I have and XML-file in my resources which looks like this (removed other stage-elemets):
<?xml version="1.0" encoding="utf-8"?> <schedule name="Irgend ein besondere Zuchtname"> <stages> <stage interval="0" token="3"> <name>Name</name> <descrition>Some description...</descrition> <image>image_to_retrieve.jpg</image> </stage> </stages> </schedule> I want to get the text of the image-element for a specific stage (by a token). My approach is this:
public String GetImage(int stageToken) { // because this is a helper class, the context is set in the constructor XmlResourceParser parser = context.getResources().getXml(R.xml.schedule_default); XPath xPath = XPathFactory.newInstance().newXPath(); String image; try { // error occurs here: image = xPath.evaluate("//stage[@token=3]/image/text()", parser); } catch (XPathExpressionException e) { Log.e(LOG_TAG, "Error evaluating xpath expression."); e.printStackTrace(); return null; } parser.close(); return image; } The expression shouldn't be the problem, because I tested it with other XPath-programms. Same for the validity of the XML. This is the exception I get:
01-17 00:12:05.044 30417-30417/at.beekeeper W/System.err: javax.xml.xpath.XPathExpressionException: javax.xml.transform.TransformerException: Attempt to invoke interface method 'org.apache.xml.dtm.DTMAxisTraverser org.apache.xml.dtm.DTM.getAxisTraverser(int)' on a null object reference 01-17 00:12:05.045 30417-30417/at.beekeeper W/System.err: at org.apache.xpath.jaxp.XPathImpl.evaluate(XPathImpl.java:295) 01-17 00:12:05.045 30417-30417/at.beekeeper W/System.err: at org.apache.xpath.jaxp.XPathImpl.evaluate(XPathImpl.java:371) 01-17 00:12:05.045 30417-30417/at.beekeeper W/System.err: at at.beekeeper.util.ScheduleParser.GetImage(ScheduleParser.java:108) 01-17 00:12:05.045 30417-30417/at.beekeeper W/System.err: at at.beekeeper.view.StageActivity.onCreate(StageActivity.java:52) 01-17 00:12:05.045 30417-30417/at.beekeeper W/System.err: at android.app.Activity.performCreate(Activity.java:5953) 01-17 00:12:05.045 30417-30417/at.beekeeper W/System.err: at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1128) 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2267) 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2388) 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: at android.app.ActivityThread.access$800(ActivityThread.java:148) 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1292) 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: at android.os.Handler.dispatchMessage(Handler.java:102) 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: at android.os.Looper.loop(Looper.java:135) 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: at android.app.ActivityThread.main(ActivityThread.java:5312) 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: at java.lang.reflect.Method.invoke(Native Method) 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: at java.lang.reflect.Method.invoke(Method.java:372) 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901) 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696) 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: Caused by: javax.xml.transform.TransformerException: Attempt to invoke interface method 'org.apache.xml.dtm.DTMAxisTraverser org.apache.xml.dtm.DTM.getAxisTraverser(int)' on a null object reference 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: at org.apache.xpath.XPath.execute(XPath.java:365) 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: at org.apache.xpath.jaxp.XPathImpl.eval(XPathImpl.java:219) 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: at org.apache.xpath.jaxp.XPathImpl.evaluate(XPathImpl.java:281) 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: ... 16 more 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'org.apache.xml.dtm.DTMAxisTraverser org.apache.xml.dtm.DTM.getAxisTraverser(int)' on a null object reference 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: at org.apache.xpath.axes.AxesWalker.setRoot(AxesWalker.java:221) 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: at org.apache.xpath.axes.WalkingIterator.setRoot(WalkingIterator.java:157) 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: at org.apache.xpath.axes.NodeSequence.setRoot(NodeSequence.java:265) 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: at org.apache.xpath.axes.LocPathIterator.execute(LocPathIterator.java:212) 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: at org.apache.xpath.XPath.execute(XPath.java:337) 01-17 00:12:05.046 30417-30417/at.beekeeper W/System.err: ... 18 more
No comments:
Post a Comment