好的，我正在开发一款Android应用程序，它可以向您展示一些内容，如电视时间表，新闻，天气预报和使用RSS的星座运势。该应用程序可以在Android 2.1或2.3.X上运行，但是当我在4.0或4.1上启动时，它会在我从main选择任何选项后停止工作。
app的结构是：
- 主要
- 具有视图的特定事物（如新闻）的活动
-XML由前一个类
调用的Parser类- Signle View的活动（就像一大堆新闻中的一条信息）及其视图
这里我提供了Manifest，Log和几个类：
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.mtel.vodic"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="7"
android:targetSdkVersion="14" />
<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".Vodic"
android:label="@string/title_activity_pocetna" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".Pomoc"
android:label="@string/m_tel_vodi_za_odlu_ne"
></activity>
<activity
android:name=".Pomocna"
android:label="@string/m_tel_vodi_za_odlu_ne"
></activity>
<activity
android:name=".SingleMenuItemActivity"
android:label="@string/m_tel_vodi_za_odlu_ne"
></activity>
.
.
.
</application>
<uses-permission android:name="android.permission.INTERNET" />
<!-- Needed to check when the network connection changes -->
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
</manifest>
错误日志：
10-18 20:35:05.457: E/Trace(730): error opening trace file: No such file or directory (2)
10-18 20:35:06.197: I/Choreographer(730): Skipped 30 frames! The application may be doing too much work on its main thread.
10-18 20:35:06.257: D/gralloc_goldfish(730): Emulator without GPU emulation detected.
10-18 20:35:11.316: D/AndroidRuntime(730): Shutting down VM
10-18 20:35:11.316: W/dalvikvm(730): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
10-18 20:35:11.347: E/AndroidRuntime(730): FATAL EXCEPTION: main
10-18 20:35:11.347: E/AndroidRuntime(730): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mtel.vodic/com.mtel.vodic.Vijesti}: java.lang.NullPointerException
10-18 20:35:11.347: E/AndroidRuntime(730): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
10-18 20:35:11.347: E/AndroidRuntime(730): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
10-18 20:35:11.347: E/AndroidRuntime(730): at android.app.ActivityThread.access$600(ActivityThread.java:130)
10-18 20:35:11.347: E/AndroidRuntime(730): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
10-18 20:35:11.347: E/AndroidRuntime(730): at android.os.Handler.dispatchMessage(Handler.java:99)
10-18 20:35:11.347: E/AndroidRuntime(730): at android.os.Looper.loop(Looper.java:137)
10-18 20:35:11.347: E/AndroidRuntime(730): at android.app.ActivityThread.main(ActivityThread.java:4745)
10-18 20:35:11.347: E/AndroidRuntime(730): at java.lang.reflect.Method.invokeNative(Native Method)
10-18 20:35:11.347: E/AndroidRuntime(730): at java.lang.reflect.Method.invoke(Method.java:511)
10-18 20:35:11.347: E/AndroidRuntime(730): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
10-18 20:35:11.347: E/AndroidRuntime(730): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
10-18 20:35:11.347: E/AndroidRuntime(730): at dalvik.system.NativeStart.main(Native Method)
10-18 20:35:11.347: E/AndroidRuntime(730): Caused by: java.lang.NullPointerException
10-18 20:35:11.347: E/AndroidRuntime(730): at com.mtel.vodic.Vijesti.onCreate(Vijesti.java:61)
10-18 20:35:11.347: E/AndroidRuntime(730): at android.app.Activity.performCreate(Activity.java:5008)
10-18 20:35:11.347: E/AndroidRuntime(730): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
10-18 20:35:11.347: E/AndroidRuntime(730): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
10-18 20:35:11.347: E/AndroidRuntime(730): ... 11 more
10-18 20:35:13.926: I/Process(730): Sending signal. PID: 730 SIG: 9
主：
public class Vodic extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_pocetna);
Button tv = (Button)findViewById(R.id.tv);
Button vijesti = (Button)findViewById(R.id.vijesti);
Button horoskop = (Button)findViewById(R.id.horoskop);
Button vremenska_prognoza = (Button)findViewById(R.id.vremenska_prognoza);
Button o_aplikaciji = (Button)findViewById(R.id.o_aplikaciji);
Button pomoc = (Button)findViewById(R.id.pomoc);
.
.
.
vijesti.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
Intent xw = new Intent(getApplicationContext(), Vijesti.class );
//xw.putExtra("A", "http://bih-x.info/feed/");
xw.putExtra("A", "http://klix.ba/rss/naslovnica");
if(!isOnline()) {
Toast.makeText(getApplicationContext(), "Niste povezani sa internetom!", Toast.LENGTH_SHORT).show();
} else {
startActivity(xw);
}
}
});
.
.
.
public boolean isOnline() {
ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo netInfo = cm.getActiveNetworkInfo();
if(netInfo != null && netInfo.isConnected()) {
return true;
}
return false;
}
}
的活动：
public class Vijesti extends ListActivity {
static String url =null;
// XML node keys
static final String KEY_ITEM = "item"; // parent node
static final String KEY_TITLE = "title";
static final String KEY_DATE = "pubDate";
static final String KEY_DESC = "encoded";
static final String UVOD = "uvod";
static final String CLANAK = "clanak";
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.vijesti_m);
Intent in = getIntent();
// Get XML values from previous intent
url = in.getStringExtra("A");
final ArrayList<HashMap<String,String>> menuItems = new ArrayList<HashMap<String,String>>();
ArrayList<String> xqw = new ArrayList<String>();
ParserVijesti parser=null;
Document doc=null;
try {
parser = new ParserVijesti();
String xml = parser.getXmlFromUrl(url); //get XML
doc = parser.getDomElement(xml);
} catch (Exception e1) {
finish();
}
NodeList nl = doc.getElementsByTagName(KEY_ITEM);
//loop
for (int i=0; i< nl.getLength(); i++){
HashMap<String, String> map = new HashMap<String, String>();
HashMap<String, String> mapq = new HashMap<String, String>();
Element e = (Element) nl.item(i);
//add to map
map.put(KEY_TITLE, parser.getValue(e, KEY_TITLE));
map.put(KEY_DATE, parser.getValue(e, KEY_DATE));
map.put(UVOD, parser.getValue(e,UVOD));
map.put(CLANAK, parser.getValue(e,CLANAK));
menuItems.add(map);
xqw.add(parser.getValue(e,KEY_TITLE));
}
for(int gf=0; gf<xqw.size(); gf++){
Log.w("ISPISI: ", xqw.get(gf));
}
ArrayAdapter adapterx = new ArrayAdapter(this, R.layout.vijesti_m,R.id.tetkica, xqw);
setListAdapter(adapterx);
//singleView
ListView lv = getListView();
lv.setOnItemClickListener(new OnItemClickListener(){
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id){
int hg = position;
HashMap<String, String> kaktus = menuItems.get(hg);
String uvod1 = kaktus.get(UVOD);
String clanak1 = kaktus.get(CLANAK);
String dat1 = kaktus.get(KEY_DATE);
String tit1 = kaktus.get(KEY_TITLE);
//intent
Intent inx = new Intent(getApplicationContext(), VijestiSingle.class);
inx.putExtra(KEY_TITLE, tit1);
inx.putExtra(KEY_DATE, dat1);
inx.putExtra(UVOD, uvod1);
inx.putExtra(CLANAK, clanak1);
startActivity(inx);
}
});
}
}
XML解析类：
public class ParserVijesti {
// constructor
public ParserVijesti() {
}
/**
* Getting XML from URL making HTTP request
* @param url string
* */
public String getXmlFromUrl(String url) {
String xml = null;
try {
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
xml = EntityUtils.toString(httpEntity, "UTF-8");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
// return XML
return xml;
}
/**
* Getting XML DOM element
* @param XML string
* */
public Document getDomElement(String xml){
Document doc = null;
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
dbf.setCoalescing(true);
dbf.setNamespaceAware(true);
try {
DocumentBuilder db = dbf.newDocumentBuilder();
InputSource is = new InputSource();
is.setByteStream(new ByteArrayInputStream(xml.getBytes("UTF-8")));
doc = db.parse(is);
} catch (ParserConfigurationException e) {
Log.e("Error: ", e.getMessage());
return null;
} catch (SAXException e) {
Log.e("Error: ", e.getMessage());
return null;
} catch (IOException e) {
Log.e("Error: ", e.getMessage());
return null;
}
return doc;
}
/** Getting node value
* @param elem element
*/
public final String getElementValue( Node elem ) {
Node child;
if( elem != null){
if (elem.hasChildNodes()){
for( child = elem.getFirstChild(); child != null; child = child.getNextSibling() ){
if(child.getNodeType() == Node.TEXT_NODE || child.getNodeType() == Node.CDATA_SECTION_NODE){
return child.getNodeValue();
}
}
}
}
return "";
}
public final String getElementValue2( Node elem ) {
Node child;
if( elem != null){
if (elem.hasChildNodes()){
for( child = elem.getFirstChild(); child != null; child = child.getNextSibling() ){
if(child.getNodeType() == Node.CDATA_SECTION_NODE){
return child.getNodeValue();
}
}
}
}
return "SRANJE";
}
/**
* Getting node value
* @param Element node
* @param key string
* */
public String getValue(Element item, String str) {
NodeList n = item.getElementsByTagName(str);
return this.getElementValue(n.item(0));
}
public String getValue3(Element item, String str){
NodeList n = item.getElementsByTagNameNS("http://purl.org/rss/1.0/modules/content/", str);
String ses = this.getElementValue2(n.item(0));
//String mim =ses.replaceAll("(?s)\\<.*?\\>", " \n");
String html = ses;
Spanned strxa = Html.fromHtml(html);
String fffx=strxa.toString();
//return this.getElementValue2(n.item(0));
//return ses;
//return Promjena(ses);
return fffx;
}
}
总结一下：应用程序在2.1或2.3.x上工作，但在我从Android 4.0或4.1上的主要活动中选择任何内容后停止。我不知道它有什么用......有人可以帮忙吗？
答案 0 :(得分：2)
根据日志，你在Vijesti.java:61上得到一个空指针。你说这行是：
NodeList nl = doc.getElementsByTagName(KEY_ITEM);
这意味着doc必须为null。由于您使用getDomElement()进行分配，这意味着您的问题在于该方法。我看到它可能为null的唯一方法（因为DocumentBuilder.parse()不能返回null）是你正在点击你的catch语句之一。
您是否在logcat中收到任何catch异常消息？您显示的部分仅列出空指针产生的实际错误。你的消息可能会在此之前。检查一下，你就能分辨出你得到的异常，并据此处理。
答案 1 :(得分：0)
这不会解决您的原始问题，但是：
我认为这是您遇到的另一个问题：您发布的应用程序的targetSdkVersion高于您测试的版本，并确认您的应用程序可以使用。
您已将targetSdkVersion设置为14.但如果您阅读此内容：
Android Min SDK Version vs. Target SDK Version
你会理解将targetSdkVersion设置为14意味着你正在告诉Android“我已经在API 14上测试了我的应用程序并确认它正在运行，请禁用低于API 14的版本的所有兼容性设置”。
但事实并非如此，你实际上确认了相反，该应用程序不适用于4.0！
如果将targetSdkVersion设置为14，它将使Android 4.0禁用其通常用于确保旧API的应用程序工作的兼容性设置（f.i. GPU渲染，JNI更改）
所以现在你应该在发布应用时设置minSdkVersion而不是targetSdkVersion，以保持4.0中的兼容性行为。
只有在您修复原始错误并针对API 14测试您的应用程序之后，才将targetSdkVersion提升为14。