Optimize code in WithViewPagerActivity

app/build.gradle

@@ -27,8 +27,8 @@ dependencies {
     androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
         exclude group: 'com.android.support', module: 'support-annotations'
     })
-    compile 'com.android.support:appcompat-v7:25.0.0'
-    compile 'com.android.support:design:25.0.0'
+    compile 'com.android.support:appcompat-v7:25.0.1'
+    compile 'com.android.support:design:25.0.1'
     testCompile 'junit:junit:4.12'
     compile project(':widget')
 }

app/src/main/java/com/ittianyu/bottomnavigationviewexsample/viewpager/WithViewPagerActivity.java

@@ -5,14 +5,13 @@
 import android.support.annotation.NonNull;
 import android.support.design.widget.BottomNavigationView;
 import android.support.v4.app.Fragment;
-import android.support.v4.app.FragmentTransaction;
-import android.support.v4.view.PagerAdapter;
+import android.support.v4.app.FragmentManager;
+import android.support.v4.app.FragmentPagerAdapter;
 import android.support.v4.view.ViewPager;
 import android.support.v7.app.AppCompatActivity;
 import android.util.Log;
+import android.util.SparseArray;
 import android.view.MenuItem;
-import android.view.View;
-import android.view.ViewGroup;
 
 import com.ittianyu.bottomnavigationviewexsample.R;
 import com.ittianyu.bottomnavigationviewexsample.databinding.ActivityWithViewPagerBinding;
@@ -21,69 +20,79 @@
 import java.util.List;
 
 public class WithViewPagerActivity extends AppCompatActivity {
-    private static final String TAG = "WithViewPagerActivity";
-    private ActivityWithViewPagerBinding binding;
-    private List<Item> items;
+    private static final String TAG = WithViewPagerActivity.class.getCanonicalName();
+    private ActivityWithViewPagerBinding bind;
     private VpAdapter adapter;
 
+    // collections
+    private SparseArray<Integer> fragmentMap;// used for change ViewPager selected item
+    private List<Fragment> fragments;// used for ViewPager adapter
+
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
 //        setContentView(R.layout.activity_with_view_pager);
-        binding = DataBindingUtil.setContentView(this, R.layout.activity_with_view_pager);
+        bind = DataBindingUtil.setContentView(this, R.layout.activity_with_view_pager);
 
         initView();
         initData();
         initEvent();
     }
 
+    /**
+     * change BottomNavigationViewEx style
+     */
     private void initView() {
-        binding.bnve.enableItemShiftingMode(true);
-        binding.bnve.enableAnimation(false);
+        bind.bnve.enableItemShiftingMode(true);
+        bind.bnve.enableAnimation(false);
     }
 
+    /**
+     * create fragments
+     */
     private void initData() {
-        items = new ArrayList<>(3);
-        // get transaction
-        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
+        fragments = new ArrayList<>(3);
+        fragmentMap = new SparseArray<>(3);
 
         // create music fragment and add it
         BaseFragment musicFragment = new BaseFragment();
         Bundle bundle = new Bundle();
         bundle.putString("title", getString(R.string.music));
         musicFragment.setArguments(bundle);
-        transaction.add(musicFragment, "music");
 
         // create backup fragment and add it
         BaseFragment backupFragment = new BaseFragment();
         bundle = new Bundle();
         bundle.putString("title", getString(R.string.backup));
         backupFragment.setArguments(bundle);
-        transaction.add(backupFragment, "backup");
 
         // create friends fragment and add it
         BaseFragment friendsFragment = new BaseFragment();
         bundle = new Bundle();
         bundle.putString("title", getString(R.string.friends));
         friendsFragment.setArguments(bundle);
-        transaction.add(friendsFragment, "friends");
 
-        // commit
-        transaction.commit();
+        // add to fragments for adapter
+        fragments.add(musicFragment);
+        fragments.add(backupFragment);
+        fragments.add(friendsFragment);
 
-        // add fragment root view to view pager
-        items.add(new Item(R.id.menu_music, musicFragment));
-        items.add(new Item(R.id.menu_backup, backupFragment));
-        items.add(new Item(R.id.menu_friends, friendsFragment));
+        // add to fragmentMap for change ViewPager item
+        fragmentMap.put(R.id.menu_music, 0);
+        fragmentMap.put(R.id.menu_backup, 1);
+        fragmentMap.put(R.id.menu_friends, 2);
 
         // set adapter
-        adapter = new VpAdapter(items);
-        binding.vp.setAdapter(adapter);
+        adapter = new VpAdapter(getSupportFragmentManager(), fragments);
+        bind.vp.setAdapter(adapter);
     }
 
+    /**
+     * set listeners
+     */
     private void initEvent() {
         // set listener to change the current item of view pager when click bottom nav item
-        binding.bnve.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
+        bind.bnve.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
             @Override
             public boolean onNavigationItemSelected(@NonNull MenuItem item) {
 //                int id = 0;
@@ -98,17 +107,17 @@ public boolean onNavigationItemSelected(@NonNull MenuItem item) {
 //                        id = 2;
 //                        break;
 //                }
-//                binding.vp.setCurrentItem(id, false);
+//                bind.vp.setCurrentItem(id, false);
 
                 // you can write as above.
-                // I recommend this method. You can change the item order or count without update code here.
-                binding.vp.setCurrentItem(items.indexOf(new Item(item.getItemId(), null)), false);
-                return false;
+                // I recommend this method. You can change the item order or counts without update code here.
+                bind.vp.setCurrentItem(fragmentMap.get(item.getItemId()));
+                return true;
             }
         });
 
         // set listener to change the current checked item of bottom nav when scroll view pager
-        binding.vp.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
+        bind.vp.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
             @Override
             public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
 
@@ -117,9 +126,9 @@ public void onPageScrolled(int position, float positionOffset, int positionOffse
             @Override
             public void onPageSelected(int position) {
                 // check whether current item is equal position
-                if (binding.bnve.getCurrentItem() != position) {
+                if (bind.bnve.getCurrentItem() != position) {
                     // only set item when scroll view pager by hand
-                    binding.bnve.setCurrentItem(position);
+                    bind.bnve.setCurrentItem(position);
                     Log.i(TAG, "setCurrentItem:" + position);
                 }
             }
@@ -134,10 +143,11 @@ public void onPageScrollStateChanged(int state) {
     /**
      * view pager adapter
      */
-    private static class VpAdapter extends PagerAdapter {
-        private List<Item> data;
+    private static class VpAdapter extends FragmentPagerAdapter {
+        private List<Fragment> data;
 
-        public VpAdapter(List<Item> data) {
+        public VpAdapter(FragmentManager fm, List<Fragment> data) {
+            super(fm);
             this.data = data;
         }
 
@@ -147,50 +157,9 @@ public int getCount() {
         }
 
         @Override
-        public boolean isViewFromObject(View view, Object object) {
-            return view == object;
-        }
-
-        @Override
-        public Object instantiateItem(ViewGroup container, int position) {
-            View view = data.get(position).fragment.getView();
-            container.addView(view);
-            return view;
-        }
-
-        @Override
-        public void destroyItem(ViewGroup container, int position, Object object) {
-            container.removeView((View) object);
+        public Fragment getItem(int position) {
+            return data.get(position);
         }
     }
 
-    /**
-     * used for view pager data bean
-     */
-    private static class Item {
-        int resId;
-        Fragment fragment;
-
-        public Item(int resId, Fragment fragment) {
-            this.resId = resId;
-            this.fragment = fragment;
-        }
-
-        // rewrite equal and hashcode by resId
-        @Override
-        public boolean equals(Object o) {
-            if (this == o) return true;
-            if (o == null || getClass() != o.getClass()) return false;
-
-            Item item = (Item) o;
-
-            return resId == item.resId;
-
-        }
-
-        @Override
-        public int hashCode() {
-            return resId;
-        }
-    }
 }

build.gradle

@@ -5,7 +5,7 @@ buildscript {
         jcenter()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:2.2.2'
+        classpath 'com.android.tools.build:gradle:2.2.3'
 
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files

widget/build.gradle

@@ -29,7 +29,7 @@ dependencies {
     androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
         exclude group: 'com.android.support', module: 'support-annotations'
     })
-    compile 'com.android.support:appcompat-v7:25.0.0'
-    compile 'com.android.support:design:25.0.0'
+    compile 'com.android.support:appcompat-v7:25.0.1'
+    compile 'com.android.support:design:25.0.1'
     testCompile 'junit:junit:4.12'
 }