Question

编写UPnP控制点应用程序。但是我一直得到一个nullpointerexception：这里的第一个代码是导致npe的原因。以粗体显示，调用createAbsoluteURL。其余的是不同类（URIUtil）中的方法，持有对createAbsoluteURL / URI的不同调用

content = new MediaStoreContent(
                    context,
                    **new URLBuilder() {
                        public String getURL(DIDLObject object) {
                            return URIUtil.createAbsoluteURL(
                                    addy,
                                    getHttpServerService().getLocalPort(),
                                    URI.create("/" + object.getId())
                            ).toString();
                        }**

                        public String getObjectId(String urlPath) {
                            return urlPath.substring(1); // Cut the slash
                        }
                    }
            );



public static URL createAbsoluteURL(InetAddress address, int localStreamPort, URI relativeOrNot) throws IllegalArgumentException {
        try {
            if (address instanceof Inet6Address) {
                return createAbsoluteURL(new URL("http://[" + address.getHostAddress() + "]:" + localStreamPort), relativeOrNot);
            } else if (address instanceof Inet4Address) {
                return createAbsoluteURL(new URL("http://" + address.getHostAddress() + ":" + localStreamPort), relativeOrNot);
            } else {
                throw new IllegalArgumentException("InetAddress is neither IPv4 nor IPv6: " + address);
            }
        } catch (Exception ex) {
            throw new IllegalArgumentException("Address, port, and URI can not be converted to URL", ex);
        }
    }

public static URL createAbsoluteURL(URL base, URI relativeOrNot) throws IllegalArgumentException {

        if (base == null && !relativeOrNot.isAbsolute()) {
            throw new IllegalArgumentException("Base URL is null and given URI is not absolute");
        } else if (base == null && relativeOrNot.isAbsolute()) {
            try {
                return relativeOrNot.toURL();
            } catch (Exception ex) {
                throw new IllegalArgumentException("Base URL was null and given URI can't be converted to URL");
            }
        } else {
            try {
                assert base != null;
                URI baseURI = base.toURI();
                URI absoluteURI = createAbsoluteURI(baseURI, relativeOrNot);
                return absoluteURI.toURL();
            } catch (Exception ex) {
                throw new IllegalArgumentException(
                        "Base URL is not an URI, or can't create absolute URI (null?), " +
                                "or absolute URI can not be converted to URL", ex);
            }
        }
    }



 public static URI createAbsoluteURI(URI base, URI relativeOrNot) throws IllegalArgumentException {
            if (base == null && !relativeOrNot.isAbsolute()) {
                throw new IllegalArgumentException("Base URI is null and given URI is not absolute");
            } else if (base == null && relativeOrNot.isAbsolute()) {
                return relativeOrNot;
            } else {
                assert base != null;
                // If the given base URI has no path we give it a root path
                if (base.getPath().length() == 0) {
                    try {
                        base = new URI(base.getScheme(), base.getAuthority(), "/", base.getQuery(), base.getFragment());
                    } catch (Exception ex) {
                        throw new IllegalArgumentException(ex);
                    }
                }
                return base.resolve(relativeOrNot);
            }
        }

这是我的日志：

E/AndroidRuntime( 9824): Caused by: java.lang.NullPointerException
E/AndroidRuntime( 9824):        at org.teleal.cling.android.browser.MediaServerS
erviceImpl$ContentHttpServerConnection.<init>(MediaServerServiceImpl.java:159)
E/AndroidRuntime( 9824):        at org.teleal.cling.android.browser.MediaServerS
erviceImpl.onCreate(MediaServerServiceImpl.java:72)
E/AndroidRuntime( 9824):        at android.app.ActivityThread.handleCreateServic
e(ActivityThread.java:2959)
E/AndroidRuntime( 9824):        ... 10 more

Answer 1

至少有两件事可能为空并导致您突出显示的部分中的NPE：

getHttpServerService()
object

在调用该方法之前，您确定您的对象已初始化吗？

NullPointerException让我疯了

1 个答案: