Image Slider in Android using ViewPager - GeeksforGeeks

15 Sep, 2020
When talking about Android Apps, the first thing that comes to mind is variety. There are so many varieties of Android apps providing the user with beautiful dynamic UI. One such feature is to navigate in the Android Apps using the left and right swipes as opposed to clicking on Buttons. Not only does it look more simple and elegant but also provides ease of access to the user. There are many apps that use this swipe feature to swipe through different activities in the app. For example, the popular chatting app, Snapchat, uses it to swipe through lenses, chats, and stories. Here let’s discuss how to create an Image Slider using ViewPager. ViewPager is a class in Java that is used in conjunction with Fragments. It is mostly used for designing the UI of the app. A sample GIF is given below to get an idea about what we are going to do in this article.
Step 1: Create a New Project
To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. Note that select Java as the programming language.
Step 2: Designing the UI
Below is the code for the activity_main.xml file. We have added only a ViewPager to show the images. Below is the complete code for the activity_main.xml file.
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:layout_width="match_parent"    android:layout_height="match_parent"    tools:context=".MainActivity">    <!-- viewpager to show images -->  <androidx.viewpager.widget.ViewPager      android:id="@+id/viewPagerMain"      android:layout_width="match_parent"      android:layout_height="match_parent"/>  </RelativeLayout>
Create a new Layout Resource File item.xml inside the app -> res -> layout folder. Add only an ImageView. Below is the code of the item.xml file.
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="match_parent">      <!-- image viwer to view the images -->    <ImageView        android:id="@+id/imageViewMain"        android:layout_width="match_parent"        android:layout_height="match_parent"/>  </LinearLayout>
Step 3: Coding Part
First, create an Adapter for the ViewPager and named it as ViewPagerAdapter class below is the complete code of ViewPagerAdapter.java class. Comments are added inside the code to understand each line of the code.
Java
import android.content.Context;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.ImageView;import android.widget.LinearLayout;import androidx.annotation.NonNull;import androidx.viewpager.widget.PagerAdapter;import java.util.Objects;  class ViewPagerAdapter extends PagerAdapter {      // Context object     Context context;          // Array of images    int[] images;          // Layout Inflater    LayoutInflater mLayoutInflater;        // Viewpager Constructor     public ViewPagerAdapter(Context context, int[] images) {        this.context = context;        this.images = images;        mLayoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);    }      @Override    public int getCount() {        // return the number of images        return images.length;    }      @Override    public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {        return view == ((LinearLayout) object);    }      @NonNull    @Override    public Object instantiateItem(@NonNull ViewGroup container, final int position) {        // inflating the item.xml         View itemView = mLayoutInflater.inflate(R.layout.item, container, false);          // referencing the image view from the item.xml file         ImageView imageView = (ImageView) itemView.findViewById(R.id.imageViewMain);                  // setting the image in the imageView        imageView.setImageResource(images[position]);          // Adding the View        Objects.requireNonNull(container).addView(itemView);          return itemView;    }      @Override    public void destroyItem(ViewGroup container, int position, Object object) {                  container.removeView((LinearLayout) object);    }}
After creating the Adapter for the ViewPager, reference the ViewPager from the XML and set the adapter to it in the MainActivity.java file. Create an array of integer which contains the images which we will show in the ViewPager. Below is the complete code for the MainActivity.java file. Comments are added inside the code to understand each line of the code.
Java
import androidx.appcompat.app.AppCompatActivity;import androidx.viewpager.widget.ViewPager;import android.os.Bundle;  public class MainActivity extends AppCompatActivity {      // creating object of ViewPager    ViewPager mViewPager;      // images array    int[] images = {R.drawable.a1, R.drawable.a2, R.drawable.a3, R.drawable.a4,                    R.drawable.a5, R.drawable.a6, R.drawable.a7, R.drawable.a8};          // Creating Object of ViewPagerAdapter    ViewPagerAdapter mViewPagerAdapter;        @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);          // Initializing the ViewPager Object        mViewPager = (ViewPager)findViewById(R.id.viewPagerMain);          // Initializing the ViewPagerAdapter        mViewPagerAdapter = new ViewPagerAdapter(MainActivity.this, images);          // Adding the Adapter to the ViewPager        mViewPager.setAdapter(mViewPagerAdapter);    }}
Additional Links:
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