Android 12(S) ALooper AHandler AMessage（二）

来写个demo试试看到底是ALooper AHandler AMessage是怎么运行的，源文件以及Android.bp如下：

// EvenHandler.h

#ifndef __MESSAGE_TEST_H__

#define __MESSAGE_TEST_H__

#include <media/stagefright/foundation/AMessage.h>

#include <media/stagefright/foundation/AHandler.h>

#include <media/stagefright/foundation/ALooper.h>

#include <media/stagefright/foundation/ADebug.h>

namespace android{

class EventHandler : public AHandler

{

public:

    EventHandler();

    enum {

        kWhatSetDataSource,

        kWhatPrepare,

        kWhatStart,

        kWhatStop

    };

    void setDataSource(const char* url);

    void prepare();

    void start();

    void stop();

protected:

    virtual void onMessageReceived(const sp<AMessage> &msg);

private:

    void onSetDataSource(const char* url);

    void onPrepare();

    void onStart();

    void onStop();

};

}

#endif

// EventHandler.cpp

#define LOG_TAG "MyEventHandler"

#include "EventHandler.h"

#include <string.h>

namespace android{

EventHandler::EventHandler()

{

    ALOGD("tid = %d, func = %s", gettid(), __func__);

}

void EventHandler::onMessageReceived(const sp<AMessage> &msg)

{

    ALOGD("(%d)oMessageReceived: %s", gettid() ,msg->debugString().c_str());

    switch(msg->what()){

        case kWhatSetDataSource:

        {

            AString url;

            CHECK(msg->findString("url", &url));

            onSetDataSource(url.c_str());

            break;

        }

        case kWhatPrepare:

        {

            sp<AReplyToken> replyID;

            CHECK(msg->senderAwaitsResponse(&replyID));

            onPrepare();

            sp<AMessage> response = new AMessage;

            response->setInt32("err", 0);

            response->postReply(replyID);

            break;

        }

        case kWhatStart:

        {

            onStart();

            break;

        }

        case kWhatStop:

        {

            onStop();

            break;

        }

        default:

            break;

    }

}

void EventHandler::setDataSource(const char* url)

{

    ALOGD("tid = %d, func = %s", gettid(), __func__);

    sp<AMessage> msg = new AMessage(kWhatSetDataSource, this);

    msg->setString("url", url, strlen(url));

    msg->post();

}

void EventHandler::prepare()

{

    ALOGD("tid = %d, func = %s", gettid(), __func__);

    sp<AMessage> msg = new AMessage(kWhatPrepare, this);

    sp<AMessage> response;

    msg->postAndAwaitResponse(&response);

    int err;

    CHECK(response->findInt32("err", &err));

    ALOGD("tid = %d, func = %s, err = %d", gettid(), __func__, err);

}

void EventHandler::start()

{

    ALOGD("tid = %d, func = %s", gettid(), __func__);

    sp<AMessage> msg = new AMessage(kWhatStart, this);

    msg->post();

}

void EventHandler::stop()

{

    ALOGD("tid = %d, func = %s", gettid(), __func__);

    sp<AMessage> msg = new AMessage(kWhatStop, this);

    msg->post();

}

void EventHandler::onSetDataSource(const char *url)

{

    ALOGD("tid = %d, func = %s, url = %s", gettid(), __func__, url);

}

void EventHandler::onPrepare()

{

    ALOGD("tid = %d, func = %s", gettid(), __func__);

    int cnt = 0;

    while(cnt < 3)

    {

        ALOGD("tid = %d, func = %s, cnt = %d", gettid(), __func__, cnt);

        sleep(1);

        cnt++;

    }

}

void EventHandler::onStart()

{

    ALOGD("tid = %d, func = %s", gettid(), __func__);

    int cnt = 0;

    while(cnt < 10)

    {

        ALOGD("tid = %d, func = %s, cnt = %d", gettid(), __func__, cnt);

        sleep(1);

        cnt++;

    }

}

void EventHandler::onStop()

{

    ALOGD("tid = %d, func = %s", gettid(), __func__);

}

}

// main.cpp

#define LOG_TAG "MyEventHandlerTest"

#include "EventHandler.h"

using namespace android;

int main(int argc, char **argv)

{

    ALOGD("tid = %d, func = %s", gettid(), __func__);

    sp<EventHandler> handler = new EventHandler;

    sp<ALooper> looper = new ALooper;

    looper->setName("MyLooper");

    looper->start();

    looper->registerHandler(handler);

    handler->setDataSource("ABC");

    handler->prepare();

    handler->start();

    handler->stop();

    int wait = 0;

    while(wait < 20)

    {

        ALOGD("wait = %d", wait);

        sleep(1);

        wait++;

    }

}

// Android.bp

cc_binary {

    name: "EventHandlerTest",

    srcs: [

        "EventHandler.cpp",

        "main.cpp"

    ],

    shared_libs: [

        "libstagefright_foundation",

        "libutils",

        "liblog"

    ],

    include_dirs: [

        "frameworks/av/media/libstagefright/foundation/include"

    ],

    cflags: [

        "-Wno-unused-parameter"

    ]

}

来看执行结果吧，试验了两种情况：

1、先说失败的，将looper->start(true)，这个时候好像直接卡住不动了，

2、直接调用looper->start()，这里的参数默认为false，也就是会在一个新的线程当中做消息处理。从log中来看onMessageReceived方法都是在子线程中完成，在非阻塞的情况下是和主线程并行执行的。

这边还有个现象，main函数最后没有加while循环等待时，子线程执行完onStart方法进程就结束了，并没有等待处理完stop消息

03-25 17:08:23.437 16962 16962 D MyEventHandlerTest: tid = 16962, func = main

03-25 17:08:23.437 16962 16962 D MyEventHandler: tid = 16962, func = EventHandler

03-25 17:08:23.437 16962 16962 D MyEventHandler: tid = 16962, func = setDataSource

03-25 17:08:23.438 16962 16962 D MyEventHandler: tid = 16962, func = prepare

03-25 17:08:23.438 16962 16963 D MyEventHandler: (16963)oMessageReceived: AMessage(what = 0x00000000, target = 1) = {

03-25 17:08:23.438 16962 16963 D MyEventHandler:   string url = "ABC"

03-25 17:08:23.438 16962 16963 D MyEventHandler: }

03-25 17:08:23.438 16962 16963 D MyEventHandler: tid = 16963, func = onSetDataSource, url = ABC

03-25 17:08:23.438 16962 16963 D MyEventHandler: (16963)oMessageReceived: AMessage(what = 0x00000001, target = 1) = {

03-25 17:08:23.438 16962 16963 D MyEventHandler:   RefBase *replyID = 0xf5b01180

03-25 17:08:23.438 16962 16963 D MyEventHandler: }

03-25 17:08:23.438 16962 16963 D MyEventHandler: tid = 16963, func = onPrepare

03-25 17:08:23.438 16962 16963 D MyEventHandler: tid = 16963, func = onPrepare, cnt = 0

03-25 17:08:24.438 16962 16963 D MyEventHandler: tid = 16963, func = onPrepare, cnt = 1

03-25 17:08:25.438 16962 16963 D MyEventHandler: tid = 16963, func = onPrepare, cnt = 2

03-25 17:08:26.438 16962 16962 D MyEventHandler: tid = 16962, func = prepare, err = 0

03-25 17:08:26.439 16962 16962 D MyEventHandler: tid = 16962, func = start

03-25 17:08:26.439 16962 16962 D MyEventHandler: tid = 16962, func = stop

03-25 17:08:26.439 16962 16962 D MyEventHandlerTest: wait = 0

03-25 17:08:26.439 16962 16963 D MyEventHandler: (16963)oMessageReceived: AMessage(what = 0x00000002, target = 1) = {

03-25 17:08:26.439 16962 16963 D MyEventHandler: }

03-25 17:08:26.439 16962 16963 D MyEventHandler: tid = 16963, func = onStart

03-25 17:08:26.439 16962 16963 D MyEventHandler: tid = 16963, func = onStart, cnt = 0

03-25 17:08:27.439 16962 16962 D MyEventHandlerTest: wait = 1

03-25 17:08:27.439 16962 16963 D MyEventHandler: tid = 16963, func = onStart, cnt = 1

03-25 17:08:28.439 16962 16962 D MyEventHandlerTest: wait = 2

03-25 17:08:28.439 16962 16963 D MyEventHandler: tid = 16963, func = onStart, cnt = 2

03-25 17:08:29.439 16962 16963 D MyEventHandler: tid = 16963, func = onStart, cnt = 3

03-25 17:08:29.439 16962 16962 D MyEventHandlerTest: wait = 3

03-25 17:08:30.439 16962 16963 D MyEventHandler: tid = 16963, func = onStart, cnt = 4

03-25 17:08:30.439 16962 16962 D MyEventHandlerTest: wait = 4

03-25 17:08:31.439 16962 16963 D MyEventHandler: tid = 16963, func = onStart, cnt = 5

03-25 17:08:31.440 16962 16962 D MyEventHandlerTest: wait = 5

03-25 17:08:32.439 16962 16963 D MyEventHandler: tid = 16963, func = onStart, cnt = 6

03-25 17:08:32.440 16962 16962 D MyEventHandlerTest: wait = 6

03-25 17:08:33.440 16962 16963 D MyEventHandler: tid = 16963, func = onStart, cnt = 7

03-25 17:08:33.440 16962 16962 D MyEventHandlerTest: wait = 7

03-25 17:08:34.440 16962 16963 D MyEventHandler: tid = 16963, func = onStart, cnt = 8

03-25 17:08:34.440 16962 16962 D MyEventHandlerTest: wait = 8

03-25 17:08:35.440 16962 16963 D MyEventHandler: tid = 16963, func = onStart, cnt = 9

03-25 17:08:35.440 16962 16962 D MyEventHandlerTest: wait = 9

03-25 17:08:36.440 16962 16963 D MyEventHandler: (16963)oMessageReceived: AMessage(what = 0x00000003, target = 1) = {

03-25 17:08:36.440 16962 16963 D MyEventHandler: }

03-25 17:08:36.440 16962 16963 D MyEventHandler: tid = 16963, func = onStop

03-25 17:08:36.441 16962 16962 D MyEventHandlerTest: wait = 10

03-25 17:08:37.441 16962 16962 D MyEventHandlerTest: wait = 11

03-25 17:08:38.441 16962 16962 D MyEventHandlerTest: wait = 12

03-25 17:08:39.441 16962 16962 D MyEventHandlerTest: wait = 13

03-25 17:08:40.441 16962 16962 D MyEventHandlerTest: wait = 14

03-25 17:08:41.441 16962 16962 D MyEventHandlerTest: wait = 15

03-25 17:08:42.441 16962 16962 D MyEventHandlerTest: wait = 16

03-25 17:08:43.442 16962 16962 D MyEventHandlerTest: wait = 17

03-25 17:08:44.442 16962 16962 D MyEventHandlerTest: wait = 18

03-25 17:08:45.442 16962 16962 D MyEventHandlerTest: wait = 19

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