Android里的C++代码经常会看到AutoMutex _l(mLock);

AutoMutex其实就是Thread的一种自动的互斥锁，定义在framework/base/include/utils/thread.h中；

/*

* Automatic mutex.  Declare one of these at the top of a function.

* When the function returns, it will go out of scope, and release the

* mutex.

*/

typedef Mutex::Autolock AutoMutex;

 

Autolock是Mutex的内嵌类（Java叫内部类），

// Manages the mutex automatically. It'll be locked when Autolock is

// constructed and released when Autolock goes out of scope.

class Autolock {

public:

    inline Autolock(Mutex& mutex) : mLock(mutex)  { mLock.lock(); }

    inline Autolock(Mutex* mutex) : mLock(*mutex) { mLock.lock(); }

    inline ~Autolock() { mLock.unlock(); }

private:

    Mutex& mLock;

};

 

看红色部分的注释就明白了，在函数代码中使用 AutoMutex 就可以锁定对象，而代码执行完AutoMutex所在的代码域之后，就自动释放锁，它的原理是充分的利用了c++的构造和析构函数~