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我是android studio中的初学者。我在我的计划活动中添加了可扩展列表视图，但是当单击主页上的按钮时，它不会导航计划活动，我将强制关闭并返回到登录页面。如何解决任何人请帮帮我。？展开式列表视图活动未显示。如何修复？
我将添加下面
我的每一项活动和代码1.Scheme.java
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.ExpandableListView;
import android.widget.ExpandableListView.OnChildClickListener;
import android.widget.ExpandableListView.OnGroupClickListener;
import android.widget.ExpandableListView.OnGroupCollapseListener;
import android.widget.ExpandableListView.OnGroupExpandListener;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
public class Scheme extends Activity {
My_Adapter listAdapter;
ExpandableListView expListView;
List<String> listDataHeader;
HashMap<String, List<String>> listDataChild;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_iistview);
// get the listview
expListView = (ExpandableListView) findViewById(R.id.expandableListView);
// preparing list data
prepareListData();
listAdapter = new My_Adapter(this, listDataHeader, listDataChild);
// setting list adapter
expListView.setAdapter(listAdapter);
// Listview Group click listener
expListView.setOnGroupClickListener(new OnGroupClickListener() {
@Override
public boolean onGroupClick(ExpandableListView parent, View v,
int groupPosition, long id) {
// Toast.makeText(getApplicationContext(),
// "Group Clicked " + listDataHeader.get(groupPosition),
// Toast.LENGTH_SHORT).show();
return false;
}
});
// Listview Group expanded listener
expListView.setOnGroupExpandListener(new OnGroupExpandListener() {
@Override
public void onGroupExpand(int groupPosition) {
Toast.makeText(getApplicationContext(),
listDataHeader.get(groupPosition) + " Expanded",
Toast.LENGTH_SHORT).show();
}
});
// Listview Group collasped listener
expListView.setOnGroupCollapseListener(new OnGroupCollapseListener() {
@Override
public void onGroupCollapse(int groupPosition) {
Toast.makeText(getApplicationContext(),
listDataHeader.get(groupPosition) + " Collapsed",
Toast.LENGTH_SHORT).show();
}
});
// Listview on child click listener
expListView.setOnChildClickListener(new OnChildClickListener() {
@Override
public boolean onChildClick(ExpandableListView parent, View v,
int groupPosition, int childPosition, long id) {
// TODO Auto-generated method stub
Toast.makeText(
getApplicationContext(),
listDataHeader.get(groupPosition)
+ " : "
+ listDataChild.get(
listDataHeader.get(groupPosition)).get(
childPosition), Toast.LENGTH_SHORT)
.show();
return false;
}
});
}
/*
* Preparing the list data
*/
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);
}
}
2.activity方案
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/sce"
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.agte.vivo.Scheme">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Current Schemes"
android:id="@+id/textView"
android:textSize="30dp"
android:layout_below="@+id/textClock"
android:layout_centerHorizontal="true"
android:textColor="#040404" />
<TextClock
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/textClock"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true" />
<ExpandableListView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/expandableListView"
android:indicatorLeft="?android:attr/expandableListPreferredItemIndicatorLeft"
android:divider="#A4C739"
android:dividerHeight="0.5dp"
android:layout_below="@+id/textView"
android:layout_centerHorizontal="true"
android:layout_marginTop="86dp" />
</RelativeLayout>
3.myadapter
package com.agte.vivo;
import android.content.Context;
import android.graphics.Typeface;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseExpandableListAdapter;
import android.widget.TextView;
import java.util.HashMap;
import java.util.List;
public class My_Adapter 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 My_Adapter(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.child_layout,parent, false);
}
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.parent_layout,parent, false);
}
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;
}
}
4.parent布局
<TextView
android:id="@+id/lblListHeader"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:paddingLeft="?android:attr/expandableListPreferredItemPaddingLeft"
android:textSize="17dp"
android:textColor="#f9f93d" />
</LinearLayout>
5.child布局
<TextView
android:id="@+id/lblListItem"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textSize="17dip"
android:paddingTop="5dp"
android:paddingBottom="5dp"
android:paddingLeft="?android:attr/expandableListPreferredChildPaddingLeft" />
</LinearLayout>
6.activity iistview
<?xml version="1.0" encoding="utf-8"?>
<!--<RelativeLayout
xmlns:tools="http://schemas.android.com/tools"
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.agte.vivo.iistview">
</RelativeLayout>-->
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:text="New Text"
android:id="@+id/textView4"
android:layout_alignParentTop="true"
android:layout_alignParentStart="true"
android:padding="10dip"
android:textSize="16dip"
android:textStyle="bold" >
没有错误，但显示了运行监控器将在显示空指针问题
08-16 16:43:24.211 25818-25818/com.agte.vivo E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.agte.vivo, PID: 25818
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.agte.vivo/com.agte.vivo.Scheme}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ExpandableListView.setAdapter(android.widget.ExpandableListAdapter)' on a null object reference
在android.app.ActivityThread。 performLaunchActivity（ActivityThread.java:2342）
在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2404）
在android.app.ActivityThread.access $ 800（ActivityThread.java:154）
在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1315）
在android.os.Handler.dispatchMessage（Handler.java:102）
在android.os.Looper.loop（ Looper.java:135）
在android.app.ActivityThread.main（ActivityThread.java:5290）
在java.lang.reflect.Method.invoke（本机方法）
在java.lang.reflect.Method中。调用（Method.java:372）
在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:908）
在com.android.internal.os.ZygoteInit.main（ ZygoteInit.java:703）
引起：java.lang.NullPointerException：试图在空对象引用上调用虚拟方法'void android.widget.ExpandableListView.setAdapter（android.widget.ExpandableListAdapter）'
at com.agte.vivo.Scheme。 onCreate（Scheme.java:40）
at android.app.Activity.performCreate（Activity。的java：6039）
在android.app.Instrumentation.callActivityOnCreate（Instrumentation.java:1106）
在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2295）
在android.app .ActivityThread.handleLaunchActivity（ActivityThread.java:2404）
在android.app.ActivityThread.access $ 800（ActivityThread.java:154）
在android.app.ActivityThread $ H.handleMessage（ActivityThread.java： 1315）
在android.os.Handler.dispatchMessage（Handler.java:102）
在android.os.Looper.loop（Looper.java:135）
在android.app.ActivityThread.main （ActivityThread.java:5290）
在java.lang.reflect.Method.invoke（本机方法）
在java.lang.reflect.Method.invoke（Method.java:372）
在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:908）
在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:703）
请帮助meee
“*但是，当点击按钮主页上*”>是什么意思？而你的问题太长，只显示重要的事情。 – Apurva
雅这意味着我有4个按钮在主页计划产品和其他2点击计划时，我需要去计划页面，但它不导航到， –
我已尝试不同的方式，但我无法得到solution.please帮助，在计划活动我添加了一个expandablelistview但它不工作 –