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Handling TouchEvents concurrentModificationException android

I was trying to draw some balloons on screeen using canvas in SurfaceView class, I was successfully able to draw Multiple balloons on canvas and animate them by swapping different images. The problem is When I try touching on Oneballoon I need to remove it from screen .Here I get this exception and I am stuck
Code:
MainActivity:
package com.pradhul.game.touchball;
import android.app.Activity;
import android.os.Bundle;
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new GameView(this));
/*TODO Hide the bottom navigation bar */
}
}
GameView.java
package com.pradhul.game.touchball;
import android.annotation.SuppressLint;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.util.Log;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
public class GameView extends SurfaceView implements SurfaceHolder.Callback, View.OnTouchListener {
private static final int NUM_OF_BALLOONS = 5; //TODO for more than one balloons animations dont work(?)
/*use SurfaceView because we want complete control over the screen.
* unlike extending View class the oDraw() Method will not be called automatically
* from the method onSurfaceCreated() we have to call it Manually and pass a canvas object into it
* */
private final SurfaceHolder holder;
private GameLoopThread gameLoopThread;
private List<Balloon> balloons = new ArrayList<>();
public GameView(Context context) {
super(context);
gameLoopThread = new GameLoopThread(this);
holder = getHolder();
holder.addCallback(this);
createBalloons(NUM_OF_BALLOONS);
this.setOnTouchListener(this);
}
private void createBalloons(int count) {
for(int i=0 ; i< count ;i++){
balloons.add(createBalloon());
}
}
#Override
protected void onDraw(Canvas canvas) {
if(canvas != null) {
canvas.drawColor(Color.WHITE);
for(Balloon balloon : balloons){
try {
gameLoopThread.sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
balloon.onDraw(canvas);
}
}
}
#SuppressLint("WrongCall")
#Override
public void surfaceCreated(SurfaceHolder holder) {
/*this is called when the view is created*/
gameLoopThread.setRunning(true);
gameLoopThread.start();
}
#Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
}
#Override
public void surfaceDestroyed(SurfaceHolder holder) {
/*pausing game Thread*/
gameLoopThread.setRunning(false);
while (true){
try {
gameLoopThread.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
private Balloon createBalloon(){
return new Balloon(this);
}
#Override
public synchronized boolean onTouch(View v, MotionEvent event) {
Log.d("OnTouch real -", "x: " + event.getX() + ", Y: " + event.getY());
/* for (int i = balloons.size()-1; i >= 0; i--) {
Balloon balloon = balloons.get(i);
Log.d("OnTouch collision -", !balloon.isCollision(event.getX(), event.getY())+"");
if (!balloon.isCollision(event.getX(), event.getY())) {
balloons.remove(0);
break;
}
}*/
Iterator<Balloon> balloonIterator = balloons.iterator();
while(balloonIterator.hasNext()){
Balloon balloon = balloonIterator.next();
balloons.remove(0);
}
return true;
}
}
GameLoopThread.java
package com.pradhul.game.touchball;
import android.annotation.SuppressLint;
import android.graphics.Canvas;
public class GameLoopThread extends Thread {
private GameView view;
private boolean running = false;
public GameLoopThread(GameView view){
this.view = view;
}
public void setRunning(boolean run){
running = run;
}
#SuppressLint("WrongCall")
public void run(){
while (running){
Canvas canvas = null;
try{
canvas = view.getHolder().lockCanvas();
synchronized (view.getHolder()){
view.onDraw(canvas);
}
}finally{
if(canvas != null) {
view.getHolder().unlockCanvasAndPost(canvas);
}
}
}
}
}
Balloon.java
package com.pradhul.game.touchball;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.util.Log;
import java.util.Random;
public class Balloon {
private static final int BALLOON_SPEED = 10;
private int y = 0;
private int x = 0;
private int speed = 1;
private GameView gameView;
private Bitmap balloon;
public Bitmap[] normalBalloons;
private int balloonIndex = 0;
private int normalImages[] = {R.drawable.normal_01,R.drawable.normal_02,R.drawable.normal_03,
R.drawable.normal_04,R.drawable.normal_05,R.drawable.normal_06,R.drawable.normal_07,
R.drawable.normal_08,
};
private int crackingImages[] = {R.drawable.crack_01,R.drawable.crack_02,R.drawable.crack_03,
R.drawable.crack_04, R.drawable.crack_05,R.drawable.crack_04,R.drawable.crack_03,
R.drawable.crack_02
};
private boolean reverseSwap = false;
public Balloon(GameView gameView){
this.gameView = gameView;
normalBalloons = new Bitmap[8];
setUpImages();
}
public void onDraw(Canvas canvas){
/*draws the balloon in canvas */
animateBalloon();
update(canvas.getWidth());
canvas.drawBitmap(balloon, x, y, null);
}
public boolean isCollision(float x2, float y2) {
return x2 > x && x2 < x + balloon.getWidth() && y2 > y && y2 < y + balloon.getHeight();
}
private int getRandomX(int maxVal) {
Random rand = new Random();
return rand.nextInt(maxVal);
}
private void animateBalloon() {
/*Animates the balloon by swapping resource image at each call*/
this.balloon = getBalloons();
Log.d("Balloon",balloonIndex % normalBalloons.length + "");
}
private void update(int canvasWidth) {
/*updates the y position for moving the balloon*/
if (y <= 0){
/*so that the balloon starts from bottom
* gameView will return a height only after the View is ready
* getting 0 in constructor of this class*/
y = gameView.getHeight();
/*x is assigned a random between the width od the canvas
* so that the balloons will appear random positions from below*/
x = getRandomX(canvasWidth - balloon.getWidth());
}
if (y > gameView.getHeight() - balloon.getHeight() - speed) {
speed = -BALLOON_SPEED;
}
y = y + speed;
Log.d("Balloon","Positions:"+x+","+y);
}
private Bitmap getBalloons() {
if(balloonIndex == normalBalloons.length-1) {
reverseSwap = true;
}
if(balloonIndex == 0){
reverseSwap = false;
}
balloonIndex = reverseSwap?balloonIndex-1:balloonIndex+1;
return normalBalloons[balloonIndex];
}
private void setUpImages() {
/*setting up resources array*/
for(int count =0; count < normalImages.length; count++){
Bitmap balloon = BitmapFactory.decodeResource(gameView.getResources(), normalImages[count]);
normalBalloons[count] = balloon;
}
}
}
I am confused that why it causes an error like this , Can anybody can take look at it and suggest me a solution, is this the right way to remove ?
please share any suggestion
Thanks

It's the wrong way to remove.
If you iterate over a Collection / List, and want to remove the current element, you must use Iterator.remove() method.
In your case, simply call balloonIterator.remove() instead of balloons.remove(0)
Even simpler, since you want to remove all elements from the list - you should simply call balloons.clear() and remove the loop completely.

This exception is due to concurrent modification of list balloons.
As soon as you touch surface view onDraw() gets invoked with onTouch(), in which you are working on list balloons.
I think you should add touch listener to balloon instead of GameView.

okay ,
I need to wrap all my code inside a synchronized holder inorder this to work
(don't know much about it)
#Override
public boolean onTouch(View v, MotionEvent event) {
Log.d("OnTouch","x:"+event.getX()+"Y:"+event.getY());
synchronized (getHolder()){
for (int i=0 ;i<balloons.size();i++){
balloons.remove(0);
break;
}
}
return true;
}

Swing 2D game low performance

I am making a clone of Flappy Bird. I was doing just fine performance-wise: 60 fps. This was when it had 1 pillar/obstacle only. As soon as I added 3 of them my fps dropped to 30 and below. Then game is unplayable now. I get that this has something to do with doing repaint() all the time.
Here is the code:
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.util.ArrayList;
/**
* Created by Lazar on 25/05/15.
*/
public class Environment extends JComponent implements ActionListener {
public static final Dimension dimension = new Dimension(800,600);
BufferedImage img;
BufferedImage ptica1;
BufferedImage ptica2;
double skokbrojac = 0;
int brzina = 4; // speed // MUST Background % brzina = 0
int dx;
int dx2;
int pad = 0; //drop
Timer timer;
boolean parno;
boolean skok = false;
//Stubovi // Pillars
Stub stub1 = new Stub();
Stub stub2 = new Stub();
Stub stub3 = new Stub();
ArrayList<Stub>stubovi = new ArrayList<Stub>();
int razmakStub; // Space between pillars
public Environment() {
setPreferredSize(dimension);
img = Util.openImage("pozadina.png");
ptica1 = Util.openImage("ptica1.png");
ptica2 = Util.openImage("ptica2.png");
stubovi.add(stub1);
stubovi.add(stub2);
stubovi.add(stub3);
dx = img.getWidth()/2;
timer = new Timer(1000/60,this);
timer.start();
addMouseListener(new MouseAdapter() {
#Override
public void mousePressed(MouseEvent e) {
super.mousePressed(e);
skok = true; // start jump
skokbrojac = 0; //jump frame counter
}
});
}
protected void paintComponent(Graphics g){
Graphics2D g2d = (Graphics2D)g;
//g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
//g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
if(dx == img.getWidth()){ //image horizontal scroll
dx2 = 0;
}
if(dx2 == img.getWidth()/2){ //image horizontal scroll
dx = dimension.width;
}
g2d.drawImage(img,getWidth() - dx, 0, null); //draw background
if(dx >= img.getWidth()){
g2d.drawImage(img,getWidth() - dx2, 0, null);
}
if(parno){
g2d.drawImage(ptica1,dimension.width/2, 290 + pad, null); //draw bird
}
else{
g2d.drawImage(ptica2,dimension.width/2, 290 + pad, null); //draw bird
}
stub1.postoji = true; //pillar1 exists?
if(razmakStub > 240){
stub2.postoji = true;
}
if(razmakStub > 480){ //pillar1 exists?
stub3.postoji = true;
}
for(Stub i : stubovi){ //draw pillars if they exist
if(i.postoji)
i.crtaj(g2d);
}
}
#Override
public void actionPerformed(ActionEvent e) {
dx = dx + brzina;
dx2 = dx2 + brzina;
if(skokbrojac > 5) // jump frame lenght
skok = false;
if(skok){
pad -= 15; // jump height
}
else{
pad += 8; //rate of the fall
}
skokbrojac++;
parno ^= true; // for different bird images
if(290 + pad >= 536 || 290 + pad<= 3) //border hit detect
timer.stop();
razmakStub += brzina;
for(Stub i : stubovi){ //reset pillars and make them move
if(i.postoji){
if(i.getDx() < -50){
i.setDx(800);
i.randomDy();
}
i.setDx(i.getDx() - brzina);
}
}
repaint();
}
}
Complete project source
Also bear in mind this is really unpolished version so the code is ugly. I am looking for a solution to boost performance.
Main Class:
import javax.swing.*;
/**
* Created by Lazar on 25/05/15.
*/
public class Main {
public static void main(String[] args){
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new Frame(new Environment());
}
});
}
}
Frame class:
import javax.swing.*;
/**
* Created by Lazar on 25/05/15.
*/
public class Frame extends JFrame{
public Frame(JComponent content){
setContentPane(content);
setTitle("Flappy");
setDefaultCloseOperation(EXIT_ON_CLOSE);
setSize(getPreferredSize());
setResizable(false);
setVisible(true);
setLocationRelativeTo(null);
}
}
Stub/Pillar class:
import java.awt.*;
import java.awt.image.BufferedImage;
import java.util.Random;
/**
* Created by Lazar on 26/05/15.
*/
public class Stub {
BufferedImage dole;
BufferedImage gore;
Random r = new Random();
int dx = 700;
int dy = r.nextInt(250) + 250;
boolean postoji = false;
public void crtaj(Graphics2D g2d){
dole = Util.openImage("stub_dole.png");
gore = Util.openImage("stub_gore.png");
g2d.drawImage(dole, dx, dy, null);
g2d.drawImage(gore, dx, -(560-dy), null);
}
public void setDx(int dx) {
this.dx = dx;
}
public void randomDy(){
this.dy = r.nextInt(250) + 250;
}
public int getDx() {
return dx;
}
}
Ptica/Brid class:
import java.awt.Graphics;
import java.awt.image.BufferedImage;
/**
* Created by Lazar on 26/05/15.
*/
public class Ptica {
BufferedImage ptica1;
BufferedImage ptica2;
boolean ptica;
boolean skok = false;
int pad = 0;
double skokBrojac = 0;
public Ptica(){
ptica1 = Util.openImage("/slike/ptica1.png");
ptica2 = Util.openImage("/slike/ptica2.png");
}
public void crtajPticu(Graphics g2d){
ptica ^= true;
if(ptica){
g2d.drawImage(ptica1, Environment.dimension.width/2, Environment.dimension.height/2-110 + pad, null);
}
else{
g2d.drawImage(ptica2, Environment.dimension.width/2, Environment.dimension.height/2-110 + pad, null);
}
System.out.println(pad);
}
public void setSkok(boolean skok) {
this.skok = skok;
}
public void setSkokBrojac(double skokBrojac) {
this.skokBrojac = skokBrojac;
}
public double getSkokBrojac() {
return skokBrojac;
}
public boolean isSkok() {
return skok;
}
public void setPad(int pad) {
this.pad = pad;
}
public int getPad() {
return pad;
}
}
Util class:
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.IOException;
/**
* Created by Lazar on 25/05/15.
*/
public class Util {
public static BufferedImage openImage(String name){
try {
if(!name.startsWith("/slike/")){
name="/slike/"+name;
}
return ImageIO.read(Util.class.getResource(name));
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
}

Avoid adding all you classes to the default package, this could cause issues with class loading on some versions of Java
Painting should paint the state and should not be making decisions or changing the state
Don't, repeatedly, load resources
For example, from you Stub class, which Environment's paintComponent calls crtaj, you do the following...
public void crtaj(Graphics2D g2d){
dole = Util.openImage("stub_dole.png");
gore = Util.openImage("stub_gore.png");
g2d.drawImage(dole, dx, dy, null);
g2d.drawImage(gore, dx, -(560-dy), null);
}
Loading the images can take time. You should either have a "cache" class which managers them (loading them once) or load them when the Stub class is created (I'd prefer the cache class, as if you create and destroy many Stubs, loading the resources within the Stub class (constructor for example) could become a bottle neck
For example, which was able to go from 200-300 objects moving simultaneously, to over 4000 through the use of a re-usable object cache (rather the re-creating the objects and re-loading their resources)

Use a profiler to determine where you code is actually spending time (Note that YourKit has a 15 day free trial license available).
Once you know what your bottleneck is then determine if there's an easy fix, if not consider better algorithms and data-structures to reduce the algorithmic complexity of your code.

Profiling, as suggested by #alex-fitzpatrick, is always good. Also:
Is the type of images created by your Util.openImage call compliant with the graphics2D object you paint on? You may be spending some with the conversions (image types).
eliminate calls to getWidth() etc. You know these values after object initialization, cache them.
If possible, don't call repaint on the entire component. Use the overloaded version that specifies the area to repaint.
... and consider using JavaFX for games :-)

Android: Audio Recording with voice level visualization

I need to create a android application which is for recording voice while showing the voice(sound) level visualization.
I already created an audio recording application but I can not add sound level visualization. How can I do it?
please someone help me a giving suggestion or a sample tutorials link or code.

Create a xml activity_recording.xml like this.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="180dp"
android:layout_alignParentBottom="true"
android:background="#231f20" >
<ali.visualiser.VisualizerView
android:id="#+id/visualizer"
android:layout_width="220dp"
android:layout_height="75dp"
android:layout_centerHorizontal="true"
android:layout_margin="5dp" />
<TextView
android:id="#+id/txtRecord"
android:layout_width="wrap_content"
android:layout_height="40dp"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:layout_marginBottom="25dp"
android:gravity="center"
android:text="Start Recording"
android:textColor="#android:color/white"
android:textSize="30sp" />
</RelativeLayout>
Create a custom visualizerView as given below.
package ali.visualiser;
import java.util.ArrayList;
import java.util.List;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.View;
public class VisualizerView extends View {
private static final int LINE_WIDTH = 1; // width of visualizer lines
private static final int LINE_SCALE = 75; // scales visualizer lines
private List<Float> amplitudes; // amplitudes for line lengths
private int width; // width of this View
private int height; // height of this View
private Paint linePaint; // specifies line drawing characteristics
// constructor
public VisualizerView(Context context, AttributeSet attrs) {
super(context, attrs); // call superclass constructor
linePaint = new Paint(); // create Paint for lines
linePaint.setColor(Color.GREEN); // set color to green
linePaint.setStrokeWidth(LINE_WIDTH); // set stroke width
}
// called when the dimensions of the View change
#Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
width = w; // new width of this View
height = h; // new height of this View
amplitudes = new ArrayList<Float>(width / LINE_WIDTH);
}
// clear all amplitudes to prepare for a new visualization
public void clear() {
amplitudes.clear();
}
// add the given amplitude to the amplitudes ArrayList
public void addAmplitude(float amplitude) {
amplitudes.add(amplitude); // add newest to the amplitudes ArrayList
// if the power lines completely fill the VisualizerView
if (amplitudes.size() * LINE_WIDTH >= width) {
amplitudes.remove(0); // remove oldest power value
}
}
// draw the visualizer with scaled lines representing the amplitudes
#Override
public void onDraw(Canvas canvas) {
int middle = height / 2; // get the middle of the View
float curX = 0; // start curX at zero
// for each item in the amplitudes ArrayList
for (float power : amplitudes) {
float scaledHeight = power / LINE_SCALE; // scale the power
curX += LINE_WIDTH; // increase X by LINE_WIDTH
// draw a line representing this item in the amplitudes ArrayList
canvas.drawLine(curX, middle + scaledHeight / 2, curX, middle
- scaledHeight / 2, linePaint);
}
}
}
Create RecordingActivity class as given below.
package ali.visualiser;
import java.io.File;
import java.io.IOException;
import android.app.Activity;
import android.media.MediaRecorder;
import android.media.MediaRecorder.OnErrorListener;
import android.media.MediaRecorder.OnInfoListener;
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.TextView;
public class RecordingActivity extends Activity {
public static final String DIRECTORY_NAME_TEMP = "AudioTemp";
public static final int REPEAT_INTERVAL = 40;
private TextView txtRecord;
VisualizerView visualizerView;
private MediaRecorder recorder = null;
File audioDirTemp;
private boolean isRecording = false;
private Handler handler; // Handler for updating the visualizer
// private boolean recording; // are we currently recording?
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_recording);
visualizerView = (VisualizerView) findViewById(R.id.visualizer);
txtRecord = (TextView) findViewById(R.id.txtRecord);
txtRecord.setOnClickListener(recordClick);
audioDirTemp = new File(Environment.getExternalStorageDirectory(),
DIRECTORY_NAME_TEMP);
if (audioDirTemp.exists()) {
deleteFilesInDir(audioDirTemp);
} else {
audioDirTemp.mkdirs();
}
// create the Handler for visualizer update
handler = new Handler();
}
OnClickListener recordClick = new OnClickListener() {
#Override
public void onClick(View v) {
if (!isRecording) {
// isRecording = true;
txtRecord.setText("Stop Recording");
recorder = new MediaRecorder();
recorder.setAudioSource(MediaRecorder.AudioSource.MIC);
recorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
recorder.setOutputFile(audioDirTemp + "/audio_file"
+ ".mp3");
OnErrorListener errorListener = null;
recorder.setOnErrorListener(errorListener);
OnInfoListener infoListener = null;
recorder.setOnInfoListener(infoListener);
try {
recorder.prepare();
recorder.start();
isRecording = true; // we are currently recording
} catch (IllegalStateException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
handler.post(updateVisualizer);
} else {
txtRecord.setText("Start Recording");
releaseRecorder();
}
}
};
private void releaseRecorder() {
if (recorder != null) {
isRecording = false; // stop recording
handler.removeCallbacks(updateVisualizer);
visualizerView.clear();
recorder.stop();
recorder.reset();
recorder.release();
recorder = null;
}
}
public static boolean deleteFilesInDir(File path) {
if( path.exists() ) {
File[] files = path.listFiles();
if (files == null) {
return true;
}
for(int i=0; i<files.length; i++) {
if(files[i].isDirectory()) {
}
else {
files[i].delete();
}
}
}
return true;
}
#Override
protected void onDestroy() {
super.onDestroy();
releaseRecorder();
}
// updates the visualizer every 50 milliseconds
Runnable updateVisualizer = new Runnable() {
#Override
public void run() {
if (isRecording) // if we are already recording
{
// get the current amplitude
int x = recorder.getMaxAmplitude();
visualizerView.addAmplitude(x); // update the VisualizeView
visualizerView.invalidate(); // refresh the VisualizerView
// update in 40 milliseconds
handler.postDelayed(this, REPEAT_INTERVAL);
}
}
};
}
Result
This is how it looks:
https://www.youtube.com/watch?v=BoFG6S02GH0
When it reaches the end, the animation continues as expected: erasing the beginning of the graph.

I like Ali's answer, but here's a simpler version that performs much better. The real speed comes from making the view class's onDraw method as fast as possible. Store the correct values in memory first by doing any computations not required for drawing outside the draw loop, and pass fully populated structures to draw routines to allow the hardware to optimize drawing many lines.
I launched my RecordingActivity and set it full screen, but you can create a layout resource or add the view anywhere.
Actvity:
public class RecordingActivity extends Activity {
private VisualizerView visualizerView;
private MediaRecorder recorder = new MediaRecorder();
private Handler handler = new Handler();
final Runnable updater = new Runnable() {
public void run() {
handler.postDelayed(this, 1);
int maxAmplitude = recorder.getMaxAmplitude();
if (maxAmplitude != 0) {
visualizerView.addAmplitude(maxAmplitude);
}
}
};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_recording);
visualizerView = (VisualizerView) findViewById(R.id.visualizer);
try {
recorder.setAudioSource(MediaRecorder.AudioSource.MIC);
recorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
recorder.setOutputFile("/dev/null");
recorder.prepare();
recorder.start();
} catch (IllegalStateException | IOException ignored) {
}
}
#Override
protected void onDestroy() {
super.onDestroy();
handler.removeCallbacks(updater);
recorder.stop();
recorder.reset();
recorder.release();
}
#Override
public void onWindowFocusChanged(boolean hasFocus) {
super.onWindowFocusChanged(hasFocus);
handler.post(updater);
}
}
View:
public class VisualizerView extends View {
private static final int MAX_AMPLITUDE = 32767;
private float[] amplitudes;
private float[] vectors;
private int insertIdx = 0;
private Paint pointPaint;
private Paint linePaint;
private int width;
private int height;
public VisualizerView(Context context, AttributeSet attrs) {
super(context, attrs);
linePaint = new Paint();
linePaint.setColor(Color.GREEN);
linePaint.setStrokeWidth(1);
pointPaint = new Paint();
pointPaint.setColor(Color.BLUE);
pointPaint.setStrokeWidth(1);
}
#Override
protected void onSizeChanged(int width, int h, int oldw, int oldh) {
this.width = width;
height = h;
amplitudes = new float[this.width * 2]; // xy for each point across the width
vectors = new float[this.width * 4]; // xxyy for each line across the width
}
/**
* modifies draw arrays. cycles back to zero when amplitude samples reach max screen size
*/
public void addAmplitude(int amplitude) {
invalidate();
float scaledHeight = ((float) amplitude / MAX_AMPLITUDE) * (height - 1);
int ampIdx = insertIdx * 2;
amplitudes[ampIdx++] = insertIdx; // x
amplitudes[ampIdx] = scaledHeight; // y
int vectorIdx = insertIdx * 4;
vectors[vectorIdx++] = insertIdx; // x0
vectors[vectorIdx++] = 0; // y0
vectors[vectorIdx++] = insertIdx; // x1
vectors[vectorIdx] = scaledHeight; // y1
// insert index must be shorter than screen width
insertIdx = ++insertIdx >= width ? 0 : insertIdx;
}
#Override
public void onDraw(Canvas canvas) {
canvas.drawLines(vectors, linePaint);
canvas.drawPoints(amplitudes, pointPaint);
}
}

If you're using the MediaRecorder class and visualization based on peak amplitude is ok you can use the getMaxAmplitude() method to continuously poll for the "maximum absolute amplitude that was sampled since the last call".
Scale that amplitude down into an index that determines how many of your app's graphical volume bars to light up and you're set.

My approach to this is based on activedecay's and Ali's answers, and I added a display DPI scale, since dp is scaled by the screen density so, 1 pixel in 320 dpi is not 1 pixel in 420 dpi. I had that problem that the visualizer was not moving at the same rate in different screens.
I also haven't found out, why the canvas doesn't start drawing from the beginning of the view API 28 only. But is not looking bad in any way.
Info about dpi scaling:
Android Developers/Support different pixel densities
package com.example.mediarecorderdemo.views;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
import androidx.annotation.Nullable;
import java.util.ArrayList;
import static com.example.mediarecorderdemo.RecordingActivity.DEBUG;
public class VisualizerView extends View {
private static final int MAX_AMPLITUDE = 32767;
private ArrayList<Float> amplitudes;
private Paint linePaint;
private int width;
private int height;
private int density;
private float stroke;
public VisualizerView(Context context, #Nullable AttributeSet attrs) {
super(context, attrs);
density = this.getResources().getDisplayMetrics().densityDpi; //Get the display DPI
linePaint = new Paint();
linePaint.setColor(Color.GREEN);
linePaint.setAntiAlias(true); //Add AntiAlias for displaying strokes that are less than 1
}
#Override
protected void onSizeChanged(int w, int h, int oldW, int oldH) {
width = w;
height = h;
amplitudes = new ArrayList<>(width * 2);
stroke =(width * ((float)density / 160)) / 1000; //Calculate actual pixel size for the view based on view width and dpi
linePaint.setStrokeWidth(stroke);
}
/**
* Add a new value of int to the visualizer array
* #param amplitude Int value
*/
public void addAmplitude(int amplitude){
invalidate();
float scaledHeight = ((float) amplitude / MAX_AMPLITUDE) * (height -1);
amplitudes.add(scaledHeight);
}
/**
* Clears Visualization
*/
public void clear(){
amplitudes.clear();
}
#Override
protected void onDraw(Canvas canvas) {
int middle = height / 2; // get the middle of the View
float curX = 0; // start curX at zero
// for each item in the amplitudes ArrayList
for (float power : amplitudes) {
// draw a line representing this item in the amplitudes ArrayList
canvas.drawLine(curX, middle + power / 2, curX, middle
- power / 2, linePaint);
curX += stroke; // increase X by line width
}
}
}

Android Multitouch - Irregular Finger Tracking

I have designed a simple multitouch system that tracks finger location, and their status on the screen. The way that the program is designed, when two fingers are put down, they are assigned a number based on the order of placement. If finger one is lifted, finger two is still called finger two.
This code works perfectly part of the time. Meaning that I'll run my application in testing and sometimes multitouch works every time, and sometimes using more than one finger makes the application completely fail. It is irregularly reliable.
I am curious if this is a hardware error, or something about the way that I am handling touch input. The source is all available below.
Thanks for any help that you can offer!
-Nathan Tornquist
EDIT: I think that the issue may be with the way that eventListeners are registered and unregistered. Occasionally the application will crash, and work perfectly again when I reopen it.
EDIT2: The issue is simply how irregular the program is. Sometimes when I open it, it tracks the fingers perfectly. The first finger put down stays number 1, the second finger stays number 2, etc. Regardless of if you lift finger 1 after placing 2, the numbers stay assigned. Other times you'll place two fingers and which finger is 1 and which is 2 changes. The application seems to lose track of them, and the numbers switch as you leave the fingers on the screen.
EDIT3: I have tried "Touchscreen boosters" to try to try the screen to always respond correctly. It did not solve the problem.
EDIT4: After more testing, this is clearly a code error. When the application is first started, it always works perfectly. After the device is locked (when the activity is paused) and then unlocked (when the activity is resumed) multitouch stops working and I get an application that works well for single touch and is confused by multitouch.
MultitouchGameFixActivity.java
package com.nathantornquist.multitouchgame;
import android.app.Activity;
import android.content.pm.ActivityInfo;
import android.os.Bundle;
import android.view.Window;
import android.view.WindowManager;
public class MultiTouchGameFixActivity extends Activity{
/** Called when the activity is first created. */
MainGamePanel viewPanel;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//Window state functions.
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
//This works without declaring a viewPanel instance here.
//The instance declaration is needed to pass the
//onPause and onResume commands though.
viewPanel = new MainGamePanel(this);
setContentView(viewPanel);
}
//Restarts the accelerometer after onPause
protected void onResume() {
super.onResume();
viewPanel.resume(this);
}
//Standard Method run when the Application loses focus.
//This runs the pause() function in the viewPanel so that
//the accelerometer can be paused.
protected void onPause() {
super.onPause();
viewPanel.pause();
}
protected void onDestroy() {
super.onDestroy();
viewPanel.destroy();
}
}
MainThread.java
package com.nathantornquist.multitouchgame;
import com.nathantornquist.multitouchgame.MainGamePanel;
import android.graphics.Canvas;
import android.view.SurfaceHolder;
public class MainThread extends Thread {
private SurfaceHolder surfaceHolder;
private MainGamePanel gamePanel;
private boolean running;
public boolean pleaseWait = true;
public void setRunning(boolean running) {
this.running = running;
}
public MainThread(SurfaceHolder surfaceHolder, MainGamePanel gamePanel) {
super();
this.surfaceHolder = surfaceHolder;
this.gamePanel = gamePanel;
}
#Override
public void run()
{
Canvas canvas;
while (running) {
if(!pleaseWait) {
canvas = null;
// try locking the canvas for exclusive pixel editing on the surface
try {
canvas = this.surfaceHolder.lockCanvas();
synchronized (surfaceHolder) {
// update game state
this.gamePanel.update();
// draws the canvas on the panel
this.gamePanel.onDraw(canvas);
}
} finally {
// in case of an exception the surface is not left in
// an inconsistent state
if (canvas != null) {
surfaceHolder.unlockCanvasAndPost(canvas);
}
} // end finally
}
else {
synchronized (this) {
try {
wait();
} catch (Exception e) { }
}
}
}
}
}
MainGamePanel.java
package com.nathantornquist.multitouchgame;
import android.R.string;
import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.util.Log;
import android.view.Display;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
public class MainGamePanel extends SurfaceView implements SensorEventListener, SurfaceHolder.Callback
{
//Variable Declarations.
private MainThread thread;
public int screenWidth;
public int screenHeight;
private SensorManager mSensorManager;
private Sensor mAccelerometer;
Paint paint;
public int fingerOneDown;
public int fingerTwoDown;
public int fingerThreeDown;
public int fingerFourDown;
public float fingerOneX;
public float fingerOneY;
public float fingerTwoX;
public float fingerTwoY;
public float fingerThreeX;
public float fingerThreeY;
public float fingerFourX;
public float fingerFourY;
public MainGamePanel(Context context)
{
super(context);
getHolder().addCallback(this);
thread = new MainThread(getHolder(),this);
paint = new Paint();
paint.setAntiAlias(true);
Display display = ((Activity) context).getWindowManager().getDefaultDisplay();
screenWidth = display.getWidth();
screenHeight = display.getHeight();
mSensorManager = (SensorManager) context.getSystemService(Context.SENSOR_SERVICE);
mAccelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
mSensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_FASTEST);
fingerOneDown = 0;
fingerTwoDown = 0;
fingerThreeDown = 0;
fingerFourDown = 0;
fingerOneX = 0;
fingerOneY = 0;
fingerTwoX = 0;
fingerTwoY = 0;
fingerThreeX = 0;
fingerThreeY = 0;
fingerFourX = 0;
fingerFourY = 0;
setFocusable(true);
thread.setRunning(true);
thread.start();
}
#Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
}
#Override
public void surfaceCreated(SurfaceHolder holder) {
//continue the thread
synchronized (thread) {
thread.pleaseWait = false;
thread.notifyAll();
}
}
#Override
public void surfaceDestroyed(SurfaceHolder holder) {
//pause the thread
synchronized (thread) {
thread.pleaseWait = true;
}
}
#Override
public boolean onTouchEvent(MotionEvent event) {
int action = event.getAction() & MotionEvent.ACTION_MASK;
int pointerIndex = (event.getAction() & MotionEvent.ACTION_POINTER_ID_MASK) >> MotionEvent.ACTION_POINTER_ID_SHIFT;
int pointerId = event.getPointerId(pointerIndex);
switch (action) {
case MotionEvent.ACTION_DOWN:
case MotionEvent.ACTION_POINTER_DOWN:
Log.d("pointer id - down",Integer.toString(pointerId));
if (pointerId == 0)
{
fingerOneDown = 1;
fingerOneX = event.getX(pointerIndex);
fingerOneY = event.getY(pointerIndex);
}
if (pointerId == 1)
{
fingerTwoDown = 1;
fingerTwoX = event.getX(pointerIndex);
fingerTwoY = event.getY(pointerIndex);
}
if(pointerId == 2)
{
fingerThreeDown = 1;
fingerThreeX = event.getX(pointerIndex);
fingerThreeY = event.getY(pointerIndex);
}
if(pointerId == 3)
{
fingerFourDown = 1;
fingerFourX = event.getX(pointerIndex);
fingerFourY = event.getY(pointerIndex);
}
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_POINTER_UP:
case MotionEvent.ACTION_CANCEL:
Log.d("pointer id - cancel",Integer.toString(pointerId));
if (pointerId == 0)
{
fingerOneDown = 0;
fingerOneX = event.getX(pointerIndex);
fingerOneY = event.getY(pointerIndex);
}
if (pointerId == 1)
{
fingerTwoDown = 0;
fingerTwoX = event.getX(pointerIndex);
fingerTwoY = event.getY(pointerIndex);
}
if(pointerId == 2)
{
fingerThreeDown = 0;
fingerThreeX = event.getX(pointerIndex);
fingerThreeY = event.getY(pointerIndex);
}
if(pointerId == 3)
{
fingerFourDown = 0;
fingerFourX = event.getX(pointerIndex);
fingerFourY = event.getY(pointerIndex);
}
break;
case MotionEvent.ACTION_MOVE:
int pointerCount = event.getPointerCount();
for(int i = 0; i < pointerCount; ++i)
{
pointerIndex = i;
pointerId = event.getPointerId(pointerIndex);
Log.d("pointer id - move",Integer.toString(pointerId));
if(pointerId == 0)
{
fingerOneDown = 1;
fingerOneX = event.getX(pointerIndex);
fingerOneY = event.getY(pointerIndex);
}
if(pointerId == 1)
{
fingerTwoDown = 1;
fingerTwoX = event.getX(pointerIndex);
fingerTwoY = event.getY(pointerIndex);
}
if(pointerId == 2)
{
fingerThreeDown = 1;
fingerThreeX = event.getX(pointerIndex);
fingerThreeY = event.getY(pointerIndex);
}
if(pointerId == 3)
{
fingerFourDown = 1;
fingerFourX = event.getX(pointerIndex);
fingerFourY = event.getY(pointerIndex);
}
}
break;
}
return true;
}
#Override
protected void onDraw(Canvas canvas)
{
paint.setColor(Color.WHITE);
paint.setStyle(Style.FILL);
canvas.drawPaint(paint);
if (fingerOneDown == 1)
{
paint.setColor(Color.BLUE);
paint.setTextSize(20);
canvas.drawText("1", fingerOneX, fingerOneY - 30, paint);
}
if (fingerTwoDown == 1)
{
paint.setColor(Color.RED);
paint.setTextSize(20);
canvas.drawText("2", fingerTwoX, fingerTwoY - 30, paint);
}
if (fingerThreeDown == 1)
{
paint.setColor(Color.GREEN);
paint.setTextSize(20);
canvas.drawText("3", fingerThreeX, fingerThreeY - 30, paint);
}
if (fingerFourDown == 1)
{
paint.setColor(Color.BLACK);
paint.setTextSize(20);
canvas.drawText("4", fingerFourX, fingerFourY - 30, paint);
}
}
public void update() {
}
#Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {
}
#Override
public void onSensorChanged(SensorEvent event) {
}
public void pause() {
mSensorManager.unregisterListener(this);
}
public void resume(Context context) {
mSensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_FASTEST);
}
public void destroy() {
thread.setRunning(false);
if (thread != null)
{
Thread killThread = thread;
thread = null;
killThread.interrupt();
}
}
}

I'll throw out some ideas, even though my android skills are a bit lacking...
How are you testing this? On a real device I guess? Can this be tested on the emulator? It seems like it would be prone to hardware issues.
If the there is a glitch and the screen looses track of the fingers even just for a millisec, wont it start over with indexing the fingers? If that is the case it would number the fingers pretty randomly causing the issues you are experiencing.
Some ideas:
Dont track the index of fingers, just keep list of the fingers and their relative positions. But I guess part of the game requires you to keep an index of each finger.
Log if you loose connection with a finger, that will show if this is an isse. I guess MotionEvent.ACTION_POINTER_UP is the event you should log then. In fact, I'd add a log for each event possible just to see what is happening.
Add a method that tries to determine which finger has been placed on the screen, i.e it compares the current position of the finger with the known values of previous fingers and if its within a threshold, assume its the same finger. Probably want to add a timer to "forget" previous fingers aswell.
I guess you have been looking at the multitouch example on Android developer blog to make sure you are using the APIs correctly?
Hope it may give you some help.

The problem is solved by disabling WidgetLocker. That application seems to mess up some programs occasionally. I've noticed issues in other applications as well when I lock the screen while playing a game.

Android while touch and touch release

Hi, I have recently started trying to make android apps
and have currently made a few simple ones, but, I am still really confused with the touch methods.
What I'm trying to do is: When your finger is held down on the screen, x increments, but it stops when you release your finger. The problem is that I can't find any method or any way of doing this.
Here is my code:
import java.util.Timer;
import java.util.TimerTask;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
public class zombView extends SurfaceView{
private Bitmap bmp, grass, joystick;
private SurfaceHolder holder;
Timer t = new Timer();
float x = 0, y = 0;
boolean forward;
public zombView(Context context) {
super(context);
holder = getHolder();
holder.addCallback(new SurfaceHolder.Callback() {
#Override
public void surfaceDestroyed(SurfaceHolder holder) {
}
#Override
public void surfaceCreated(final SurfaceHolder holder) {
t.scheduleAtFixedRate(new TimerTask(){
public void run(){
Canvas c = holder.lockCanvas(null);
onDraw(c);
holder.unlockCanvasAndPost(c);
if(forward == true){
x++;
}
}
},200,200);
}
#Override
public void surfaceChanged(SurfaceHolder holder, int format,
int width, int height) {
}
});
bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
grass = BitmapFactory.decodeResource(getResources(), R.drawable.grassland);
joystick = BitmapFactory.decodeResource(getResources(), R.drawable.joystic);
}
#Override
protected void onDraw(Canvas canvas) {
canvas.drawColor(Color.BLACK);
canvas.drawBitmap(grass, getWidth() - getWidth(), getHeight() - getHeight(), null);
canvas.drawBitmap(joystick, getWidth() - getWidth(),joystick.getHeight(), null);
canvas.drawBitmap(bmp, x, y, null);
}
#Override
public boolean onTouchEvent(MotionEvent event) {
if(event.getX() > 10 && event.getX() < 1000){
if(event.getY() > 10 && event.getY() < 1000){
x++;
}
}
return super.onTouchEvent(event);
}
}

The MotionEvent class has a getAction method, which specifies what kind of event did your onTouchEvent method has just received. There are three actions that you will use more often:
ACTION_DOWN, which tells you that the user has just put his finger on the screen;
ACTION_MOVE, which tells that the user is still holding his finger on the screen;
ACTION_UP, which tells that the user has taken his finger off the screen.
Depending on what kind of event has just been acquired by your listener you can change the behavior of your code. For more information check the documentation. Hope this helps.