java.lang.NullPointerException: tentative d'appeler la méthode virtuelle 'int Android.view.View.getImportantForAccessibility ()' sur une référence d'objet null

Question

J'essaie de créer une application de liste d'achat basée sur les champs de saisie, ArrayList et ListView. L'application sera basée sur Fragments. Cependant, j'ai rencontré un problème et je ne sais pas comment le résoudre.

J'ai regardé autour de moi à la fois sur Google et StackOverflow et j'ai trouvé des informations. Cependant, je ne l'ai pas obtenu au travail. Maintenant, j'espère pouvoir obtenir de l'aide pour mon code.

Je suis relativement inexpérimenté en développement Android.

Merci d'avance

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>

Journal

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)

Answer 1

Dans votre méthode public View getView, changez return null; en return convertView;.

Answer 2

#use return convertView; 

Code:

public View getView(final int position, View convertView, ViewGroup parent) {

    //convertView = null;

    if (convertView == null) {

        LayoutInflater mInflater = (LayoutInflater) context.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
        convertView = mInflater.inflate(R.layout.list_item, null);     

        TextView tv = (TextView) convertView.findViewById(R.id.name);
        Button rm_btn = (Button) convertView.findViewById(R.id.rm_btn);

        Model m = modelList.get(position);
        tv.setText(m.getName());

        // click listener for remove button  คลิกลบปุ่ม
        rm_btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                modelList.remove(position);
                notifyDataSetChanged();
            }
        });
    }

    ///#use    return convertView;
    return convertView;
}

Answer 3

dans votre baseadapter class constructeur essayez d'initialiser LayoutInflater , normalement, j'ai préféré de cette façon,

public ClassBaseAdapter(Context context,ArrayList<Integer> listLoanAmount) {
    this.context = context;
    this.listLoanAmount = listLoanAmount;
    this.layoutInflater = LayoutInflater.from(context);
}

en haut de la classe, créez LayoutInflater variable, espérons que cela vous aidera

Answer 4

cela se produit parfois lorsque nous utilisons un adaptateur personnalisé dans toute activité de fragment. et nous retournons l'objet null, c'est-à-dire la vue null, de sorte que l'activité soit confondue avec la vue à charger.

indique la position où changer de vue