java - 当我尝试将项目添加到集合时出现 ConcurrentModificationException

Question

我花了一整天的时间试图解决这个问题。我尝试使用迭代？同步，以及许多其他萨满方法，但我一直收到 ConcurrentModificationException。这里是代码。

package com.androidgui.test;

import java.util.ArrayList;
import java.util.ListIterator;

import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;

import android.os.Message;
import android.util.Log;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.SurfaceHolder.Callback;
import android.widget.Toast;

public class CustomView extends SurfaceView implements Callback {
    private UpdateThread thread;
    private AButton btn;
    private AWindow wnd;
    private ArrayList<AControl> globalControls;
    private Object sync;
    public static int posX;
    public static int posY;

    public CustomView(Context context) {
        super(context);
        this.getHolder().addCallback(this);
        this.LoadResourse();
        sync =  new Object();
        this.globalControls = new ArrayList<AControl>();
        btn = new AButton(10, 10,null,AControl.InterfaceImages.Button); 
        this.globalControls.add(btn);
        wnd = new AWindow(10, 10, 200, 100, null);
        this.SetDelegates();

    }
    private void LoadResourse()
    {
        AControl.InterfaceImages.Button = BitmapFactory.decodeResource(getResources(), R.drawable.button);
    }
    private void SetDelegates()
    {
        btn.setEventHandler(new EventHandler() {

            @Override
            public void ProcessEvent() {
                synchronized (sync) {
                    globalControls.add(wnd);
                }
            }
        });
    }
    @Override
    public void onSizeChanged(int w, int h, int oldw, int oldh)
    {
        posX = (this.getWidth()- AControl.InterfaceImages.Button.getWidth()) /2;
        posY = (this.getHeight()- AControl.InterfaceImages.Button.getHeight()) /2;
    }

    @Override
    public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) {
        // TODO Auto-generated method stub

    }

    @Override
    public void surfaceCreated(SurfaceHolder arg0) {
        thread = new UpdateThread(this.getHolder(), this);
        thread.setRunning(true);
        thread.start();

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder arg0) {
        thread.setRunning(false);
        boolean _retry=true;
        try
        {
        while(_retry)
        {
            thread.join();
            _retry=false;
        }
        }catch(Exception ex)
        {

        }
    }
    public boolean onTouchEvent(MotionEvent event)
    {
        synchronized (sync) {
            for(AControl item :this.globalControls)
                item.onClick(event);
        }

        return true;
    }
    public void onDraw(Canvas canvas)
    {
        synchronized (sync) {   
        ArrayList<AControl> temp  = (ArrayList<AControl>) this.globalControls.clone();
            for(AControl item :temp)
                item.onDraw(canvas);
        }
    }

}

Answer 1

您在此处克隆了您的列表:

 public void onDraw(Canvas canvas)
    {
        synchronized (sync) {   
        ArrayList<AControl> temp  = (ArrayList<AControl>) this.globalControls.clone();
            for(AControl item :temp)
                item.onDraw(canvas);
        }
    }

但不在它之前的方法中:

  public boolean onTouchEvent(MotionEvent event)
    {
        synchronized (sync) {
            for(AControl item :this.globalControls)
                item.onClick(event);
        }

        return true;
    }

我想说这就是问题所在。但事实上，您没有包含堆栈跟踪，这使得猜测变得更加困难。添加同步并不能解决您的问题，因为问题是您可能在遍历列表时修改列表。