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java.lang.NullPointerException: попытка вызвать виртуальный метод int Android.view.View.getImportantForAccessibility () для ссылки на пустой объект

Я пытаюсь собрать приложение со списком покупок на основе полей ввода ArrayList и ListView. Приложение будет основано на Fragments. Однако я столкнулся с проблемой и не знаю, как ее решить.

Я посмотрел вокруг на Google и StackOverflow, и я нашел некоторую информацию. Тем не менее, я не получил его на работу. Теперь я надеюсь, что смогу получить помощь с моим кодом.

Я относительно неопытен в разработке Android.

Заранее спасибо

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>

Журнал

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)
128
user2734182

В вашем методе public View getView измените return null; на return convertView;.

363
Pavya

#use return convertView; 

Код:

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;
}
13
Pong Petrung

в вашем baseadapter class constructor попытаться инициализировать LayoutInflater , обычно я предпочел этот путь,

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

в верхней части класса create LayoutInflater variable, надеюсь, это поможет вам

2
Ashana.Jackol

это иногда происходит, когда мы используем пользовательский адаптер в любой активности фрагмента. и мы возвращаем нулевой объект, т. е. нулевое представление, так что действие запутывается, какое представление загружать, поэтому возникает это исключение

показывает положение, где изменить вид

0
Aakib Jabbar