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
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;
}
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);
}
