例子一：

GlobalScope.launch(Dispatchers.Main) {
    //开启子协程
    withContext(Dispatchers.IO) {
        for (i in 0 until 1000) {
        }
        Log.d("MainActivityXX", "withContext-> thread:" + Thread.currentThread().name)
    }
    Log.d("MainActivityXX", "GlobalScope-> thread:" + Thread.currentThread().name)
}
Log.d("MainActivityXX", "onCreate-> thread:" + Thread.currentThread().name)

打印log：

2022-10-09 20:24:21.100 8371-8371/com.example.xiecheng D/MainActivityXX: onCreate-> thread:main
2022-10-09 20:24:21.131 8371-8412/com.example.xiecheng D/MainActivityXX: withContext-> thread:DefaultDispatcher-worker-1
2022-10-09 20:24:21.258 8371-8371/com.example.xiecheng D/MainActivityXX: GlobalScope-> thread:main

 

例子二：

GlobalScope.launch(Dispatchers.Main) {
    //开启子协程
    withContext(Dispatchers.IO) {
        for (i in 0 until 1000) {
        }
        Log.d("MainActivityXX", "withContext1-> thread:" + Thread.currentThread().name)
        withContext(Dispatchers.IO) {
            for (i in 0 until 1000) {
            }
            Log.d("MainActivityXX", "withContext2-> thread:" + Thread.currentThread().name)
        }
    }
    withContext(Dispatchers.IO) {
        for (i in 0 until 1000) {
        }
        Log.d("MainActivityXX", "withContext3-> thread:" + Thread.currentThread().name)
    }
    Log.d("MainActivityXX", "GlobalScope-> thread:" + Thread.currentThread().name)
}
Log.d("MainActivityXX", "onCreate-> thread:" + Thread.currentThread().name)

打印log：

onCreate-> thread:main
withContext1-> thread:DefaultDispatcher-worker-1
withContext2-> thread:DefaultDispatcher-worker-1
withContext3-> thread:DefaultDispatcher-worker-1
GlobalScope-> thread:main

主线程开启一个协程，并不会阻碍主线程的执行，单个协程内部是串行执行的，这里整一个都是串行执行的是因为withContext是一个挂起函数。

 

GlobalScope.launch(Dispatchers.Main) {
    //开启子协程
    GlobalScope.launch (Dispatchers.IO) {
        Log.d("MainActivityXX", "withContext-> thread:" + Thread.currentThread().name)
    }
    Log.d("MainActivityXX", "GlobalScope-> thread:" + Thread.currentThread().name)
}

打印log：

GlobalScope-> thread:main
withContext-> thread:DefaultDispatcher-worker-1

 

例子二：

GlobalScope.launch(Dispatchers.Main) {
    //开启子协程
    withContext(Dispatchers.IO) {
        get()
        Log.d("MainActivityXX", "withContext-> thread:" + Thread.currentThread().name)
    }
    Log.d("MainActivityXX", "GlobalScope-> thread:" + Thread.currentThread().name)
}

suspend fun get() {
    Thread {
        Thread.sleep(5000)
        Log.d("MainActivityXX", "get-> thread:" + Thread.currentThread().name)
    }.start()
}

打印log：

2022-11-01 20:56:25.220 20058-20100/com.example.xiecheng D/MainActivityXX: withContext-> thread:DefaultDispatcher-worker-1
2022-11-01 20:56:25.264 20058-20058/com.example.xiecheng D/MainActivityXX: GlobalScope-> thread:main
2022-11-01 20:56:30.222 20058-20103/com.example.xiecheng D/MainActivityXX: get-> thread:Thread-8

协程里面开启线程，那么线程不会受协程影响。

 

例子三：

GlobalScope.launch(Dispatchers.Main) {
    fetchDocs()
}

suspend fun fetchDocs() {                             // Dispatchers.Main
    val result = g