布尔值在线程中不变

Question

我有一个 class MPClient 和 MultiplayerMatch。 MultiplayerMatch 在他的构造函数中创建了一个 MPClient 运行nable 线程。

为了避免数据溢出，我在 MultiplayerMatch 中有一个名为 "moved" 的布尔值，当玩家移动时它会变为 true。

在 updateMatch 方法中，如果有任何玩家移动，"moved" 变为 true，这允许 MPClient 输入一个 if 语句（在 while 内）。这样 MPClient 仅在游戏发生变化时才向服务器发送数据。

然而，当标志为真时，在 MPClient 中没有注册更改！ MPClient 仍然 "thinks" 移动等于 false，即使在 MultiplayerMatch 中更改了该标志之后，结果，没有任何内容被发送到服务器...

经过几次测试，我注意到如果我在调试模式下运行它，因为我有一些断点，该更改被注册并且一切正常！为什么在调试模式下布尔值仅更改 "seen"？是不是和app有关系"running speed"，因为有断点？

这里只是代码的重要部分：

MP 客户端：

public class MPClient {
static final int TIME_OUT = 5000;
Client client;
MultiPlayMatch match;

public MPClient(String name, int team, MultiPlayMatch match) {
    this.match = match;
    client = new Client();
    client.start();

    Network.registerPackets(client);
    addListeners();

    try {
        client.connect(TIME_OUT, "127.0.0.1", Network.PORT);
    } catch (IOException e) {
        e.printStackTrace();
        client.stop();
    }

    /*this comment is just to show that here is the place where the login information is sent to the server, instead of showing all the code*/

    PlayerInfo playerInfo = new PlayerInfo();
    Network.UpdatePlayer updatePlayer = new Network.UpdatePlayer();
    updatePlayer.name = name;
    updatePlayer.team = team;

    while(true) {
        if(match.moved) {       //--> this is the variable that is always false
            playerInfo.x = match.getClientPlayerX(team);
            playerInfo.y = match.getClientPlayerY(team);

            updatePlayer.x = playerInfo.x;
            updatePlayer.y = playerInfo.y;
            client.sendTCP(updatePlayer);
            match.moved = false;
        }
    }

}

private void addListeners() {
    client.addListener(new Listener.ThreadedListener(new Listener() {
        @Override
        public void received(Connection connection, Object object) {
            if(object instanceof Network.UpdatePlayer) {
                Network.UpdatePlayer updatePlayer = (Network.UpdatePlayer) object;
                match.setPlayerPosition(updatePlayer.x, updatePlayer.y, updatePlayer.name, updatePlayer.team);
            }
        }
    }));
}
}

多人比赛：

public class MultiPlayMatch extends Match {

public boolean moved;

public MultiPlayMatch(){
    super(0);

    Random r = new Random();
    int aux = r.nextInt(2);
    aux = 0;
    if(aux == 0){
        homeTeam = new Team("Benfica", Team.TeamState.Attacking, w);
        visitorTeam = new Team("Porto", Team.TeamState.Defending, w);
    } else{
        homeTeam = new Team("Benfica", Team.TeamState.Defending, w);
        visitorTeam = new Team("Porto", Team.TeamState.Attacking, w);
    }
    //homeTeam.controlPlayer(0);

    numberOfPlayers = 0;
    moved = false;
}

@Override
public void updateMatch(float x, float y, Rain rain, float dt) {
    homeTeam.updateControlledPlayerOnline(x, y);

    rain.update();
    w.step(Constants.GAME_SIMULATION_SPEED, 6, 2);

    if(x != 0 || y != 0) moved = true;      //this is the place the variable is changed, but if it isn't in debug mode, MPClient thinks it's always false
}

public void setPlayerPosition(float x, float y, String name, int team) {
    if(team == 0)
        homeTeam.changePlayerPosition(x, y, name);
    else
        visitorTeam.changePlayerPosition(x, y, name);
}
}

Answer 1

这是因为它正在读取 match.moved 变量的缓存值而不是最新的值。为避免这种情况，将变量声明为 volatile

public volatile boolean moved;

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