蛋疼的Android BaseAdapter

package com.moniter.helperclasses;

import java.util.List;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import com.hanvon.moniter.R;

public class SiteListAdapter extends BaseAdapter {

    // 地点列表
    private List<SiteInformation> sites = null;
    private LayoutInflater mInflater;

    // Constructor
    public SiteListAdapter(Context context, List<SiteInformation> sites) {
        this.sites = sites;
        this.mInflater = LayoutInflater.from(context);
    }

    // 返回列表项数
    @Override
    public int getCount() {
        return sites.size();
    }

    @Override
    public Object getItem(int position) {
        return sites.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @SuppressWarnings("null")
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // 取得位置position对应的site信息
        SiteInformation siteInfo = sites.get(position);

        //取得ListView的布局文件
        convertView = mInflater.inflate(R.layout.site_list_item, null);
        
        //初始化viewHolder
        ViewHolder viewHolder = null;
        
        //View的绑定
        if (convertView == null) {
            viewHolder = new ViewHolder();
            viewHolder.site_name = (TextView) convertView
                    .findViewById(R.id.name_site);
            viewHolder.value_noise = (TextView) convertView
                    .findViewById(R.id.noise);
            viewHolder.value_dust = (TextView) convertView
                    .findViewById(R.id.dust);
            viewHolder.status_noise = (ImageView) convertView
                    .findViewById(R.id.color_indicator_noise);
            viewHolder.status_dust = (ImageView) convertView
                    .findViewById(R.id.color_indicator_dust);
            
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }

        //取得相应的值：抱错！！！！！为什么？？？？
        viewHolder.site_name.setText("123");  //???siteInfo.getSiteName()
        viewHolder.value_noise.setText(siteInfo.getNoiseValue());
        viewHolder.value_dust.setText(siteInfo.getDustValue());
        viewHolder.status_noise.setBackgroundResource(siteInfo.getNoiseStatus());
        viewHolder.status_dust.setBackgroundResource(siteInfo.getDustStatus());
        
        //返回Poistion对应的view
        return convertView;
    }
    
    static class ViewHolder {
        public TextView site_name;
        public TextView value_noise;
        public TextView value_dust;
        public ImageView status_noise;
        public ImageView status_dust;
    }
}

老是在第75行报错。搞了一天了没有发现原因。

06-16 18:09:50.232: E/AndroidRuntime(10487): FATAL EXCEPTION: main
06-16 18:09:50.232: E/AndroidRuntime(10487): java.lang.NullPointerException
06-16 18:09:50.232: E/AndroidRuntime(10487): at com.moniter.helperclasses.SiteListAdapter.getView(SiteListAdapter.java:75)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.widget.AbsListView.obtainView(AbsListView.java:2040)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.widget.ListView.makeAndAddView(ListView.java:1772)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.widget.ListView.fillDown(ListView.java:672)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.widget.ListView.fillFromTop(ListView.java:732)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.widget.ListView.layoutChildren(ListView.java:1625)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.widget.AbsListView.onLayout(AbsListView.java:1870)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.view.View.layout(View.java:11418)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.view.ViewGroup.layout(ViewGroup.java:4328)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1652)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1510)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.widget.LinearLayout.onLayout(LinearLayout.java:1415)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.view.View.layout(View.java:11418)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.view.ViewGroup.layout(ViewGroup.java:4328)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1652)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1510)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.widget.LinearLayout.onLayout(LinearLayout.java:1415)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.view.View.layout(View.java:11418)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.view.ViewGroup.layout(ViewGroup.java:4328)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1652)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1510)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.widget.LinearLayout.onLayout(LinearLayout.java:1415)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.view.View.layout(View.java:11418)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.view.ViewGroup.layout(ViewGroup.java:4328)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.widget.RelativeLayout.onLayout(RelativeLayout.java:930)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.view.View.layout(View.java:11418)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.view.ViewGroup.layout(ViewGroup.java:4328)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.widget.FrameLayout.onLayout(FrameLayout.java:443)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.view.View.layout(View.java:11418)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.view.ViewGroup.layout(ViewGroup.java:4328)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1652)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1510)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.widget.LinearLayout.onLayout(LinearLayout.java:1415)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.view.View.layout(View.java:11418)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.view.ViewGroup.layout(ViewGroup.java:4328)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.widget.FrameLayout.onLayout(FrameLayout.java:443)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.view.View.layout(View.java:11418)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.view.ViewGroup.layout(ViewGroup.java:4328)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1489)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2442)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.os.Handler.dispatchMessage(Handler.java:99)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.os.Looper.loop(Looper.java:137)
06-16 18:09:50.232: E/AndroidRuntime(10487): at android.app.ActivityThread.main(ActivityThread.java:4441)
06-16 18:09:50.232: E/AndroidRuntime(10487): at java.lang.reflect.Method.invokeNative(Native Method)
06-16 18:09:50.232: E/AndroidRuntime(10487): at java.lang.reflect.Method.invoke(Method.java:511)
06-16 18:09:50.232: E/AndroidRuntime(10487): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
06-16 18:09:50.232: E/AndroidRuntime(10487): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
06-16 18:09:50.232: E/AndroidRuntime(10487): at dalvik.system.NativeStart.main(Native Method)

 最后只好求助.Stackoverflow发问题时网页经常出问题，只好改加QQ群，最后得到android学习交流群的“成都-Young”提点，终于解决问题：

第50行的

convertView

//取得ListView的布局文件
50         convertView = mInflater.inflate(com.hanvon.moniter.R.layout.site_list_item, null);

放到56行的if语句里面进行初始化，这样convertView在为Null的时候就能正常初始化，而不是每次都提前初始化一个值，就直接运行71行的代码。

55         //View的绑定

56         if (convertView == null) {convertView = mInflater.inflate(com.hanvon.moniter.R.layout.site_list_item, null);

}