Limitations of Android Asynctask and source code analysis

Reference: http://blog.csdn.net/hitlion2008/article/details/7983449

2.3 Before the asynctask has a global thread pool the maximum value is 5 more than after waiting to be executed

3.0 added the Excuteonexcutor method to set the custom thread pool. However, the default thread pool is a sequential thread pool that can only perform one task at a time and in order.

Asynctask part of the source code.

Public abstract class Asynctask<params, Progress, result> {private static final String Log_tag = "Asynctask";    private static final int cpu_count = Runtime.getruntime (). Availableprocessors ();    private static final int core_pool_size = Cpu_count + 1;    private static final int maximum_pool_size = Cpu_count * 2 + 1;    private static final int keep_alive = 1; private static final Threadfactory sthreadfactory = new Threadfactory () {private final Atomicinteger MCount = new        Atomicinteger (1);        Public Thread Newthread (Runnable R) {return new Thread (R, "Asynctask #" + mcount.getandincrement ());    }    }; private static final blockingqueue<runnable> Spoolworkqueue = new Linkedblockingqueue<runnable> (128    );     /** * A {@link Executor} that can is used to the execute tasks in parallel. */public static final Executor thread_pool_executor = new Threadpoolexecutor (core_pool_size, maximum_pool_s IZE, Keep_aliVE, Timeunit.seconds, Spoolworkqueue, sthreadfactory);  /** * An {@link Executor} This executes tasks one at a time in serial * order.     This serialization are global to a particular process.    */public static final Executor serial_executor = new Serialexecutor ();    private static final int message_post_result = 0x1;    private static final int message_post_progress = 0x2;    private static final Internalhandler Shandler = new Internalhandler ();    private static volatile Executor sdefaultexecutor = Serial_executor;    Private final Workerrunnable<params, result> Mworker;    Private final futuretask<result> mfuture;        Private volatile Status mstatus = status.pending;    Private final Atomicboolean mcancelled = new Atomicboolean ();    Private final Atomicboolean mtaskinvoked = new Atomicboolean (); private static class Serialexecutor implements Executor {final arraydeque<runnable> mtasks = new arraydeque& Lt Runnable> ();        Runnable mactive; Public synchronized void Execute (final Runnable R) {Mtasks.offer (new Runnable () {public void R                    Un () {try {r.run ();                    } finally {Schedulenext ();            }                }            });            if (mactive = = null) {Schedulenext ();                }} protected synchronized void Schedulenext () {if ((mactive = Mtasks.poll ()) = null) {            Thread_pool_executor.execute (mactive); }}}/** * Indicates the current status of the task.     Each status would be set to only once * during the lifetime of a task.         */public enum Status {/** * indicates the task have not been executed yet.         */PENDING,/** * Indicates the task is running. */RUNNING,/** * indicates that {@link ASynctask#onpostexecute} has finished. */Finished,}/** @hide used to force static handler to be created.    */public static void Init () {shandler.getlooper ();    }/** @hide */public static void Setdefaultexecutor (Executor exec) {sdefaultexecutor = exec; }/** * Creates a new asynchronous task.     This constructor must is invoked on the UI thread. */Public Asynctask () {mworker = new workerrunnable<params, result> () {public Result call () t                Hrows Exception {Mtaskinvoked.set (true);                Process.setthreadpriority (Process.thread_priority_background);            Noinspection unchecked return Postresult (Doinbackground (mparams));        }        }; Mfuture = new Futuretask<result> (mworker) {@Override protected void done () {T                ry {postresultifnotinvoked (get ()); } catch (InterRuptedexception e) {ANDROID.UTIL.LOG.W (Log_tag, E); } catch (Executionexception e) {throw new RuntimeException ("An error occured while executing doinbackg                Round () ", E.getcause ());                } catch (Cancellationexception e) {postresultifnotinvoked (null);    }            }        }; }

View Thread_pool_executor default settings for several parameters

    private static final int cpu_count = Runtime.getruntime (). Availableprocessors ();    private static final int core_pool_size = Cpu_count + 1;    private static final int maximum_pool_size = Cpu_count * 2 + 1;    private static final int keep_alive = 1;

Core Size:cpucount+1

Max Size:cupcount*2 +1

Alivetime:1 sec

Limitations of Android Asynctask and source code analysis