Update MousePadActivity to support doubletap drag

This MR is a continuation of !439 , which changes the default 
behavior of the remote mouse plugin's drag and drop trigger
to be a double-tap to drag, and adds a new SwitchPreference
that toggles between the old (hold to drag) and new behavior.

res/values/strings.xml

@@ -85,6 +85,7 @@ SPDX-License-Identifier: GPL-2.0-only OR GPL-3.0-only OR LicenseRef-KDE-Accepted
     <string name="mousepad_scroll_sensitivity_title">Scroll sensitivity</string>
     <string name="gyro_mouse_enabled" translatable="false">gyro_mouse_enabled</string>
     <string name="mousepad_mouse_buttons_enabled_pref" translatable="false">mouse_buttons_enabled</string>
+    <string name="mousepad_doubletap_drag_enabled_pref" translatable="false">doubletap_drag_enabled</string>
     <string name="gyro_mouse_enabled_title">Enable gyroscope mouse</string>
     <string name="gyro_mouse_sensitivity_title">Gyroscope sensitivity</string>
     <string name="gyro_mouse_sensitivity" translatable="false">gyro_mouse_sensitivity</string>
@@ -513,6 +514,8 @@ SPDX-License-Identifier: GPL-2.0-only OR GPL-3.0-only OR LicenseRef-KDE-Accepted
   <string name="send_compose">Send</string>
   <string name="compose_send_title">Compose send</string>
   <string name="open_compose_send">Compose text</string>
+  <string name="double_tap_to_drag">Double tap to drag</string>
+  <string name="hold_to_drag">Hold to drag</string>
 
     <string name="about_kde_about"><![CDATA[
       <h1>About</h1>

res/xml/mousepadplugin_preferences.xml

@@ -90,6 +90,15 @@ SPDX-License-Identifier: GPL-2.0-only OR GPL-3.0-only OR LicenseRef-KDE-Accepted
         android:key="@string/mousepad_mouse_buttons_enabled_pref"
         android:title="@string/mousepad_mouse_buttons_title" />
 
+    <SwitchPreference
+        android:id="@+id/mousepad_double_tap_drag_enabled_pref"
+        android:defaultValue="true"
+        android:key="@string/mousepad_doubletap_drag_enabled_pref"
+        android:title="Drag and drop behavior"
+        android:summaryOn="@string/double_tap_to_drag"
+        android:summaryOff="@string/hold_to_drag"
+        />
+
 
     <org.kde.kdeconnect.Helpers.LongSummaryPreferenceCategory
         android:key="@string/sendkeystrokes_pref_category"

src/org/kde/kdeconnect/Plugins/MousePadPlugin/MousePadActivity.java

@@ -13,6 +13,7 @@ import android.hardware.SensorEvent;
 import android.hardware.SensorEventListener;
 import android.hardware.SensorManager;
 import android.os.Bundle;
+import android.util.Log;
 import android.view.GestureDetector;
 import android.view.HapticFeedbackConstants;
 import android.view.Menu;
@@ -55,6 +56,7 @@ public class MousePadActivity
     private double scrollCoefficient = 1.0;
     private boolean allowGyro = false;
     private boolean gyroEnabled = false;
+    private boolean doubleTapDragEnabled = false;
     private int gyroscopeSensitivity = 100;
     private boolean isScrolling = false;
     private float accumulatedDistanceY = 0;
@@ -376,14 +378,16 @@ public class MousePadActivity
 
     @Override
     public void onLongPress(MotionEvent e) {
-        getWindow().getDecorView().performHapticFeedback(HapticFeedbackConstants.VIRTUAL_KEY);
+        if (!doubleTapDragEnabled) {
-        MousePadPlugin plugin = KdeConnect.getInstance().getDevicePlugin(deviceId, MousePadPlugin.class);
+            getWindow().getDecorView().performHapticFeedback(HapticFeedbackConstants.VIRTUAL_KEY);
-        if (plugin == null) {
+            MousePadPlugin plugin = KdeConnect.getInstance().getDevicePlugin(deviceId, MousePadPlugin.class);
-            finish();
+            if (plugin == null) {
-            return;
+                finish();
+                return;
+            }
+            plugin.sendSingleHold();
+            dragging = true;
         }   
-        plugin.sendSingleHold();
-        dragging = true;
     }
 
     @Override
@@ -415,13 +419,18 @@ public class MousePadActivity
             finish();
             return true;
         }
-        plugin.sendDoubleClick();
+        if (doubleTapDragEnabled) {
+            plugin.sendSingleHold();
+            dragging = true;
+        } else {
+            plugin.sendDoubleClick();
+        }
         return true;
     }
 
     @Override
     public boolean onDoubleTapEvent(MotionEvent e) {
-        return false;
+        return true;
     }
 
     @Override
@@ -578,6 +587,8 @@ public class MousePadActivity
             findViewById(R.id.mouse_buttons).setVisibility(View.GONE);
         }
 
+        doubleTapDragEnabled = prefs.getBoolean(getString(R.string.mousepad_doubletap_drag_enabled_pref), true);
+
         prefsApplied = true;
     }