Add better support for FragmentStatePagerAdapter

Author: Daniel Novak

library/build.gradle

@@ -48,7 +48,6 @@ task androidSourcesJar(type: Jar) {
 
 artifacts {
     archives androidSourcesJar
-    archives androidJavadocsJar
 }
 
 uploadArchives {

library/src/main/java/eu/inloop/viewmodel/IView.java

@@ -1,16 +1,31 @@
 package eu.inloop.viewmodel;
 
+import android.app.Activity;
 import android.support.annotation.Nullable;
 
+import eu.inloop.viewmodel.base.ViewModelBaseActivity;
+import eu.inloop.viewmodel.base.ViewModelBaseFragment;
 import eu.inloop.viewmodel.binding.ViewModelBindingConfig;
 
+/**
+ * Any Activity or Fragment that needs a ViewModel needs to implement this interface.
+ * You don't need to implement it yourself - use {@link ViewModelBaseActivity} and
+ * {@link ViewModelBaseFragment} instead.
+ */
 public interface IView {
     /**
-     * This method is used for Data Binding to bind correct layout and variable atomatically
+     * This method is used for Data Binding to bind correct layout and variable automatically
      * Can return null value in case that Data Binding is not used.
      *
      * @return defined ViewModelBinding Config for a specific screen.
      */
     @Nullable
     ViewModelBindingConfig getViewModelBindingConfig();
+
+    /**
+     * Implement this method to remove the ViewModel associated with the Fragment or Activity.
+     * This is usually implemented by calling {@link ViewModelHelper#removeViewModel(Activity)},
+     * see {@link ViewModelBaseActivity#removeViewModel()} and {@link ViewModelBaseFragment#removeViewModel()}.
+     */
+    void removeViewModel();
 }

library/src/main/java/eu/inloop/viewmodel/ViewModelHelper.java

@@ -79,7 +79,7 @@ public void onCreate(@NonNull Activity activity,
         if (viewModelWrapper.wasCreated) {
             // detect that the system has killed the app - saved instance is not null, but the model was recreated
             if (BuildConfig.DEBUG && savedInstanceState != null) {
-                Log.d("model", "Fragment recreated by system - restoring viewmodel"); //NON-NLS
+                Log.d("model", "Fragment recreated by system or ViewModelStatePagerAdapter - restoring viewmodel"); //NON-NLS
             }
             mViewModel.onCreate(arguments, savedInstanceState);
         }
@@ -252,7 +252,7 @@ public ViewDataBinding getBinding() {
         return mBinding;
     }
 
-    private void removeViewModel(@NonNull final Activity activity) {
+    public void removeViewModel(@NonNull final Activity activity) {
         if (mViewModel != null && !mModelRemoved) {
             final ViewModelProvider viewModelProvider = getViewModelProvider(activity).getViewModelProvider();
             if (null == viewModelProvider) {

library/src/main/java/eu/inloop/viewmodel/base/ViewModelBaseActivity.java

@@ -70,4 +70,8 @@ public R getViewModel() {
         return mViewModeHelper.getViewModel();
     }
 
+    @Override
+    public void removeViewModel() {
+        mViewModeHelper.removeViewModel(this);
+    }
 }

library/src/main/java/eu/inloop/viewmodel/base/ViewModelBaseFragment.java

@@ -15,47 +15,47 @@
 public abstract class ViewModelBaseFragment<T extends IView, R extends AbstractViewModel<T>> extends Fragment implements IView {
 
     @NonNull
-    private final ViewModelHelper<T, R> mViewModeHelper = new ViewModelHelper<>();
+    private final ViewModelHelper<T, R> mViewModelHelper = new ViewModelHelper<>();
 
     @CallSuper
     @Override
     public void onCreate(@Nullable final Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
-        getViewModeHelper().onCreate(getActivity(), savedInstanceState, getViewModelClass(), getArguments());
+        getViewModelHelper().onCreate(getActivity(), savedInstanceState, getViewModelClass(), getArguments());
     }
 
     @CallSuper
     @Override
     public void onSaveInstanceState(@NonNull final Bundle outState) {
         super.onSaveInstanceState(outState);
-        getViewModeHelper().onSaveInstanceState(outState);
+        getViewModelHelper().onSaveInstanceState(outState);
     }
 
     @CallSuper
     @Override
     public void onStart() {
         super.onStart();
-        getViewModeHelper().onStart();
+        getViewModelHelper().onStart();
     }
 
     @CallSuper
     @Override
     public void onStop() {
         super.onStop();
-        getViewModeHelper().onStop();
+        getViewModelHelper().onStop();
     }
 
     @CallSuper
     @Override
     public void onDestroyView() {
-        getViewModeHelper().onDestroyView(this);
+        getViewModelHelper().onDestroyView(this);
         super.onDestroyView();
     }
 
     @CallSuper
     @Override
     public void onDestroy() {
-        getViewModeHelper().onDestroy(this);
+        getViewModelHelper().onDestroy(this);
         super.onDestroy();
     }
 
@@ -68,7 +68,7 @@ public void onDestroy() {
     @NonNull
     @SuppressWarnings("unused")
     public R getViewModel() {
-        return getViewModeHelper().getViewModel();
+        return getViewModelHelper().getViewModel();
     }
 
     @Nullable
@@ -78,8 +78,13 @@ public ViewModelBindingConfig getViewModelBindingConfig() {
     }
 
     @NonNull
-    public ViewModelHelper<T, R> getViewModeHelper() {
-        return mViewModeHelper;
+    public ViewModelHelper<T, R> getViewModelHelper() {
+        return mViewModelHelper;
+    }
+
+    @Override
+    public void removeViewModel() {
+        mViewModelHelper.removeViewModel(getActivity());
     }
 
     /**
@@ -89,6 +94,6 @@ public ViewModelHelper<T, R> getViewModeHelper() {
      * @param view view
      */
     protected void setModelView(@NonNull final T view) {
-        getViewModeHelper().setView(view);
+        getViewModelHelper().setView(view);
     }
 }

library/src/main/java/eu/inloop/viewmodel/binding/ViewModelBaseBindingFragment.java

@@ -20,14 +20,14 @@ public abstract class ViewModelBaseBindingFragment<T extends IView, R extends Ab
     @Override
     public void onCreate(@Nullable Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
-        getViewModeHelper().performBinding(this);
+        getViewModelHelper().performBinding(this);
     }
 
     @Nullable
     @Override
     public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
-        getViewModeHelper().performBinding(this);
-        final ViewDataBinding binding = getViewModeHelper().getBinding();
+        getViewModelHelper().performBinding(this);
+        final ViewDataBinding binding = getViewModelHelper().getBinding();
         if (binding != null) {
             return binding.getRoot();
         } else {
@@ -39,7 +39,7 @@ public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,
     @NotNull
     public B getBinding() {
         try {
-            return (B) getViewModeHelper().getBinding();
+            return (B) getViewModelHelper().getBinding();
         } catch (ClassCastException ex) {
             throw new IllegalStateException("Method getViewModelBindingConfig() has to return same " +
                     "ViewDataBinding type as it is set to base Fragment");

library/src/main/java/eu/inloop/viewmodel/support/ViewModelStatePagerAdapter.java

@@ -0,0 +1,40 @@
+package eu.inloop.viewmodel.support;
+
+import android.app.Activity;
+import android.support.annotation.NonNull;
+import android.support.v4.app.Fragment;
+import android.support.v4.app.FragmentManager;
+import android.support.v4.app.FragmentStatePagerAdapter;
+import android.util.Log;
+import android.view.ViewGroup;
+
+import eu.inloop.viewmodel.BuildConfig;
+import eu.inloop.viewmodel.IView;
+
+/**
+ * This class extends {@link FragmentStatePagerAdapter}. It removes the ViewModel once the
+ * pager item is destroyed ({@link #destroyItem(ViewGroup, int, Object)}). The ViewModel state
+ * is stored and then restored once you return back to this pager item and {@link #instantiateItem(ViewGroup, int)}
+ * is called.
+ */
+public abstract class ViewModelStatePagerAdapter extends FragmentStatePagerAdapter {
+
+    public ViewModelStatePagerAdapter(@NonNull final FragmentManager fm) {
+        super(fm);
+    }
+
+    @Override
+    public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
+        super.destroyItem(container, position, object);
+        final Fragment fragment = (Fragment) object;
+
+        if (fragment instanceof IView) {
+            IView viewModelBaseFragment = (IView) fragment;
+            viewModelBaseFragment.removeViewModel();
+        } else {
+            if (BuildConfig.DEBUG) {
+                Log.w("model", "Fragment " + fragment + " in FragmentStatePagerAdapter " + this + " doesn't implent IView"); //NON-NLS
+            }
+        }
+    }
+}

sample/src/main/java/eu/inloop/viewmodel/sample/activity/ViewPagerActivity.java

@@ -3,13 +3,12 @@
 import android.os.Bundle;
 import android.support.v4.app.Fragment;
 import android.support.v4.app.FragmentManager;
-import android.support.v4.app.FragmentStatePagerAdapter;
 import android.support.v4.view.ViewPager;
 
-import eu.inloop.viewmodel.base.ViewModelBaseActivity;
 import eu.inloop.viewmodel.base.ViewModelBaseEmptyActivity;
 import eu.inloop.viewmodel.sample.R;
 import eu.inloop.viewmodel.sample.fragment.PagerFragment;
+import eu.inloop.viewmodel.support.ViewModelStatePagerAdapter;
 
 public class ViewPagerActivity extends ViewModelBaseEmptyActivity {
 
@@ -22,7 +21,7 @@ protected void onCreate(Bundle savedInstanceState) {
         viewPager.setAdapter(new TestPagerAdapter(getSupportFragmentManager()));
     }
 
-    private final static class TestPagerAdapter extends FragmentStatePagerAdapter {
+    private final static class TestPagerAdapter extends ViewModelStatePagerAdapter {
         public TestPagerAdapter(FragmentManager fm) {
             super(fm);
         }