Consolidates Screen, @layout, @view into @screen.

square#2

flow/src/main/java/com/squareup/flow/Backstack.java

@@ -26,14 +26,16 @@
 import java.util.Iterator;
 import java.util.List;
 
-/** Describes the history of a {@link Flow} at a specific point in time. For persisting the
- * supplied {@link Parcer} needs to be able to handle all screen types. */
+/**
+ * Describes the history of a {@link Flow} at a specific point in time. For persisting the supplied
+ * {@link Parcer} needs to be able to handle all screen types.
+ */
 public final class Backstack implements Iterable<Backstack.Entry> {
   private final long highestId;
   private final Deque<Entry> backstack;
 
   /** Restore a saved backstack from a {@link Parcelable} using the supplied {@link Parcer}. */
-  public static Backstack from(Parcelable parcelable, Parcer<Screen> parcer) {
+  public static Backstack from(Parcelable parcelable, Parcer<Object> parcer) {
     ParcelableBackstack backstack = (ParcelableBackstack) parcelable;
     return backstack.getBackstack(parcer);
   }
@@ -43,7 +45,7 @@ public static Builder emptyBuilder() {
   }
 
   /** Create a backstack that contains a single screen. */
-  public static Backstack single(Screen screen) {
+  public static Backstack single(Object screen) {
     return emptyBuilder().push(screen).build();
   }
 
@@ -61,7 +63,7 @@ public Iterator<Entry> reverseIterator() {
   }
 
   /** Get a {@link Parcelable} of this backstack using the supplied {@link Parcer}. */
-  public Parcelable getParcelable(Parcer<Screen> parcer) {
+  public Parcelable getParcelable(Parcer<Object> parcer) {
     return new ParcelableBackstack.Memory(this, parcer);
   }
 
@@ -84,9 +86,9 @@ public Builder buildUpon() {
 
   public static final class Entry {
     private final long id;
-    private final Screen screen;
+    private final Object screen;
 
-    private Entry(long id, Screen screen) {
+    private Entry(long id, Object screen) {
       this.id = id;
       this.screen = screen;
     }
@@ -95,7 +97,7 @@ public long getId() {
       return id;
     }
 
-    public Screen getScreen() {
+    public Object getScreen() {
       return screen;
     }
 
@@ -113,14 +115,14 @@ private Builder(long highestId, Collection<Entry> backstack) {
       this.backstack = new ArrayDeque<Entry>(backstack);
     }
 
-    public Builder push(Screen screen) {
+    public Builder push(Object screen) {
       backstack.push(new Entry(++highestId, screen));
 
       return this;
     }
 
-    public Builder addAll(Collection<Screen> c) {
-      for (Screen screen : c) {
+    public Builder addAll(Collection<Object> c) {
+      for (Object screen : c) {
         backstack.push(new Entry(++highestId, screen));
       }
 
@@ -167,8 +169,9 @@ public ReadIterator(Iterator<T> iterator) {
   }
 
   private interface ParcelableBackstack extends Parcelable {
-    Backstack getBackstack(Parcer<Screen> parcer);
+    Backstack getBackstack(Parcer<Object> parcer);
 
+    @SuppressWarnings("UnusedDeclaration")
     Parcelable.Creator<ParcelableBackstack> CREATOR =
         new Parcelable.Creator<ParcelableBackstack>() {
           @Override public ParcelableBackstack createFromParcel(Parcel in) {
@@ -185,14 +188,14 @@ private interface ParcelableBackstack extends Parcelable {
 
     static class Memory implements ParcelableBackstack {
       private final Backstack backstack;
-      private final Parcer<Screen> parcer;
+      private final Parcer<Object> parcer;
 
-      Memory(Backstack backstack, Parcer<Screen> parcer) {
+      Memory(Backstack backstack, Parcer<Object> parcer) {
         this.backstack = backstack;
         this.parcer = parcer;
       }
 
-      @Override public Backstack getBackstack(Parcer<Screen> parcer) {
+      @Override public Backstack getBackstack(Parcer<Object> parcer) {
         return backstack;
       }
 
@@ -220,7 +223,7 @@ static class Parcelled implements ParcelableBackstack {
         this.entries = entries;
       }
 
-      @Override public Backstack getBackstack(Parcer<Screen> parcer) {
+      @Override public Backstack getBackstack(Parcer<Object> parcer) {
         List<Entry> backstack = new ArrayList<Entry>();
         for (ParcelableEntry entry : entries) {
           backstack.add(entry.toRealEntry(parcer));
@@ -249,7 +252,7 @@ private static class ParcelableEntry implements Parcelable {
       this.parcelable = parcelable;
     }
 
-    public Entry toRealEntry(Parcer<Screen> parcer) {
+    public Entry toRealEntry(Parcer<Object> parcer) {
       return new Entry(id, parcer.unwrap(parcelable));
     }
 

flow/src/main/java/com/squareup/flow/Flow.java

@@ -42,13 +42,13 @@ public Backstack getBackstack() {
   }
 
   /** Push the screen onto the backstack. */
-  public void goTo(Screen screen) {
+  public void goTo(Object screen) {
     Backstack newBackstack = backstack.buildUpon().push(screen).build();
     forward(newBackstack);
   }
 
   /** Reset to the specified screen. Pops until the screen is found (inclusive) and appends.  */
-  public void resetTo(Screen screen) {
+  public void resetTo(Object screen) {
     Backstack.Builder builder = backstack.buildUpon();
     int count = 0;
     for (Iterator<Backstack.Entry> it = backstack.reverseIterator(); it.hasNext();) {
@@ -70,10 +70,10 @@ public void resetTo(Screen screen) {
   }
 
   /** Replaces the current backstack with the up stack of the screen. */
-  public void replaceTo(Screen screen) {
-    LinkedList<Screen> newBackstack = new LinkedList<Screen>();
+  public void replaceTo(Object screen) {
+    LinkedList<Object> newBackstack = new LinkedList<Object>();
 
-    Screen current = screen;
+    Object current = screen;
     while (current instanceof HasParent<?>) {
       newBackstack.addFirst(current);
       current = ((HasParent) current).getParent();
@@ -91,7 +91,7 @@ public void replaceTo(Screen screen) {
    * @return false if going up is not possible.
    */
   public boolean goUp() {
-    Screen current = backstack.current().getScreen();
+    Object current = backstack.current().getScreen();
     if (current instanceof HasParent<?>) {
       replaceTo(((HasParent) current).getParent());
       return true;

flow/src/main/java/com/squareup/flow/HasParent.java

@@ -20,6 +20,6 @@
  * Describes the parent of a specific screen which is used to support the up affordance.
  * Implementing screens are required to be able to return an instance of their parent.
  */
-public interface HasParent<T extends Screen> {
+public interface HasParent<T> {
   T getParent();
 }

flow/src/main/java/com/squareup/flow/Screen.java

@@ -16,9 +16,27 @@
 
 package com.squareup.flow;
 
+import android.view.View;
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+import static java.lang.annotation.ElementType.TYPE;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
 /**
- * Marker interface that designates a screen. A screen is a distinct part of an application
- * containing all information that describes this state.
+ * Marks a class that designates a screen. A screen is a distinct part of an application
+ * containing all information that describes this state. Optionally specifies its view or layout.
+ *
+ * <p>For example, <pre><code>
+ * {@literal@}Screen(R.layout.welcome_layout)
+ * public class WelcomeScreen { ... }
+ *
+ * {@literal@}Screen(view=Conversation.class)
+ * public class ConversationScreen { ... }
+ * </code></pre>
  */
-public interface Screen {
+@Retention(RUNTIME) @Target(TYPE)
+public @interface Screen {
+  int layout() default View.NO_ID;
+  Class<? extends android.view.View> value() default View.class;
 }

flow/src/main/java/com/squareup/flow/Screens.java

@@ -19,34 +19,32 @@
 import android.content.Context;
 import android.util.AttributeSet;
 import android.view.LayoutInflater;
-import com.squareup.flow.annotation.Layout;
-import com.squareup.flow.annotation.View;
+import android.view.View;
 import java.lang.reflect.Constructor;
 
 public final class Screens {
   private static final Class<?>[] VIEW_CONSTRUCTOR = new Class[] {
       Context.class, AttributeSet.class
   };
 
-  /** Create an instance of the view specified in a {@link View} or {@link Layout} annotation. */
-  public static android.view.View createView(Context context, Screen screen) {
+  /** Create an instance of the view specified in a {@link Screen} annotation. */
+  public static android.view.View createView(Context context, Object screen) {
     return createView(context, screen.getClass());
   }
 
-  /** Create an instance of the view specified in a {@link View} or {@link Layout} annotation. */
-  public static android.view.View createView(Context context, Class<? extends Screen> screenType) {
-    View view = screenType.getAnnotation(View.class);
-    if (view != null) {
-      return instantiateView(context, view.value());
+  /** Create an instance of the view specified in a {@link Screen} annotation. */
+  public static android.view.View createView(Context context, Class<?> screenType) {
+    Screen screen = screenType.getAnnotation(Screen.class);
+    if (screen == null) {
+      throw new IllegalArgumentException(
+          String.format("@%s annotation not found on class %s", Screen.class.getSimpleName(),
+              screenType.getName()));
     }
 
-    Layout layout = screenType.getAnnotation(Layout.class);
-    if (layout != null) {
-      return inflateLayout(context, layout.value());
-    }
+    int layout = screen.layout();
+    if (layout != View.NO_ID) return inflateLayout(context, layout);
 
-    throw new IllegalArgumentException(
-        screenType + " does not have either a @View or @Layout annotation");
+    return instantiateView(context, screen.value());
   }
 
   private static android.view.View inflateLayout(Context context, int layoutId) {

sample/src/main/java/com/example/flow/App.java

@@ -24,20 +24,18 @@
 import com.example.flow.view.MessageView;
 import com.squareup.flow.HasParent;
 import com.squareup.flow.Screen;
-import com.squareup.flow.annotation.Layout;
-import com.squareup.flow.annotation.View;
 import dagger.Module;
 import dagger.Provides;
 
 public @interface App {
-  @View(ConversationListView.class) //
-  @Module(injects = ConversationListView.class, complete =  false)
-  public static class ConversationList implements Screen {
+  @Screen(ConversationListView.class) //
+  @Module(injects = ConversationListView.class, complete = false)
+  public static class ConversationList {
   }
 
-  @View(ConversationView.class) //
+  @Screen(ConversationView.class) //
   @Module(injects = ConversationView.class, addsTo = MainActivity.ActivityModule.class)
-  public static class Conversation implements Screen, HasParent<ConversationList> {
+  public static class Conversation implements HasParent<ConversationList> {
     public final int conversationIndex;
 
     public Conversation(int conversationIndex) {
@@ -53,9 +51,9 @@ public Conversation(int conversationIndex) {
     }
   }
 
-  @Layout(R.layout.message_view) //
+  @Screen(layout = R.layout.message_view) //
   @Module(injects = MessageView.class, addsTo = MainActivity.ActivityModule.class)
-  public static class Message implements Screen, HasParent<Conversation> {
+  public static class Message implements HasParent<Conversation> {
     public final int conversationIndex;
     public final int messageId;
 
@@ -73,17 +71,17 @@ public Message(int conversationIndex, int messageId) {
     }
   }
 
-  @View(FriendListView.class) //
+  @Screen(FriendListView.class) //
   @Module(injects = FriendListView.class, addsTo = MainActivity.ActivityModule.class)
-  public static class FriendList implements Screen, HasParent<ConversationList> {
+  public static class FriendList implements HasParent<ConversationList> {
     @Override public ConversationList getParent() {
       return new ConversationList();
     }
   }
 
-  @View(FriendView.class) //
+  @Screen(FriendView.class) //
   @Module(injects = FriendView.class)
-  public static class Friend implements Screen, HasParent<FriendList> {
+  public static class Friend implements HasParent<FriendList> {
     public final int index;
 
     public Friend(int index) {