Android 使用HttpURLConnection

修改activity_main.xml 中的代码，如下所示：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
 
    <Button
        android:id="@+id/sendRequestBtn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Send Request" />
 
    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent">
 
        <TextView
            android:id="@+id/responseText"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />
    </ScrollView>
</LinearLayout>

修改MainActivity 中的代码，如下所示：

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        sendRequestBtn.setOnClickListener {
            sendRequestWithHttpURLConnection()
        }
    }
 
    private fun sendRequestWithHttpURLConnection() {
        // 开启线程发起网络请求
        thread {
            var connection: HttpURLConnection? = null
            try {
                val response = StringBuilder()
                // 获取HttpURLConnection 的实例，一般只需创建一个URL对象，
                // 并传入目标的网络地址，然后调用一下openConnection()方法即可
                val url = URL("https://www.baidu.com")
                connection = url.openConnection() as HttpURLConnection
                // 设置连接超时、读取超时的毫秒数
                connection.connectTimeout = 8000
                connection.readTimeout = 8000
                // 调用getInputStream()方法就可以获取到服务器返回的输入流了
                val input = connection.inputStream
                // 下面对获取到的输入流进行读取
                val reader = BufferedReader(InputStreamReader(input))
                reader.use {
                    reader.forEachLine {
                        response.append(it)
                    }
                }
                showResponse(response.toString())
            } catch (e: Exception) {
                e.printStackTrace()
            } finally {
                // 调用disconnect()方法将这个HTTP连接关闭
                connection?.disconnect()
            }
        }
    }
 
    private fun showResponse(response: String) {
        // Android 是不允许在子线程中进行UI操作的，
        // 而runOnUiThread()方法其实就是对异步消息处理机制进行了一层封装
        runOnUiThread {
            // 在这里进行UI操作，将结果显示到界面上
            responseText.text = response
        }
    }
}