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Android 12(S) ALooper AHandler AMessage（二）

2022-03-25 17:32:28  阅读：172  来源： 互联网

标签：25 12 17 03 08 16962 func ALooper Android


talk is cheap，show me the code！

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

 

标签：25,12,17,03,08,16962,func,ALooper,Android
来源： https://www.cnblogs.com/rongmiao/p/16055798.html

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