android - 创建android expandablelist View 不要强制关闭

Question

我正在创建使用可扩展列表 View 的android应用，每个子项都包括图像 View 和扩展了 BaseExpandableAdapter 的文本。

图像在可绘制的forlder中，我使用数组检索它。
当我尝试选择一个组来扩展它时，应用程序强制关闭并在日志猫中播放了我不理解的错误。

谁能帮我解决这个错误？

LogCat

03-23 20:21:15.927: E/AndroidRuntime(8513): FATAL EXCEPTION: main
03-23 20:21:15.927: E/AndroidRuntime(8513): java.lang.NullPointerException
03-23 20:21:15.927: E/AndroidRuntime(8513):     at com.devleb.expandablelistdemo3.ExpandableAdapter.getChildView(ExpandableAdapter.java:129)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.widget.ExpandableListConnector.getView(ExpandableListConnector.java:451)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.widget.AbsListView.obtainView(AbsListView.java:2177)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.widget.ListView.makeAndAddView(ListView.java:1840)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.widget.ListView.fillDown(ListView.java:675)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.widget.ListView.fillSpecific(ListView.java:1333)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.widget.ListView.layoutChildren(ListView.java:1633)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.widget.AbsListView.onLayout(AbsListView.java:2012)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.view.View.layout(View.java:14289)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.view.ViewGroup.layout(ViewGroup.java:4562)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1076)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.view.View.layout(View.java:14289)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.view.ViewGroup.layout(ViewGroup.java:4562)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.view.View.layout(View.java:14289)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.view.ViewGroup.layout(ViewGroup.java:4562)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at com.android.internal.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:349)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.view.View.layout(View.java:14289)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.view.ViewGroup.layout(ViewGroup.java:4562)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.view.View.layout(View.java:14289)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.view.ViewGroup.layout(ViewGroup.java:4562)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:1976)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1730)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1004)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5481)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.view.Choreographer.doCallbacks(Choreographer.java:562)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.view.Choreographer.doFrame(Choreographer.java:532)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.os.Handler.handleCallback(Handler.java:730)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.os.Handler.dispatchMessage(Handler.java:92)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.os.Looper.loop(Looper.java:137)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at android.app.ActivityThread.main(ActivityThread.java:5103)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at java.lang.reflect.Method.invokeNative(Native Method)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at java.lang.reflect.Method.invoke(Method.java:525)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
03-23 20:21:15.927: E/AndroidRuntime(8513):     at dalvik.system.NativeStart.main(Native Method)

ExpandableAdapter.java

package com.devleb.expandablelistdemo3;

import android.app.Activity;
import android.content.Context;
import android.text.Html;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseExpandableListAdapter;
import android.widget.ExpandableListAdapter;

public class ExpandableAdapter extends BaseExpandableListAdapter implements ExpandableListAdapter {

    public Context context;
    private LayoutInflater vi;
    private String[][] data;
    int _objInt;

    private static final int GROUP_ITEM_RESOURCE = R.layout.group_layout;
    private static final int CHILD_ITEM_RESOURCE = R.layout.child_layout;

    public ExpandableAdapter(Context context, Activity activity, String[][] data) {
        this.data = data;
        this.context = context;
        vi = (LayoutInflater) activity
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        _objInt = data.length;

    }

    @Override
    public String getChild(int groupPosition, int childPosition) {
        // TODO Auto-generated method stub
        return data[groupPosition][childPosition];
    }

    @Override
    public long getChildId(int arg0, int arg1) {
        // TODO Auto-generated method stub
        return arg1;
    }

    @Override
    public View getChildView(int groupPosition, int childPosition,
            boolean isLastChild, View v, ViewGroup parent) {
        // TODO Auto-generated method stub
        String child = getChild(groupPosition, childPosition);
        int id_res = 0;
        if (groupPosition == 0) {
            if (childPosition == 0)
                id_res = R.drawable.algeria_flag;
            if (childPosition == 1)
                id_res = R.drawable.cote_divoire_flag;
            if (childPosition == 3)
                id_res = R.drawable.nigeria_flag;
            if (childPosition == 4)
                id_res = R.drawable.cameroon_flag;
            if (childPosition == 5)
                id_res = R.drawable.ghana_flag;

        } else if (groupPosition == 1) {
            if (childPosition == 0)
                id_res = R.drawable.australia;
            if (childPosition == 1)
                id_res = R.drawable.japan;
            if (childPosition == 2)
                id_res = R.drawable.iran_flag;
            if (childPosition == 3)
                id_res = R.drawable.korea_flag;

        } else if (groupPosition == 2) {
            if (childPosition == 0)
                id_res = R.drawable.belgium_flag;
            if (childPosition == 1)
                id_res = R.drawable.croatian_flag;
            if (childPosition == 2)
                id_res = R.drawable.france_flag;
            if (childPosition == 3)
                id_res = R.drawable.gress;
            if (childPosition == 4)
                id_res = R.drawable.netherlands_flag;
            if (childPosition == 5)
                id_res = R.drawable.russia_flag;
            if (childPosition == 6)
                id_res = R.drawable.switzerland;
            if (childPosition == 7)
                id_res = R.drawable.bousna;
            if (childPosition == 8)
                id_res = R.drawable.england_flag;
            if (childPosition == 9)
                id_res = R.drawable.germany_flag;
            if (childPosition == 10)
                id_res = R.drawable.italy_flag;
            if (childPosition == 11)
                id_res = R.drawable.portugal;
            if (childPosition == 12)
                id_res = R.drawable.spain;

        } else if (groupPosition == 3) {
            if (childPosition == 0)
                id_res = R.drawable.costa_rica_flag;
            if (childPosition == 1)
                id_res = R.drawable.mexico_flag;
            if (childPosition == 2)
                id_res = R.drawable.honduras_flag;
            if (childPosition == 3)
                id_res = R.drawable.united_states_flag;

        } else if (groupPosition == 4) {
            if (childPosition == 0)
                id_res = R.drawable.argentina_flag;
            if (childPosition == 1)
                id_res = R.drawable.czech_republic_flag;
            if (childPosition == 2)
                id_res = R.drawable.ecuador_flag;
            if (childPosition == 3)
                id_res = R.drawable.brazil_flag;
            if (childPosition == 4)
                id_res = R.drawable.colombia_flag;
            if (childPosition == 5)
                id_res = R.drawable.uruguay_flag;

        }

        if (child != null) {
            v = vi.inflate(CHILD_ITEM_RESOURCE, null);
            ViewHolder holder = new ViewHolder(v);
            //holder.text.setText(Html.fromHtml(child));
            holder.text.setText(child);

            holder.imageview.setImageResource(id_res);
        }
        return v;

    }

    @Override
    public int getChildrenCount(int arg0) {
        // TODO Auto-generated method stub
        return data[arg0].length;
    }

    @Override
    public Object getGroup(int arg0) {
        // TODO Auto-generated method stub
        return "group: " + arg0;
    }

    @Override
    public int getGroupCount() {
        // TODO Auto-generated method stub
        return data.length;
    }

    @Override
    public long getGroupId(int arg0) {
        // TODO Auto-generated method stub
        return arg0;
    }

    @Override
    public View getGroupView(int groupPosition, boolean arg1, View v,
            ViewGroup arg3) {
        // TODO Auto-generated method stub

        String group = null;
        // int id_res = 0;
        long group_id = getGroupId(groupPosition);
        if (group_id == 0) {
            group = "Africa";
            // id_res = R.drawable.audi;
        } else if (group_id == 1) {
            group = "Asia";
            // id_res = R.drawable.bmw;
        } else if (group_id == 2) {
            group = "Europe";
            // id_res = R.drawable.ferrari;
        } else if (group_id == 3) {
            group = "North and Central America";
        } else if (group_id == 4) {
            group = "South America";
        }

        if (group != null) {
            v = vi.inflate(GROUP_ITEM_RESOURCE, null);
            ViewHolder holder = new ViewHolder(v);

            holder.text.setText(Html.fromHtml(group));
            // holder.imageview.setImageResource(id_res);

        }
        return v;

    }

    @Override
    public boolean hasStableIds() {
        // TODO Auto-generated method stub
        return true;
    }

    @Override
    public boolean isChildSelectable(int arg0, int arg1) {
        // TODO Auto-generated method stub
        return true;
    }

}

MainActivity.java

package com.devleb.expandablelistdemo3;

import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.view.Menu;
import android.widget.ExpandableListView;

public class MainActivity extends Activity {
    final Context context = this;
    private static final String[][] data = {
            { "Alegria", " Côte d'Ivoire", " Nigeria", "Cameroon", "Ghana" },
            { "Australia", " Japan", "Iran", "Korea" },
            { "Belgium", " Croatia", " France", "Greece", " Netherlands",
                    " Russia", " Switzerland", "Bosnia and Herzegovina",
                    " England", " Germany", "Italy", "Portugal", "Spain" },
            { "Costa Rica", " Mexico", "Honduras", " USA" },
            { "Argentina", " Chile", "Ecuador", " Brazil", "Colombia",
                    "Uruguay" } };

    private ExpandableListView expandableListView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        expandableListView = (ExpandableListView) findViewById(R.id.listView);
        expandableListView
                .setAdapter(new ExpandableAdapter(context, this, data));

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

ViewHolder.java

package com.devleb.expandablelistdemo3;

import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;

public class ViewHolder {

    public TextView text;
    public ImageView imageview;

    public ViewHolder(View v) {
        this.text = (TextView) v.findViewById(R.id.text1);
        this.imageview = (ImageView) v.findViewById(R.id.image1);
    }
}

Answer 1

该问题似乎与未设置ViewHolder的文本字段有关。

从堆栈跟踪中观察到，它在ExpandableAdapter.java:129上给出了NullPointerException。当您在ViewHolder的构造函数中正确设置字段时，在我看来，您使用的布局资源实际上并不包含id text1，因此FindViewById(R.id.text1)返回null。