Java Android findViewById()为自定义视图返回null
因此,我反复检查了关于这个主题的所有其他线程,但没有一个线程给出了解决方案。代码如下: XML文件Java Android findViewById()为自定义视图返回null,java,android,nullpointerexception,android-custom-view,custom-view,Java,Android,Nullpointerexception,Android Custom View,Custom View,因此,我反复检查了关于这个主题的所有其他线程,但没有一个线程给出了解决方案。代码如下: XML文件 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="ma
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<android.support.v7.widget.RecyclerView
android:id="@+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<com.turingtechnologies.materialscrollbar.DragScrollBar
android:layout_width="wrap_content"
android:id="@+id/dragScrollBar"
android:layout_height="match_parent"/>
</RelativeLayout>
DragScrollBar.java
public class DragScrollBar extends MaterialScrollBar<DragScrollBar>{
public DragScrollBar(Context context, AttributeSet attrs){
super(context, attrs);
}
}
abstract class MaterialScrollBar<T> extends RelativeLayout {
MaterialScrollBar(Context context, AttributeSet attrs){
super(context, attrs);
initialise(context);
}
//Stuff
}
作为早期方案的一部分,我在initalise内部运行了setID(),并没有想到在重构过程中删除它。是xml
activity\u main.xml
?post stacktrace,如果any@Blackbelt是的
abstract class MaterialScrollBar<T> extends RelativeLayout {
MaterialScrollBar(Context context, AttributeSet attrs){
super(context, attrs);
initialise(context);
}
//Stuff
}
fail
Shutting down VM
FATAL EXCEPTION: main
Process: com.turingtechnologies.materialscrollbardemo, PID: 31890 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.turingtechnologies.materialscrollbardemo/com.turingtechnologies.materialscrollbardemo.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object com.turingtechnologies.materialscrollbar.DragScrollBar.bindRecyclerView(android.support.v7.widget.RecyclerView)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object com.turingtechnologies.materialscrollbar.DragScrollBar.bindRecyclerView(android.support.v7.widget.RecyclerView)' on a null object reference
at com.turingtechnologies.materialscrollbardemo.MainActivity.onCreate(MainActivity.java:26)
at android.app.Activity.performCreate(Activity.java:6251)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)