Java回调机制使用（以Android网络请求为例）

1、先定义了一个接口HttpCallbackListener

public interface HttpCallbackListener {

    void onFinish(String response);

    void onError(Exception e);

}

2、HttpUtil工具类  （接收回调对象，并调用回调对象的方法）

public class HttpUtil {

    public static void sendHttpRequest(final String address, final HttpCallbackListener listener) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                HttpURLConnection connection = null;
                try {
                    URL url = new URL(address);
                    connection = (HttpURLConnection) url.openConnection();
                    connection.setRequestMethod("GET");
                    connection.setConnectTimeout(8000);
                    connection.setReadTimeout(8000);
                    connection.setDoInput(true);
                    connection.setDoOutput(true);
                    InputStream in = connection.getInputStream();
                    BufferedReader reader = new BufferedReader(new InputStreamReader(in));
                    StringBuilder response = new StringBuilder();
                    String line;
                    while ((line = reader.readLine()) != null) {
                        response.append(line);
                    }
                    if (listener != null) {
                        // 回调onFinish()方法
                        listener.onFinish(response.toString());
                    }
                } catch (Exception e) {
                    if (listener != null) {
                        // 回调onError()方法
                        listener.onError(e);
                    }
                } finally {
                    if (connection != null) {
                        connection.disconnect();
                    }
                }
            }
        }).start();
    }

}

3、Main使用方法 （实例化一个回调对象，实现接口方法）

注：代码来自《第一行代码》