Deprecate handling of "up" and HasParent interface

In practice, handling "up" is rarely wanted and the current implementation complicates internal semantics and pollutes clients' Path class hierarchies. We may revisit the idea later.
sarvex · Feb 22, 2015 · 471283c · 471283c
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -18,6 +18,8 @@ Version 0.9 *(TBD)*
 
   * Listener is now called Dispatcher, and can be set on a Flow after construction.
 
+  * Deprecated "up" navigation. We may revisit with a better implementation later.
+
   * Updated sample app to demonstrate all of the above.
 
 Version 0.8 *(2014-09-17)*

diff --git a/flow-sample/src/main/java/com/example/flow/MainActivity.java b/flow-sample/src/main/java/com/example/flow/MainActivity.java
@@ -22,7 +22,6 @@
 import android.view.Menu;
 import android.view.MenuItem;
 import com.example.flow.pathview.HandlesBack;
-import com.example.flow.pathview.HandlesUp;
 import com.example.flow.util.FlowBundler;
 import flow.Flow;
 import flow.HasParent;
@@ -36,7 +35,6 @@
 public class MainActivity extends Activity implements Flow.Dispatcher {
   private PathContainerView container;
   private HandlesBack containerAsBackTarget;
-  private HandlesUp containerAsUpTarget;
 
   private Flow flow;
 
@@ -69,7 +67,6 @@ protected void onCreate(Bundle savedInstanceState) {
 
     container = (PathContainerView) findViewById(R.id.container);
     containerAsBackTarget = (HandlesBack) container;
-    containerAsUpTarget = (HandlesUp) container;
   }
 
   @Override protected void onResume() {
@@ -111,7 +108,8 @@ protected void onCreate(Bundle savedInstanceState) {
 
   @Override public boolean onOptionsItemSelected(MenuItem item) {
     if (item.getItemId() == android.R.id.home) {
-      return containerAsUpTarget.onUpPressed();
+      onBackPressed();
+      return true;
     } else {
       return super.onOptionsItemSelected(item);
     }
@@ -123,18 +121,19 @@ protected void onCreate(Bundle savedInstanceState) {
     }
   }
 
-  @Override public void dispatch(Traversal traversal, TraversalCallback callback) {
+  @Override public void dispatch(Traversal traversal, final TraversalCallback callback) {
     Path path = traversal.destination.current();
-    container.dispatch(traversal, callback);
-
     setTitle(path.getClass().getSimpleName());
-
     ActionBar actionBar = getActionBar();
-    boolean hasUp = path instanceof HasParent;
-    actionBar.setDisplayHomeAsUpEnabled(hasUp);
-    actionBar.setHomeButtonEnabled(hasUp);
-
-    invalidateOptionsMenu();
+    boolean canGoBack = traversal.destination.size() > 1;
+    actionBar.setDisplayHomeAsUpEnabled(canGoBack);
+    actionBar.setHomeButtonEnabled(canGoBack);
+    container.dispatch(traversal, new TraversalCallback() {
+      @Override public void onTraversalCompleted() {
+        invalidateOptionsMenu();
+        callback.onTraversalCompleted();
+      }
+    });
   }
 
   private FlowBundler getFlowBundler() {

diff --git a/.../com/example/flow/pathview/UpAndBack.java → ...om/example/flow/pathview/BackSupport.java b/.../com/example/flow/pathview/UpAndBack.java → ...om/example/flow/pathview/BackSupport.java
@@ -20,18 +20,9 @@
 import flow.Flow;
 
 /**
- * Support for {@link HandlesUp} and {@link HandlesBack}.
+ * Support for {@link HandlesBack}.
  */
-public class UpAndBack {
-  public static boolean onUpPressed(View childView) {
-    if (childView instanceof HandlesUp) {
-      if (((HandlesUp) childView).onUpPressed()) {
-        return true;
-      }
-    }
-    // Try to go up.  If up isn't supported, go back.
-    return Flow.get(childView).goUp() || onBackPressed(childView);
-  }
+public class BackSupport {
 
   public static boolean onBackPressed(View childView) {
     if (childView instanceof HandlesBack) {
@@ -42,6 +33,6 @@ public static boolean onBackPressed(View childView) {
     return Flow.get(childView).goBack();
   }
 
-  private UpAndBack() {
+  private BackSupport() {
   }
 }
diff --git a/flow-sample/src/main/java/com/example/flow/pathview/FramePathContainerView.java b/flow-sample/src/main/java/com/example/flow/pathview/FramePathContainerView.java
@@ -29,7 +29,7 @@
 
 /** A FrameLayout that can show screens for a {@link flow.Flow}. */
 public class FramePathContainerView extends FrameLayout
-    implements HandlesBack, HandlesUp, PathContainerView {
+    implements HandlesBack, PathContainerView {
   private final PathContainer container;
   private boolean disabled;
 
@@ -69,12 +69,8 @@ protected FramePathContainerView(Context context, AttributeSet attrs, PathContai
     });
   }
 
-  @Override public boolean onUpPressed() {
-    return UpAndBack.onUpPressed(getCurrentChild());
-  }
-
   @Override public boolean onBackPressed() {
-    return UpAndBack.onBackPressed(getCurrentChild());
+    return BackSupport.onBackPressed(getCurrentChild());
   }
 
   @Override public ViewGroup getCurrentChild() {

diff --git a/flow-sample/src/main/java/com/example/flow/pathview/HandlesUp.java b/flow-sample/src/main/java/com/example/flow/pathview/HandlesUp.java
diff --git a/flow-sample/src/main/java/com/example/flow/view/TabletMasterDetailRoot.java b/flow-sample/src/main/java/com/example/flow/view/TabletMasterDetailRoot.java
@@ -9,8 +9,7 @@
 import com.example.flow.R;
 import com.example.flow.pathview.FramePathContainerView;
 import com.example.flow.pathview.HandlesBack;
-import com.example.flow.pathview.HandlesUp;
-import com.example.flow.pathview.UpAndBack;
+import com.example.flow.pathview.BackSupport;
 import flow.Flow;
 import flow.Path;
 import flow.PathContainerView;
@@ -21,7 +20,7 @@
  * the explanation in {@link com.example.flow.MainActivity#onCreate}.
  */
 public class TabletMasterDetailRoot extends LinearLayout
-    implements HandlesBack, HandlesUp, PathContainerView {
+    implements HandlesBack, PathContainerView {
   private FramePathContainerView masterContainer;
   private FramePathContainerView detailContainer;
 
@@ -78,11 +77,7 @@ class CountdownCallback implements Flow.TraversalCallback {
     masterContainer.dispatch(traversal, callback);
   }
 
-  @Override public boolean onUpPressed() {
-    return UpAndBack.onUpPressed(detailContainer);
-  }
-
   @Override public boolean onBackPressed() {
-    return UpAndBack.onBackPressed(detailContainer);
+    return BackSupport.onBackPressed(detailContainer);
   }
 }
diff --git a/flow/src/main/java/flow/Backstack.java b/flow/src/main/java/flow/Backstack.java
@@ -107,7 +107,10 @@ public Builder buildUpon() {
     return backstack.toString();
   }
 
-  public static Backstack fromUpChain(Path path) {
+  /**
+   * @deprecated Applications should implement this themselves, if necessary.
+   */
+  @Deprecated public static Backstack fromUpChain(Path path) {
     LinkedList<Path> newBackstack = new LinkedList<>();
 
     Path current = path;

diff --git a/flow/src/main/java/flow/Flow.java b/flow/src/main/java/flow/Flow.java
@@ -198,8 +198,9 @@ public void replaceTo(final Path path) {
    * Go up one screen.
    *
    * @return false if going up is not possible.
+   * @deprecated Applications should handle "up" themselves, if necessary.
    */
-  public boolean goUp() {
+  @Deprecated public boolean goUp() {
     boolean canGoUp = false;
     if (backstack.current() instanceof HasParent || (pendingTraversal != null
         && pendingTraversal.state != TraversalState.FINISHED)) {

diff --git a/flow/src/main/java/flow/HasParent.java b/flow/src/main/java/flow/HasParent.java
@@ -19,7 +19,9 @@
 /**
  * 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.
+ *
+ * @deprecated Up handling is deprecated, left to applications to implement if needed.
  */
-public interface HasParent {
+@Deprecated public interface HasParent {
   Path getParent();
 }