我尝试从url中读取json字符串：
String message = "http://cs-server.usc.edu:12695/examples/servlet/Moviefb?title=batman&title_type=feature";
URL website;
String str1 = "";
try {
website = new URL(message);
URLConnection connection = website.openConnection();
BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
String inputLine;
while ((inputLine = in.readLine()) != null)
str1 += inputLine;
} catch (MalformedURLException e1) {
// TODO Auto-generated catch block
Toast.makeText(getBaseContext(),
"catch1",
Toast.LENGTH_LONG).show();
e1.printStackTrace();
} catch (Exception e) {
Toast.makeText(getBaseContext(),
"catch2",
Toast.LENGTH_LONG).show();
e.printStackTrace();
}
然后我使用Toast来显示str1
Toast.makeText(getBaseContext(),
str1,
Toast.LENGTH_LONG).show();
但我一无所获。我得到一个例外，它显示catch2。这些代码在我的Eclipse中的Android应用程序项目中。
当我将这些代码复制并复制到我的普通Java项目时，它可以工作。
新的堆栈跟踪：
12-13 09:02:28.909: W/System.err(1015): java.lang.SecurityException: Permission denied (missing INTERNET permission?)
12-13 09:02:28.949: W/System.err(1015): at java.net.InetAddress.lookupHostByName(InetAddress.java:418)
12-13 09:02:29.079: W/Trace(1015): Unexpected value from nativeGetEnabledTags: 0
12-13 09:02:29.149: W/System.err(1015): at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236)
12-13 09:02:29.159: W/System.err(1015): at java.net.InetAddress.getAllByName(InetAddress.java:214)
12-13 09:02:29.179: W/Trace(1015): Unexpected value from nativeGetEnabledTags: 0
12-13 09:02:29.219: W/Trace(1015): Unexpected value from nativeGetEnabledTags: 0
12-13 09:02:29.239: W/System.err(1015): at libcore.net.http.HttpConnection.<init>(HttpConnection.java:70)
12-13 09:02:29.328: W/Trace(1015): Unexpected value from nativeGetEnabledTags: 0
12-13 09:02:29.428: W/System.err(1015): at libcore.net.http.HttpConnection.<init>(HttpConnection.java:50)
12-13 09:02:29.549: W/System.err(1015): at libcore.net.http.HttpConnection$Address.connect(HttpConnection.java:340)
12-13 09:02:29.609: W/System.err(1015): at libcore.net.http.HttpConnectionPool.get(HttpConnectionPool.java:87)
12-13 09:02:29.669: W/System.err(1015): at libcore.net.http.HttpConnection.connect(HttpConnection.java:128)
12-13 09:02:29.669: W/System.err(1015): at libcore.net.http.HttpEngine.openSocketConnection(HttpEngine.java:316)
12-13 09:02:29.719: W/System.err(1015): at libcore.net.http.HttpEngine.connect(HttpEngine.java:311)
12-13 09:02:29.819: W/System.err(1015): at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:290)
12-13 09:02:29.879: W/System.err(1015): at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:240)
12-13 09:02:29.959: W/System.err(1015): at libcore.net.http.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:282)
12-13 09:02:29.959: W/System.err(1015): at libcore.net.http.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:177)
12-13 09:02:29.959: W/System.err(1015): at com.example.hwnine.Show$1.doInBackground(Show.java:48)
12-13 09:02:30.229: W/System.err(1015): at com.example.hwnine.Show$1.doInBackground(Show.java:1)
12-13 09:02:30.268: W/System.err(1015): at android.os.AsyncTask$2.call(AsyncTask.java:287)
12-13 09:02:30.268: W/System.err(1015): at java.util.concurrent.FutureTask.run(FutureTask.java:234)
12-13 09:02:30.308: W/Trace(1015): Unexpected value from nativeGetEnabledTags: 0
12-13 09:02:30.308: W/Trace(1015): Unexpected value from nativeGetEnabledTags: 0
12-13 09:02:30.348: W/Trace(1015): Unexpected value from nativeGetEnabledTags: 0
12-13 09:02:30.368: W/System.err(1015): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
12-13 09:02:30.398: W/Trace(1015): Unexpected value from nativeGetEnabledTags: 0
12-13 09:02:30.479: W/System.err(1015): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
12-13 09:02:30.489: W/System.err(1015): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
12-13 09:02:30.499: W/System.err(1015): at java.lang.Thread.run(Thread.java:856)
12-13 09:02:30.499: W/System.err(1015): Caused by: libcore.io.GaiException: getaddrinfo failed: EAI_NODATA (No address associated with hostname)
12-13 09:02:30.519: W/System.err(1015): at libcore.io.Posix.getaddrinfo(Native Method)
12-13 09:02:30.519: W/System.err(1015): at libcore.io.ForwardingOs.getaddrinfo(ForwardingOs.java:59)
12-13 09:02:30.529: W/System.err(1015): at java.net.InetAddress.lookupHostByName(InetAddress.java:405)
12-13 09:02:30.539: W/System.err(1015): ... 21 more
12-13 09:02:30.539: W/System.err(1015): Caused by: libcore.io.ErrnoException: getaddrinfo failed: EACCES (Permission denied)
12-13 09:02:30.559: W/System.err(1015): ... 24 more
12-13 09:02:30.589: W/Trace(1015): Unexpected value from nativeGetEnabledTags: 0
答案 0 :(得分：1)
如果您在Android 3.0+上运行此代码，您可能会获得NetworkOnMainThreadException，因为它看起来像是在主线程上执行此操作。您需要使用AsyncTask来执行此类任务。
你能做的是：
final String message = "http://cs-server.usc.edu:12695/examples/servlet/Moviefb?title=batman&title_type=feature";
new AsyncTask<Void, Void, String>() {
private String mErrDesc = null;
@Override
protected String doInBackground(Void... paramArrayOfParams) {
URL website;
String str1 = null;
try {
website = new URL(message);
URLConnection connection = website.openConnection();
BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
String inputLine;
while ((inputLine = in.readLine()) != null)
str1 += inputLine;
} catch (MalformedURLException e1) {
mErrDesc = "MalformedURLException thrown";
e1.printStackTrace();
return null;
} catch (Exception e) {
mErrDesc = "Exception thrown";
e.printStackTrace();
return null;
}
return str1;
}
@Override
protected void onPostExecute(String str) {
if (str != null)
Toast.makeText(getBaseContext(), str, Toast.LENGTH_LONG).show();
else if (mErrDesc != null)
Toast.makeText(getBaseContext(), mErrDesc, Toast.LENGTH_LONG).show();
else
Toast.makeText(getBaseContext(), "Unknown error", Toast.LENGTH_LONG).show();
}
}.execute();
答案 1 :(得分：0)
也许这取决于您正在构建的Android平台。不是2.3或4.0的相同构建。如果您使用HttpClient构建2.2或低于3.0。 here一个例子。