Android 与 Kotlin 如何使用 HttpUrlConnection

以下是问题和答案的简化.

为什么这会失败呢？

val connection = HttpURLConnection()
val data = connection.inputStream.bufferedReader().readText()
// ... do something with "data"

有错误:

Kotlin:无法访问"":它在"HttpURLConnection"中为""Protected/protected and package/""

这会失败，因为您正在构造一个不打算直接构造的类.它是由URL类openConnection()方法中的工厂创建的.这也不是原始问题中示例Java代码的直接端口.

The most idiomatic way in Kotlin to open this connection and read the contents as a string would be:

val connection = URL("http://www.android.com/").openConnection() as HttpURLConnection
val data = connection.inputStream.bufferedReader().readText()

This form will auto close everything when done reading the text or on an exception. If you want to do custom reading:

val connection = URL("http://www.android.com/").openConnection() as HttpURLConnection
connection.inputStream.bufferedReader().use { reader ->
    // ... do something with the reader
}

NOTE: the use() extension function will open and close the reader and handle closing on errors automatically.

About the disconnect() method

disconnect人的doctor 说:

Each HttpURLConnection instance is used to make a single request but the underlying network connection to the HTTP server may be transparently shared by other instances. Calling the close() methods on the InputStream or OutputStream of an HttpURLConnection after a request may free network resources associated with this instance but has no effect on any shared persistent connection. Calling the disconnect() method may close the underlying socket if a persistent connection is otherwise idle at that time.

So you decide if you want to call it or not. Here is a version of the code that calls disconnect:

val connection = URL("http://www.android.com/").openConnection() as HttpURLConnection
try {
    val data = connection.inputStream.bufferedReader().use { it.readText() }
    // ... do something with "data"
} finally {
    connection.disconnect()
}