我在尝试调用一个方法上的一个按钮,当一个NullPointerException异常:NullPointerException:尝试调用空对象引用上的虚方法?
private FButton fButton1;
...
...
fButton1 = (FButton) findViewById(R.id.FButton1);
fButton1.setButtonColor(ContextCompat.getColor(this, fbutton_color_turquoise)); //Exception here
我使用this library here,我不知道为什么我得到的异常?
错误日志:
FATAL EXCEPTION: main
Process: com.user.app, PID: 11209
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.user.app/com.user.app.activities.StartUpScreen}: java.lang.NullPointerException: Attempt to invoke virtual method 'void info.hoang8f.widget.FButton.setButtonColor(int)' 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 'void info.hoang8f.widget.FButton.setButtonColor(int)' on a null object reference
at com.user.app.activities.StartUpScreen.onCreate(StartUpScreen.java:44)
at android.app.Activity.performCreate(Activity.java:6237)
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)
我layout.xml其中FButton是:
<info.hoang8f.widget.FButton
fbutton:buttonColor="@color/fbutton_color_turquoise"
fbutton:shadowColor="@color/fbutton_color_green_sea"
fbutton:shadowEnabled="true"
fbutton:shadowHeight="5dp"
android:text="Celcius"
android:textColor="#FFF"
fbutton:cornerRadius="5dp"
android:layout_marginTop="8dp"
app:layout_constraintTop_toBottomOf="@+id/imageButton3"
android:layout_marginLeft="8dp"
app:layout_constraintLeft_toLeftOf="parent"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_width="match_parent"
android:id="@+id/FButton1"
app:layout_constraintRight_toLeftOf="@+id/FButton2"
android:layout_marginRight="8dp"
android:layout_marginEnd="8dp"
app:layout_constraintHorizontal_bias="1.0" />
我ids.xml文件,我不得不创建,由于Android没有recoginze的ID:
<?xml version="1.0" encoding="utf-8"?>
<resources>
<item name="FButton1" type="id" />
</resources>
写完整的调用堆栈 – Vyacheslav
@Vyacheslav完成编辑下的检查! – Carlton
@AndyTurner这个NullPointerException没有任何意义,所有其他视图在我的代码中以这种方式声明,它们都工作得很好。 – Carlton