手寫最簡handler

前言

最近閱讀Android 源代碼，就想着寫個最簡單的Android線程間通訊的方案。這裏主要是還粘貼寫的代碼

正文

循環等待的核心loop函數：
looper.java

public class Looper {

    private long ptr;

    private Message m;
    public Looper(){
        ptr = Init();
    }


    public void postRunabledealy(Message message,long delay){

        synchronized (this) {
            message.delay = SystemClock.uptimeMillis() + delay;
            if (m == null) {
                m = message;
            } else {
                Message tmp = m;
                Message priv = m;
                while (message.delay > tmp.delay){
                    if (tmp.next == null){
                        tmp.next = message;
                        break;
                    }
                    priv = tmp;
                    tmp = tmp.next;

                }
                //這是插入情況
                if (tmp.next != message){
                    priv.next = message;
                    message.next = tmp;
                }
            }
            Intrupt(ptr);
            Log.e("addrunable", "postRunabledealy:");
        }
    }

    public void Loop(){

        while (true){
            Log.e("loop", "Loop: ");

            if (m == null){
                Wait(ptr, 0);
                continue;
            }
            long now = SystemClock.uptimeMillis();
            //需要立即處理，
            if (now >= m.delay) {
                m.run();
                Log.e("loop", "Loop: after run()");
                if (null == m.next) {
                    m = null;
                } else {
                    m = m.next;
                }
                Log.e("-----------", "Loop: hava remove message");
                continue;
            }

            Wait(ptr, (int) (m.delay-now));


        }
    }


    public native long Init();
    public native void Wait(long ptr,int delay) ;
    public native void Intrupt(long ptr);

}

這個需要在使用異步線程通訊的線程中初始化
然後當然需要一個消息了：
message.java

package com.baigui.simplehandler;

public abstract class Message implements Runnable {

    public Message next;

    public long delay;
    public Runnable run;
}

最核心的確實cpp層的線程阻塞
調用的接口如下:

extern "C" JNIEXPORT jlong JNICALL
Java_com_baigui_simplehandler_Looper_Init(
        JNIEnv *env,
        jobject /* this */) {
    Looper* nativeMessageQueue = new Looper();
//    NativeMessageQueue* nativeMessageQueue = reinterpret_cast<NativeMessageQueue*>(ptr);
    return reinterpret_cast<jlong>(nativeMessageQueue);
}

extern "C" JNIEXPORT void JNICALL
Java_com_baigui_simplehandler_Looper_Wait(
        JNIEnv *env,
        jobject, /* this */
        jlong ptr,
        jint dealay) {
    Looper* nativeMessageQueue = reinterpret_cast<Looper*>(ptr);
    nativeMessageQueue->wait(dealay);
}


extern "C" JNIEXPORT void JNICALL
Java_com_baigui_simplehandler_Looper_Intrupt(
        JNIEnv *env,
        jobject, /* this */
        jlong ptr) {
    Looper* nativeMessageQueue = reinterpret_cast<Looper*>(ptr);
    nativeMessageQueue->intrupt();
}

cpp層用來阻塞的關鍵組件:
loop.cpp

Looper::Looper() {

    int pendingEventCount;
    int pendingEventIndex;
    epollFd = epoll_create(1);
    inotifyFd = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
//    int result_notify = inotify_add_watch(inotifyFd, argv[1], IN_CREATE | IN_DELETE);

    struct epoll_event eventItem;
    eventItem.events = EPOLLIN|EPOLLET;
    eventItem.data.fd = inotifyFd;
    epoll_ctl(epollFd, EPOLL_CTL_ADD, inotifyFd, &eventItem);

}

Looper::~Looper() {

}

void Looper::wait(int delay) {

    if (delay == 0) {
        int pollResult = epoll_wait(epollFd, pendingEventItems, 16, -1);
    } else {
        int pollResult = epoll_wait(epollFd, pendingEventItems, 16,delay);
    }

    __android_log_print(ANDROID_LOG_ERROR, "zj", "%s", "after wait");
}

void Looper::intrupt() {
    uint64_t inc = 1;
    write(inotifyFd, &inc, sizeof(uint64_t));
}

詳細源碼可移步github倉庫地址

後記

這個主要是pst一下自己寫的代碼部分，