diff --git a/MidiPlayer.Droid/MainActivity.Component.cs b/MidiPlayer.Droid/MainActivity.Component.cs
index 304d653..accabdd 100644
--- a/MidiPlayer.Droid/MainActivity.Component.cs
+++ b/MidiPlayer.Droid/MainActivity.Component.cs
@@ -2,6 +2,7 @@
 using Android.Support.V7.App;
 using Android.Widget;
 
+using System;
 using System.Collections.Generic;
 using System.Linq;
 
@@ -44,27 +45,127 @@ public partial class MainActivity : AppCompatActivity {
         /// initialize the component.
         /// </summary>
         void initializeComponent() {
+
+            /// <summary>
+            /// buttonLoadSoundFont
+            /// </summary>
             _buttonloadSoundFont = FindViewById<Button>(Resource.Id.button_load_soundfont);
-            _buttonloadSoundFont.Click += buttonLoadSoundFont_Click;
+            _buttonloadSoundFont.Click += (object sender, EventArgs e) => {
+                Log.Info("buttonLoadSoundFont clicked.");
+                try {
+                    if (Synth.Playing) {
+                        stopSong();
+                    }
+                    callIntent(Env.SoundFontDirForIntent, (int) Request.SoundFont);
+                } catch (Exception ex) {
+                    Log.Error(ex.Message);
+                }
+            };
 
+            /// <summary>
+            /// buttonLoadMidiFile
+            /// </summary>
             _buttonloadMidiFile = FindViewById<Button>(Resource.Id.button_load_midifile);
-            _buttonloadMidiFile.Click += buttonLoadMidiFile_Click;
+            _buttonloadMidiFile.Click += (object sender, EventArgs e) => {
+                Log.Info("buttonLoadMidiFile clicked.");
+                try {
+                    if (Synth.Playing) {
+                        stopSong();
+                    }
+                    callIntent(Env.MidiFileDirForIntent, (int) Request.MidiFile);
+                } catch (Exception ex) {
+                    Log.Error(ex.Message);
+                }
+            };
 
+            /// <summary>
+            /// buttonStart
+            /// </summary>
             _buttonStart = FindViewById<Button>(Resource.Id.button_start);
-            _buttonStart.Click += buttonStart_Click;
+            _buttonStart.Click += (object sender, EventArgs e) => {
+                Log.Info("buttonStart clicked.");
+                try {
+                    if (!_midiFilePath.HasValue()) { // FIXME: case sounFdont
+                        Log.Warn("midiFilePath has no value.");
+                        return;
+                    }
+                    playSong();
+                } catch (Exception ex) {
+                    Log.Error(ex.Message);
+                }
+            };
 
+            /// <summary>
+            /// buttonStop
+            /// </summary>
             _buttonStop = FindViewById<Button>(Resource.Id.button_stop);
-            _buttonStop.Click += buttonStop_Click;
+            _buttonStop.Click += (object sender, EventArgs e) => {
+                Log.Info("buttonStop clicked.");
+                try {
+                    stopSong();
+                } catch (Exception ex) {
+                    Log.Error(ex.Message);
+                }
+            };
 
+            /// <summary>
+            /// buttonAddPlaylist
+            /// </summary>
             _buttonAddPlaylist = FindViewById<Button>(Resource.Id.button_add_playlist);
-            _buttonAddPlaylist.Click += buttonAddPlaylist_Click;
+            _buttonAddPlaylist.Click += (object sender, EventArgs e) => {
+                Log.Info("buttonAddPlaylist clicked.");
+                try {
+                    callIntent(Env.MidiFileDir, (int) Request.AddPlayList);
+                } catch (Exception ex) {
+                    Log.Error(ex.Message);
+                }
+            };
 
+            /// <summary>
+            /// buttonDeletePlaylist
+            /// </summary>
             _buttonDeletePlaylist = FindViewById<Button>(Resource.Id.button_delete_playlist);
-            _buttonDeletePlaylist.Click += buttonDeletePlaylist_Click;
+            _buttonDeletePlaylist.Click += (object sender, EventArgs e) => {
+                Log.Info("buttonDeletePlaylist clicked.");
+                try {
+                    _playList.Clear();
+                } catch (Exception ex) {
+                    Log.Error(ex.Message);
+                }
+            };
 
-            // fader
+            /// <summary>
+            /// buttonSendSynth
+            /// </summary>
+            _buttonSendSynth = FindViewById<Button>(Resource.Id.button_send_synth);
+            _buttonSendSynth.Click += (object sender, EventArgs e) => {
+                Log.Info("buttonSendSynth clicked.");
+                try {
+                    Mixer.Fader fader = Mixer.GetCurrent();
+                    Log.Debug($"track index {fader.Index}: send a data to MIDI {fader.Channel} channel.");
+                    Log.Debug($"prog: {fader.Program} pan: {fader.Pan} vol: {fader.Volume}.");
+                    Data data = new() {
+                        Channel = fader.Channel,
+                        Program = fader.Program,
+                        Pan = fader.Pan,
+                        Volume = fader.Volume,
+                        Mute = !fader.Sounds
+                    };
+                    EventQueue.Enqueue(fader.Index, data);
+                } catch (Exception ex) {
+                    Log.Error(ex.Message);
+                }
+            };
+
+            /// <summary>
+            /// textViewNo, textViewChannel
+            /// </summary>
             _textViewNo = FindViewById<TextView>(Resource.Id.text_view_no);
             _textViewChannel = FindViewById<TextView>(Resource.Id.text_view_channel);
+
+            /// <summary>
+            /// numberPickerProg
+            /// </summary>
             _numberPickerProg = FindViewById<NumberPicker>(Resource.Id.number_picker_prog);
             _numberPickerProg.MinValue = 1;
             _numberPickerProg.MaxValue = 128;
@@ -73,6 +174,10 @@ void initializeComponent() {
                 Log.Debug($"_numberPickerProg.Value: {_numberPickerProg.Value}");
                 fader.ProgramAsOneBased = _numberPickerProg.Value;
             };
+
+            /// <summary>
+            /// numberPickerPan
+            /// </summary>
             _numberPickerPan = FindViewById<NumberPicker>(Resource.Id.number_picker_pan);
             _numberPickerPan.MinValue = 1;
             _numberPickerPan.MaxValue = 128;
@@ -82,6 +187,10 @@ void initializeComponent() {
                 Log.Debug($"_numberPickerPan.Value: {_numberPickerPan.Value}");
                 fader.Pan = _numberPickerPan.Value;
             };
+
+            /// <summary>
+            /// numberPickerVol
+            /// </summary>
             _numberPickerVol = FindViewById<NumberPicker>(Resource.Id.number_picker_vol);
             _numberPickerVol.MinValue = 1;
             _numberPickerVol.MaxValue = 128;
@@ -91,21 +200,27 @@ void initializeComponent() {
                 Log.Debug($"_numberPickerVol.Value: {_numberPickerVol.Value}");
                 fader.Volume = _numberPickerVol.Value;
             };
+
+            /// <summary>
+            /// checkBoxMute
+            /// </summary>
             _checkBoxMute = FindViewById<CheckBox>(Resource.Id.check_box_mute);
             _checkBoxMute.CheckedChange += (object sender, CheckBox.CheckedChangeEventArgs e) => {
                 var fader = Mixer.GetCurrent();
                 fader.Sounds = !_checkBoxMute.Checked;
             };
-            _buttonSendSynth = FindViewById<Button>(Resource.Id.button_send_synth);
-            _buttonSendSynth.Click += buttonSendSynth_Click;
 
-            // list view title
+            /// <summary>
+            /// titleListView
+            /// </summary>
             var titleList = new List<ListTitle>();
             titleList.Add(new ListTitle() { Name = "Name", Instrument = "Voice", Channel = "Ch" });
             _titleListView = FindViewById<ListView>(Resource.Id.list_view_title);
             _titleListView.Adapter = new ListTitleAdapter(this, 0, titleList);
 
-            // list view item
+            /// <summary>
+            /// itemListView
+            /// </summary>
             Enumerable.Range(MIDI_TRACK_BASE, MIDI_TRACK_COUNT).ToList().ForEach(x => {
                 _itemList.Add(new ListItem() { Name = "------", Instrument = "------", Channel = "---" });
             });
diff --git a/MidiPlayer.Droid/MainActivity.EventCallback.cs b/MidiPlayer.Droid/MainActivity.EventCallback.cs
deleted file mode 100644
index c079729..0000000
--- a/MidiPlayer.Droid/MainActivity.EventCallback.cs
+++ /dev/null
@@ -1,120 +0,0 @@
-
-using Android.Support.V7.App;
-
-using System;
-
-namespace MidiPlayer.Droid {
-    /// <summary>
-    ///  partial class for event callback functions.
-    /// </summary>
-    public partial class MainActivity : AppCompatActivity {
-#nullable enable
-
-        ///////////////////////////////////////////////////////////////////////////////////////////////
-        // private Methods [verb, verb phrases]
-
-        /// <summary>
-        /// buttonLoadSoundFont Click.
-        /// </summary>
-        void buttonLoadSoundFont_Click(object sender, EventArgs e) {
-            Log.Info("buttonLoadSoundFont clicked.");
-            try {
-                if (Synth.Playing) {
-                    stopSong();
-                }
-                callIntent(Env.SoundFontDirForIntent, (int) Request.SoundFont);
-            } catch (Exception ex) {
-                Log.Error(ex.Message);
-            }
-        }
-
-        /// <summary>
-        /// buttonLoadMidiFile Click.
-        /// </summary>
-        void buttonLoadMidiFile_Click(object sender, EventArgs e) {
-            Log.Info("buttonLoadMidiFile clicked.");
-            try {
-                if (Synth.Playing) {
-                    stopSong();
-                }
-                callIntent(Env.MidiFileDirForIntent, (int) Request.MidiFile);
-            } catch (Exception ex) {
-                Log.Error(ex.Message);
-            }
-        }
-
-        /// <summary>
-        /// buttonStart Click.
-        /// </summary>
-        void buttonStart_Click(object sender, EventArgs e) {
-            Log.Info("buttonStart clicked.");
-            try {
-                if (!_midiFilePath.HasValue()) { // FIXME: case sounFdont
-                    Log.Warn("midiFilePath has no value.");
-                    return;
-                }
-                playSong();
-            } catch (Exception ex) {
-                Log.Error(ex.Message);
-            }
-        }
-
-        /// <summary>
-        /// buttonStop Click.
-        /// </summary>
-        void buttonStop_Click(object sender, EventArgs e) {
-            Log.Info("buttonStop clicked.");
-            try {
-                stopSong();
-            } catch (Exception ex) {
-                Log.Error(ex.Message);
-            }
-        }
-
-        /// <summary>
-        /// buttonAddPlaylist Click.
-        /// </summary>
-        void buttonAddPlaylist_Click(object sender, EventArgs e) {
-            Log.Info("buttonAddPlaylist clicked.");
-            try {
-                callIntent(Env.MidiFileDir, (int) Request.AddPlayList);
-            } catch (Exception ex) {
-                Log.Error(ex.Message);
-            }
-        }
-
-        /// <summary>
-        /// buttonDeletePlaylist Click.
-        /// </summary>
-        void buttonDeletePlaylist_Click(object sender, EventArgs e) {
-            Log.Info("buttonDeletePlaylist clicked.");
-            try {
-                _playList.Clear();
-            } catch (Exception ex) {
-                Log.Error(ex.Message);
-            }
-        }
-
-        /// <summary>
-        /// buttonSendSynth Click.
-        /// </summary>
-        void buttonSendSynth_Click(object sender, EventArgs e) {
-            Log.Info("buttonSendSynth clicked.");
-            try {
-                Mixer.Fader fader = Mixer.GetCurrent();
-                Log.Debug($"track index {fader.Index}: send a data to MIDI {fader.Channel} channel.");
-                Log.Debug($"prog: {fader.Program} pan: {fader.Pan} vol: {fader.Volume}.");
-                Data data = new() {
-                    Channel = fader.Channel,
-                    Program = fader.Program,
-                    Pan = fader.Pan,
-                    Volume = fader.Volume,
-                    Mute = !fader.Sounds
-                };
-                EventQueue.Enqueue(fader.Index, data);
-            } catch (Exception ex) {
-                Log.Error(ex.Message);
-            }
-        }
-    }
-}
diff --git a/MidiPlayer.Droid/MidiPlayer.Droid.csproj b/MidiPlayer.Droid/MidiPlayer.Droid.csproj
index c496bc8..56594f7 100644
--- a/MidiPlayer.Droid/MidiPlayer.Droid.csproj
+++ b/MidiPlayer.Droid/MidiPlayer.Droid.csproj
@@ -70,7 +70,6 @@
   <ItemGroup>
     <AndroidEnvironment Include="env.conf" />
     <Compile Include="ListViewAdapter.cs" />
-    <Compile Include="MainActivity.EventCallback.cs" />
     <Compile Include="MainActivity.cs" />
     <Compile Include="MainActivity.Component.cs" />
     <Compile Include="Resources\Resource.designer.cs" />