Android AsyncTask中执行的方法不适用于字符串

我尝试像这样执行

AsyncTask

private static final String REQUESTED_URL = "//my url";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.earthquake_activity);
    EarthQuakeAsyncTask task = new EarthQuakeAsyncTask();
    task.execute(REQUESTED_URL); //this is where the error is
}

但Android Studio表示，它无法解析方法

execute（String）

。我有一个来自

Udacity

的教程，它们的示例非常相似

/** URL for earthquake data from the USGS dataset */
private static final String USGS_REQUEST_URL =
        "//url";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    EarthquakeAsyncTask task = new EarthquakeAsyncTask();
    task.execute(USGS_REQUEST_URL); //it works
}

有人能告诉我为什么会发生这种情况吗

编辑：这是我的

地震异步任务

类：

private class EarthQuakeAsyncTask extends AsyncTask<URL,Void,ArrayList<EarthQuake>> {
    @Override
    protected ArrayList<EarthQuake> doInBackground(URL... urls) {
        if(urls.length==0||urls[0]== null){
            return null;
        }
        // Create URL object
        URL url = createUrl(REQUESTED_URL);
        try {
            jsonResponse = makeHttpRequest(url);
        } catch (IOException e) {
            // TODO Handle the IOException
        }
        ArrayList<EarthQuake> earthquake = QueryUtils.extractEarthquakes(jsonResponse);
        return earthquake;
    }

    @Override
    protected void onPostExecute(ArrayList<EarthQuake> earthquake) {
        if (earthquake == null) {
            return;
        }
        updateUi();
    }


    private URL createUrl(String stringUrl) {
        URL url;
        try {
            url = new URL(stringUrl);
        } catch (MalformedURLException exception) {
            Log.e(LOG_TAG, "Error with creating URL", exception);
            return null;
        }
        return url;
    }

    private String makeHttpRequest(URL url) throws IOException {
        // If the URL is null, then return early.
        if (url == null) {
            return jsonResponse;
        }

        HttpURLConnection urlConnection = null;
        InputStream inputStream = null;
        try {
            urlConnection = (HttpURLConnection) url.openConnection();
            urlConnection.setReadTimeout(10000 /* milliseconds */);
            urlConnection.setConnectTimeout(15000 /* milliseconds */);
            urlConnection.setRequestMethod("GET");
            urlConnection.connect();
            // If the request was successful (response code 200),
            // then read the input stream and parse the response.
            if (urlConnection.getResponseCode() == 200) {
                inputStream = urlConnection.getInputStream();
                jsonResponse = readFromStream(inputStream);
            } else {
                Log.e(LOG_TAG, "Error response code: " + urlConnection.getResponseCode());
            }
        } catch (IOException e) {
            Log.e(LOG_TAG, "Problem retrieving the earthquake JSON results.", e);
        } finally {
            if (urlConnection != null) {
                urlConnection.disconnect();
            }
            if (inputStream != null) {
                inputStream.close();
            }
        }
        return jsonResponse;
    }

    private String readFromStream(InputStream inputStream) throws IOException {
        StringBuilder output = new StringBuilder();
        if (inputStream != null) {
            InputStreamReader inputStreamReader = new InputStreamReader(inputStream, Charset.forName("UTF-8"));
            BufferedReader reader = new BufferedReader(inputStreamReader);
            String line = reader.readLine();
            while (line != null) {
                output.append(line);
                line = reader.readLine();
            }
        }
        return output.toString();
    }
}

私有类EarthQuakeAsyncTask扩展了AsyncTask{
@凌驾
受保护的ArrayList doInBackground（URL…URL）{
if（url.length==0 | | url[0]==null）{
返回null；
}
//创建URL对象
URL URL=createUrl（请求的URL）；
试一试{
jsonResponse=makeHttpRequest（url）；
}捕获（IOE异常）{
//TODO处理IOException
}
ArrayList地震=QueryUtils.地震（jsonResponse）；
回归地震；
}
@凌驾
执行后受保护的空隙（ArrayList地震）{
如果（地震==null）{
返回；
}
updateUi（）；
}
私有URL createUrl（字符串stringUrl）{
网址；
试一试{
url=新url（stringUrl）；
}捕获（畸形异常异常）{
Log.e（Log_标记，“创建URL时出错”，异常）；
返回null；
}
返回url；
}
私有字符串makeHttpRequest（URL）引发IOException{
//如果URL为空，则提前返回。
如果（url==null）{
返回jsonResponse；
}
HttpURLConnection-urlConnection=null；
InputStream InputStream=null；
试一试{
urlConnection=（HttpURLConnection）url.openConnection（）；
setReadTimeout（10000/*毫秒*/）；
setConnectTimeout（15000/*毫秒*/）；
urlConnection.setRequestMethod（“GET”）；
urlConnection.connect（）；
//如果请求成功（响应代码200），
//然后读取输入流并解析响应。
if（urlConnection.getResponseCode（）==200）{
inputStream=urlConnection.getInputStream（）；
jsonResponse=readFromStream（inputStream）；
}否则{
e（Log_标记，“错误响应代码：”+urlConnection.getResponseCode（））；
}
}捕获（IOE异常）{
e（Log_标签，“检索地震JSON结果时出现问题”，e）；
}最后{
if（urlConnection！=null）{
urlConnection.disconnect（）；
}
如果（inputStream！=null）{
inputStream.close（）；
}
}
返回jsonResponse；
}
私有字符串readFromStream（InputStream InputStream）引发IOException{
StringBuilder输出=新的StringBuilder（）；
如果（inputStream！=null）{
InputStreamReader InputStreamReader=新的InputStreamReader（inputStream，Charset.forName（“UTF-8”）；
BufferedReader reader=新的BufferedReader（inputStreamReader）；
字符串行=reader.readLine（）；
while（行！=null）{
输出。追加（行）；
line=reader.readLine（）；
}
}
返回output.toString（）；
}
}

---

}

这是因为您的AsyncTask类的定义方式不适合使用字符串参数处理execute方法。让我解释一下

您开发的AsyncTask类如下所示：

private class MyAsyncTask extends AsyncTask<TYPE1, TYPE2, TYPE3> {

     protected TYPE3 doInBackground(TYPE1... type1_variables) {
         // Do some long process here..
         return variable_of_type_TYPE3;
     }

     protected void onPostExecute(TYPE3 result) {
         // Do something here
     }
 }

private class EarthQuakeAsyncTask extends AsyncTask<String, Void, Void> {
     ...
}

---

您的类签名表明您希望URL类型作为参数，但在execute（）方法中传递的是字符串类型。您所需要做的就是更改您的类签名，使其预期的字符串与此代码中的字符串相同

 private class EarthQuakeAsyncTask extends AsyncTask<String,Void,ArrayList<EarthQuake>> {
        @Override
        protected ArrayList<EarthQuake> doInBackground(String... urls) {
            if(urls.length==0||urls[0]== null){
                return null;
            }
            // Create a URL object from the String passed to the execute method
            URL url = createUrl(urls[0]);
            try {
                jsonResponse = makeHttpRequest(url);
            } catch (IOException e) {
                // TODO Handle the IOException
            }
            ArrayList<EarthQuake> earthquake = QueryUtils.extractEarthquakes(jsonResponse);
            return earthquake;
        }

        @Override
        protected void onPostExecute(ArrayList<EarthQuake> earthquake) {
            if (earthquake == null) {
                return;
            }
            updateUi();
        }


        private URL createUrl(String stringUrl) {
            URL url;
            try {
                url = new URL(stringUrl);
            } catch (MalformedURLException exception) {
                Log.e(LOG_TAG, "Error with creating URL", exception);
                return null;
            }
            return url;
        }

        private String makeHttpRequest(URL url) throws IOException {
            // If the URL is null, then return early.
            if (url == null) {
                return jsonResponse;
            }

            HttpURLConnection urlConnection = null;
            InputStream inputStream = null;
            try {
                urlConnection = (HttpURLConnection) url.openConnection();
                urlConnection.setReadTimeout(10000 /* milliseconds */);
                urlConnection.setConnectTimeout(15000 /* milliseconds */);
                urlConnection.setRequestMethod("GET");
                urlConnection.connect();
                // If the request was successful (response code 200),
                // then read the input stream and parse the response.
                if (urlConnection.getResponseCode() == 200) {
                    inputStream = urlConnection.getInputStream();
                    jsonResponse = readFromStream(inputStream);
                } else {
                    Log.e(LOG_TAG, "Error response code: " + urlConnection.getResponseCode());
                }
            } catch (IOException e) {
                Log.e(LOG_TAG, "Problem retrieving the earthquake JSON results.", e);
            } finally {
                if (urlConnection != null) {
                    urlConnection.disconnect();
                }
                if (inputStream != null) {
                    inputStream.close();
                }
            }
            return jsonResponse;
        }

        private String readFromStream(InputStream inputStream) throws IOException {
            StringBuilder output = new StringBuilder();
            if (inputStream != null) {
                InputStreamReader inputStreamReader = new InputStreamReader(inputStream, Charset.forName("UTF-8"));
                BufferedReader reader = new BufferedReader(inputStreamReader);
                String line = reader.readLine();
                while (line != null) {
                    output.append(line);
                    line = reader.readLine();
                }
            }
            return output.toString();
        }
    }
    }

私有类EarthQuakeAsyncTask扩展了AsyncTask{
@凌驾
受保护的ArrayList doInBackground（字符串…URL）{
if（url.length==0 | | url[0]==null）{
返回null；
}
//从传递给execute方法的字符串创建URL对象
URL URL=createUrl（URL[0]）；
试一试{
jsonResponse=makeHttpRequest（url）；
}捕获（IOE异常）{
//TODO处理IOException
}
ArrayList地震=QueryUtils.地震（jsonResponse）；
回归地震；
}
@凌驾
执行后受保护的空隙（ArrayList地震）{
如果（地震==null）{
返回；
}
updateUi（）；
}
私有URL createUrl（字符串stringUrl）{
网址；
试一试{
url=新url（stringUrl）；
}捕获（畸形异常异常）{
Log.e（Log_标记，“创建URL时出错”，异常）；
返回null；
}
返回url；
}
私有字符串makeHttpRequest（URL）引发IOException{
//如果URL为空，则提前返回。
如果（url==null）{
返回jsonResponse；
}
HttpURLConnection-urlConnection=null；
InputStream InputStream=null；
试一试{
urlConnection=（HttpURLConnection）url.openConnection（）；
setReadTimeout（10000/*毫秒*/）；
setConnectTimeout（15000/*毫秒*/）；
urlConnection.setRequestMethod（“GET”）；
urlConnection.connect（）；
//如果请求成功（响应代码200），
//然后读取输入流并解析响应。
if（urlConnection.getResponseCode（）==200）{
inputStream=urlConnection.getInputStream（）；
jsonResponse=readFromStream（inputStream）；