假设我有这个布局:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<ImageButton
android:id="@+id/add_dep_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentEnd="true"
android:layout_alignParentRight="true"
android:layout_marginEnd="5dp"
android:layout_marginRight="5dp"
android:src="@android:drawable/ic_input_add" />
<EditText
android:id="@+id/add_dep_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="@id/add_dep_btn"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignTop="@id/add_dep_btn"
android:layout_marginLeft="5dp"
android:layout_marginStart="5dp"
android:layout_toLeftOf="@id/add_dep_btn"
android:layout_toStartOf="@id/add_dep_btn" />
<android.support.v7.widget.RecyclerView
android:id="@+id/dep_list"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@id/add_dep_btn" />
<TextView
android:id="@+id/empty_text"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@id/add_dep_text"
android:layout_margin="20dp"
android:gravity="center"
android:text="@string/no_dep"
android:textSize="22sp" />
</RelativeLayout>
我在一个DialogFragment中使用它:
class DepartmentChoiceDialog : DialogFragment() {
override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {
val builder = AlertDialog.Builder(activity)
builder.setTitle(R.string.choose_or_create_dep)
.setView(R.layout.department_chooser_dialog)
.setNegativeButton(android.R.string.cancel, { d, i ->
d.cancel()
})
return builder.create()
}
}
如果我使用合成方式引用小部件:
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
dep_list.layoutManager = LinearLayoutManager(activity)
dep_list.itemAnimator = DefaultItemAnimator()
dep_list.setHasFixedSize(true)
}
运行时出现以下错误:
java.lang.NullPointerException: 尝试在空对象引用上调用虚拟方法 'android.view.View android.view.View.findViewById(int)' at MyDialog._$_findCachedViewById(DepartmentChoiceDialog.kt:0)
我不明白如何在DialogFragment中使用synthetic。在Fragment和Activity中它都正常工作。