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问题描述
我收到以下错误,当我尝试从内存到对象读取XML文件。好像问题得到上下文。谁能告诉我什么是错我的code?
code:
公共类WifiScanning延伸服务{
私有静态最后字符串变量=WifiScanning;
私人定时器定时;
公众诠释的刷新率;
公共WifiScanning(){
超();
配置配置=新配置();
的SAXParserFactory SPF = SAXParserFactory.newInstance();
SAXParser的SP;
XMLReader的XR = NULL;
的DataHandler DataHandler的= NULL;
尝试 {
SP = spf.newSAXParser();
XR = sp.getXMLReader();
DataHandler的=新的DataHandler();
xr.setContentHandler(DataHandler的);
xr.parse(新的InputSource(this.openFileInput(config.xml文件)));
}赶上(的ParserConfigurationException E){
// TODO自动生成的catch块
e.printStackTrace();
}赶上(的SAXException E){
// TODO自动生成的catch块
e.printStackTrace();
}赶上(FileNotFoundException异常E){
// TODO自动生成的catch块
e.printStackTrace();
}赶上(IOException异常E){
// TODO自动生成的catch块
e.printStackTrace();
}
配置= dataHandler.getConfig();
刷新率=的Integer.parseInt(config.getMa prefreshRate());
// TODO自动生成构造函数存根
}
私人TimerTask的updateTask =新的TimerTask(){
@覆盖
公共无效的run(){
Log.i(TAG,定时任务做工作);
}
};
@覆盖
公众的IBinder onBind(意向意图){
// TODO自动生成方法存根
返回null;
}
@覆盖
公共无效的onCreate(){
super.onCreate();
Log.i(TAG,服务创造);
定时器=新的定时器(TweetCollectorTimer);
Log.i(TAG,刷新率+将String.valueOf(刷新率));
timer.schedule(updateTask,0,3000L);
}
@覆盖
公共无效的onDestroy(){
super.onDestroy();
Log.i(TAG,服务破坏);
如果(定时器!= NULL){
timer.cancel();
timer.purge();
定时器= NULL;
}
}
公共无效的onStop(){
Log.i(TAG,服务破坏);
如果(定时器!= NULL){
timer.cancel();
timer.purge();
定时器= NULL;
}
}
}
LogCat中:
11月一十号日至1日:08:49.804:ERROR / AndroidRuntime(21514):java.lang.RuntimeException的:无法实例化服务android.wps.WifiScanning:显示java.lang.NullPointerException
十一月10日至一号:08:49.804:ERROR / AndroidRuntime(21514):在android.app.ActivityThread.handleCreateService(ActivityThread.java:2764)
十一月10日至一号:08:49.804:ERROR / AndroidRuntime(21514):在android.app.ActivityThread.access $ 3200(ActivityThread.java:119)
十一月10日至一号:08:49.804:ERROR / AndroidRuntime(21514):在android.app.ActivityThread $ H.handleMessage(ActivityThread.java:1917)
十一月10日至一号:08:49.804:ERROR / AndroidRuntime(21514):在android.os.Handler.dispatchMessage(Handler.java:99)
十一月10日至一号:08:49.804:ERROR / AndroidRuntime(21514):在android.os.Looper.loop(Looper.java:123)
十一月10日至一号:08:49.804:ERROR / AndroidRuntime(21514):在android.app.ActivityThread.main(ActivityThread.java:4363)
十一月10日至一号:08:49.804:ERROR / AndroidRuntime(21514):在java.lang.reflect.Method.invokeNative(本机方法)
十一月10日至一号:08:49.804:ERROR / AndroidRuntime(21514):在java.lang.reflect.Method.invoke(Method.java:521)
十一月10日至一号:08:49.804:ERROR / AndroidRuntime(21514):在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:860)
十一月10日至一号:08:49.804:ERROR / AndroidRuntime(21514):在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
十一月10日至一号:08:49.804:ERROR / AndroidRuntime(21514):在dalvik.system.NativeStart.main(本机方法)
十一月10日至一号:08:49.804:ERROR / AndroidRuntime(21514):由:显示java.lang.NullPointerException
十一月10日至一号:08:49.804:ERROR / AndroidRuntime(21514):在android.content.ContextWrapper.openFileInput(ContextWrapper.java:152)
十一月10日至一号:08:49.804:ERROR / AndroidRuntime(21514):在android.wps.WifiScanning< INIT>(WifiScanning.java:52)
十一月10日至一号:08:49.804:ERROR / AndroidRuntime(21514):在java.lang.Class.newInstanceImpl(本机方法)
十一月10日至一号:08:49.804:ERROR / AndroidRuntime(21514):在java.lang.Class.newInstance(Class.java:1479)
十一月10日至一号:08:49.804:ERROR / AndroidRuntime(21514):在android.app.ActivityThread.handleCreateService(ActivityThread.java:2761)
十一月10日至一号:08:49.804:ERROR / AndroidRuntime(21514):10 ...更多
解决方案
您应该这样做不是在构造函数中,但只之间(含)的onCreate()和的onDestroy()。
I am getting the following error when i try to read a XML file from the memory and into an object. Seems like problem with getting the Context. Can anyone tell me whats wrong with my code?
Code:
public class WifiScanning extends Service {
private static final String TAG = "WifiScanning";
private Timer timer;
public int refreshRate;
public WifiScanning() {
super();
Configuration config = new Configuration();
SAXParserFactory spf = SAXParserFactory.newInstance();
SAXParser sp;
XMLReader xr = null;
DataHandler dataHandler = null;
try {
sp = spf.newSAXParser();
xr = sp.getXMLReader();
dataHandler = new DataHandler();
xr.setContentHandler(dataHandler);
xr.parse(new InputSource(this.openFileInput("config.xml")));
} catch (ParserConfigurationException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SAXException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
config = dataHandler.getConfig();
refreshRate = Integer.parseInt(config.getMapRefreshRate());
// TODO Auto-generated constructor stub
}
private TimerTask updateTask = new TimerTask() {
@Override
public void run() {
Log.i(TAG, "Timer task doing work");
}
};
@Override
public IBinder onBind(Intent intent) {
// TODO Auto-generated method stub
return null;
}
@Override
public void onCreate() {
super.onCreate();
Log.i(TAG, "Service creating");
timer = new Timer("TweetCollectorTimer");
Log.i(TAG, "Refresh Rate: "+ String.valueOf(refreshRate));
timer.schedule(updateTask, 0, 3000L);
}
@Override
public void onDestroy() {
super.onDestroy();
Log.i(TAG, "Service destroying");
if (timer != null){
timer.cancel();
timer.purge();
timer = null;
}
}
public void onStop() {
Log.i(TAG, "Service destroying");
if (timer != null){
timer.cancel();
timer.purge();
timer = null;
}
}
}
LogCat:
10-01 11:08:49.804: ERROR/AndroidRuntime(21514): java.lang.RuntimeException: Unable to instantiate service android.wps.WifiScanning: java.lang.NullPointerException
10-01 11:08:49.804: ERROR/AndroidRuntime(21514): at android.app.ActivityThread.handleCreateService(ActivityThread.java:2764)
10-01 11:08:49.804: ERROR/AndroidRuntime(21514): at android.app.ActivityThread.access$3200(ActivityThread.java:119)
10-01 11:08:49.804: ERROR/AndroidRuntime(21514): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1917)
10-01 11:08:49.804: ERROR/AndroidRuntime(21514): at android.os.Handler.dispatchMessage(Handler.java:99)
10-01 11:08:49.804: ERROR/AndroidRuntime(21514): at android.os.Looper.loop(Looper.java:123)
10-01 11:08:49.804: ERROR/AndroidRuntime(21514): at android.app.ActivityThread.main(ActivityThread.java:4363)
10-01 11:08:49.804: ERROR/AndroidRuntime(21514): at java.lang.reflect.Method.invokeNative(Native Method)
10-01 11:08:49.804: ERROR/AndroidRuntime(21514): at java.lang.reflect.Method.invoke(Method.java:521)
10-01 11:08:49.804: ERROR/AndroidRuntime(21514): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
10-01 11:08:49.804: ERROR/AndroidRuntime(21514): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
10-01 11:08:49.804: ERROR/AndroidRuntime(21514): at dalvik.system.NativeStart.main(Native Method)
10-01 11:08:49.804: ERROR/AndroidRuntime(21514): Caused by: java.lang.NullPointerException
10-01 11:08:49.804: ERROR/AndroidRuntime(21514): at android.content.ContextWrapper.openFileInput(ContextWrapper.java:152)
10-01 11:08:49.804: ERROR/AndroidRuntime(21514): at android.wps.WifiScanning.<init>(WifiScanning.java:52)
10-01 11:08:49.804: ERROR/AndroidRuntime(21514): at java.lang.Class.newInstanceImpl(Native Method)
10-01 11:08:49.804: ERROR/AndroidRuntime(21514): at java.lang.Class.newInstance(Class.java:1479)
10-01 11:08:49.804: ERROR/AndroidRuntime(21514): at android.app.ActivityThread.handleCreateService(ActivityThread.java:2761)
10-01 11:08:49.804: ERROR/AndroidRuntime(21514): ... 10 more
解决方案
You should do this not in the constructor, but only between (inclusive) onCreate() and onDestroy().
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