创建自定义对话框时出错

Question

我试图用两个微调器（spinner_month和spinner_year）创建一个自定义对话框。

有关指导，我参考了Google开发指南中提供的示例。

MainActivity代码：

AlertDialog.Builder builder = new AlertDialog.Builder(this); 
builder.setView(R.layout.calender_view); 
AlertDialog alertDialog = builder.create(); 
Spinner spinner = (Spinner) alertDialog.findViewById(R.id.spinner_month); 
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this,R.array.months_array,  android.R.layout.simple_spinner_item); 
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); 
spinner.setAdapter(adapter); 

我calender_view.xml如下

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
      xmlns:app="http://schemas.android.com/apk/res-auto" 
      xmlns:tools="http://schemas.android.com/tools" 
      android:id="@+id/layout_category" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:layout_weight="1" 
      android:orientation="horizontal" 
      android:padding="5dp"> 

    <Spinner 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:id="@+id/spinner_year" 
     android:layout_weight="1"/> 

    <Spinner 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:id="@+id/spinner_month" 
     android:layout_weight="1" 
     android:spinnerMode="dialog"/> 
</LinearLayout> 

当我运行它，我得到以下错误：

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method void android.widget.Spinner.setAdapter(android.widget.SpinnerAdapter) on a null object reference

这是因为'微调对象是null，但我不知道为什么。有什么我失踪？

Answer 1

试试这个

AlertDialog.Builder builder = new AlertDialog.Builder(this); 
    LayoutInflater li = LayoutInflater.from(this); 
    View view = li.inflate(R.layout.calender_view, null, false); 
    builder.setView(view); 
    AlertDialog alertDialog = builder.create(); 

    Spinner spinner = (Spinner) view.findViewById(R.id.spinner_month); 
    ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this,R.array.months_array,  android.R.layout.simple_spinner_item); 
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); 
    spinner.setAdapter(adapter);