java.lang.NullPointerException：nullオブジェクト参照に対して仮想メソッド 'int Android.view.View.getImportantForAccessibility（）'を呼び出そうとしました

Question

入力フィールド、ArrayList、およびListViewに基づいて、買い物リストアプリをまとめようとしています。アプリはFragmentsに基づいています。しかし、私は問題に遭遇したし、それを解決する方法がわかりません。

私はGoogleとStackOverflowの両方を見回しましたが、いくつかの情報を見つけました。しかし、私はそれを機能させることができませんでした。今私は私のコードで助けを得ることができると思います。

私はAndroidの開発には比較的未熟です。

前もって感謝します

メインジャワ

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>

ログ

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

public View getViewメソッドで、return null;をreturn convertView;に変更します。

Answer 2

#use return convertView;

コード：

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

あなたの baseadapter class コンストラクタ を初期化してみてください LayoutInflater 、通常私はこのようにして好みました、

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

クラスの一番上に LayoutInflater variableを作成してください。

Answer 4

フラグメントのアクティビティでカスタムアダプタを使用したときに発生することがあります。 nullオブジェクト、つまりnullビューを返すので、アクティビティはどのビューをロードするか混乱します。そのため、この例外が発生します。

ビューを変更する位置を示します