处理素描中的并发修改异常

Question

我正在修改来自毒物库的毒物库示例，使其由Leap运动传感器的手势控制，而不是示例中的鼠标。

我在Open应用程序中做所有手势识别，并通过OSC发送。

当发生Gesture 0事件时，我调用下面的方法从physics对象中删除gestureAttractor：

void resetAttraction() {
  if (gestureAttractor != null){
      physics.removeBehavior(gestureAttractor);
      println("ATTRACTOR NULL");
     } else {
        println("not null");
     }
}

如果发生Gesture 1事件，则调用此方法来创建新的gestureAttractor，并将其添加回physics对象：

void addAttraction(){ 
   if (gestureAttractor == null) { 
       println("ATTRACTOR NULL"); 
       position1.set(340, 191); 
       gestureAttractor = new AttractionBehavior2D(position1, 250, 0.9f); 
       physics.addBehavior(gestureAttractor); 
   } else { 
       println("not null"); 
   } 
}

似乎一贯发生的情况是，每当手势状态发生变化时，我将在ConcurrentModificationException方法中的physics.update();中得到一个draw崩溃。

我确信这与处理这些对象的生命周期有关，但我还无法确定任何东西--有人有任何想法吗？

以下是草图的全部内容：

import toxi.geom.*;
import toxi.physics2d.*;
import toxi.physics2d.behaviors.*;

import oscP5.*;
import netP5.*;

OscP5 oscP5;

int NUM_PARTICLES = 750;

VerletPhysics2D physics;
//AttractionBehavior2D mouseAttractor;
AttractionBehavior2D gestureAttractor;


//Vec2D mousePos;
Vec2D position1;


boolean isGestureAttractorAdded;

void setup() {
  size(680, 382,P3D);
  // setup physics with 10% drag
  physics = new VerletPhysics2D();
  physics.setDrag(0.05f);
  physics.setWorldBounds(new Rect(0, 0, width, height));
  // the NEW way to add gravity to the simulation, using behaviors
  physics.addBehavior(new GravityBehavior2D(new Vec2D(0, 0.15f)));

  // start oscP5, listening for incoming messages at port 12000 
  oscP5 = new OscP5(this, 6000);

  position1 = new Vec2D(340, 191);

  addAttraction();

  //gestureAttractor = new AttractionBehavior2D(position1, 250, 0.9f);
  //physics.addBehavior(gestureAttractor);
}

void addParticle() {
  VerletParticle2D p = new VerletParticle2D(Vec2D.randomVector().scale(5).addSelf(width / 2, 0));
  physics.addParticle(p);
  // add a negative attraction force field around the new particle
  physics.addBehavior(new AttractionBehavior2D(p, 20, -1.2f, 0.01f));
}

void draw() {
  background(255,0,0);
  noStroke();
  fill(255);
  if (physics.particles.size() < NUM_PARTICLES) {
    addParticle();
  }
  physics.update();
  for (VerletParticle2D p : physics.particles) {
    ellipse(p.x, p.y, 5, 5);
  }
}

void mousePressed() {
  //position1 = new Vec2D(mouseX, mouseY);
   //create a new positive attraction force field around the mouse position (radius=250px)
  //gestureAttractor = new AttractionBehavior2D(position1, 250, 0.9f);
  //physics.addBehavior(gestureAttractor);

  //println(physics.behaviors);
}

void mouseDragged() {
  // update mouse attraction focal point
  //position1.set(mouseX, mouseY);
}

void mouseReleased() {
  // remove the mouse attraction when button has been released
  //physics.removeBehavior(gestureAttractor);
}


///// OSC RECEIVING

void oscEvent(OscMessage theOscMessage) {
  /* check if theOscMessage has the address pattern we are looking for. */

  if (theOscMessage.checkAddrPattern("/gesture_classification") == true)  {
    /* check if the typetag is the right one. */
    if(theOscMessage.checkTypetag("i")) {
      /* parse theOscMessage and extract the values from the osc message arguments. */
      int gestureClassLabel = theOscMessage.get(0).intValue();  
      println(" Gesture is: ", gestureClassLabel);

      if (gestureClassLabel == 0){   
        resetAttraction();
      } else if (gestureClassLabel == 1) {       
        addAttraction();
      } else if (gestureClassLabel == 2) {
          //physics.removeBehavior(gestureAttractor);
      } 
    }  
  } 

}

//////METHODS FOR SETTING POSITION / REMOVAL OF ATTRACTORS...

void resetAttraction() {
  if (gestureAttractor != null){
      physics.removeBehavior(gestureAttractor);
      println("ATTRACTOR NULL");
     } else {
        println("not null");
     }
 }

void addAttraction(){
     if (gestureAttractor == null) {
         println("ATTRACTOR NULL");
         position1.set(340, 191);
         gestureAttractor = new AttractionBehavior2D(position1, 250, 0.9f);
         physics.addBehavior(gestureAttractor);
     } else {
       println("not null");
     }
}

Answer 1

tl;dr:，在从另一个线程迭代数据结构时，不应该用一个线程来修改它。

draw()函数发生在一个线程上，它正在访问和修改物理库中的数据结构。

oscEvent()函数发生在另一个线程上，它还访问和修改这些相同的数据结构。这就是导致你错误的原因。请注意，将其封装在try块中是而不是修复任何东西。当错误发生时，它只是打印出更多的信息。

要真正解决这个问题，您需要读取线程之间的同步数据访问。例如，可以使用同步块来防止不同的线程访问相同的数据结构。如果你谷歌你的错误，你会发现大量的结果。