我在manifest.xml中遇到问题我尝试了一切，但我不明白为什么我得到了一个＆＃34;不能分配给app.activity＆＃34;错误。我的expandablelist 是一个活动，而不是一个片段或其他东西。它只是扩展BaseExpandableListAdapter以显示ExpandableListView。请帮我。 这是我的归属班：
public class Expandablelist extends BaseExpandableListAdapter {
private Context _context;
private List<String> _listDataHeader; // header titles
// child data in format of header title, child title
private HashMap<String, List<String>> _listDataChild;
public Expandablelist(){
}
public Expandablelist(Context context, List<String> listDataHeader,
HashMap<String, List<String>> listChildData) {
this._context = context;
this._listDataHeader = listDataHeader;
this._listDataChild = listChildData;
}
@Override
public Object getChild(int groupPosition, int childPosititon) {
return this._listDataChild.get(this._listDataHeader.get(groupPosition))
.get(childPosititon);
}
@Override
public long getChildId(int groupPosition, int childPosition) {
return childPosition;
}
@Override
public View getChildView(int groupPosition, final int childPosition,
boolean isLastChild, View convertView, ViewGroup parent) {
final String childText = (String) getChild(groupPosition, childPosition);
if (convertView == null) {
LayoutInflater infalInflater = (LayoutInflater) this._context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = infalInflater.inflate(R.layout.list_item, null);
}
TextView txtListChild = (TextView) convertView
.findViewById(R.id.lblListItem);
txtListChild.setText(childText);
return convertView;
}
@Override
public int getChildrenCount(int groupPosition) {
return this._listDataChild.get(this._listDataHeader.get(groupPosition))
.size();
}
@Override
public Object getGroup(int groupPosition) {
return this._listDataHeader.get(groupPosition);
}
@Override
public int getGroupCount() {
return this._listDataHeader.size();
}
@Override
public long getGroupId(int groupPosition) {
return groupPosition;
}
@Override
public View getGroupView(int groupPosition, boolean isExpanded,
View convertView, ViewGroup parent) {
String headerTitle = (String) getGroup(groupPosition);
if (convertView == null) {
LayoutInflater infalInflater = (LayoutInflater) this._context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = infalInflater.inflate(R.layout.list_group, null);
}
TextView lblListHeader = (TextView) convertView
.findViewById(R.id.lblListHeader);
lblListHeader.setTypeface(null, Typeface.BOLD);
lblListHeader.setText(headerTitle);
return convertView;
}
@Override
public boolean hasStableIds() {
return false;
}
@Override
public boolean isChildSelectable(int groupPosition, int childPosition) {
return true;
}
}
这是我的mainactivity.java：
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
Expandablelist listAdapter;
// ExpandableListView expListView;
List<String> listDataHeader;
HashMap<String, List<String>> listDataChild;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// auf anderes xml layout zugreifen
setContentView(R.layout.activity_main);
// LayoutInflater inflater = LayoutInflater.from(getApplicationContext());
// inflater.inflate(R.layout.activity_expandablelist,null);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
final ImageButton generaldiscriptionbutton = (ImageButton) findViewById(R.id.imageButton);
setSupportActionBar(toolbar);
checkFirstRun();
View expandablelistview = getLayoutInflater().inflate(R.layout.activity_expandablelist, null, false);
ExpandableListView expListView = (ExpandableListView) expandablelistview.findViewById(R.id.lvExp);
// get the listview
// expListView = (ExpandableListView) findViewById(R.id.lvExp);
// preparing list data
prepareListData();
listAdapter = new Expandablelist(this, listDataHeader, listDataChild);
// setting list adapter
expListView.setAdapter(listAdapter);
private void prepareListData() {
listDataHeader = new ArrayList<String>();
listDataChild = new HashMap<String, List<String>>();
// Adding child data
listDataHeader.add("Top 250");
listDataHeader.add("Now Showing");
listDataHeader.add("Coming Soon..");
// Adding child data
List<String> top250 = new ArrayList<String>();
top250.add("The Shawshank Redemption");
top250.add("The Godfather");
top250.add("The Godfather: Part II");
top250.add("Pulp Fiction");
top250.add("The Good, the Bad and the Ugly");
top250.add("The Dark Knight");
top250.add("12 Angry Men");
List<String> nowShowing = new ArrayList<String>();
nowShowing.add("The Conjuring");
nowShowing.add("Despicable Me 2");
nowShowing.add("Turbo");
nowShowing.add("Grown Ups 2");
nowShowing.add("Red 2");
nowShowing.add("The Wolverine");
List<String> comingSoon = new ArrayList<String>();
comingSoon.add("2 Guns");
comingSoon.add("The Smurfs 2");
comingSoon.add("The Spectacular Now");
comingSoon.add("The Canyons");
comingSoon.add("Europa Report");
listDataChild.put(listDataHeader.get(0), top250); // Header, Child data
listDataChild.put(listDataHeader.get(1), nowShowing);
listDataChild.put(listDataHeader.get(2), comingSoon);
}
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_basics) {
// Handle the camera action
Intent i = new Intent(MainActivity.this, Explain.class);
startActivity(i);
} else if (id == R.id.nav_explaination) {
} else if (id == R.id.nav_materials) {
Intent i = new Intent(MainActivity.this, Expandablelist.class);
startActivity(i);
}
这是我的manifest.xml，其中声明了我的Expandableist活动：
<?xml version="1.0" encoding="utf-8"?>
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity
android:name=".MainActivity"
android:label="@string/app_name"
android:theme="@style/AppTheme.NoActionBar">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<!-- <activity android:name=".Explain"></activity> -->
<activity
android:name=".Explain"
android:parentActivityName=".MainActivity">
<!-- The meta-data tag is required if you support API level 15 and lower -->
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value=".MainActivity" />
</activity>
<!-- <activity android:name=".BasicMaterials"></activity> -->
<activity
android:name=".BasicMaterials"
android:parentActivityName=".Explain">
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value=".Explain" />
</activity>
<activity
android:name=".Generaldiscription"
android:label="@string/title_activity_generaldiscription"
android:parentActivityName=".MainActivity"
android:theme="@style/AppTheme.NoActionBar" />
<activity
android:name=".Expandablelist"> // here is the error
</activity>
</application>
问题：为什么我的android清单xml出现错误？我怎么解决这个问题。该应用程序工作，但当我点击侧栏上的R.id.nav.materials时，它崩溃了。它似乎无法将我的可扩展列表识别为活动，我不知道为什么
这是我的崩溃日志：
FATAL EXCEPTION: main
Process: com.example.cem.fahrzeugewaschen, PID: 25196
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.user.project/com.example.user.project.Expandablelist}: java.lang.ClassCastException: com.example.user.project.Expandablelist cannot be cast to android.app.Activity
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2555)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2767)
at android.app.ActivityThread.access$900(ActivityThread.java:177)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1449)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5951)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1388)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1183)
Caused by: java.lang.ClassCastException: com.example.cem.fahrzeugewaschen.Expandablelist cannot be cast to android.app.Activity
at android.app.Instrumentation.newActivity(Instrumentation.java:1079)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2545)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2767)
at android.app.ActivityThread.access$900(ActivityThread.java:177)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1449)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5951)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1388)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1183)