Add getViewOptional method - NonNull getView variant

Author: Juraj Novák

library/build.gradle

@@ -3,7 +3,7 @@ apply plugin: 'maven'
 
 android {
     compileSdkVersion 25
-    buildToolsVersion '24.0.3'
+    buildToolsVersion '25.0.2'
 
     defaultConfig {
         minSdkVersion 15
@@ -25,7 +25,7 @@ android {
 }
 
 dependencies {
-    compile 'com.android.support:appcompat-v7:25.1.0'
+    compile 'com.android.support:appcompat-v7:25.1.1'
 }
 
 task androidJavadocs(type: Javadoc) {

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

@@ -4,6 +4,7 @@
 import android.content.Intent;
 import android.os.Bundle;
 import android.support.annotation.CallSuper;
+import android.support.annotation.CheckResult;
 import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
 import android.support.v4.app.Fragment;
@@ -18,8 +19,15 @@ public abstract class AbstractViewModel<T extends IView> {
     @Nullable
     private T mView;
 
+    @Nullable
+    private final Class<?> mClassType;
+
     private boolean mBindViewWasCalled;
 
+    public AbstractViewModel() {
+        mClassType = ProxyViewHelper.getGenericType(getClass(), IView.class);
+    }
+
     void setUniqueIdentifier(@NonNull final String uniqueIdentifier) {
         mUniqueIdentifier = uniqueIdentifier;
     }
@@ -59,11 +67,25 @@ public void onBindView(@NonNull T view) {
         mView = view;
     }
 
+    @CheckResult
     @Nullable
     public T getView() {
         return mView;
     }
 
+    @CheckResult
+    @NonNull
+    public T getViewOptional() {
+        if (mView != null) {
+            return mView;
+        } else {
+            if (mClassType == null) {
+                throw new IllegalStateException("Your view must implement IView");
+            }
+            return ProxyViewHelper.init(mClassType);
+        }
+    }
+
     @CallSuper
     public void clearView() {
         mView = null;

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

@@ -0,0 +1,53 @@
+package eu.inloop.viewmodel;
+
+
+import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
+
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.Method;
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Proxy;
+import java.lang.reflect.Type;
+
+class ProxyViewHelper {
+
+    private static final class ProxyDummyClass {
+    }
+
+    private static final ProxyDummyClass sDummyClass = new ProxyDummyClass();
+    private static final Class[] sInterfaces = new Class[1];
+
+    private ProxyViewHelper() {
+    }
+
+    @SuppressWarnings("unchecked")
+    @NonNull
+    static <T> T init(@NonNull Class<?> in) {
+        sInterfaces[0] = in;
+        return (T) Proxy.newProxyInstance(sDummyClass.getClass().getClassLoader(), sInterfaces, sInvocationHandler);
+    }
+
+    @Nullable
+    static Class<?> getGenericType(@NonNull Class<?> in, @NonNull Class<?> whichExtends) {
+        final Type genericSuperclass = in.getGenericSuperclass();
+        if (genericSuperclass instanceof ParameterizedType) {
+            final Type[] typeArgs = ((ParameterizedType) genericSuperclass).getActualTypeArguments();
+            for (Type arg : typeArgs) {
+                final Class<?> argClass = (Class<?>) arg;
+                if (whichExtends.isAssignableFrom(argClass)) {
+                    return argClass;
+                }
+            }
+        }
+        return null;
+    }
+
+    private static final InvocationHandler sInvocationHandler = new InvocationHandler() {
+        @Override
+        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
+            return null;
+        }
+    };
+
+}

sample/build.gradle

@@ -2,12 +2,12 @@ apply plugin: 'com.android.application'
 
 android {
     compileSdkVersion 24
-    buildToolsVersion '24.0.2'
+    buildToolsVersion '25.0.2'
 
     defaultConfig {
         applicationId 'eu.inloop.viewmodel.sample'
         minSdkVersion 15
-        targetSdkVersion 24
+        targetSdkVersion 25
         versionCode 1
         versionName '1.0'
     }
@@ -30,7 +30,7 @@ android {
 }
 
 dependencies {
-    compile 'com.android.support:appcompat-v7:24.2.1'
+    compile 'com.android.support:appcompat-v7:25.1.1'
     debugCompile 'com.squareup.leakcanary:leakcanary-android:1.4'
     releaseCompile 'com.squareup.leakcanary:leakcanary-android-no-op:1.4'
     compile 'com.jakewharton:butterknife:5.1.2'