可扩展列表适配器问题

Question

我是Android开发新手，所以我希望有人可以帮我解决这个问题。

我想创建一个可扩展列表，我试过Google搜索，并通过谷歌文档阅读。但不知何故，我无法把头围住它。我的代码在eclipse中不会出错。但是在模拟器中运行时，它会在启动时崩溃。我想我做错了什么，当我设置适配器到视图。

这里是我的代码：这里

import android.os.Bundle; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.TextView; 
import android.widget.ExpandableListView; 
import android.widget.ExpandableListAdapter; 
import android.widget.BaseExpandableListAdapter; 
import android.view.LayoutInflater; 
import android.content.Context; 

public class hmenyActivity extends MyActivity { 

    ExpandableListAdapter adapter; 

    private Context context; 

    /** Called when the activity is first created. */ 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.hmeny); 

     adapter = new MyExpandableListAdapter(); 

     ExpandableListView listView = (ExpandableListView) findViewById(R.id.listView); 

     listView.setOnChildClickListener(new OnChildClickListener() 
     { 
      @Override 
      public boolean onChildClick(ExpandableListView arg0, View arg1, int arg2, int arg3, long arg4) 
      { 
      Toast.makeText(getBaseContext(), "Child clicked", Toast.LENGTH_LONG).show(); 
      return false; 
      } 

     }); 


     listView.setAdapter(adapter); 

    } 

    public class MyExpandableListAdapter extends BaseExpandableListAdapter { 

     private String[] groups = { 
       "Test1", 
       "Test2", 
       "Test3" 
      }; 

     private String[][] children = { 

       { 
        "foo1", 
        "foo2", 
        "foo3" 
       }, 

       { 
        "foo1", 
        "foo2", 
        "foo3" 
       }, 

       { 
        "foo1", 
        "foo2", 
        "foo3" 
       } 
      }; 

     public Object getChild(int groupPosition, int childPosition) { 
      return children[groupPosition][childPosition]; 
     } 

     public long getChildId(int groupPosition, int childPosition) { 
      return childPosition; 
     } 

     public int getChildrenCount(int groupPosition) { 
      return children[groupPosition].length; 
     } 

     public View getChildView(int groupPosition, int childPosition, boolean isLastChild, 
       View convertView, ViewGroup parent) { 

      if (convertView == null) { 
       LayoutInflater infalInflater = (LayoutInflater) context 
       .getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
       convertView = infalInflater.inflate(R.layout.underkat_layout, null); 
      } 

      TextView textView = (TextView) convertView.findViewById(R.id.tvChild); 
      textView.setText(getChild(groupPosition, childPosition).toString()); 
      return convertView; 
     } 

     public Object getGroup(int groupPosition) { 
      return groups[groupPosition]; 
     } 

     public int getGroupCount() { 
       return groups.length; 
     } 

     public long getGroupId(int groupPosition) { 
      return groupPosition; 
     } 

     public View getGroupView(int groupPosition, boolean isExpanded, View convertView, 
       ViewGroup parent) { 
      if (convertView == null) { 
       LayoutInflater infalInflater = (LayoutInflater) context 
       .getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
       convertView = infalInflater.inflate(R.layout.kat_layout, null); 
      } 
      TextView textView = (TextView) convertView.findViewById(R.id.tvGroup); 
      textView.setText(getGroup(groupPosition).toString()); 
      return convertView; 
     } 

     public boolean isChildSelectable(int groupPosition, int childPosition) { 
      return true; 
     } 

     public boolean hasStableIds() { 
      return true; 
     } 
    } 
} 

@ingo是logcat的输出：

02-14 14:49:26.673: ERROR/AndroidRuntime(302): Uncaught handler: thread main exiting due to uncaught exception 
02-14 14:49:26.693: ERROR/AndroidRuntime(302): java.lang.NullPointerException 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at com.android.quizapp.hmenyActivity$MyExpandableListAdapter.getGroupView(hmenyActivity.java:151) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.widget.ExpandableListConnector.getView(ExpandableListConnector.java:446) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.widget.AbsListView.obtainView(AbsListView.java:1273) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.widget.ListView.measureHeightOfChildren(ListView.java:1147) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.widget.ListView.onMeasure(ListView.java:1060) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.view.View.measure(View.java:7703) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:2989) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:888) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.widget.LinearLayout.measureVertical(LinearLayout.java:350) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.widget.LinearLayout.onMeasure(LinearLayout.java:278) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.view.View.measure(View.java:7703) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:2989) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:245) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.view.View.measure(View.java:7703) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.widget.LinearLayout.measureVertical(LinearLayout.java:464) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.widget.LinearLayout.onMeasure(LinearLayout.java:278) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.view.View.measure(View.java:7703) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:2989) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:245) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.view.View.measure(View.java:7703) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.view.ViewRoot.performTraversals(ViewRoot.java:747) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.view.ViewRoot.handleMessage(ViewRoot.java:1613) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.os.Handler.dispatchMessage(Handler.java:99) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.os.Looper.loop(Looper.java:123) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at android.app.ActivityThread.main(ActivityThread.java:4203) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at java.lang.reflect.Method.invokeNative(Native Method) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at java.lang.reflect.Method.invoke(Method.java:521) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549) 
02-14 14:49:26.693: ERROR/AndroidRuntime(302):  at dalvik.system.NativeStart.main(Native Method) 
02-14 14:49:26.713: INFO/Process(51): Sending signal. PID: 302 SIG: 3 
02-14 14:49:26.713: INFO/dalvikvm(302): threadid=7: reacting to signal 3 
02-14 14:49:26.713: ERROR/dalvikvm(302): Unable to open stack trace file '/data/anr/traces.txt': Permission denied 
02-14 14:49:36.493: WARN/ActivityManager(51): Launch timeout has expired, giving up wake lock! 
02-14 14:49:36.506: WARN/ActivityManager(51): Activity idle timeout for HistoryRecord{43919b58 com.android.skiquiz/.hmenyActivity} 
02-14 14:49:41.533: WARN/ActivityManager(51): Activity destroy 

Answer 1

我想通了。对于任何感兴趣的人，你所要做的就是在“MyExpandableListAdapter”中放置“Context”声明，并将“this”添加到适配器声明中。看到我的代码如下：

import android.os.Bundle; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.TextView; 
import android.widget.ExpandableListView; 
import android.widget.ExpandableListAdapter; 
import android.widget.BaseExpandableListAdapter; 
import android.view.LayoutInflater; 
import android.content.Context; 

public class hmenyActivity extends MyActivity { 

    ExpandableListAdapter adapter; 

    /** Called when the activity is first created. */ 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.hmeny); 

     adapter = new MyExpandableListAdapter(this); 

     ExpandableListView listView = (ExpandableListView) findViewById(R.id.listView); 

     listView.setOnChildClickListener(new OnChildClickListener() 
     { 
      @Override 
      public boolean onChildClick(ExpandableListView arg0, View arg1, int arg2, int arg3, long arg4) 
      { 
      Toast.makeText(getBaseContext(), "Child clicked", Toast.LENGTH_LONG).show(); 
      return false; 
      } 

     }); 


     listView.setAdapter(adapter); 

    } 

    public class MyExpandableListAdapter extends BaseExpandableListAdapter { 

     private String[] groups = { 
       "Test1", 
       "Test2", 
       "Test3" 
      }; 

     private String[][] children = { 

       { 
        "foo1", 
        "foo2", 
        "foo3" 
       }, 

       { 
        "foo1", 
        "foo2", 
        "foo3" 
       }, 

       { 
        "foo1", 
        "foo2", 
        "foo3" 
       } 
      }; 

    //Add these lines to your code  
    private Context context; 

    public MyExpandableListAdapter(Context context) { 
     this.context = context; 
    } 

     public Object getChild(int groupPosition, int childPosition) { 
      return children[groupPosition][childPosition]; 
     } 

     public long getChildId(int groupPosition, int childPosition) { 
      return childPosition; 
     } 

     public int getChildrenCount(int groupPosition) { 
      return children[groupPosition].length; 
     } 

     public View getChildView(int groupPosition, int childPosition, boolean isLastChild, 
       View convertView, ViewGroup parent) { 

      if (convertView == null) { 
       LayoutInflater infalInflater = (LayoutInflater) context 
       .getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
       convertView = infalInflater.inflate(R.layout.underkat_layout, null); 
      } 

      TextView textView = (TextView) convertView.findViewById(R.id.tvChild); 
      textView.setText(getChild(groupPosition, childPosition).toString()); 
      return convertView; 
     } 

     public Object getGroup(int groupPosition) { 
      return groups[groupPosition]; 
     } 

     public int getGroupCount() { 
       return groups.length; 
     } 

     public long getGroupId(int groupPosition) { 
      return groupPosition; 
     } 

     public View getGroupView(int groupPosition, boolean isExpanded, View convertView, 
       ViewGroup parent) { 
      if (convertView == null) { 
       LayoutInflater infalInflater = (LayoutInflater) context 
       .getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
       convertView = infalInflater.inflate(R.layout.kat_layout, null); 
      } 
      TextView textView = (TextView) convertView.findViewById(R.id.tvGroup); 
      textView.setText(getGroup(groupPosition).toString()); 
      return convertView; 
     } 

     public boolean isChildSelectable(int groupPosition, int childPosition) { 
      return true; 
     } 

     public boolean hasStableIds() { 
      return true; 
     } 
    } 
}