android: add an option to ignore volume keys or use them to turn pages

frontend/device/android/device.lua

@@ -182,6 +182,11 @@ function Device:init()
         self:toggleFullscreen()
     end
 
+    -- check if we ignore volume keys and then they're forwarded to system services.
+    if G_reader_settings:isTrue("android_ignore_volume_keys") then
+        android.setVolumeKeysIgnored(true);
+    end
+
     Generic.init(self)
 end
 

frontend/ui/elements/common_settings_menu_table.lua

@@ -175,6 +175,17 @@ if Device:isAndroid() then
     -- screen timeout options, disabled if device needs wakelocks.
     common_settings.screen_timeout = require("ui/elements/screen_android"):getTimeoutMenuTable()
 
+    -- volume key events
+    common_settings.android_volume_keys = {
+        text = _("Volume key page turning"),
+        checked_func = function() return not android.getVolumeKeysIgnored() end,
+        callback = function()
+            local is_ignored = android.getVolumeKeysIgnored()
+            android.setVolumeKeysIgnored(not is_ignored)
+            G_reader_settings:saveSetting("android_ignore_volume_keys", not is_ignored)
+        end,
+    }
+
     -- fullscreen toggle on devices with compatible fullscreen methods (apis 14-18)
     if Device.firmware_rev < 19 then
         common_settings.fullscreen = {

frontend/ui/elements/filemanager_menu_order.lua

@@ -49,6 +49,7 @@ local order = {
         "back_to_exit",
         "back_in_filemanager",
         "enable_back_history",
+        "android_volume_keys",
         "----------------------------",
         "invert_page_turn_buttons",
     },

frontend/ui/elements/reader_menu_order.lua

@@ -68,6 +68,7 @@ local order = {
         "back_to_exit",
         "back_in_filemanager",
         "enable_back_history",
+        "android_volume_keys",
         "----------------------------",
         "invert_page_turn_buttons",
     },