Question

原谅我可能是最愚蠢的问题，但我不知道是什么导致我的应用程序崩溃（这一次）。我只是试图将xml布局文件扩展为可扩展列表视图。

package com.anthonyce.mcathomie;

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

public class PlayoptionsActivity extends Activity {

ExpandableListView Mtopics;
ExpandableAdapter MtopicsAdapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_playoptions);
    //set up adapter
    MtopicsAdapter = new ExpandableAdapter();
    Mtopics = (ExpandableListView) findViewById(R.id.mtopicsListView);
    Mtopics.setAdapter(MtopicsAdapter);
    //Mtopics.setGroupIndicator(null);
}

public class ExpandableAdapter extends BaseExpandableListAdapter {
    private Context context;
    private String[] groups = { "People Names", "Dog Names", "Cat Names",
            "Fish Names" };
    private String[][] children = { { "Arnold" }, { "Ace" }, { "Fluffy" },
            { "Goldy" } };

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

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

    public View getChildView(int groupPosition, int childPosition,
            boolean isLastChild, View convertView, ViewGroup parent) {
        View childView;
        LayoutInflater childInflate = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        childView = childInflate.inflate(R.layout.mtopics_childrow, parent, false);

        TextView childtxt = (TextView)childView.findViewById(R.id.mtopicchildtext);
        childtxt.setText(getChild(groupPosition, childPosition).toString());

        return childView;

    }

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

    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) {   
        View groupView;
        groupView = new View(context);
        LayoutInflater groupInflate = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        groupView = groupInflate.inflate(R.layout.mtopics_grouprow, parent, false);

        TextView grouptxt = (TextView)groupView.findViewById(R.id.mtopicgrouptext);
        grouptxt.setText(getGroup(groupPosition).toString());

        return groupView;
    }

    public boolean hasStableIds() {
        return true;
    }

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

这是我试图充气的组布局的xml

    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/mtopicgrouplin"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content" 
    android:gravity="fill">

    <TextView
        android:gravity="left"
        android:id="@+id/mtopicgrouptext"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:ems="10"
        android:textStyle="bold" />



    <CheckBox
        android:id="@+id/checkBoxgroup"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</LinearLayout>

在它工作之前但没有显示任何文本，现在使用此代码它只是崩溃了。我不认为这个问题会出现在这个问题上，但是这里就是

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/mtopicchildlin"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content" 
    android:gravity="fill">

    <CheckBox
        android:paddingLeft="10dp"
        android:id="@+id/checkBoxchild"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

    <TextView 
        android:id="@+id/mtopicchildtext"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        />
</LinearLayout>

这是我发现难以辨认的logCat

09-05 17:09:33.919: E/AndroidRuntime(429): FATAL EXCEPTION: main
09-05 17:09:33.919: E/AndroidRuntime(429): java.lang.NullPointerException
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.view.ViewConfiguration.get(ViewConfiguration.java:228)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.view.View.<init>(View.java:1878)
09-05 17:09:33.919: E/AndroidRuntime(429):  at com.anthonyce.mcathomie.PlayoptionsActivity$ExpandableAdapter.getGroupView(PlayoptionsActivity.java:118)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.widget.ExpandableListConnector.getView(ExpandableListConnector.java:445)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.widget.AbsListView.obtainView(AbsListView.java:1430)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.widget.ListView.measureHeightOfChildren(ListView.java:1216)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.widget.ListView.onMeasure(ListView.java:1127)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.view.View.measure(View.java:8313)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1017)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.widget.LinearLayout.measureVertical(LinearLayout.java:386)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.widget.LinearLayout.onMeasure(LinearLayout.java:309)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.view.View.measure(View.java:8313)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.view.View.measure(View.java:8313)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.widget.LinearLayout.measureVertical(LinearLayout.java:531)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.widget.LinearLayout.onMeasure(LinearLayout.java:309)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.view.View.measure(View.java:8313)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.view.View.measure(View.java:8313)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.view.ViewRoot.performTraversals(ViewRoot.java:839)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.view.ViewRoot.handleMessage(ViewRoot.java:1859)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.os.Handler.dispatchMessage(Handler.java:99)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.os.Looper.loop(Looper.java:123)
09-05 17:09:33.919: E/AndroidRuntime(429):  at android.app.ActivityThread.main(ActivityThread.java:3683)
09-05 17:09:33.919: E/AndroidRuntime(429):  at java.lang.reflect.Method.invokeNative(Native Method)
09-05 17:09:33.919: E/AndroidRuntime(429):  at java.lang.reflect.Method.invoke(Method.java:507)
09-05 17:09:33.919: E/AndroidRuntime(429):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
09-05 17:09:33.919: E/AndroidRuntime(429):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
09-05 17:09:33.919: E/AndroidRuntime(429):  at dalvik.system.NativeStart.main(Native Method)

Answer 1

您永远不会为context变量设置值，因此当您执行groupView = new View(context)时，上下文为空并抛出NullPointerException。

请改用当前活动上下文：

groupView = new View(PlayoptionsActivity.this);

您还可以创建构造函数：

ExpandableAdapter(Context context)
{
    this.context = context;
}

Answer 2

删除

groupView = new View(context);

并运行程序。

可扩展列表适配器不断崩溃活动

2 个答案: