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我一直在試圖解決一個問題幾個小時了，但我沒能弄明白。我嘗試一個設置適配器的可擴展列表視圖，但我拿這個錯誤。謝謝。 「嘗試上的空對象引用調用虛擬方法 '無效android.widget.ExpandableListView.setAdapter（android.widget.ExpandableListAdapter）'」設置適配器空指針
Main_Activity
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;}
}
適配器類別
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;
}
}
活動_主題XML
<?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>
list_group.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/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>
的error_log
E/AndroidRuntime：致命例外：main 進程：com.yeni，PID：2404 java.lang.RuntimeException：無法啓動活動ComponentInfo {com.yeni/com.yeni.MainActivity}： java.lang.NullPointerException：嘗試到上一個空對象引用 在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2646） 在android.app調用虛擬方法 '無效 android.widget.ExpandableListView.setAdapter（android.widget.ExpandableListAdapter）' 。在android.app.ActivityThread中使用ActivityThread.handleLaunchActivity（ActivityThread.java:2707） at android.app.ActivityThread.-wrap12（ActivityThread.java） $ hhandleMessage（ActivityThread.java:1460） at android.os.Handler.dispatchMessage（Handler.java:102） at android.os.Looper.loop（Looper.java:154） at android.app.ActivityThread.main（ActivityThread.java:6077） at java。 lang.reflect.Method.invoke（Native Method） at com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:865） at com.android.internal.os.ZygoteInit.main（ZygoteInit.java ：755） 引起：顯示java.lang.NullPointerException：嘗試在上一個com.yeni.MainActivity空對象引用 調用虛擬方法 '無效 android.widget.ExpandableListView.setAdapter（android.widget.ExpandableListAdapter）' 。 onCreate（MainActivity.java:55） at android.app.Activity.perfo rmCreate（Activity.java:6662） at android.app.Instrumentation.callActivityOnCreate（Instrumentation.java:1118） at android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2599） at android.app.ActivityThread.handleLaunchActivity（ （ActivityThread.java:2607） at android.app.ActivityThread.-wrap12 。的java：102） 在android.os.Looper.loop（Looper.java:154） 在android.app.ActivityThread.main（ActivityThread.java:6077） 在java.lang.reflect.Method.invoke（本地方法） 在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:865） 在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:755）
絕對是。非常感謝你的粘液。 –