使用 AsyncTask 读取网站的 html 代码

Question

我也清理并重建了我的代码，但问题仍未解决。

下面是代码：

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        String result = null;
        String stringUrl = "https://www.ecowebhosting.co.uk/";
        DownloadTask downloadTask = new DownloadTask();

        downloadTask.execute(stringUrl);
    }

    public class DownloadTask extends AsyncTask<String, Void, String> {
        @Override
        protected String doInBackground(String... urls) {
            String result = "";
            URL url;
            HttpURLConnection httpURLConnection = null;
            try {
                url = new URL(urls[0]);
                //It is like opening a browser
                httpURLConnection = (HttpURLConnection) url.openConnection();
                InputStream in = httpURLConnection.getInputStream();
                InputStreamReader reader = new InputStreamReader(in);
                int data = reader.read();
                while (data != -1) {
                    char currentChar = (char) data;
                    result = result + currentChar;
                    data = reader.read();
                }
                return result;
            } catch (Exception e) {
                e.printStackTrace();
                return "Failed";
            }
        }
        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);

            Log.i("Results",s);
        }
    }
}

代码运行良好，但日志中没有打印任何内容。以下是日志：

Answer 1

AsyncTask 是一个异步进程。所以当你调用Log.i("Result:", result);的时候，AsyncTask没有完成，result还是空的。

您应该从onPostExecute() 方法打印您的结果。 你可以关注this page。

以下是一些关于如何正确实现AsyncTask 的示例：

• https://www.upwork.com/hiring/mobile/why-you-should-use-asynctask-in-android-development/
• How to use AsyncTask correctly in Android

最好的

Answer 2

您只需更改 doInBackGround 中的代码

public class DownloadTask extends AsyncTask<String, Void, String> {
    @Override
    protected String doInBackground(String... urls) {
        String result;
        String inputLine;
        try {
            URL myUrl = new URL(urls[0]);
            HttpURLConnection connection =(HttpURLConnection)
                    myUrl.openConnection();
            connection.setReadTimeout(150000); 
            connection.setConnectTimeout(15000); 
            connection.setRequestMethod("GET");
            connection.connect();
            InputStreamReader streamReader = new InputStreamReader(connection.getInputStream());
            //Create a new buffered reader and String Builder
            BufferedReader reader = new BufferedReader(streamReader);
            StringBuilder stringBuilder = new StringBuilder();
            //Check if the line we are reading is not null
            while((inputLine = reader.readLine()) != null){
                stringBuilder.append(inputLine);
            }
            //Close our InputStream and Buffered reader
            reader.close();
            streamReader.close();
            //Set our result equal to our stringBuilder
            result = stringBuilder.toString();
        } catch (Exception e) {
            e.printStackTrace();
            return "error";
        }
        return result;
    }

    @Override
    protected void onPostExecute(String s) {
        super.onPostExecute(s);

        Log.i("Results",s);
    }
}