSVToColor(alpha, new float[]{hue, saturation, value});
        // Return the color
        return color;
    }

    // Custom method to create a GradientDrawable object
    protected GradientDrawable getGradientDrawable(){
        GradientDrawable gradient = new GradientDrawable();
        gradient.setGradientType(GradientDrawable.SWEEP_GRADIENT);
        gradient.setColors(new int[]{getRandomHSVColor(), getRandomHSVColor(),getRandomHSVColor()});
        return gradient;
    }

    // Custom method to get a darker color
    protected int getDarkerColor(int color){
        float[] hsv = new float[3];
        Color.colorToHSV(color, hsv);
        hsv[2] = 0.8f *hsv[2];
        return Color.HSVToColor(hsv);
    }

    // Custom method to get a lighter color
    protected int getLighterColor(int color){
        float[] hsv = new float[3];
        Color.colorToHSV(color,hsv);
        hsv[2] = 0.2f + 0.8f * hsv[2];
        return Color.HSVToColor(hsv);
    }

    // Custom method to get reverse color
    protected int getReverseColor(int color){
        float[] hsv = new float[3];
        Color.RGBToHSV(
                Color.red(color), // Red value
                Color.green(color), // Green value
                Color.blue(color), // Blue value
                hsv
        );
        hsv[0] = (hsv[0] + 180) % 360;
        return Color.HSVToColor(hsv);
    }
}

build.gradle [dependencies]


compile 'com.android.support:recyclerview-v7:23.0.1'
compile 'com.android.support:cardview-v7:23.0.1'

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