Android -- ConditionVariable

线程操作经常用到wait和notify，用起来稍显繁琐，而Android给我们封装好了一个ConditionVariable类，用于线程同步。提供了三个方法block()、open()、close()。

void block()
//阻塞当前线程，直到条件为open
void block(long timeout)
//阻塞当前线程，直到条件为open或超时
void open()
//释放所有阻塞的线程
void close()
//将条件重置为close

ConditionVariable 在创建时还有一种构造方法是 public ConditionVariable (boolean state) ，如果为true，默认时为opened，如果为false则是closed. ，默认public ConditionVariable()为closed.

源码

其实很好理解

private volatile boolean mCondition;

成员内部变量。

//默认构造函数
 public ConditionVariable()
{
        mCondition = false;
}

public ConditionVariable(boolean state)
{
        mCondition = state;
}

open，释放阻塞，即notifyAll一下，此时成员变量变为true。

public void open()
{
         synchronized (this) {
             boolean old = mCondition;
             mCondition = true;
             if (!old) {
                 this.notifyAll();
             }
         }
}

close，重置成员变量为false

public void close()
{
         synchronized (this) {
             mCondition = false;
         }
}

block，只有在成员变量为false的时候进行wait等待

public void block()
{
         synchronized (this) {
             while (!mCondition) {
                 try {
                     this.wait();
                 }
                 catch (InterruptedException e) {
                }
            }
        }
}

public boolean block(long timeout)
{
       // Object.wait(0) means wait forever, to mimic this, we just
        // call the other block() method in that case.  It simplifies
        // this code for the common case.
        if (timeout != 0) {
            synchronized (this) {
                long now = System.currentTimeMillis();
                long end = now + timeout;
                while (!mCondition && now < end) {
                    try {
                        this.wait(end-now);
                    }
                    catch (InterruptedException e) {
                    }
                    now = System.currentTimeMillis();
                }
                return mCondition;
            }
        } else {
            this.block();
            return true;
        }
}

code

简单的延时：

new Thread(new Runnable() {
            @Override
            public void run() {
                // TODO Auto-generated method stub
                while(isStart) {
                    //延时等待3秒
                    mConditionVariable.block(3000);
                    //将条件重置，否则block会失效
                    mConditionVariable.close();
                    //线程唤醒后通知主线程

                    mHandler.sendEmptyMessage(REFRESHTEXT);
                }
            }
        }).start();

我是天王盖地虎的分割线