android – 检查服务器上是否存在URL

概述这是我用来验证的代码,Url是否存在于服务器上,但始终不存在但链接仍然存在 在我的代码中我犯了错误,为什么我总是“不存在！” public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCrea 这是我用来验证的代码,Url是否存在于服务器上,但始终不存在但链接仍然存在

在我的代码中我犯了错误,为什么我总是“不存在！”

public class MainActivity extends Activity {    @OverrIDe    protected voID onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentVIEw(R.layout.activity_main);             String customURL = "http://www.desicomments.com/dc3/08/273858/273858.jpg";        boolean bResponse = exists(customURL);        if (bResponse==true)        {            Toast.makeText(MainActivity.this,"file exists!",Toast.LENGTH_SHORT).show();              }        else        {                       Toast.makeText(MainActivity.this,"file does not exist!",Toast.LENGTH_SHORT).show();        }       }    public static boolean exists(String URLname){        try {            httpURLConnection.setFollowRedirects(false);            httpURLConnection con =  (httpURLConnection) new URL(URLname).openConnection();            con.setRequestMethod("head");            return (con.getResponseCode() == httpURLConnection.http_OK);        }        catch (Exception e) {            e.printstacktrace();            return false;        }    }}

解决方法 您将获得Network On Main Thread Exception

看看NetworkOnMainThreadException

所以你的方法总是返回false,因为：

catch (Exception e) {        e.printstacktrace();        return false;    }

快速解决：

public class MainActivity extends Activity {    @OverrIDe    protected voID onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentVIEw(R.layout.activity_main);             String customURL = "http://www.desicomments.com/dc3/08/273858/273858.jpg";        MyTask task = new MyTask();        task.execute(customURL);    }    private class MyTask extends AsyncTask<String,VoID,Boolean> {        @OverrIDe        protected voID onPreExecute() {        }        @OverrIDe        protected Boolean doInBackground(String... params) {             try {                    httpURLConnection.setFollowRedirects(false);                    httpURLConnection con =  (httpURLConnection) new URL(params[0]).openConnection();                    con.setRequestMethod("head");                    System.out.println(con.getResponseCode());                     return (con.getResponseCode() == httpURLConnection.http_OK);                }                catch (Exception e) {                       e.printstacktrace();                        return false;                }        }        @OverrIDe        protected voID onPostExecute(Boolean result) {            boolean bResponse = result;             if (bResponse==true)                {                    Toast.makeText(MainActivity.this,Toast.LENGTH_SHORT).show();                      }                else                {                               Toast.makeText(MainActivity.this,Toast.LENGTH_SHORT).show();                }                          }               }}

使用ScheduledThreadPoolExecutor：

但记得关闭它!!

public class MainActivity extends Activity {     String customURL;     String msg = "";    @OverrIDe    protected voID onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentVIEw(R.layout.activity_main);             customURL = "http://www.desicomments.com/dc3/08/273858/273858.jpg";        final ScheduledThreadPoolExecutor myTimer = new ScheduledThreadPoolExecutor(1);        myTimer.scheduleAtFixedrate(new Runnable() {            @OverrIDe            public voID run() {                try {                    httpURLConnection.setFollowRedirects(false);                    httpURLConnection con =  (httpURLConnection) new URL(customURL).openConnection();                    con.setRequestMethod("head");                    System.out.println(con.getResponseCode());                     if(con.getResponseCode() == httpURLConnection.http_OK){                        msg = "file exist!";                    }else{                        msg = "file does not exist!";                    }                    runOnUiThread(new Runnable() {                            @OverrIDe                            public voID run() {                                Toast.makeText(MainActivity.this,msg,Toast.LENGTH_SHORT).show();                                  }                        });                }                catch (Exception e) {                       e.printstacktrace();                        return;                }            }        },10000,TimeUnit.MILliSECONDS);    }

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