Migrate to ViewPager2

Author: pranavpandey

build.gradle

@@ -22,7 +22,8 @@ buildscript {
             'buildTools'      : '29.0.3',
             'appcompat'       : '1.2.0-alpha02',
             'constraintlayout': '2.0.0-beta4',
-            'kotlin'          : '1.3.61'
+            'kotlin'          : '1.3.61',
+            'viewpager2'      : '1.0.0'
     ]
 
     repositories {

dynamic-motion/build.gradle

@@ -36,6 +36,7 @@ android {
 
 dependencies {
     api "androidx.constraintlayout:constraintlayout:${versions.constraintlayout}"
+    api "androidx.viewpager2:viewpager2:${versions.viewpager2}"
 }
 
 if (project.rootProject.file('local.properties').exists()) {

dynamic-motion/src/main/java/com/pranavpandey/android/dynamic/motion/adapter/ViewPagerAdapter.java

@@ -16,59 +16,77 @@
 
 package com.pranavpandey.android.dynamic.motion.adapter;
 
-import android.content.Context;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
-import android.widget.LinearLayout;
-
-import com.pranavpandey.android.dynamic.motion.R;
-
-import java.util.ArrayList;
-import java.util.List;
 
 import androidx.annotation.NonNull;
-import androidx.viewpager.widget.PagerAdapter;
+import androidx.recyclerview.widget.RecyclerView;
+
+import com.pranavpandey.android.dynamic.motion.R;
 
 /**
- * A PagerAdapter to show different views as pages.
+ * A {@link RecyclerView.Adapter} to show different views as pages.
  * <p>It will be used internally to add dummy views inside the view pager.
  */
-public class ViewPagerAdapter extends PagerAdapter {
+public class ViewPagerAdapter extends RecyclerView.Adapter<ViewPagerAdapter.ViewHolder> {
 
     /**
-     * A list to hold the views.
+     * Item count for this adapter.
      */
-    private List<View> mPages;
+    final int mPageCount;
 
-    public ViewPagerAdapter(@NonNull Context context, int pages) {
-        this.mPages = new ArrayList<>();
-
-        for (int i = 0; i < pages; i++) {
-            mPages.add(LayoutInflater.from(context).inflate(
-                    R.layout.adm_dummy_layout, new LinearLayout(context), false));
-        }
+    /**
+     * Constructor to initialize an object of this class.
+     *
+     * @param pageCount The item count for this adapter.
+     */
+    public ViewPagerAdapter(int pageCount) {
+        this.mPageCount = pageCount;
     }
 
     @Override
-    public @NonNull Object instantiateItem(@NonNull ViewGroup container, int position) {
-        View page = mPages.get(position);
-        container.addView(page);
-        return page;
+    public @NonNull ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
+        return new ViewHolder(LayoutInflater.from(parent.getContext())
+                .inflate(R.layout.adm_dummy_layout, parent, false));
     }
 
     @Override
-    public int getCount() {
-        return mPages.size();
-    }
+    public void onBindViewHolder(@NonNull ViewHolder holder, int position) { }
 
     @Override
-    public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {
-        return view.equals(object);
+    public int getItemCount() {
+        return mPageCount;
     }
 
-    @Override
-    public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
-        container.removeView((View) object);
+    /**
+     * View holder to hold the dummy pages.
+     */
+    static class ViewHolder extends RecyclerView.ViewHolder {
+
+        /**
+         * Root view used by this view holder.
+         */
+        private final ViewGroup root;
+
+        /**
+         * Constructor to initialize views from the supplied root.
+         *
+         * @param view The view for this view holder.
+         */
+        ViewHolder(@NonNull View view) {
+            super(view);
+
+            root = view.findViewById(R.id.adm_dummy_layout);
+        }
+
+        /**
+         * Get the root view used by this view holder.
+         *
+         * @return The root view used by this view holder.
+         */
+        @NonNull ViewGroup getRoot() {
+            return root;
+        }
     }
 }

dynamic-motion/src/main/java/com/pranavpandey/android/dynamic/motion/widget/DynamicMotionLayout.java

@@ -24,14 +24,15 @@
 import androidx.annotation.Nullable;
 import androidx.constraintlayout.motion.widget.MotionLayout;
 import androidx.viewpager.widget.ViewPager;
+import androidx.viewpager2.widget.ViewPager2;
 
 import com.pranavpandey.android.dynamic.motion.R;
 import com.pranavpandey.android.dynamic.motion.adapter.ViewPagerAdapter;
 
 /**
- * A MotionLayout to perform operations according to the {@link ViewPager} page offset.
+ * A {@link MotionLayout} to perform operations according to the {@link ViewPager2} page offset.
  */
-public class DynamicMotionLayout extends MotionLayout implements ViewPager.OnPageChangeListener {
+public class DynamicMotionLayout extends MotionLayout {
 
     /**
      * Constant for the unknown page count.
@@ -46,7 +47,7 @@ public class DynamicMotionLayout extends MotionLayout implements ViewPager.OnPag
     /**
      * View pager used by this view.
      */
-    private ViewPager mViewPager;
+    private ViewPager2 mViewPager;
 
     public DynamicMotionLayout(Context context) {
         this(context, null);
@@ -93,17 +94,6 @@ public void initialize() {
         }
     }
 
-    @Override
-    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
-        setProgress((position + positionOffset) / (mPageCount - 1));
-    }
-
-    @Override
-    public void onPageSelected(int position) { }
-
-    @Override
-    public void onPageScrollStateChanged(int state) { }
-
     /**
      * Set the page count for the view pager.
      *
@@ -120,12 +110,16 @@ public void setPageCount(int pageCount,
             mViewPager = findViewById(R.id.adm_view_pager);
         }
 
-        mViewPager.setAdapter(new ViewPagerAdapter(getContext(), pageCount));
-        mViewPager.addOnPageChangeListener(this);
+        mViewPager.setAdapter(new ViewPagerAdapter(pageCount));
+        mViewPager.registerOnPageChangeCallback(new ViewPager2.OnPageChangeCallback() {
+            @Override
+            public void onPageScrolled(int position,
+                    float positionOffset, int positionOffsetPixels) {
+                super.onPageScrolled(position, positionOffset, positionOffsetPixels);
 
-        if (onPageChangeListener != null) {
-            mViewPager.addOnPageChangeListener(onPageChangeListener);
-        }
+                setProgress((position + positionOffset) / (mPageCount - 1));
+            }
+        });
 
         if (mViewPager.getAdapter() != null) {
             mViewPager.getAdapter().notifyDataSetChanged();
@@ -146,7 +140,7 @@ public int getPageCount() {
      *
      * @return The view pager used by this view.
      */
-    public @Nullable ViewPager getViewPager() {
+    public @Nullable ViewPager2 getViewPager() {
         return mViewPager;
     }
 }

dynamic-motion/src/main/res/layout/adm_view_pager.xml

@@ -15,7 +15,7 @@
 	limitations under the License.
 -->
 
-<androidx.viewpager.widget.ViewPager
+<androidx.viewpager2.widget.ViewPager2
     xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     android:id="@+id/adm_view_pager"

sample/src/main/java/com/pranavpandey/android/dynamic/motion/sample/widget/DynamicImageView.java

@@ -26,7 +26,7 @@
 import androidx.appcompat.widget.AppCompatImageView;
 
 /**
- * An ImageView to apply color filter according to the supplied parameters.
+ * An {@link AppCompatImageView} to apply color filter according to the supplied parameters.
  */
 public class DynamicImageView extends AppCompatImageView {
 
@@ -39,7 +39,7 @@ public DynamicImageView(@NonNull Context context, @Nullable AttributeSet attrs)
     }
 
     public DynamicImageView(@NonNull Context context,
-                            @Nullable AttributeSet attrs, int defStyleAttr) {
+            @Nullable AttributeSet attrs, int defStyleAttr) {
         super(context, attrs, defStyleAttr);
     }
 

sample/src/main/res/drawable/ic_android.xml

@@ -20,8 +20,7 @@
     android:height="24dp"
     android:width="24dp"
     android:viewportHeight="24"
-    android:viewportWidth="24"
-    android:autoMirrored="true">
+    android:viewportWidth="24">
 
     <path
         android:fillColor="#FF000000"

sample/src/main/res/drawable/ic_launcher_foreground.xml

@@ -17,11 +17,13 @@
 
 <vector
     xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
     android:width="108dp"
     android:height="108dp"
     android:viewportHeight="108"
     android:viewportWidth="108"
-    android:autoMirrored="true">
+    android:autoMirrored="true"
+    tools:targetApi="kitkat">
 
     <path
         android:fillColor="@color/color_accent"

sample/src/main/res/layout/activity_dynamic_motion.xml

@@ -38,4 +38,4 @@
         android:contentDescription="@null"
         app:srcCompat="@drawable/ic_android" />
 
-</com.pranavpandey.android.dynamic.motion.widget.DynamicMotionLayout>
+</com.pranavpandey.android.dynamic.motion.widget.DynamicMotionLayout>

sample/src/main/res/mipmap-anydpi-v26/ic_launcher.xml

@@ -28,4 +28,4 @@
 
     </foreground>
 
-</adaptive-icon>
+</adaptive-icon>