액티비티를 시작할 수 없습니다. ComponentInfo Java.lang.nullExeption

Question

저는 안드로이드가 처음이고 HTTP를 통해 localhost에서 데이터를 제공하고 XML로 파싱하여 android에 목록으로 표시하는 프로그램을 가지고 있습니다.하지만 할 수 없습니다. 새 페이지 (목록을 표시하는 페이지)로 전환하십시오. 내 프로그램에는 java.lang.NullPointerException 예외가 있으며 어디에서 null.please를 제공하는지 알 수 없으며 무엇을해야하는지 알려줍니다.

이 내 메인 레이아웃입니다

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.sara.patientapplication/com.example.sara.patientapplication.ViewAllPatientActivity}: java.lang.NullPointerException 
     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059) 
     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084) 
     at android.app.ActivityThread.access$600(ActivityThread.java:130) 
     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195) 
     at android.os.Handler.dispatchMessage(Handler.java:99) 
     at android.os.Looper.loop(Looper.java:137) 
     at android.app.ActivityThread.main(ActivityThread.java:4745) 
     at java.lang.reflect.Method.invokeNative(Native Method) 
     at java.lang.reflect.Method.invoke(Method.java:511) 
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786) 
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
     at dalvik.system.NativeStart.main(Native Method) 
Caused by: java.lang.NullPointerException 
     at com.example.sara.patientapplication.ViewAllPatientActivity.onCreate(ViewAllPatientActivity.java:45) 
     at android.app.Activity.performCreate(Activity.java:5008) 
     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079) 
     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)at android.app.ActivityThread.access$600(ActivityThread.java:130)at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)at android.os.Handler.dispatchMessage(Handler.java:99)at android.os.Looper.loop(Looper.java:137)at android.app.ActivityThread.main(ActivityThread.java:4745)at java.lang.reflect.Method.invokeNative(Native Method)at java.lang.reflect.Method.invoke(Method.java:511)at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)at dalvik.system.NativeStart.main(Native Method) 
     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079) 
     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)at android.app.ActivityThread.access$600(ActivityThread.java:130)at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)at android.os.Handler.dispatchMessage(Handler.java:99)at android.os.Looper.loop(Looper.java:137)at android.app.ActivityThread.main(ActivityThread.java:4745)at java.lang.reflect.Method.invokeNative(Native Method)at java.lang.reflect.Method.invoke(Method.java:511)at 

com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786) 
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
            at dalvik.system.NativeStart.main(Native Method)  

: 이 오류 메시지입니다

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" 
android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin" 
android:paddingRight="@dimen/activity_horizontal_margin" 
android:paddingTop="@dimen/activity_vertical_margin" 
android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".mainActivity"> 
<Button 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:text="Show All Patients" 
    android:id="@+id/ShowAllPatients" 
    android:layout_marginTop="25dp"/> 
    <Button 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:text="Add New Patient" 
    android:id="@+id/AddNewP" 
    android:layout_below="@+id/ShowAllPatients" 
    android:layout_marginTop="10dp"/> 
</RelativeLayout>  

이것은 Activity.there가 버튼입니다 주요 내가 그것을 누를 때 나는 목록에 있지만에서 이동 예상 시간 예외가 발생합니다.

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    if (android.os.Build.VERSION.SDK_INT > 9) { 
     StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build(); 
     StrictMode.setThreadPolicy(policy); 
    } 

    Button ShowAllPatient=(Button)findViewById(R.id.ShowAllPatients); 
    Button AddNewPatient=(Button)findViewById(R.id.AddNewP); 


    ShowAllPatient.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      Intent i=new Intent(getApplicationContext(),ViewAllPatientActivity.class); 
      startActivity(i); 
     } 
    }); 
} 

이 내 목록 레이아웃 :

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
android:layout_width="match_parent" android:layout_height="match_parent"> 
<ListView 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:id="@android:id/list"></ListView> 
</LinearLayout> 

이 내 목록 활동 :

public class ViewAllPatientActivity extends ListActivity { 
ArrayList<HashMap<String, String>> menuItems = new ArrayList<HashMap<String, String>>(); 
XMLParser parser=new XMLParser(); 
static final String URL="http://localhost/AllPatient.php"; 
static final String Patient_ID="PatientId"; 
static final String First_Name="PatientFirstName"; 
static final String Last_Name="PatientLastName"; 
//static final String Blood_Type="BloodType"; 
//static final String Phone_Number="phoneNumber"; 
//static final String Practitioner_ID="practitionerId"; 
//static final String Email="Email"; 

public void onCreate(Bundle savedInstanceState){ 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.all_patient); 



    // String xml=parser.GetXml(URL); 
    Document doc=parser.DomElement("http://localhost/AllPatient.php"); 

    NodeList nl = doc.getElementsByTagName(Patient_ID); 
    for (int i=0;i<nl.getLength();i++){ 
     HashMap<String, String> map = new HashMap<String, String>(); 
     Element e = (Element) nl.item(i); 
     map.put(Patient_ID,parser.GetValue(e , Patient_ID)); 
     map.put(First_Name,parser.GetValue(e,First_Name)); 
     map.put(Last_Name,parser.GetValue(e,Last_Name)); 
     // map.put(Blood_Type,parser.GetValue(e,Blood_Type)); 
     // map.put(Phone_Number,parser.GetValue(e,Phone_Number)); 
     // map.put(Email,parser.GetValue(e,Email)); 
     // map.put(Practitioner_ID,parser.GetValue(e,Practitioner_ID)); 

     menuItems.add(map); 
    } 
    ListAdapter adapter=new SimpleAdapter(this,menuItems,R.layout.list_item, 
      new String[]{Patient_ID,First_Name,Last_Name},new int[]{R.id.pid,R.id.fName,R.id.lName}); 
    setListAdapter(adapter); 

    ListView lv=getListView(); 
    lv.setOnItemClickListener(new AdapterView.OnItemClickListener() { 
     @Override 
     public void onItemClick(AdapterView<?> parent, View view, int position, long id) { 
      String Patient_id = ((TextView) view.findViewById(R.id.pid)).getText().toString(); 
      String First_name = ((TextView) view.findViewById(R.id.fName)).getText().toString(); 
      String Last_name = ((TextView) view.findViewById(R.id.lName)).getText().toString(); 

      Intent in = new Intent(getApplicationContext(), SingleListPatient.class); 
      in.putExtra(Patient_ID, Patient_id); 
      in.putExtra(First_Name, First_name); 
      in.putExtra(Last_Name, Last_name); 
      startActivity(in); 
     } 
    }); 
} 

또한 내가 하나의리스트 항목에 대한 몇 가지 레이아웃이 있습니다

<LinearLayout 
xmlns:android="http://schemas.android.com/apk/res/android" 
android:layout_height="match_parent" 
android:layout_width="match_parent" 
android:orientation="horizontal"><TextView xmlns:android="http://schemas.android.com/apk/res/android" 
android:id="@+id/pid" 
android:layout_width="fill_parent" 
android:layout_height="fill_parent" 
android:padding="10dip" 
android:textSize="16dip" 
android:textStyle="bold" /> 
<TextView xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@+id/fName" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:padding="10dip" 
    android:textSize="16dip" 
    android:textStyle="bold" /><TextView xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@+id/lName" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:padding="10dip" 
    android:textSize="16dip" 
    android:textStyle="bold" /></LinearLayout>  

을

및

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
android:layout_width="match_parent" android:layout_height="match_parent"> 
<TextView 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:textSize="25dp" 
    android:textStyle="bold" 
    android:padding="10dp" 
    android:id="@+id/firstN"/> 

<TextView 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:textSize="25dp" 
    android:textStyle="bold" 
    android:padding="10dp" 
    android:id="@+id/lastN" 
    android:layout_toRightOf="@+id/firstN"/> 

<TextView 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:textSize="15dp" 
    android:textStyle="bold" 
    android:padding="10dp" 
    android:text="Patient ID: " 
    android:id="@+id/paId" 
    android:layout_below="@+id/firstN"/> 

<TextView 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:textSize="15dp" 
    android:textStyle="bold" 
    android:padding="10dp" 
    android:id="@+id/patientid" 
    android:layout_toRightOf="@+id/paId"/> 

<TextView 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:textSize="15dp" 
    android:textStyle="bold" 
    android:padding="10dp" 
    android:text="Blood Type: " 
    android:id="@+id/bt" 
    android:layout_below="@+id/paId"/> 

<TextView 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:textSize="15dp" 
    android:textStyle="bold" 
    android:padding="10dp" 
    android:id="@+id/btype" 
    android:layout_toRightOf="@+id/bt"/> 
<TextView 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:textSize="15dp" 
    android:textStyle="bold" 
    android:padding="10dp" 
    android:text="Phone Number: " 
    android:id="@+id/pn" 
    android:layout_below="@+id/bt"/> 

<TextView 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:textSize="15dp" 
    android:textStyle="bold" 
    android:padding="10dp" 
    android:id="@+id/pnum" 
    android:layout_toRightOf="@+id/pn"/> 
<TextView 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:textSize="15dp" 
    android:textStyle="bold" 
    android:padding="10dp" 
    android:text="Email: " 
    android:id="@+id/em" 
    android:layout_below="@+id/pn"/> 

<TextView 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:textSize="15dp" 
    android:textStyle="bold" 
    android:padding="10dp" 
    android:id="@+id/mail" 
    android:layout_toRightOf="@+id/em"/> 
</RelativeLayout> 

도와주세요. 덕분에 .

Answer 1

변경 :

Intent i=new Intent(getApplicationContext(),ViewAllPatientActivity.class); 
      startActivity(i); 

사람 :

Intent i=new Intent(mainActivity.this,ViewAllPatientActivity.class); 
      startActivity(i); 

그리고 확인하는 경우 : ViewAllPatientActivity.java의

Document doc is null