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蛋疼的Android BaseAdapter

2024-07-08 11:38:40   224人阅读

 1 package com.moniter.helperclasses; 2  3 import java.util.List; 4  5 import android.content.Context; 6 import android.view.LayoutInflater; 7 import android.view.View; 8 import android.view.ViewGroup; 9 import android.widget.BaseAdapter;10 import android.widget.ImageView;11 import android.widget.TextView;12 13 import com.hanvon.moniter.R;14 15 public class SiteListAdapter extends BaseAdapter {16 17     // 地点列表18     private List<SiteInformation> sites = null;19     private LayoutInflater mInflater;20 21     // Constructor22     public SiteListAdapter(Context context, List<SiteInformation> sites) {23         this.sites = sites;24         this.mInflater = LayoutInflater.from(context);25     }26 27     // 返回列表项数28     @Override29     public int getCount() {30         return sites.size();31     }32 33     @Override34     public Object getItem(int position) {35         return sites.get(position);36     }37 38     @Override39     public long getItemId(int position) {40         return position;41     }42 43     @SuppressWarnings("null")44     @Override45     public View getView(int position, View convertView, ViewGroup parent) {46         // 取得位置position对应的site信息47         SiteInformation siteInfo = sites.get(position);48 49         //取得ListView的布局文件50         convertView = mInflater.inflate(R.layout.site_list_item, null);51         52         //初始化viewHolder53         ViewHolder viewHolder = null;54         55         //View的绑定56         if (convertView == null) {57             viewHolder = new ViewHolder();58             viewHolder.site_name = (TextView) convertView59                     .findViewById(R.id.name_site);60             viewHolder.value_noise = (TextView) convertView61                     .findViewById(R.id.noise);62             viewHolder.value_dust = (TextView) convertView63                     .findViewById(R.id.dust);64             viewHolder.status_noise = (ImageView) convertView65                     .findViewById(R.id.color_indicator_noise);66             viewHolder.status_dust = (ImageView) convertView67                     .findViewById(R.id.color_indicator_dust);68             69             convertView.setTag(viewHolder);70         } else {71             viewHolder = (ViewHolder) convertView.getTag();72         }73 74         //取得相应的值：抱错！！！！！为什么？？？？75         viewHolder.site_name.setText("123");  //???siteInfo.getSiteName()76         viewHolder.value_noise.setText(siteInfo.getNoiseValue());77         viewHolder.value_dust.setText(siteInfo.getDustValue());78         viewHolder.status_noise.setBackgroundResource(siteInfo.getNoiseStatus());79         viewHolder.status_dust.setBackgroundResource(siteInfo.getDustStatus());80         81         //返回Poistion对应的view82         return convertView;83     }84     85     static class ViewHolder {86         public TextView site_name;87         public TextView value_noise;88         public TextView value_dust;89         public ImageView status_noise;90         public ImageView status_dust;91     }92 }

 

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);
}


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