Added swipe to previous/next conversation

FAQ.md

@@ -35,7 +35,6 @@ Anything on this list is in random order and *might* be added in the near future
 
 ## Frequently requested features
 
-* Swipe left/right to go to previous/next message: besides that swiping left/right is already being used to move messages to archive/trash, swiping also selects message text, so this will not work reliably. You can use the bottom navigation bar instead.
 * Rich text editor: besides that very few people would use this on a small mobile device, Android doesn't support a rich text editor and most rich text editor open source projects are abandoned.
 * Widget to read e-mail: widgets can have limited user interaction only, so a widget to read e-mail would not be very useful. Moreover, it would be not very useful to duplicate functions which are already available in the app.
 * Badge count: there is no standard Android API for this and third party solutions might stop working anytime. For example *ShortcutBadger* [has lots of problems](https://github.com/leolin310148/ShortcutBadger/issues). You can use the provided widget instead.

app/src/main/java/eu/faircode/email/ActivityBase.java

@@ -26,6 +26,7 @@ import android.content.pm.PackageManager;
 import android.content.res.Configuration;
 import android.os.Bundle;
 import android.preference.PreferenceManager;
+import android.view.MotionEvent;
 import android.view.View;
 
 import java.util.ArrayList;
@@ -39,6 +40,7 @@ import androidx.fragment.app.Fragment;
 
 abstract class ActivityBase extends AppCompatActivity implements SharedPreferences.OnSharedPreferenceChangeListener {
     private boolean contacts;
+    private SwipeListener swipeListener;
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
@@ -59,6 +61,17 @@ abstract class ActivityBase extends AppCompatActivity implements SharedPreferenc
         super.onCreate(savedInstanceState);
     }
 
+    void setSwipeListener(SwipeListener.ISwipeListener listener) {
+        swipeListener = new SwipeListener(this, listener);
+    }
+
+    @Override
+    public boolean dispatchTouchEvent(MotionEvent ev) {
+        if (swipeListener != null)
+            swipeListener.onTouch(null, ev);
+        return super.dispatchTouchEvent(ev);
+    }
+
     @Override
     protected void onResume() {
         Log.i("Resume " + this.getClass().getName());

app/src/main/java/eu/faircode/email/FragmentMessages.java

@@ -297,6 +297,30 @@ public class FragmentMessages extends FragmentBase {
                     }
                 });
             }
+
+            ActivityBase activity = (ActivityBase) getActivity();
+            activity.setSwipeListener(new SwipeListener.ISwipeListener() {
+                @Override
+                public boolean onSwipeRight() {
+                    return swipe(R.id.action_prev);
+                }
+
+                @Override
+                public boolean onSwipeLeft() {
+                    return swipe(R.id.action_next);
+                }
+
+                private boolean swipe(int menu) {
+                    Intent intent = bottom_navigation.getMenu().findItem(menu).getIntent();
+                    Long id = (intent == null ? null : intent.getLongExtra("id", -1));
+                    if (id != null && id > 0) {
+                        navigate(id);
+                        return true;
+                    } else
+                        return false;
+                }
+            });
+
         } else {
             final SelectionPredicateMessage predicate = new SelectionPredicateMessage(rvMessage);
 

app/src/main/java/eu/faircode/email/SwipeListener.java

@@ -0,0 +1,46 @@
+package eu.faircode.email;
+
+import android.content.Context;
+import android.view.GestureDetector;
+import android.view.MotionEvent;
+import android.view.View;
+
+public class SwipeListener implements View.OnTouchListener {
+    private final GestureDetector gestureDetector;
+
+    public SwipeListener(Context context, final ISwipeListener listener) {
+        gestureDetector = new GestureDetector(context, new GestureDetector.SimpleOnGestureListener() {
+            private static final int MOVE_THRESHOLD = 100;
+            private static final int SPEED_THRESHOLD = 100;
+
+            @Override
+            public boolean onFling(MotionEvent me1, MotionEvent me2, float vx, float vy) {
+                boolean consumed = false;
+                float dx = me2.getX() - me1.getX();
+                float dy = me2.getY() - me1.getY();
+                if (Math.abs(dx) > Math.abs(dy)) {
+                    if (Math.abs(dx) > MOVE_THRESHOLD && Math.abs(vx) > SPEED_THRESHOLD)
+                        try {
+                            if (dx > 0)
+                                consumed = listener.onSwipeRight();
+                            else
+                                consumed = listener.onSwipeLeft();
+                        } catch (Throwable ex) {
+                            Log.e(ex);
+                        }
+                }
+                return consumed;
+            }
+        });
+    }
+
+    public boolean onTouch(final View v, final MotionEvent event) {
+        return gestureDetector.onTouchEvent(event);
+    }
+
+    interface ISwipeListener {
+        boolean onSwipeRight();
+
+        boolean onSwipeLeft();
+    }
+}