Java 中的优先级 ThreadPoolExecutor (Android)
我正在尝试创建一个具有优先级的 ThreadPoolExecutor 。所以我定义了一个
private static ThreadPoolExecutor threadpool = new ThreadPoolExecutor(30, MAXPOOL, MAXPOOL, TimeUnit.SECONDS,
queue, new mThreadFactory());
所以现在关键是队列引用。但是当我声明时：
static PriorityBlockingQueue<mDownloadThread> queue=new PriorityBlockingQueue<mDownloadThread>(MAXPOOL,new DownloadThreadComparator());
编译器在第一行给出错误：构造函数 ThreadPoolExecutor(int, int, int, TimeUnit, PriorityBlockingQueue, FileAccess.mThreadFactory) 未定义，并使用一个快速修复：将“队列”类型更改为 BlockingQueue。你能帮我了解问题所在吗？
谢谢
附加信息：
为了比较可运行对象，我实现了以下类
class mDownloadThread implements Runnable{
private Runnable mRunnable;
private int priority;
mDownloadThread(Runnable runnable){
mRunnable=runnable;
}
@Override
public void run() {
mRunnable.run();
}
public int getPriority() {
return priority;
}
public void setPriority(int priority) {
this.priority = priority;
}
}
比较器：
class DownloadThreadComparator implements Comparator<mDownloadThread>{
@Override
public int compare(mDownloadThread arg0, mDownloadThread arg1) {
if (arg0==null && arg1==null){
return 0;
} else if (arg0==null){
return -1;
} else if (arg1==null){
return 1;
}
return arg0.getPriority()-arg1.getPriority();
}
}
I'm trying to make an ThreadPoolExecutor with priority. So I define a
private static ThreadPoolExecutor threadpool = new ThreadPoolExecutor(30, MAXPOOL, MAXPOOL, TimeUnit.SECONDS,
queue, new mThreadFactory());
So the key is the queue reference now. But when I declare :
static PriorityBlockingQueue<mDownloadThread> queue=new PriorityBlockingQueue<mDownloadThread>(MAXPOOL,new DownloadThreadComparator());
The compiler gives an error in the first line: The constructor ThreadPoolExecutor(int, int, int, TimeUnit, PriorityBlockingQueue, FileAccess.mThreadFactory) is undefined with a single quickfix: Change type of 'queue' to BlockingQueue. Can you help me to understand whats the problem?
Thanks
Additional Info:
For comparing the runnables I implementd the following class
class mDownloadThread implements Runnable{
private Runnable mRunnable;
private int priority;
mDownloadThread(Runnable runnable){
mRunnable=runnable;
}
@Override
public void run() {
mRunnable.run();
}
public int getPriority() {
return priority;
}
public void setPriority(int priority) {
this.priority = priority;
}
}
The comparator:
class DownloadThreadComparator implements Comparator<mDownloadThread>{
@Override
public int compare(mDownloadThread arg0, mDownloadThread arg1) {
if (arg0==null && arg1==null){
return 0;
} else if (arg0==null){
return -1;
} else if (arg1==null){
return 1;
}
return arg0.getPriority()-arg1.getPriority();
}
}
如果你对这篇内容有疑问，欢迎到本站社区发帖提问 参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。
绑定邮箱获取回复消息
由于您还没有绑定你的真实邮箱，如果其他用户或者作者回复了您的评论，将不能在第一时间通知您！
发布评论
评论（2）
ThreadPoolExecutor构造函数接受BlockingQueue而不是BlockingQueue，因此您无法将其传递给PriorityBlockingQueue实例。您可以将
queue类型更改为PriorityBlockingQueue，但在这种情况下，您将无法实现Comparator在compare方法内进行转换。另一种解决方案是绕过通用类型检查，但您有责任仅将
mDownloadThread实例提交给execute方法：ThreadPoolExecutorconstructor acceptsBlockingQueue<Runnable>and notBlockingQueue<? extends Runnable>, thus you can't pass to itPriorityBlockingQueue<mDownloadThread>instance.You can change type of
queuetoPriorityBlockingQueue<Runnable>, but in that case you won't be able to implementComparator<mDownloadThread>without casting inside thecomparemethod.The other solution is to bypass generic type-checking but it would be your responsibility to submit only instances of
mDownloadThreadtoexecutemethod:问题是
ThreadPoolExecutor需要一个BlockingQueue而您正在传递一个PriorityBlockingQueue。PriorityBlockingQueue实现了BlockingQueue，因此这不是问题。问题在于Runnable。您无法在需要Runnable的地方传递通用类型的mDownloadThread。修复如下：
&&
如果编写
ThreadPoolExecutor来接受BlockingQueue<？扩展 Runnable>你所拥有的可以工作。The problem is that
ThreadPoolExecutoris expecting aBlockingQueue<Runnable>and you are passing aPriorityBlockingQueue<mDownloadThread>. ThePriorityBlockingQueueimplementsBlockingQueueso that is not the problem. The problem is theRunnable. You cannot pass a generic type ofmDownloadThreadwhereRunnablewas expected.Fix is the following:
&&
If
ThreadPoolExecutorwere written to accept aBlockingQueue<? extends Runnable>what you have would work.