你好我正在使用android studio创建一个App，我遇到了一个错误，这个错误很难自己解决。我想要做的就是从网址读取CSV文件，并为每一行将值添加到地图标记。我可以轻松地从文件中读取并添加到我的标记中，但是这个url csv读取对我来说是一个挑战:(。我的错误是什么，甚至更好也可以简化。< / p>
HttpURLConnection conn = null;
try {
URL url = new URL("http://www.free-map.org.uk/course/mad/ws/get.php?username=user002&format=csv");
conn = (HttpURLConnection) url.openConnection();
InputStream in = conn.getInputStream();
if(conn.getResponseCode() == 200)
{
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String inputLine;
while ((inputLine = br.readLine()) != null) {
String[] comps = inputLine.split(",");
if (comps.length == 5) {
OverlayItem currentItem = new OverlayItem(comps[0], comps[2], new GeoPoint(Double.parseDouble(comps[4]), Double.parseDouble(comps[3])));
pois.addItem(currentItem);
}
}
}
}catch (IOException e){
new AlertDialog.Builder(this).setMessage("ERROR: "+e).show();
}
finally
{
if(conn!=null)
conn.disconnect();
}
我将此代码放在我的Resume（）上，以测试它是否有效，如果有帮助的话。这些是Logcat中显示的错误。
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.edwin.mapping, PID: 2048
java.lang.RuntimeException: Unable to resume activity {com.example.edwin.mapping/com.example.edwin.mapping.HelloMap}: android.os.NetworkOnMainThreadException
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2788)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2817)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2250)
at android.app.ActivityThread.access$800(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5017)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
at dalvik.system.NativeStart.main(Native Method)
Caused by: android.os.NetworkOnMainThreadException
at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1145)
at java.net.InetAddress.lookupHostByName(InetAddress.java:385)
at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236)
at java.net.InetAddress.getAllByName(InetAddress.java:214)
at com.android.okhttp.internal.Dns$1.getAllByName(Dns.java:28)
at com.android.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:216)
at com.android.okhttp.internal.http.RouteSelector.next(RouteSelector.java:122)
at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:292)
at com.android.okhttp.internal.http.HttpEngine.sendSocketRequest(HttpEngine.java:255)
at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:206)
at com.android.okhttp.internal.http.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:345)
at com.android.okhttp.internal.http.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:296)
at com.android.okhttp.internal.http.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:179)
at com.example.edwin.mapping.HelloMap.onResume(HelloMap.java:158)
at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1192)
at android.app.Activity.performResume(Activity.java:5310)
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2778)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2817)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2250)
at android.app.ActivityThread.access$800(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5017)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
at dalvik.system.NativeStart.main(Native Method)
Application terminated.
答案 0 :(得分：2)
使用Async Task执行网络操作。不要在UI线程上运行它。
例如：
private class ReadFile extends AsyncTask<String, Void, String> {
@Override
protected String doInBackground(String... params) {
HttpURLConnection conn = null;
try {
URL url = new URL("http://www.free-map.org.uk/course/mad/ws/get.php?username=user002&format=csv");
conn = (HttpURLConnection) url.openConnection();
InputStream in = conn.getInputStream();
if(conn.getResponseCode() == 200)
{
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String inputLine;
while ((inputLine = br.readLine()) != null) {
String[] comps = inputLine.split(",");
if (comps.length == 5) {
OverlayItem currentItem = new OverlayItem(comps[0], comps[2], new GeoPoint(Double.parseDouble(comps[4]), Double.parseDouble(comps[3])));
pois.addItem(currentItem);
}
}
}
}catch (Exception e){
Log.e("Error, e.toString());
}
finally
{
if(conn!=null)
conn.disconnect();
}
return null;
}
@Override
protected void onPostExecute(String result) {
}
@Override
protected void onPreExecute() {}
}
现在使用：
调用它new ReadFile().execute("");