Android native stack bugfixes. (#190)

A few bugs fixed with android native stack in this commit:
 - fixed a problem with views not resizing when keyboard appears, the bug was due to onMeasure forwardin getHeight which was the old height of the container instead of the changed one
 - fixed a problem with back button behavior not being consistent. Now back button is controlled by 'gestureEnabled' to emulate iOS behavior where there is no hw back button but you can swipe back instead.
 - added compatibility for "contained" modal styles - for now we always render "containted" fragments on Android, plan to add a way to render in dialogs in the future

android/src/main/java/com/swmansion/rnscreens/Screen.java

@@ -2,7 +2,6 @@
 
 import android.content.Context;
 import android.graphics.Paint;
-import android.util.Log;
 import android.view.View;
 import android.view.ViewGroup;
 import android.view.inputmethod.InputMethodManager;
@@ -13,7 +12,6 @@
 
 import com.facebook.react.bridge.GuardedRunnable;
 import com.facebook.react.bridge.ReactContext;
-import com.facebook.react.uimanager.MeasureSpecAssertions;
 import com.facebook.react.uimanager.PointerEvents;
 import com.facebook.react.uimanager.ReactPointerEventsView;
 import com.facebook.react.uimanager.UIManagerModule;

android/src/main/java/com/swmansion/rnscreens/ScreenStack.java

@@ -25,6 +25,10 @@ public void dismiss(ScreenStackFragment screenFragment) {
     onUpdate();
   }
 
+  public Screen getTopScreen() {
+    return mTopScreen.getScreen();
+  }
+
   public Screen getRootScreen() {
     for (int i = 0, size = getScreenCount(); i < size; i++) {
       Screen screen = getScreenAt(i);
@@ -51,9 +55,7 @@ protected void onLayout(boolean changed, int l, int t, int r, int b) {
   protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
     super.onMeasure(widthMeasureSpec, heightMeasureSpec);
     for (int i = 0, size = getChildCount(); i < size; i++) {
-      getChildAt(i).measure(
-              MeasureSpec.makeMeasureSpec(getWidth(), MeasureSpec.EXACTLY),
-              MeasureSpec.makeMeasureSpec(getHeight(), MeasureSpec.EXACTLY));
+      getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);
     }
   }
 
@@ -169,5 +171,9 @@ public void run() {
     mStack.addAll(mScreenFragments);
 
     tryCommitTransaction();
+
+    for (ScreenStackFragment screen : mStack) {
+      screen.onStackUpdate();
+    }
   }
 }

android/src/main/java/com/swmansion/rnscreens/ScreenStackFragment.java

@@ -52,6 +52,13 @@ public void setToolbarShadowHidden(boolean hidden) {
     }
   }
 
+  public void onStackUpdate() {
+    View child = mScreenView.getChildAt(0);
+    if (child instanceof ScreenStackHeaderConfig) {
+      ((ScreenStackHeaderConfig) child).onUpdate();
+    }
+  }
+
   @Override
   public View onCreateView(LayoutInflater inflater,
                            @Nullable ViewGroup container,

android/src/main/java/com/swmansion/rnscreens/ScreenStackHeaderConfig.java

@@ -1,7 +1,6 @@
 package com.swmansion.rnscreens;
 
 import android.content.Context;
-import android.graphics.Color;
 import android.graphics.PorterDuff;
 import android.graphics.drawable.Drawable;
 import android.util.TypedValue;
@@ -29,17 +28,26 @@ public class ScreenStackHeaderConfig extends ViewGroup {
   private int mTitleFontSize;
   private int mBackgroundColor;
   private boolean mIsHidden;
+  private boolean mGestureEnabled = true;
   private boolean mIsBackButtonHidden;
   private boolean mIsShadowHidden;
   private int mTintColor;
   private final Toolbar mToolbar;
 
+  private boolean mIsAttachedToWindow = false;
+
   private OnBackPressedCallback mBackCallback = new OnBackPressedCallback(false) {
     @Override
     public void handleOnBackPressed() {
-      getScreenStack().dismiss(getScreenFragment());
+      ScreenStack stack = getScreenStack();
+      Screen current = getScreen();
+      if (stack.getTopScreen() == current) {
+        stack.dismiss(getScreenFragment());
+      }
+      mBackCallback.remove();
     }
   };
+
   private OnClickListener mBackClickListener = new OnClickListener() {
     @Override
     public void onClick(View view) {
@@ -68,7 +76,14 @@ protected void onLayout(boolean changed, int l, int t, int r, int b) {
   @Override
   protected void onAttachedToWindow() {
     super.onAttachedToWindow();
-    update();
+    mIsAttachedToWindow = true;
+    onUpdate();
+  }
+
+  @Override
+  protected void onDetachedFromWindow() {
+    super.onDetachedFromWindow();
+    mIsAttachedToWindow = false;
   }
 
   private Screen getScreen() {
@@ -101,14 +116,27 @@ private ScreenStackFragment getScreenFragment() {
     return null;
   }
 
-  private void installBackCallback() {
+  public void onUpdate() {
+    Screen parent = (Screen) getParent();
+    final ScreenStack stack = getScreenStack();
+    boolean isRoot = stack == null ? true : stack.getRootScreen() == parent;
+    boolean isTop = stack == null ? true : stack.getTopScreen() == parent;
+
+    // we need to clean up back handler especially in the case given screen is no longer on top
+    // because we don't want it to capture back event if it is not responsible for handling it
+    // as that would block other handlers from running
     mBackCallback.remove();
-    Fragment fragment = getScreenFragment();
-    fragment.requireActivity().getOnBackPressedDispatcher().addCallback(fragment, mBackCallback);
-  }
 
-  private void update() {
-    Screen parent = (Screen) getParent();
+    if (!mIsAttachedToWindow || !isTop) {
+      return;
+    }
+
+    if (!isRoot && isTop && mGestureEnabled) {
+      Fragment fragment = getScreenFragment();
+      fragment.requireActivity().getOnBackPressedDispatcher().addCallback(fragment, mBackCallback);
+      mBackCallback.setEnabled(true);
+    }
+
     if (mIsHidden) {
       if (mToolbar.getParent() != null) {
         getScreenFragment().removeToolbar();
@@ -125,13 +153,7 @@ private void update() {
     ActionBar actionBar = activity.getSupportActionBar();
 
     // hide back button
-    final ScreenStack stack = getScreenStack();
-    boolean isRoot = stack == null ? true : stack.getRootScreen() == parent;
     actionBar.setDisplayHomeAsUpEnabled(isRoot ? false : !mIsBackButtonHidden);
-    if (!isRoot) {
-      installBackCallback();
-    }
-    mBackCallback.setEnabled(!isRoot);
 
     // when setSupportActionBar is called a toolbar wrapper gets initialized that overwrites
     // navigation click listener. The default behavior set in the wrapper is to call into
@@ -268,6 +290,10 @@ public void setHideShadow(boolean hideShadow) {
     mIsShadowHidden = hideShadow;
   }
 
+  public void setGestureEnabled(boolean gestureEnabled) {
+    mGestureEnabled = gestureEnabled;
+  }
+
   public void setHideBackButton(boolean hideBackButton) {
     mIsBackButtonHidden = hideBackButton;
   }

android/src/main/java/com/swmansion/rnscreens/ScreenStackHeaderConfigViewManager.java

@@ -82,6 +82,11 @@ public void setHideShadow(ScreenStackHeaderConfig config, boolean hideShadow) {
     config.setHideShadow(hideShadow);
   }
 
+  @ReactProp(name = "gestureEnabled", defaultBoolean = true)
+  public void setGestureEnabled(ScreenStackHeaderConfig config, boolean gestureEnabled) {
+    config.setGestureEnabled(gestureEnabled);
+  }
+
   @ReactProp(name = "hideBackButton")
   public void setHideBackButton(ScreenStackHeaderConfig config, boolean hideBackButton) {
     config.setHideBackButton(hideBackButton);

android/src/main/java/com/swmansion/rnscreens/ScreenViewManager.java

@@ -35,9 +35,11 @@ public void setActive(Screen view, float active) {
   public void setStackPresentation(Screen view, String presentation) {
     if ("push".equals(presentation)) {
       view.setStackPresentation(Screen.StackPresentation.PUSH);
-    } else if ("modal".equals(presentation)) {
+    } else if ("modal".equals(presentation) || "containedModal".equals(presentation)) {
+      // at the moment Android implementation does not handle contained vs regular modals
       view.setStackPresentation(Screen.StackPresentation.MODAL);
-    } else if ("transparentModal".equals(presentation)) {
+    } else if ("transparentModal".equals(presentation) || "containedTransparentModal".equals((presentation))) {
+      // at the moment Android implementation does not handle contained vs regular modals
       view.setStackPresentation(Screen.StackPresentation.TRANSPARENT_MODAL);
     } else {
       throw new JSApplicationIllegalArgumentException("Unknown presentation type " + presentation);