From 9d80a79cda52ab0cbc1d6b26c84711ed3487cf83 Mon Sep 17 00:00:00 2001
From: Roman Musin <musinrr@gmail.com>
Date: Tue, 8 Jun 2021 23:39:20 +0100
Subject: [PATCH] Android: Resolves #4216: Focus note editor where tapped
 instead of scrolling to the end (#4998)

---
 .../net/cozic/joplin/MainApplication.java     |  2 +
 .../joplin/textinput/TextInputPackage.java    | 63 +++++++++++++++++++
 2 files changed, 65 insertions(+)
 create mode 100644 packages/app-mobile/android/app/src/main/java/net/cozic/joplin/textinput/TextInputPackage.java

diff --git a/packages/app-mobile/android/app/src/main/java/net/cozic/joplin/MainApplication.java b/packages/app-mobile/android/app/src/main/java/net/cozic/joplin/MainApplication.java
index f4792fe3e6..3ebccf791e 100644
--- a/packages/app-mobile/android/app/src/main/java/net/cozic/joplin/MainApplication.java
+++ b/packages/app-mobile/android/app/src/main/java/net/cozic/joplin/MainApplication.java
@@ -16,6 +16,7 @@ import com.facebook.soloader.SoLoader;
 
 import net.cozic.joplin.share.SharePackage;
 import net.cozic.joplin.ssl.SslPackage;
+import net.cozic.joplin.textinput.TextInputPackage;
 
 import java.lang.reflect.Field;
 import java.lang.reflect.InvocationTargetException;
@@ -44,6 +45,7 @@ public class MainApplication extends Application implements ReactApplication {
           // Packages that cannot be autolinked yet can be added manually here, for example:
           packages.add(new SharePackage());
           packages.add(new SslPackage());
+          packages.add(new TextInputPackage());
           return packages;
         }
 
diff --git a/packages/app-mobile/android/app/src/main/java/net/cozic/joplin/textinput/TextInputPackage.java b/packages/app-mobile/android/app/src/main/java/net/cozic/joplin/textinput/TextInputPackage.java
new file mode 100644
index 0000000000..2a11c295d2
--- /dev/null
+++ b/packages/app-mobile/android/app/src/main/java/net/cozic/joplin/textinput/TextInputPackage.java
@@ -0,0 +1,63 @@
+package net.cozic.joplin.textinput;
+
+import android.text.Selection;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+import com.facebook.react.bridge.NativeModule;
+import com.facebook.react.bridge.ReactApplicationContext;
+import com.facebook.react.bridge.ReadableArray;
+import com.facebook.react.uimanager.ViewManager;
+import com.facebook.react.views.textinput.ReactEditText;
+import com.facebook.react.views.textinput.ReactTextInputManager;
+
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * This class provides a workaround for <a href="https://github.com/facebook/react-native/issues/29911">
+ *     https://github.com/facebook/react-native/issues/29911</a>
+ *
+ * The reason the editor is scrolled seems to be due to this block in
+ * <pre>android.widget.Editor#onFocusChanged:</pre>
+ *
+ * <pre>
+ *                 // The DecorView does not have focus when the 'Done' ExtractEditText button is
+ *                 // pressed. Since it is the ViewAncestor's mView, it requests focus before
+ *                 // ExtractEditText clears focus, which gives focus to the ExtractEditText.
+ *                 // This special case ensure that we keep current selection in that case.
+ *                 // It would be better to know why the DecorView does not have focus at that time.
+ *                 if (((mTextView.isInExtractedMode()) || mSelectionMoved)
+ *                         && selStart >= 0 && selEnd >= 0) {
+ *                      Selection.setSelection((Spannable)mTextView.getText(),selStart,selEnd);
+ *                 }
+ * </pre>
+ * When using native Android TextView mSelectionMoved is false so this block is skipped,
+ * with RN however it's true and this is where the scrolling comes from.
+ *
+ * The below workaround resets the selection before a focus event is passed on to the native component.
+ * This way when the above condition is reached <pre>selStart == selEnd == -1</pre> and no scrolling
+ * happens.
+ */
+public class TextInputPackage implements com.facebook.react.ReactPackage {
+    @NonNull
+    @Override
+    public List<NativeModule> createNativeModules(@NonNull ReactApplicationContext reactContext) {
+        return Collections.emptyList();
+    }
+
+    @NonNull
+    @Override
+    public List<ViewManager> createViewManagers(@NonNull ReactApplicationContext reactContext) {
+        return Collections.singletonList(new ReactTextInputManager() {
+            @Override
+            public void receiveCommand(ReactEditText reactEditText, String commandId, @Nullable ReadableArray args) {
+                if ("focus".equals(commandId) || "focusTextInput".equals(commandId)) {
+                    Selection.removeSelection(reactEditText.getText());
+                }
+                super.receiveCommand(reactEditText, commandId, args);
+            }
+        });
+    }
+}