Gallery-like RecyclerView + CardView example

A long long time ago, we have android.widget.Gallery to shows items (ex. photos) in a center-locked, horizontally scrolling list. My example "Implement Android Gallery widget". But it deprecated and no longer supported.

So in long time ago at 2012, I have another example to "Implement Gallery-like HorizontalScrollView".

Now, with RecyclerView and CardView, it's another example to implement Gallery-like RecyclerView + CardView. It display files in ExternalStorageDirectoryPath + "/test/" folder.
(If you want to load from other user selectable folder, refer "Intent.ACTION_OPEN_DOCUMENT (from API level 19) to load images in RecyclerView + CardView".)


To use RecyclerView + CardView, we have to "Add Support Libraries of RecyclerView, CardView to Android Studio Project".

Create our RecyclerView.Adapter, MyRecyclerViewAdapter.java

package com.blogspot.android_er.androidgallery;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.support.v7.widget.CardView;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;

import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.List;

public class MyRecyclerViewAdapter extends RecyclerView.Adapter<MyRecyclerViewAdapter.ItemHolder>{

    private List<Uri> itemsUri;
    private LayoutInflater layoutInflater;
    private Context context;
    private OnItemClickListener onItemClickListener;
    MainActivity mainActivity;

    public MyRecyclerViewAdapter(Context context, MainActivity mainActivity){
        this.context = context;
        layoutInflater = LayoutInflater.from(context);
        itemsUri = new ArrayList<Uri>();

        this.mainActivity = mainActivity;
    }

    @Override
    public MyRecyclerViewAdapter.ItemHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        CardView itemCardView = (CardView)layoutInflater.inflate(R.layout.layout_cardview, parent, false);
        return new ItemHolder(itemCardView, this);
    }

    @Override
    public void onBindViewHolder(MyRecyclerViewAdapter.ItemHolder holder, int position) {
        Uri targetUri = itemsUri.get(position);
        holder.setItemUri(targetUri.getPath());

        if (targetUri != null){

            try {
                //! CAUTION !
                //I'm not sure is it properly to load bitmap here!
                holder.setImageView(loadScaledBitmap(targetUri));
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            }
        }
    }

    /*
    reference:
    Load scaled bitmap
    http://android-er.blogspot.com/2013/08/load-scaled-bitmap.html
     */
    private Bitmap loadScaledBitmap(Uri src) throws FileNotFoundException {

        //display the file to be loadScaledBitmap(),
        //such that you can know how much work on it.
        mainActivity.textInfo.append(src.getLastPathSegment() + "\n");

        // required max width/height
        final int REQ_WIDTH = 150;
        final int REQ_HEIGHT = 150;

        Bitmap bm = null;

        // First decode with inJustDecodeBounds=true to check dimensions
        final BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeStream(context.getContentResolver().openInputStream(src),
                null, options);

        // Calculate inSampleSize
        options.inSampleSize = calculateInSampleSize(options, REQ_WIDTH,
                REQ_HEIGHT);

        // Decode bitmap with inSampleSize set
        options.inJustDecodeBounds = false;
        bm = BitmapFactory.decodeStream(
                context.getContentResolver().openInputStream(src), null, options);

        return bm;
    }

    public int calculateInSampleSize(BitmapFactory.Options options,
                                     int reqWidth, int reqHeight) {
        // Raw height and width of image
        final int height = options.outHeight;
        final int width = options.outWidth;
        int inSampleSize = 1;

        if (height > reqHeight || width > reqWidth) {

            // Calculate ratios of height and width to requested height and
            // width
            final int heightRatio = Math.round((float) height
                    / (float) reqHeight);
            final int widthRatio = Math.round((float) width / (float) reqWidth);

            // Choose the smallest ratio as inSampleSize value, this will
            // guarantee
            // a final image with both dimensions larger than or equal to the
            // requested height and width.
            inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio;
        }

        return inSampleSize;
    }

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

    public void setOnItemClickListener(OnItemClickListener listener){
        onItemClickListener = listener;
    }

    public OnItemClickListener getOnItemClickListener(){
        return onItemClickListener;
    }

    public interface OnItemClickListener{
        public void onItemClick(ItemHolder item, int position);
    }

    public void add(int location, Uri iUri){
        itemsUri.add(location, iUri);
        notifyItemInserted(location);
    }

    public void clearAll(){
        int itemCount = itemsUri.size();

        if(itemCount>0){
            itemsUri.clear();
            notifyItemRangeRemoved(0, itemCount);
        }
    }


    public static class ItemHolder extends RecyclerView.ViewHolder implements View.OnClickListener{

        private MyRecyclerViewAdapter parent;
        private CardView cardView;
        ImageView imageView;
        String itemUri;

        public ItemHolder(CardView cardView, MyRecyclerViewAdapter parent) {
            super(cardView);
            itemView.setOnClickListener(this);
            this.cardView = cardView;
            this.parent = parent;
            imageView = (ImageView) cardView.findViewById(R.id.item_image);
        }

        public void setItemUri(String itemUri){
            this.itemUri = itemUri;
        }

        public String getItemUri(){
            return itemUri;
        }

        public void setImageView(Bitmap bitmap){
            imageView.setImageBitmap(bitmap);
        }

        @Override
        public void onClick(View v) {
            final OnItemClickListener listener = parent.getOnItemClickListener();
            if(listener != null){
                listener.onItemClick(this, getLayoutPosition());
                //or use
                //listener.onItemClick(this, getAdapterPosition());
            }
        }
    }
}

layout/layout_cardview.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:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="10dp"
    card_view:cardCornerRadius="5sp"
    card_view:cardElevation="5sp">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <ImageView
            android:id="@+id/item_image"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />

    </LinearLayout>
</android.support.v7.widget.CardView>

MainActivity.java

package com.blogspot.android_er.androidgallery;

import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.text.method.ScrollingMovementMethod;
import android.widget.TextView;
import android.widget.Toast;

import java.io.File;

public class MainActivity extends AppCompatActivity
        implements MyRecyclerViewAdapter.OnItemClickListener{

    private RecyclerView myRecyclerView;
    private MyRecyclerViewAdapter myRecyclerViewAdapter;
    private LinearLayoutManager linearLayoutManager;

    TextView textInfo;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        textInfo = (TextView)findViewById(R.id.info);
        textInfo.setMovementMethod(new ScrollingMovementMethod());

        myRecyclerView = (RecyclerView)findViewById(R.id.myrecyclerview);
        linearLayoutManager =
                new LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false);
        myRecyclerViewAdapter = new MyRecyclerViewAdapter(this, this);
        myRecyclerViewAdapter.setOnItemClickListener(this);
        myRecyclerView.setAdapter(myRecyclerViewAdapter);
        myRecyclerView.setLayoutManager(linearLayoutManager);

        prepareGallery();
    }

    private void prepareGallery(){
        String ExternalStorageDirectoryPath = Environment
                .getExternalStorageDirectory()
                .getAbsolutePath();
        String targetPath = ExternalStorageDirectoryPath + "/test/";

        Toast.makeText(getApplicationContext(), targetPath, Toast.LENGTH_LONG).show();
        File targetDirector = new File(targetPath);

        File[] files = targetDirector.listFiles();
        for (File file : files){
            Uri uri = Uri.fromFile(file);
            myRecyclerViewAdapter.add(
                    myRecyclerViewAdapter.getItemCount(),
                    uri);
        }
    }

    @Override
    public void onItemClick(MyRecyclerViewAdapter.ItemHolder item, int position) {

        String stringitemUri = item.getItemUri();
        Toast.makeText(MainActivity.this, stringitemUri, Toast.LENGTH_SHORT).show();
    }
}

layout/activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:autoLink="web"
        android:text="http://android-er.blogspot.com/"
        android:textStyle="bold" />

    <android.support.v7.widget.RecyclerView
        android:id="@+id/myrecyclerview"
        android:layout_width="match_parent"
        android:layout_height="170dp" />

    <TextView
        android:id="@+id/info"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:typeface="monospace"
        android:gravity="bottom"/>

</LinearLayout>

To read diles in ExternalStorage, uses-permission of "android.permission.READ_EXTERNAL_STORAGE" is needed in AndroidManifest.xml.

Download the files (Android Studio Format) .

Next:
- RecyclerView + CardView example: with Button

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~ More example of RecyclerView + CardView.