我有一个自定义适配器。我尝试比较当前日期和输入日期。 但是我有空指针异常。我无法弄清楚为什么这个例外的原因。 我的LogCat在下面，问题在于“（（ViewGroup）todoView）.getChildAt（i）.setBackgroundColor（0x01060018）; “有人能帮助我吗？
我的适配器类;
public class ToDoItemAdapter extends ArrayAdapter<ToDoItem> {
private int resource;
Context context;
ArrayList<ToDoItem> todoItem;
public ToDoItemAdapter(Context context, int resource, ArrayList<ToDoItem> objects) {
super(context, resource, objects); // TODO Auto-generated constructor stub
this.resource = resource;
this.context = context;
this.todoItem = objects;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
LinearLayout todoView;
ToDoItem todo = getItem(position);
String priorityString = todo.getPriority();
String taskString = todo.getTask();
String dateString = todo.getDeadline();
String statusString = todo.getStatus();
if (convertView == null)
{
todoView = new LinearLayout(getContext());
String inflater = Context.LAYOUT_INFLATER_SERVICE;
LayoutInflater li;
li = (LayoutInflater)getContext().getSystemService(inflater);
li.inflate(resource, todoView, true);
}
else
{
todoView = (LinearLayout) convertView;
int len = todoItem.size();
for(int i = 0; i < len; i++)
{
String deadline = todoItem.get(i).getDeadline();
String status = todoItem.get(i).getStatus();
String currentDate = findCurrentDate();
SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy");
java.util.Date data=null;
try {
data = sdf.parse(deadline);
} catch (ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (java.text.ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
java.util.Date current =null;
try {
current = sdf.parse(currentDate);
} catch (ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (java.text.ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
System.out.println(data);
}
if(status.equals("DONE"))
{
((ViewGroup) todoView).getChildAt(i).setBackgroundColor(0xff00ff00);
System.out.println(data);
}
else
{
System.out.println(data);
if(data.compareTo(current)>0 || data.compareTo(current)==0){
((ViewGroup) todoView).getChildAt(i).setBackgroundColor(0x01060018);
}else if(data.compareTo(current)<0){
((ViewGroup) todoView).getChildAt(i).setBackgroundColor(0x01060016);
}
}
}
}
TextView priorityView = (TextView) todoView.findViewById(R.id.itemPriority);
TextView taskView = (TextView) todoView.findViewById(R.id.itemTask);
TextView dateView = (TextView) todoView.findViewById(R.id.itemDeadline);
TextView statusView = (TextView) todoView.findViewById(R.id.itemStatus);
priorityView.setText(priorityString);
taskView.setText(taskString);
dateView.setText(dateString);
statusView.setText(statusString);
return todoView;
}
private String findCurrentDate() {
// TODO Auto-generated method stub
Calendar cal = Calendar.getInstance();
int year = cal.get(Calendar.YEAR);
int month = cal.get(Calendar.MONTH);
int day = cal.get(Calendar.DAY_OF_MONTH);
String date = day+"-"+(month+1)+"-"+year;
return date;
}
}
logcat的
11-16 17:32:12.357: E/AndroidRuntime(3148): FATAL EXCEPTION: main
11-16 17:32:12.357: E/AndroidRuntime(3148): java.lang.NullPointerException
11-16 17:32:12.357: E/AndroidRuntime(3148): at com.example.enhancedtodolistapplication.ToDoItemAdapter.getView(ToDoItemAdapter.java:107)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.widget.AbsListView.obtainView(AbsListView.java:2161)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.widget.ListView.measureHeightOfChildren(ListView.java:1247)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.widget.ListView.onMeasure(ListView.java:1159)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.view.View.measure(View.java:15848)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5008)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.widget.LinearLayout.measureVertical(LinearLayout.java:695)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.view.View.measure(View.java:15848)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5008)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.view.View.measure(View.java:15848)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5008)
11-16 17:32:12.357: E/AndroidRuntime(3148): at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:302)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.view.View.measure(View.java:15848)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5008)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
11-16 17:32:12.357: E/AndroidRuntime(3148): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2189)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.view.View.measure(View.java:15848)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1905)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1104)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1284)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1004)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5481)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.view.Choreographer.doCallbacks(Choreographer.java:562)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.view.Choreographer.doFrame(Choreographer.java:532)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.os.Handler.handleCallback(Handler.java:730)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.os.Handler.dispatchMessage(Handler.java:92)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.os.Looper.loop(Looper.java:137)
11-16 17:32:12.357: E/AndroidRuntime(3148): at android.app.ActivityThread.main(ActivityThread.java:5103)
11-16 17:32:12.357: E/AndroidRuntime(3148): at java.lang.reflect.Method.invokeNative(Native Method)
11-16 17:32:12.357: E/AndroidRuntime(3148): at java.lang.reflect.Method.invoke(Method.java:525)
11-16 17:32:12.357: E/AndroidRuntime(3148): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
11-16 17:32:12.357: E/AndroidRuntime(3148): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
11-16 17:32:12.357: E/AndroidRuntime(3148): at dalvik.system.NativeStart.main(Native Method)
输出（两个不同项目的日期）
11-16 18:44:30.687: I/System.out(4087): variable deadline 15-10-2012
11-16 18:44:30.697: I/System.out(4087): variable currentDate 16-11-2013
11-16 18:44:30.717: I/System.out(4087): variable data Mon Oct 15 00:00:00 EDT 2012
11-16 18:44:30.727: I/System.out(4087): variable current Sat Nov 16 00:00:00 EST 2013
11-16 18:44:30.757: I/System.out(4087): variable deadline 17-12-2014
11-16 18:44:30.757: I/System.out(4087): variable currentDate 16-11-2013
11-16 18:44:30.767: I/System.out(4087): variable data Wed Dec 17 00:00:00 EST 2014
11-16 18:44:30.777: I/System.out(4087): variable current Sat Nov 16 00:00:00 EST 2013
答案 0 :(得分：0)
看起来您没有正确初始化（convertView == null）案例的新布局。
你做
li.inflate(resource, todoView, true);
请注意“膨胀”的结果是膨胀的视图。中间参数将成为父级 - 通常这是某种ViewGroup或ListView。无论如何，它是getView（）的“父”参数。
然后，稍后，您尝试查找todoView的子视图。但它是空的，所以这些调用将返回null。后续引用将会出错。
这是一种更简单的扩充方式：
LayoutInflater inflater = context.getLayoutInflater();
todoView = (LinearLayout) inflater.inflate (resource, parent, false);