Android 在自定义ListView中获取NullPointerException

当我运行我的应用程序时，会出现如下错误：

02-27 22:59:19.331: E/AndroidRuntime(2060): FATAL EXCEPTION: main
02-27 22:59:19.331: E/AndroidRuntime(2060): java.lang.NullPointerException
02-27 22:59:19.331: E/AndroidRuntime(2060):     
        at myPlanAdapter.getView(MyPlanActivity.java:145)
        02-27 22:59:19.331: E/AndroidRuntime(2060):     at android.widget.AbsListView.obtainView(AbsListView.java:1315)
    02-27 22:59:19.331: E/AndroidRuntime(2060):     at android.widget.ListView.measureHeightOfChildren(ListView.java:1198)
    02-27 22:59:19.331: E/AndroidRuntime(2060):     at android.widget.ListView.onMeasure(ListView.java:1109)
    02-27 22:59:19.331: E/AndroidRuntime(2060):     at android.view.View.measure(View.java:8171)
    02-27 22:59:19.331: E/AndroidRuntime(2060):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132)
    02-27 22:59:19.331: E/AndroidRuntime(2060):     at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1012)
    02-27 22:59:19.331: E/AndroidRuntime(2060):     at android.widget.LinearLayout.measureVertical(LinearLayout.java:381)
    02-27 22:59:19.331: E/AndroidRuntime(2060):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:304)
    02-27 22:59:19.331: E/AndroidRuntime(2060):     at android.view.View.measure(View.java:8171)
    02-27 22:59:19.331: E/AndroidRuntime(2060):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132)
    02-27 22:59:19.331: E/AndroidRuntime(2060):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
    02-27 22:59:19.331: E/AndroidRuntime(2060):     at android.view.View.measure(View.java:8171)
    02-27 22:59:19.331: E/AndroidRuntime(2060):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132)
    02-27 22:59:19.331: E/AndroidRuntime(2060):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
    02-27 22:59:19.331: E/AndroidRuntime(2060):     at android.view.View.measure(View.java:8171)
    02-27 22:59:19.331: E/AndroidRuntime(2060):     at android.view.ViewRoot.performTraversals(ViewRoot.java:801)
    02-27 22:59:19.331: E/AndroidRuntime(2060):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1727)
    02-27 22:59:19.331: E/AndroidRuntime(2060):     at android.os.Handler.dispatchMessage(Handler.java:99)
    02-27 22:59:19.331: E/AndroidRuntime(2060):     at android.os.Looper.loop(Looper.java:123)
    02-27 22:59:19.331: E/AndroidRuntime(2060):     at android.app.ActivityThread.main(ActivityThread.java:4627)
    02-27 22:59:19.331: E/AndroidRuntime(2060):     at java.lang.reflect.Method.invokeNative(Native Method)
    02-27 22:59:19.331: E/AndroidRuntime(2060):     at java.lang.reflect.Method.invoke(Method.java:521)
    02-27 22:59:19.331: E/AndroidRuntime(2060):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)

我的源代码是：

public class MyPlanActivity extends Activity implements OnItemClickListener,
        OnClickListener {
    private String TAG = "MyPlanActivity";
    private Button addButton = null;
    private ListView listView;
    myPlanAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        viewInit();
        adapter = new myPlanAdapter(getBaseContext());
        listView.setAdapter(adapter);
        listView.setOnItemClickListener(this);

    }

    private void viewInit() {
        setContentView(R.layout.myplan);
        addButton = (Button) findViewById(R.id.AddMyPlanButtonId);
        listView = (ListView) findViewById(R.id.myPlanListViewId);
        addButton.setOnClickListener(this);

    }

    public void onClick(View v) {
        switch (v.getId()) {
        case R.id.AddMyPlanButtonId:
            startActivity(new Intent(this, AddMyPlan.class));
            break;

        default:
            break;
        }
    }

    public void onItemClick(AdapterView<?> paramAdapterView, View paramView,
            int paramInt, long paramLong) {
        // TODO Auto-generated method stub

    }

    @Override
    protected void onResume() {
        super.onResume();
        adapter.notifyDataSetChanged();
    }

    private class myPlanAdapter extends ArrayAdapter<MyPlan> {
        Context context;
        MyPlanDataSource dataSource;

        public myPlanAdapter(Context context) {
            super(context, R.layout.myplan_list_view_entry);
            this.context = context;
            dataSource = new MyPlanDataSource(context);
        }

        private ArrayList<MyPlan> getAllPlan() {

            dataSource.open();
            ArrayList<MyPlan> allPlan = dataSource.getAllPlan();
            dataSource.close();
            Log.d(TAG,allPlan.get(0).getSubjectName());
            return allPlan;
        }

        @Override
        public int getCount() {
            Log.d(TAG,"Size: "+getAllPlan().size());
            return getAllPlan().size();
        }

        @Override
        public MyPlan getItem(int position) {
            return getAllPlan().get(position);
        }

        @Override
        public View getView(final int position, View convertView,
                ViewGroup parent) {
            View row = convertView;
            if (row == null)
            {
                LayoutInflater inflater = (LayoutInflater) context
                        .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                row = inflater.inflate(R.layout.myplan_list_view_entry, parent,
                        false);

                final PlanViewHolder viewHolder = new PlanViewHolder();

                viewHolder.subjectName = (TextView) findViewById(R.id.myPlanListSubNameTextViewId);
                viewHolder.targetGrade = (TextView) findViewById(R.id.myPlanListTargetGradeTextViewId);
                viewHolder.duration = (TextView) findViewById(R.id.myPlanListDurationTextViewId);
                viewHolder.examDate = (TextView) findViewById(R.id.myPlanListExamDateTextViewId);
                viewHolder.daysTogo = (TextView) findViewById(R.id.myplanListDaystogoBoardTextViewId);
                viewHolder.delete = (ImageView) findViewById(R.id.myPlanDeleteImageViewId);
                Log.d(TAG, "" + position);

                row.setTag(viewHolder);
            }
            final PlanViewHolder holder = (PlanViewHolder) row.getTag();


            holder.subjectName.setText((getAllPlan().get(position) 
                    .getSubjectName())); // line 145
            holder.targetGrade.setText("Grade : "
                    + getAllPlan().get(position).getTargetGrade());
            holder.duration.setText(getAllPlan().get(position).getExamTime());
            holder.examDate.setText(getAllPlan().get(position).getExamDate());



            holder.daysTogo.setText(getAllPlan().get(position).getDaysTogo());

            holder.delete.setOnClickListener(new OnClickListener() {

                public void onClick(View v) {
                    AlertDialog.Builder builder = new AlertDialog.Builder(
                            context);
                    builder.setTitle("DELETE")
                            .setMessage(
                                    "Are you sure you want to delete this Subject?")
                            .setCancelable(false)
                            .setPositiveButton("Yes",
                                    new DialogInterface.OnClickListener()
                                    {
                                        public void onClick(
                                                DialogInterface dialog, int id)
                                        {

                                            dataSource.open();
                                            dataSource
                                                    .deletePlan(getItem(position));
                                            dataSource.close();
                                            notifyDataSetChanged();
                                        }
                                    })
                            .setNegativeButton("No",
                                    new DialogInterface.OnClickListener()
                                    {
                                        public void onClick(
                                                DialogInterface dialog, int id)
                                        {
                                            dialog.cancel();
                                        }
                                    });
                    AlertDialog alert = builder.create();
                    alert.show();

                }
            });


            return row;
        }
    }

    static class PlanViewHolder {
        private TextView subjectName;
        private TextView targetGrade;
        private TextView duration;
        private TextView examDate;
        private TextView daysTogo;
        private ImageView delete;
    }

}

public类MyPlanActivity扩展活动实现了McClickListener，
onclick侦听器{
私有字符串TAG=“MyPlanActivity”；
私有按钮addButton=null；
私有列表视图列表视图；
myPlanAdapter适配器；
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
//TODO自动生成的方法存根
super.onCreate（savedInstanceState）；
viewInit（）；
adapter=新的myPlanAdapter（getBaseContext（））；
setAdapter（适配器）；
setOnItemClickListener（this）；
}
私有void viewInit（）{
setContentView（R.layout.myplan）；
addButton=（按钮）findViewById（R.id.AddMyPlanButtonId）；
listView=（listView）findViewById（R.id.myPlanListViewId）；
addButton.setOnClickListener（此）；
}
公共void onClick（视图v）{
开关（v.getId（））{
案例R.id.AddMyPlanButtonId：
startActivity（新意图（this，AddMyPlan.class））；
打破
违约：
打破
}
}
public void onItemClick（AdapterView-paramAdapterView，View-paramView，
int参数int，long参数long）{
//TODO自动生成的方法存根
}
@凌驾
受保护的void onResume（）{
super.onResume（）；
adapter.notifyDataSetChanged（）；
}
私有类myPlanAdapter扩展了ArrayAdapter{
语境；
MyPlanDataSource数据源；
公共myPlanAdapter（上下文）{
super（上下文、R.layout.myplan\u列表\u视图\u条目）；
this.context=上下文；
数据源=新的MyPlanDataSource（上下文）；
}
私有ArrayList getAllPlan（）{
dataSource.open（）；
ArrayList allPlan=dataSource.getAllPlan（）；
dataSource.close（）；
Log.d（标记，allPlan.get（0.getSubjectName（））；
返回所有计划；
}
@凌驾
public int getCount（）{
Log.d（标记“Size:+getAllPlan（）.Size（））；
返回getAllPlan（）.size（）；
}
@凌驾
公共MyPlan getItem（内部位置）{
返回getAllPlan（）.get（位置）；
}
@凌驾
公共视图getView（最终整型位置，视图转换视图，
视图组（父级）{
视图行=转换视图；
if（行==null）
{
LayoutFlater充气器=（LayoutFlater）上下文
.getSystemService（上下文布局\充气机\服务）；
行=充气机。充气（R.layout.myplan\u list\u view\u条目，父项，
假）；
最终PlanViewHolder viewHolder=新的PlanViewHolder（）；
viewHolder.subjectName=（TextView）findViewById（R.id.myPlanListSubNameTextViewId）；
viewHolder.targetGrade=（TextView）findViewById（R.id.MyPlanListTargetGrade TextViewId）；
viewHolder.duration=（TextView）findViewById（R.id.myPlanListDurationTextViewId）；
viewHolder.examDate=（TextView）findViewById（R.id.myPlanListExamDateTextViewId）；
viewHolder.daysTogo=（TextView）findViewById（R.id.myplanListDaystogoBoardTextViewId）；
viewHolder.delete=（ImageView）findViewById（R.id.myPlanDeleteImageViewId）；
日志d（标签“+”位置）；
row.setTag（viewHolder）；
}
最终PlanViewHolder=（PlanViewHolder）行。getTag（）；
holder.subjectName.setText（（getAllPlan（）.get）（位置）
.getSubjectName（））；//第145行
holder.targetGrade.setText（“等级：
+getAllPlan（）.get（position.getTargetGrade（））；
holder.duration.setText（getAllPlan（）.get（position.getExamTime（））；
holder.examDate.setText（getAllPlan（）.get（position.getExamDate（））；
holder.daysTogo.setText（getAllPlan（）.get（position.getDaysTogo（））；
holder.delete.setOnClickListener（新的OnClickListener（）{
公共void onClick（视图v）{
AlertDialog.Builder=新建AlertDialog.Builder(
上下文）；
builder.setTitle（“删除”）
.setMessage(
“确实要删除此主题吗？”）
.setCancelable（错误）
.setPositiveButton（“是”，
新建DialogInterface.OnClickListener（）
{
公共空间点击(
对话框（接口对话框，int-id）
{
dataSource.open（）；
数据源
.deletePlan（getItem（position））；
dataSource.close（）；
notifyDataSetChanged（）；
}
})
.setNegativeButton（“否”，
新建DialogInterface.OnClickListener（）
{
公共空间点击(
对话框（接口对话框，int-id）
{
dialog.cancel（）；
}
});
AlertDialog alert=builder.create（）；
alert.show（）；
}
});
返回行；
}
}
静态类平面视图
viewHolder.subjectName = (TextView) row.findViewById(R.id.myPlanListSubNameTextViewId);
viewHolder.targetGrade = (TextView) row.findViewById(R.id.myPlanListTargetGradeTextViewId);
viewHolder.duration = (TextView) row.findViewById(R.id.myPlanListDurationTextViewId);
viewHolder.examDate = (TextView) row.findViewById(R.id.myPlanListExamDateTextViewId);
viewHolder.daysTogo = (TextView) row.findViewById(R.id.myplanListDaystogoBoardTextViewId);
viewHolder.delete = (ImageView) findViewById(R.id.myPlanDeleteImageViewId);

 @Override
        public View getView(final int position, View convertView,
                ViewGroup parent)
        {
            final PlanViewHolder viewHolder;

            if (row == null)
            {
                LayoutInflater inflater = (LayoutInflater) context
                        .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                convertView = inflater.inflate(R.layout.myplan_list_view_entry, parent,
                        false);

                viewHolder = new PlanViewHolder();

                viewHolder.subjectName = (TextView) findViewById(R.id.myPlanListSubNameTextViewId);
                viewHolder.targetGrade = (TextView) findViewById(R.id.myPlanListTargetGradeTextViewId);
                viewHolder.duration = (TextView) findViewById(R.id.myPlanListDurationTextViewId);
                viewHolder.examDate = (TextView) findViewById(R.id.myPlanListExamDateTextViewId);
                viewHolder.daysTogo = (TextView) findViewById(R.id.myplanListDaystogoBoardTextViewId);
                viewHolder.delete = (ImageView) findViewById(R.id.myPlanDeleteImageViewId);
                Log.d(TAG, "" + position);

                convertView.setTag(viewHolder);
            }
            else 
                viewHolder=(PlanViewHolder)convertView.getTag();   
         ... 
         return convertView;
}

holder.subjectName.setText(
  (getAllPlan()
   .get(position)
   .getSubjectName()));

viewHolder.subjectName = (TextView) row.findViewById(R.id.myPlanListSubNameTextViewId);