如何解决此错误，无法从静态上下文中引用非静态方法

Question

这是代码

protected Void doInBackground(String... params) {
   String reg_url = "http://10.0.2.2/";
    String method = params [0];
    if (method.equals("register") ){
        String first_name = params [1];
        String last_name = params [2];
        String address = params [3];
        String email = params [4];
        String password = params [5];

        try {
            URL url = new URL(reg_url);
            HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();
            HttpURLConnection.setRequestMethod("POST");
            HttpURLConnection.setDoOutput(True);

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }
    return null;
}

我在这两行上收到错误

HttpURLConnection.setRequestMethod("POST");
            HttpURLConnection.setDoOutput(True);

关于 set.RequestMethod("POST") 和“setDoOutput(true)；错误说无法从静态上下文中引用非静态方法。这一定是个愚蠢的错误，但我就是想不通所以有人可以帮我解决这个问题吗？

Answer 1

使用您在调用 openConnection 时获得的实例：

        HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();
        httpURLConnection.setRequestMethod("POST");
        httpURLConnection.setDoOutput(true);

请注意 Java 区分大小写。 HttpURLConnection 是 class 名称。 httpURLConnection 是引用 class.

实例的变量

Answer 2

HttpURLConnection.setRequestMethod("POST");
HttpURLConnection.setDoOutput(True);

您正在使用静态方法语法访问非静态方法

使用参考 httpURLConnection 也访问方法

httpURLConnection.setRequestMethod("POST");
httpURLConnection.setDoOutput(true);

Answer 3

您必须在 URLConnection 实例上调用 setRequestMethod 和 setDoOutput 方法。

protected Void doInBackground(String... params) {
   String reg_url = "http://10.0.2.2/";
    String method = params [0];
    if (method.equals("register") ){
        String first_name = params [1];
        String last_name = params [2];
        String address = params [3];
        String email = params [4];
        String password = params [5];

        try {
            URL url = new URL(reg_url);
            HttpURLConnection con = (HttpURLConnection)url.openConnection();
            con.setRequestMethod("POST");
            con.setDoOutput(True);

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }
    return null;
}

如何解决此错误，无法从静态上下文中引用非静态方法

how to solve this error, non static method cannot be referenced from a static context

java

methods

non-static