在我问我的问题之前，我会指出我对 android 编程是全新的。所以，我试图从我的资产文件夹中的 xml 文件中解析数据，并将数据放在自定义列表视图中。几天来，我一直在寻找如何正确解析文件以及如何不获取 NullPointerException 的问题。如果这里真正的问题是我尝试的编码很糟糕，那么这是一个可能的解决方案。对我无能的任何部分的任何帮助将不胜感激。代码：
public class Z_PullMain extends ListActivity {
AssetManager manager = getAssets();
private ListView lv;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_specials_weekday_list);
lv = (ListView) findViewById(android.R.id.list);
Context context=getApplicationContext();
ArrayList<HashMap<String, String>> listofspec = new ArrayList<HashMap<String, String>>();
String lowercaseday = ((GlobalVariables) getApplication()).getlowercaseday();
HashMap<String, String> specmap = new HashMap<String, String>();
try {
InputStream stream = context.getAssets().open("bar2.xml");
XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
factory.setNamespaceAware(true);
XmlPullParser xpp = factory.newPullParser();
xpp.setInput(stream, "UTF-8");
int eventType = xpp.getEventType();
while (eventType != XmlPullParser.END_DOCUMENT) {
if(eventType == XmlPullParser.START_TAG) {
String tag_name=xpp.getName();
if (tag_name==lowercaseday);{
eventType = xpp.next();
specmap.put("name", xpp.nextText().toString());
xpp.next();
specmap.put("price", xpp.nextText().toString());
xpp.next();
specmap.put("start", xpp.nextText().toString());
xpp.next();
specmap.put("end", xpp.nextText().toString());
xpp.next();
listofspec.add(specmap);
}
}
eventType = xpp.next();
}
System.out.println("End document");
} catch (XmlPullParserException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
SimpleAdapter adapter = new SimpleAdapter(
this,
listofspec,
R.layout.custom_row_view,
new String[] {"name", "price", "start", "end"},
new int[] {R.id.name,R.id.price, R.id.start, R.id.end}
);
setListAdapter(adapter);
}
}
XML 文件：
<?xml version="1.0" encoding="UTF-8"?>
<root>
<thursday>
<name>Everything</name>
<price>1/2 Price</price>
<start>10:00 PM</start>
<end>12:00 AM</end>
</thursday>
<thursday>
<name>Cover</name>
<price>Free</price>
<start>3:00 PM</start>
<end>10:00 PM</end>
</thursday>
<friday>
<name>Everything</name>
<price>1/2 Price</price>
<start>7:00 PM</start>
<end>9:00 PM</end>
</friday>
<friday>
<name>Coors Light Drafts</name>
<price>$1.00</price>
<start>3:00 PM</start>
<end>12:00 AM</end>
</friday>
<saturday>
<name>Everything</name>
<price>1/2 Price</price>
<start>7:00 PM</start>
<end>9:00 PM</end>
</saturday>
<saturday>
<name>Pinnacle</name>
<price>$3.00</price>
<start>3:00 PM</start>
<end>12:00 AM</end>
</saturday>
</root>
日志猫：
07-31 17:22:21.380: E/AndroidRuntime(2722): FATAL EXCEPTION: main
07-31 17:22:21.380: E/AndroidRuntime(2722): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.tronapps.barspecials/com.tronapps.barspecials.Z_PullMain}: java.lang.NullPointerException
07-31 17:22:21.380: E/AndroidRuntime(2722): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2106)
07-31 17:22:21.380: E/AndroidRuntime(2722): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
07-31 17:22:21.380: E/AndroidRuntime(2722): at android.app.ActivityThread.access$600(ActivityThread.java:141)
07-31 17:22:21.380: E/AndroidRuntime(2722): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
07-31 17:22:21.380: E/AndroidRuntime(2722): at android.os.Handler.dispatchMessage(Handler.java:99)
07-31 17:22:21.380: E/AndroidRuntime(2722): at android.os.Looper.loop(Looper.java:137)
07-31 17:22:21.380: E/AndroidRuntime(2722): at android.app.ActivityThread.main(ActivityThread.java:5041)
07-31 17:22:21.380: E/AndroidRuntime(2722): at java.lang.reflect.Method.invokeNative(Native Method)
07-31 17:22:21.380: E/AndroidRuntime(2722): at java.lang.reflect.Method.invoke(Method.java:511)
07-31 17:22:21.380: E/AndroidRuntime(2722): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
07-31 17:22:21.380: E/AndroidRuntime(2722): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
07-31 17:22:21.380: E/AndroidRuntime(2722): at dalvik.system.NativeStart.main(Native Method)
07-31 17:22:21.380: E/AndroidRuntime(2722): Caused by: java.lang.NullPointerException
07-31 17:22:21.380: E/AndroidRuntime(2722): at android.content.ContextWrapper.getAssets(ContextWrapper.java:83)
07-31 17:22:21.380: E/AndroidRuntime(2722): at com.tronapps.barspecials.Z_PullMain.<init>(Z_PullMain.java:22)
07-31 17:22:21.380: E/AndroidRuntime(2722): at java.lang.Class.newInstanceImpl(Native Method)
07-31 17:22:21.380: E/AndroidRuntime(2722): at java.lang.Class.newInstance(Class.java:1319)
07-31 17:22:21.380: E/AndroidRuntime(2722): at android.app.Instrumentation.newActivity(Instrumentation.java:1054)
07-31 17:22:21.380: E/AndroidRuntime(2722): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2097)
07-31 17:22:21.380: E/AndroidRuntime(2722): ... 11 more
07-31 17:23:14.881: E/Trace(2743): error opening trace file: No such file or directory (2)
编辑------- nullpointer 异常已修复，但列表为空。这是新的 logcat
07-31 18:20:22.221: W/System.err(3145): org.xmlpull.v1.XmlPullParserException: precondition: START_TAG (position:TEXT (whitespace)@3:2 in java.io.InputStreamReader@410b6a48)
07-31 18:20:22.221: W/System.err(3145): at org.kxml2.io.KXmlParser.nextText(KXmlParser.java:2053)
07-31 18:20:22.231: W/System.err(3145): at com.tronapps.barspecials.Z_PullMain.onCreate(Z_PullMain.java:49)
07-31 18:20:22.231: W/System.err(3145): at android.app.Activity.performCreate(Activity.java:5104)
07-31 18:20:22.231: W/System.err(3145): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
07-31 18:20:22.241: W/System.err(3145): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
07-31 18:20:22.241: W/System.err(3145): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
07-31 18:20:22.241: W/System.err(3145): at android.app.ActivityThread.access$600(ActivityThread.java:141)
07-31 18:20:22.251: W/System.err(3145): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
07-31 18:20:22.251: W/System.err(3145): at android.os.Handler.dispatchMessage(Handler.java:99)
07-31 18:20:22.251: W/System.err(3145): at android.os.Looper.loop(Looper.java:137)
07-31 18:20:22.251: W/System.err(3145): at android.app.ActivityThread.main(ActivityThread.java:5041)
07-31 18:20:22.263: W/System.err(3145): at java.lang.reflect.Method.invokeNative(Native Method)
07-31 18:20:22.271: W/System.err(3145): at java.lang.reflect.Method.invoke(Method.java:511)
07-31 18:20:22.282: W/System.err(3145): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
07-31 18:20:22.282: W/System.err(3145): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
07-31 18:20:22.282: W/System.err(3145): at dalvik.system.NativeStart.main(Native Method)