设置适配器空指针

Question

我已经尝试解决一个问题几个小时了，但我没有解决它。我尝试为可扩展列表视图设置适配器，但我接受了这个错误。多谢了。“尝试对空对象引用调用虚拟方法”void Android.Widget.ExpandableListView.SetAdapter（Android.Widget.ExpandableListAdapter）“”

 public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    Button b1;


    private ResideMenu resideMenu;
    private Context mContext;
    private ResideMenuItem itemAnasayfa;
    private ResideMenuItem itemRastgele;
    private ResideMenuItem itemEncok;
    private ResideMenuItem itemTarifyaz;

    private ExpandableListView listView;
    private ExpandableListAdapter listAdapter;
    private List<String> listDataHeader;
    private HashMap<String,List<String>> listHash;



    @Override
    protected void onCreate(Bundle savedInstanceState) {

        listView=(ExpandableListView)findViewById(R.id.exp2);
        initData();
        listAdapter=new com.yeni.ExpandableListAdapter(this,listDataHeader,listHash);
        listView.setAdapter(listAdapter);

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mContext = this;
        setUpMenu();
        if (savedInstanceState == null) {

            changeFragment(new F_ana_sayfa());

        }

    }

    private void initData() {
        listDataHeader=new ArrayList<>();
        listHash=new HashMap<>();

        listDataHeader.add("et");
        listDataHeader.add("tavuk");
        listDataHeader.add("sebze");
        listDataHeader.add("diger");

        List<String> l_et=new ArrayList<>();
        l_et.add("kemikli");
        l_et.add("kuşbaşı");

        List<String> l_tavuk=new ArrayList<>();
        l_tavuk.add("bonfile");
        l_tavuk.add("but");
        l_tavuk.add("bütün tavuk");

        List<String> l_sebze=new ArrayList<>();
        l_sebze.add("patates");
        l_sebze.add("biber");
        l_sebze.add("kabak");
        l_sebze.add("patlıcan");

        List<String> l_diger=new ArrayList<>();
        l_diger.add("tuz");
        l_diger.add("yağ");
        l_diger.add("kekik");

        listHash.put(listDataHeader.get(0),l_et);
        listHash.put(listDataHeader.get(1),l_tavuk);
        listHash.put(listDataHeader.get(2),l_sebze);
        listHash.put(listDataHeader.get(3),l_diger);

    }

    private void setUpMenu() {
        resideMenu = new ResideMenu(this);
        resideMenu.setBackground(R.drawable.menu_background);
        resideMenu.attachToActivity(this);


        resideMenu.setMenuListener(menuListener);
        resideMenu.setScaleValue(0.6f);
        //create menu items;
        itemAnasayfa = new ResideMenuItem(this, R.drawable.icon_home, "Ana Sayfa");
        itemRastgele = new ResideMenuItem(this, R.drawable.icon_profile, "Random tarif bul");
        itemEncok = new ResideMenuItem(this, R.drawable.icon_calendar, "En cok begenilenler");
        itemTarifyaz = new ResideMenuItem(this, R.drawable.icon_settings, "tarif Yaz");


        itemAnasayfa.setOnClickListener(this);
        itemRastgele.setOnClickListener(this);
        itemEncok.setOnClickListener(this);
        itemTarifyaz.setOnClickListener(this);


        resideMenu.addMenuItem(itemAnasayfa, ResideMenu.DIRECTION_LEFT);
        resideMenu.addMenuItem(itemRastgele, ResideMenu.DIRECTION_LEFT);
        resideMenu.addMenuItem(itemEncok, ResideMenu.DIRECTION_RIGHT);
        resideMenu.addMenuItem(itemTarifyaz, ResideMenu.DIRECTION_RIGHT);

        findViewById(R.id.title_bar_left_menu).setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View view) {

                resideMenu.openMenu(ResideMenu.DIRECTION_LEFT);
            }
        });

        findViewById(R.id.title_bar_right_menu).setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View view) {

                resideMenu.openMenu(ResideMenu.DIRECTION_RIGHT);
            }
        });
    }

    @Override

    public boolean dispatchTouchEvent(MotionEvent ev) {
        return resideMenu.dispatchTouchEvent(ev);
    }

    @Override
    public void onClick(View view) {

        if (view == itemAnasayfa) {
            changeFragment(new F_ana_sayfa());
        } else if (view == itemRastgele) {
            changeFragment(new F_rastgele_tarif());
        } else if (view == itemEncok) {
            changeFragment(new F_encok_beg());
        } else if (view == itemTarifyaz) {
            changeFragment(new F_tarif_yaz());
        }
        else
            changeFragment(new F_ana_sayfa());


        resideMenu.closeMenu();
    }


    private ResideMenu.OnMenuListener menuListener = new ResideMenu.OnMenuListener() {
        @Override
        public void openMenu() {
            Toast.makeText(mContext, "Menu is opened!", Toast.LENGTH_SHORT).show();

        }

        @Override
        public void closeMenu() {

            Toast.makeText(mContext, "Menu is closed!", Toast.LENGTH_SHORT).show();
        }


    };




    private void changeFragment(Fragment targetFragment) {
        resideMenu.clearIgnoredViewList();
        getSupportFragmentManager()
                .beginTransaction()
                .replace(R.id.main_fragment, targetFragment, "fragment")
                .setTransitionStyle(FragmentTransaction.TRANSIT_FRAGMENT_FADE)
                .commit();
    }

    public ResideMenu getResideMenu(){
        return resideMenu;}
}

    public class ExpandableListAdapter extends BaseExpandableListAdapter {

    private Context cont;
    private List<String> listDataHeader;
    private HashMap<String,List<String>> listHashMap;

    public ExpandableListAdapter(Context cont, List<String> listDataHeader, HashMap<String, List<String>> listHashMap) {
        this.cont = cont;
        this.listDataHeader = listDataHeader;
        this.listHashMap = listHashMap;
    }

    @Override
    public int getGroupCount() {
        return listDataHeader.size();
    }

    @Override
    public int getChildrenCount(int i) {
        return listHashMap.get(listDataHeader.get(i)).size();
    }

    @Override
    public Object getGroup(int i) {
        return listDataHeader.get(i);
    }

    @Override
    public Object getChild(int i, int i1) { // i=group position i=item position
        return listHashMap.get(listDataHeader.get(i)).get(i1);
    }

    @Override
    public long getGroupId(int i) {
        return i;
    }

    @Override
    public long getChildId(int i, int i1) {
        return i1;
    }

    @Override
    public boolean hasStableIds() {
        return false;
    }

    @Override
    public View getGroupView(int i, boolean b, View view, ViewGroup viewGroup) {
        String headerTitle=(String)getGroup(i);

        if (view==null){
            LayoutInflater inflater1=(LayoutInflater)this.cont.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            view=inflater1.inflate(R.layout.list_group,null);

        }

        TextView lblHeader=(TextView)view.findViewById(R.id.header);
        lblHeader.setTypeface(null, Typeface.BOLD);
        lblHeader.setText(headerTitle);
        return view;
    }

    @Override
    public View getChildView(int i, int i1, boolean b, View view, ViewGroup viewGroup) {
        final String childText=(String)getChild(i,i1);

        if (view==null){
            LayoutInflater inflater1=(LayoutInflater)this.cont.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            view=inflater1.inflate(R.layout.list_item,null);

        }

        TextView txtListChild=(TextView)view.findViewById(R.id.list_item);
        txtListChild.setText(childText);
        return view;
    }

    @Override
    public boolean isChildSelectable(int i, int i1) {
        return true;
    }
}

   
   
 
    
    
 
     
     
    <?xml version="1.0" encoding="utf-8"?>

    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:background="@android:color/white"
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <ExpandableListView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:id="@+id/exp2" />

        <LinearLayout
            android:orientation="vertical"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:id="@+id/layout_top">

            <!--<ImageView-->
                <!--android:layout_width="match_parent"-->
                <!--android:layout_height="3dp"-->
                <!--android:background="#2ea3fe"/>-->

            <FrameLayout
                android:layout_width="fill_parent"
                android:layout_height="wrap_content">

                <Button
                    android:layout_width="28dp"
                    android:layout_height="28dp"
                    android:background="@drawable/titlebar_menu_selector"
                    android:id="@+id/title_bar_left_menu"
                    android:layout_gravity="left|center_vertical"
                    android:layout_marginLeft="10dp"/>

                <TextView
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:padding="7dp"
                    android:text="Yemek Do"
                    android:textSize="24sp"
                    android:layout_gravity="center"
                    android:textColor="?attr/actionModeSplitBackground" />

                <Button
                    android:layout_width="28dp"
                    android:layout_height="28dp"
                    android:background="@drawable/titlebar_menu_selector"
                    android:id="@+id/title_bar_right_menu"
                    android:layout_gravity="right|center_vertical"
                    android:layout_marginRight="10dp"/>
            </FrameLayout>

            <View
                android:layout_width="match_parent"
                android:layout_height="5dp"
                android:background="#bcb8b8"/>

        </LinearLayout>

        <FrameLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical"
            android:id="@+id/main_fragment">

            <RelativeLayout
                android:layout_width="match_parent"
                android:layout_height="match_parent">

                <Button
                    android:text="Button"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_alignParentTop="true"
                    android:layout_alignParentLeft="true"
                    android:layout_alignParentStart="true"
                    android:layout_marginLeft="107dp"
                    android:layout_marginStart="107dp"
                    android:layout_marginTop="188dp"
                    android:id="@+id/button2" />

                <Button
                    android:text="Button"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_alignParentTop="true"
                    android:layout_alignRight="@+id/button2"
                    android:layout_alignEnd="@+id/button2"
                    android:layout_marginTop="78dp"
                    android:id="@+id/button3" />
            </RelativeLayout>
        </FrameLayout>

    </LinearLayout>
     
    <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:orientation="vertical" android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView
            android:text="TextView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/header" />
    </LinearLayout>

     
list_item.xml
     
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:text="TextView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/list_item" />
</LinearLayout>

     
错误日志
                
    
                
    


            
   


            
 共1个答案


                        
   


                
    

                    
     匿名用户

                
     

     



                
     

					
     
你在做什么：
     
 listView=(ExpandableListView)findViewById(R.id.exp2);
initData();
listAdapter=new com.yeni.ExpandableListAdapter(this,listDataHeader,listHash);
listView.setAdapter(listAdapter);

super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

     
在setContentView出错之前初始化listview对象。应该是这样的
     
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView=(ExpandableListView)findViewById(R.id.exp2);
initData();
listAdapter=new 
          com.yeni.ExpandableListAdapter(this,listDataHeader,listHash);
listView.setAdapter(listAdapter);
				
     


                
     

                
     
            
    

            
   
                      

相关问题

• 在 FXML 文件中设置自定义控件的按钮“onAction”方法？
• AngularJS-nested ng-使用select/option重复，获取/设置所选值
• 将 Keycloak 适配器与 Wildfly 26 一起使用不提供“KEYCLOAK”作为机制
• 域模式下的Keycloak JBoss EAP7适配器
• 设置ADuser和“用户下次登录时必须更改密码”的问题
• 在服务器上设置SSH身份验证时，Kerberos keytab文件的原因是什么？
• CryptoJs 的解密方法返回一个空字符串
• fx:id="grid "在控制器中保持为空
• JavaFX 第二次启动模式对话框时出现“已设置为另一个场景的根”异常
• JavaFX如何从被调用控制器设置调用控制器中标签的文本
• 为 fxml 中的所有子节点设置边距
• Eclipse/STS中的Gradle项目有可能解决同一个工作空间中其他Gradle项目的依赖关系吗？
• 如何在JavaFX中设置TabPane下拉菜单的样式
• AWS betalk 中 docker 容器中的 JVM 内存设置
• GitHub Action CI-下载并设置JDK
• 空闲时Eclipse中的高CPU使用率
• 在 Gradle Spring Boot Hibernate 项目中设置 LiquiBase
• 在Windows中设置默认堆大小[重复]
• 使用GCP证书颁发机构服务的证书设置Kafka mTLS时出现的问题
• 在单台机器和配置上设置kafka集群

Answer 1

热门标签

Answer 2

相关问题

Answer 3

你在做什么：

 listView=(ExpandableListView)findViewById(R.id.exp2);
initData();
listAdapter=new com.yeni.ExpandableListAdapter(this,listDataHeader,listHash);
listView.setAdapter(listAdapter);

super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

在setContentView出错之前初始化listview对象。应该是这样的

super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView=(ExpandableListView)findViewById(R.id.exp2);
initData();
listAdapter=new 
          com.yeni.ExpandableListAdapter(this,listDataHeader,listHash);
listView.setAdapter(listAdapter);