java.lang.NullPointerException: Versuch, die virtuelle Methode 'int android.view.View.getImportantForAccessibility ()' für eine Nullobjekt-Referenz aufzurufen
Ich versuche, um gemeinsam eine Einkaufsliste app , basiert auf der Eingabe-Felder ArrayList
, und ListView
. Die app basiert auf Fragments
. Allerdings habe ich ein problem festgestellt, und ich weiß nicht, wie es zu lösen.
Ich schaute mich um auf Google und StackOverflow gefunden haben, einige Informationen . Allerdings habe ich nicht zum laufen bekommen. Jetzt hoffe ich, dass ich Hilfe bekommen kann, mit meinem code .
Ich bin relativ unerfahren in der Android-Entwicklung .
Vielen Dank im Voraus
Main.java
import java.util.ArrayList;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.Menu;
import android.view.MenuItem;
public class Main extends FragmentActivity {
ArrayList<Detail> items = new ArrayList<Detail>();
FragmentManager FM;
FragmentTransaction FT;
Input input = new Input();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
replaceFragment(R.id.container, input);
}
public void replaceFragment(int container, Fragment fragment){
FM = getFragmentManager();
FT = FM.beginTransaction();
FT.replace(container, fragment);
FT.commit();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
//Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
//Handle action bar item clicks here. The action bar will
//automatically handle clicks on the Home/Up button, so long
//as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
ListAdapter.java
public class ListAdapter extends BaseAdapter {
Context context;
ArrayList<Detail> items;
public ListAdapter(Context context, ArrayList<Detail> items) {
this.context = context;
this.items = items;
}
@Override
public int getCount() {
return items.size();
}
@Override
public Object getItem(int position) {
return items.get(position);
}
@Override
public long getItemId(int position) {
return items.indexOf(getItem(position));
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
if(convertView == null){
LayoutInflater lInflater = (LayoutInflater)context.getSystemService(
Activity.LAYOUT_INFLATER_SERVICE);
convertView = lInflater.inflate(R.layout.list_row, null);
}
TextView title = (TextView)convertView.findViewById(R.id.itemTitle);
CheckBox done = (CheckBox)convertView.findViewById(R.id.itemDone);
Detail detail_position = items.get(position);
title.setText(detail_position.getTitle());
done.setChecked(detail_position.isDone());
return null;
}
}
List.java
import java.util.ArrayList;
import android.app.ListFragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
public class List extends ListFragment implements OnItemClickListener{
ArrayList<Detail> items;
ListAdapter adapter;
private onClickListener OCL;
interface onClickListener{
public void onItemClick(int id);
}
public List(ArrayList<Detail> items) {
this.items = items;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.list_layout, container, false);
return root;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
if(items != null){
adapter = new ListAdapter(getActivity(), items);
setListAdapter(adapter);
getListView().setOnItemClickListener(this);
}
}
@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
if(OCL != null){
OCL.onItemClick(position);
}
}
}
list_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/LinearLayout1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<ListView
android:id="@+id/android:list"
android:layout_width="match_parent"
android:layout_height="match_parent" >
</ListView>
</LinearLayout>
list_row
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal"
android:padding="10dp" >
<TextView
android:id="@+id/itemTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="0.96"
android:text="Medium Text"
android:textAppearance="?android:attr/textAppearanceMedium" />
<CheckBox
android:id="@+id/itemDone"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Done" />
</LinearLayout>
activity_main.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.com.hermods.lab2_2.Main" >
</RelativeLayout>
Log
02-19 09:10:47.421: E/AndroidRuntime(12745): Process: com.example.com.hermods.lab2_2, PID: 12745
02-19 09:10:47.421: E/AndroidRuntime(12745): java.lang.NullPointerException: Attempt to invoke virtual method 'int android.view.View.getImportantForAccessibility()' on a null object reference
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.AbsListView.obtainView(AbsListView.java:2360)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.ListView.makeAndAddView(ListView.java:1864)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.ListView.fillDown(ListView.java:698)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.ListView.fillFromTop(ListView.java:759)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.ListView.layoutChildren(ListView.java:1673)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.AbsListView.onLayout(AbsListView.java:2148)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.View.layout(View.java:15596)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.ViewGroup.layout(ViewGroup.java:4966)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.LinearLayout.onLayout(LinearLayout.java:1466)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.View.layout(View.java:15596)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.ViewGroup.layout(ViewGroup.java:4966)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1076)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.View.layout(View.java:15596)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.ViewGroup.layout(ViewGroup.java:4966)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.View.layout(View.java:15596)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.ViewGroup.layout(ViewGroup.java:4966)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.LinearLayout.onLayout(LinearLayout.java:1466)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.View.layout(View.java:15596)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.ViewGroup.layout(ViewGroup.java:4966)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.View.layout(View.java:15596)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.ViewGroup.layout(ViewGroup.java:4966)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2072)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1829)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1054)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5779)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.Choreographer.doCallbacks(Choreographer.java:580)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.Choreographer.doFrame(Choreographer.java:550)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.os.Handler.handleCallback(Handler.java:739)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.os.Handler.dispatchMessage(Handler.java:95)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.os.Looper.loop(Looper.java:135)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.app.ActivityThread.main(ActivityThread.java:5221)
02-19 09:10:47.421: E/AndroidRuntime(12745): at java.lang.reflect.Method.invoke(Native Method)
02-19 09:10:47.421: E/AndroidRuntime(12745): at java.lang.reflect.Method.invoke(Method.java:372)
02-19 09:10:47.421: E/AndroidRuntime(12745): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
02-19 09:10:47.421: E/AndroidRuntime(12745): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
InformationsquelleAutor der Frage user2734182 | 2015-02-19
Du musst angemeldet sein, um einen Kommentar abzugeben.
In Ihrem
public View getView
Methode ändernreturn null;
zureturn convertView;
.InformationsquelleAutor der Antwort Pavya
#
return convertView;
Code:
InformationsquelleAutor der Antwort Pong Petrung
in Ihrem baseadapter Klasse Konstruktor versuchen zu initialisieren LayoutInflaternormalerweise habe ich es vorgezogen diese Weise
an der Spitze der Klasse erstellen LayoutInflater variable, hoffe, das wird Ihnen helfen,
InformationsquelleAutor der Antwort Ashana.Jackol