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"Touch drag scroll" feature of the on-screen piano keyboard #16

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598499e
Implementation of the Touch Drag Scroll feature
Codereamp Jan 8, 2024
7e30dc0
Reordering of new routines for better diff
Codereamp Jan 8, 2024
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3 changes: 3 additions & 0 deletions .idea/modules.xml
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4 changes: 4 additions & 0 deletions app/src/main/java/com/manichord/synthesizer/android/ui/PianoActivity2.java
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Expand Up @@ -166,6 +166,7 @@ protected void onResume() {
onSharedPreferenceChanged(prefs, "keyboard_type");
onSharedPreferenceChanged(prefs, "vel_sens");
onSharedPreferenceChanged(prefs, "midi_channel");
onSharedPreferenceChanged(prefs, "touch_drag_action");
}

@Override
Expand All @@ -192,6 +193,9 @@ public void onSharedPreferenceChanged(SharedPreferences prefs, String key) {
Log.d("PianoActivity2", "cannot set current channel no Synth service");
}
Log.d("PianoActivity2", "set current channel:" + currentChannel);
} else if (key.equals("touch_drag_action")) {
String touchDragAction = prefs.getString(key, "TDA_PlayNotes");
keyboard_.setTouchDragAction(KeyboardView.TouchDragAction.toTouchDragAction(touchDragAction));
}
}

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9 changes: 9 additions & 0 deletions app/src/main/java/com/manichord/synthesizer/android/ui/SettingsActivity.java
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Expand Up @@ -32,6 +32,15 @@ public boolean onPreferenceChange(Preference pref, Object newVal) {
return true;
}
});
ListPreference touchDragActionPref = (ListPreference)findPreference("touch_drag_action");
updateListSummary(touchDragActionPref, touchDragActionPref.getValue());
Log.d("SettingsActivity", "touch drag action:"+touchDragActionPref.getValue());
touchDragActionPref.setOnPreferenceChangeListener(new OnPreferenceChangeListener() {
public boolean onPreferenceChange(Preference pref, Object newVal) {
updateListSummary(pref, newVal.toString());
return true;
}
});
}


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132 changes: 110 additions & 22 deletions app/src/main/java/com/manichord/synthesizer/android/widgets/keyboard/KeyboardView.java
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Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
/*
*
* Copyright 2013 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
Expand Down Expand Up @@ -26,16 +27,33 @@
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.util.Log;
import java.lang.Math;

import com.manichord.synthesizer.core.midi.MidiListener;

public class KeyboardView extends View {

public enum TouchDragAction {
TDA_PlayNotes, TDA_ScrollKeyboard;

public static TouchDragAction toTouchDragAction(String TouchDragActionString) {
try {
return valueOf(TouchDragActionString);
} catch (Exception ex) {
return TDA_PlayNotes;
}
}
}

public KeyboardView(Context context, AttributeSet attrs) {
super(context, attrs);
nKeys_ = 96;
firstKey_ = 12;
noteStatus_ = new byte[128];
noteForFinger_ = new int[FINGERS];
touchCurrentX = new float[FINGERS];

for (int i = 0; i < FINGERS; i++) {
noteForFinger_[i] = -1;
}
Expand All @@ -53,6 +71,8 @@ public KeyboardView(Context context, AttributeSet attrs) {
setKeyboardSpec(KeyboardSpec.make2Row());
velSens_ = 0.5f;
velAvg_ = 64;

touchDragAction_ = TouchDragAction.TDA_PlayNotes;
}

public void setKeyboardSpec(KeyboardSpec keyboardSpec) {
Expand All @@ -61,6 +81,11 @@ public void setKeyboardSpec(KeyboardSpec keyboardSpec) {
invalidate();
}

public void setTouchDragAction(TouchDragAction action)
{
touchDragAction_ = action;
}

public void setMidiListener(MidiListener listener) {
midiListener_ = listener;
}
Expand Down Expand Up @@ -217,13 +242,24 @@ private int computeVelocity(float pressure) {

private boolean onTouchDown(int id, float x, float y, float pressure) {
int note = hitTest(x, y);

if (note >= 0 && noteStatus_[note] == 0) {
int velocity = computeVelocity(pressure);

noteForFinger_[id] = note;

noteStatus_[note] = (byte)velocity;
if (midiListener_ != null) {
midiListener_.onNoteOn(0, note, velocity);
}

if (touchDragAction_ == TouchDragAction.TDA_ScrollKeyboard)
{
touchCurrentX[id] = x;
if (notesPressed() == 1)
touchTrackingOffset = offset_;
}

return true;
}
return false;
Expand All @@ -232,50 +268,98 @@ private boolean onTouchDown(int id, float x, float y, float pressure) {
private boolean onTouchUp(int id, float x, float y, float pressure) {
int note = noteForFinger_[id];
if (note >= 0) {

int velocity = noteStatus_[note];
if (midiListener_ != null) {
midiListener_.onNoteOff(0, note, velocity);
}
noteForFinger_[id] = -1;
noteStatus_[note] = 0;

return true;
}
return false;
}

private boolean onTouchMove(int id, float x, float y, float pressure) {
int oldNote = noteForFinger_[id];
int newNote = hitTest(x, y);
if (newNote != -1 && newNote != oldNote && noteStatus_[newNote] == 0) {
// keep consistent velocity; new is likely to be too high
if (oldNote >= 0) {
int velocity = noteStatus_[oldNote];
if (midiListener_ != null) {
midiListener_.onNoteOff(0, oldNote, velocity);
midiListener_.onNoteOn(0, newNote, velocity);
}
noteForFinger_[id] = newNote;
noteStatus_[oldNote] = 0;
noteStatus_[newNote] = (byte)velocity;
} else {
// moving onto active note from dead zone
int velocity = 64;
if (midiListener_ != null) {
midiListener_.onNoteOn(0, newNote, velocity);

if (handleScrollTouch(id, x)) {
return false;
} else {
int oldNote = noteForFinger_[id];
int newNote = hitTest(x, y);
if (newNote != -1 && newNote != oldNote && noteStatus_[newNote] == 0) {
// keep consistent velocity; new is likely to be too high
if (oldNote >= 0) {
int velocity = noteStatus_[oldNote];
if (midiListener_ != null) {
midiListener_.onNoteOff(0, oldNote, velocity);
midiListener_.onNoteOn(0, newNote, velocity);
}
noteForFinger_[id] = newNote;
noteStatus_[oldNote] = 0;
noteStatus_[newNote] = (byte)velocity;
} else {
// moving onto active note from dead zone
int velocity = 64;
if (midiListener_ != null) {
midiListener_.onNoteOn(0, newNote, velocity);
}
noteForFinger_[id] = newNote;
noteStatus_[newNote] = (byte)velocity;
}
noteForFinger_[id] = newNote;
noteStatus_[newNote] = (byte)velocity;
return true;
}
return true;

return false;
}
return false;
}

private static String noteString(int note) {
int octave = note / 12 - 1;
return NOTE_NAMES[note % 12] + Integer.toString(octave);
}

private int notesPressed()
{
int res = 0;
for (int i = 0; i < FINGERS; i++) {
if (noteForFinger_[i] != -1)
res++;
}
return res;
}

private boolean handleScrollTouch(int id, float x)
{
if (touchDragAction_ == TouchDragAction.TDA_ScrollKeyboard)
{
if (noteForFinger_[id] != -1)
{
/*
The effective scroll offset is the current touch devided by the number of current active touches
This correspondes to the following cases:
- A single touch: should scroll exactly the same amount as the touch moved, no perceived mismatch between expectations and reality
- Multi-touch: either the player moves the fingers more or less synchronously or some of them moves more or less comparing to the others
The latter might introduce the sense that the scrolling moves too much or too little because of the mathematics described.
*/
touchTrackingOffset = touchTrackingOffset + (x - touchCurrentX[id]) / notesPressed();

touchCurrentX[id] = x;

if (Math.abs(touchTrackingOffset - offset_) >= 1)
{
setScrollZoom(touchTrackingOffset, zoom_);
}
}
return true;
} else
return false;
}


private static final String TAG = "KEYBWIDGET";

private float velSens_;
private float velAvg_;

Expand All @@ -287,6 +371,10 @@ private static String noteString(int note) {
private float textSize_;
private float keyboardScale_;

private float[] touchCurrentX; // Array containing all current x positions of the note touches
private float touchTrackingOffset; // Tracking offset keeps the accurate offset x position and passes it to the scroll when the threashold of 1 is reached
private TouchDragAction touchDragAction_; // The current behavior of the touch-drag action, either the classic way (playing new notes while touch is moving ot scrolling the keyboard)

private float offset_;
private float zoom_;

Expand Down
15 changes: 13 additions & 2 deletions app/src/main/res/values/strings.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -89,12 +89,23 @@
<item>2 Row (Piano)</item>
<item>3 Row</item>
<item>3 Row Chromatic</item>
</string-array>
</string-array>
<string-array name="pref_keyboardType_values">
<item>2row</item>
<item>3row</item>
<item>3chrome</item>
</string-array>
</string-array>

<string-array name="pref_touchDragAction_entries">
<item>Play notes</item>
<item>Scroll keyboard</item>
</string-array>
<string-array name="pref_touchDragAction_values">
<item>TDA_PlayNotes</item>
<item>TDA_ScrollKeyboard</item>
</string-array>


<string name="pref_keyboardType_default">2row</string>

<string name="pref_velAvg">Velocity average value</string>
Expand Down
8 changes: 8 additions & 0 deletions app/src/main/res/xml/preferences.xml
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Expand Up @@ -25,4 +25,12 @@
android:entries="@array/pref_midi_channel_entries"
android:entryValues="@array/pref_midi_channel_values"
android:defaultValue="@string/pref_midi_channel_default" />

<ListPreference
android:key="touch_drag_action"
android:title="Touch Drag Action"
android:entries="@array/pref_touchDragAction_entries"
android:entryValues="@array/pref_touchDragAction_values"
android:defaultValue="TDA_PlayNotes" />

</PreferenceScreen>