已经为此苦苦挣扎了 2 天多了。
实施了我在这里看到的答案Java中指定任务顺序执行 https://stackoverflow.com/questions/12722396/specify-task-order-execution-in-java/12722648#12722648
public class PriorityExecutor extends ThreadPoolExecutor {
public PriorityExecutor(int corePoolSize, int maximumPoolSize,
long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue) {
super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue);
}
//Utitlity method to create thread pool easily
public static ExecutorService newFixedThreadPool(int nThreads) {
return new PriorityExecutor(nThreads, nThreads, 0L,
TimeUnit.MILLISECONDS, new PriorityBlockingQueue<Runnable>());
}
//Submit with New comparable task
public Future<?> submit(Runnable task, int priority) {
return super.submit(new ComparableFutureTask(task, null, priority));
}
//execute with New comparable task
public void execute(Runnable command, int priority) {
super.execute(new ComparableFutureTask(command, null, priority));
}
}
public class ComparableFutureTask<T> extends FutureTask<T>
implements
Comparable<ComparableFutureTask<T>> {
volatile int priority = 0;
public ComparableFutureTask(Runnable runnable, T result, int priority) {
super(runnable, result);
this.priority = priority;
}
public ComparableFutureTask(Callable<T> callable, int priority) {
super(callable);
this.priority = priority;
}
@Override
public int compareTo(ComparableFutureTask<T> o) {
return Integer.valueOf(priority).compareTo(o.priority);
}
}
我使用的Runnable：MyTask
public class MyTask implements Runnable{
public MyTask(File file, Context context, int requestId) {
this._file = file;
this.context = context;
this.requestId = requestId;
}
@Override
public void run() {
// some work
} catch (IOException e) {
Log.e("Callable try", post.toString());
}
}
我的服务：MediaDownloadService
public class MediaDownloadService extends Service {
private DBHelper helper;
Notification notification;
HashMap<Integer,Future> futureTasks = new HashMap<Integer, Future>();
final int _notificationId=1;
File file;
@Override
public IBinder onBind(Intent intent) {
return sharonsBinder;
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
helper = new DBHelper(getApplicationContext());
PriorityExecutor executor = (PriorityExecutor) PriorityExecutor.newFixedThreadPool(3);
Log.e("requestsExists", helper.requestsExists() + "");
if(helper.requestsExists()){
// map of the index of the request and the string of the absolute path of the request
Map<Integer,String> requestMap = helper.getRequestsToExcute(0);
Set<Integer> keySet = requestMap.keySet();
Iterator<Integer> iterator = keySet.iterator();
Log.e("MAP",requestMap.toString());
//checks if the DB requests exists
if(!requestMap.isEmpty()){
//execute them and delete the DB entry
while(iterator.hasNext()){
int iteratorNext = iterator.next();
Log.e("ITREATOR", iteratorNext + "");
file = new File(requestMap.get(iteratorNext));
Log.e("file", file.toString());
Log.e("thread Opened", "Thread" + iteratorNext);
Future future = executor.submit(new MyTask(file, this, iteratorNext),10);
futureTasks.put(iteratorNext, future);
helper.requestTaken(iteratorNext);
}
Log.e("The priority queue",executor.getQueue().toString());
}else{
Log.e("stopself", "stop self after this");
this.stopSelf();
}
}
return START_STICKY;
}
这条线上不断出现错误：
Future future = executor.submit(new MyTask(file, this, iteratorNext),10);
即使是 executor.submit();假设返回一个我不断得到的未来对象
Caused by: java.lang.ClassCastException: java.util.concurrent.FutureTask cannot be cast to java.lang.Comparable
at java.util.concurrent.PriorityBlockingQueue.siftUpComparable(PriorityBlockingQueue.java:318)
at java.util.concurrent.PriorityBlockingQueue.offer(PriorityBlockingQueue.java:450)
at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1331)
at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:81)
at com.vit.infibond.test.PriorityExecutor.submit(PriorityExecutor.java:26)
at com.vit.infibond.test.MediaDownloadService.onStartCommand(MediaDownloadService.java:65)
谁能把我从这场噩梦中拯救出来？
我也尝试按照这个答案的建议去做在 ThreadPoolExecutor 中测试 PriorityBlockingQueue https://stackoverflow.com/questions/16833951/testing-priorityblockingqueue-in-threadpoolexecutor/16834473#16834473
通过添加 for Task 覆盖只是为了再次获得强制转换异常，但这次是针对 RunnableFuture。
我知道我的理解中缺少一些基本的东西，并且希望得到深入的解释......
