如何在Fragment内部实现自动图像滑块

Question

我在项目中使用以下库来自动滑动图像。它在Activities内部运行良好，但当涉及到Fragment时，当上下文作为getContext();或getActivity();而不是this;传递时，它会抛出空指针异常。我现在坚持了下来。请帮忙。

库名称：链接到库

我的代码内部片段：

SliderView sliderView = view.findViewById(R.id.ImageSlider);
SliderImageAdapter adapter = new SliderImageAdapter(getContext());
adapter.setCount(5);
sliderView.setSliderAdapter(adapter);
sliderView.setIndicatorAnimation(IndicatorAnimations.SLIDE); //set indicator animation by using SliderLayout.IndicatorAnimations. :WORM or THIN_WORM or COLOR or DROP or FILL or NONE or SCALE or SCALE_DOWN or SLIDE and SWAP!!
sliderView.setSliderTransformAnimation(SliderAnimations.CUBEINROTATIONTRANSFORMATION);
sliderView.setAutoCycleDirection(SliderView.AUTO_CYCLE_DIRECTION_BACK_AND_FORTH);
sliderView.setIndicatorSelectedColor(Color.WHITE);
sliderView.setIndicatorUnselectedColor(Color.GRAY);
sliderView.startAutoCycle();

我的日志：

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.coderedinnovations.allioservices, PID: 7955
java.lang.NullPointerException: Attempt to invoke virtual method 'void com.smarteist.autoimageslider.SliderView.setSliderAdapter(com.smarteist.autoimageslider.SliderViewAdapter)' on a null object reference
at com.coderedinnovations.allioservices.AllioMain.HomeFragment.onCreateView(HomeFragment.java:53)
at androidx.fragment.app.Fragment.performCreateView(Fragment.java:2698)
at androidx.fragment.app.FragmentStateManager.createView(FragmentStateManager.java:320)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1187)
at androidx.fragment.app.FragmentManager.addAddedFragments(FragmentManager.java:2224)
at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:1997)
at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1953)
at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:1849)
at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:2629)
at androidx.fragment.app.FragmentManager.dispatchActivityCreated(FragmentManager.java:2577)
at androidx.fragment.app.Fragment.performActivityCreated(Fragment.java:2722)
at androidx.fragment.app.FragmentStateManager.activityCreated(FragmentStateManager.java:346)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1188)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1356)
at androidx.fragment.app.FragmentManager.moveFragmentToExpectedState(FragmentManager.java:1434)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1497)
at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:2625)
at androidx.fragment.app.FragmentManager.dispatchActivityCreated(FragmentManager.java:2577)
at androidx.fragment.app.FragmentController.dispatchActivityCreated(FragmentController.java:247)
at androidx.fragment.app.FragmentActivity.onStart(FragmentActivity.java:541)
at androidx.appcompat.app.AppCompatActivity.onStart(AppCompatActivity.java:201)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1433)
at android.app.Activity.performStart(Activity.java:7987)
at android.app.ActivityThread.handleStartActivity(ActivityThread.java:3521)
at android.app.servertransaction.TransactionExecutor.performLifecycleSequence(TransactionExecutor.java:226)
at android.app.servertransaction.TransactionExecutor.cycleToPath(TransactionExecutor.java:206)
at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:178)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:102)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2222)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:228)
at android.app.ActivityThread.main(ActivityThread.java:7772)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:981)

布局代码：

<androidx.cardview.widget.CardView
app:cardCornerRadius="10dp"
android:layout_margin="14dp"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<com.smarteist.autoimageslider.SliderView
android:id="@+id/imageSlider"
android:layout_width="match_parent"
android:layout_height="200dp"
app:sliderAnimationDuration="600"
app:sliderAutoCycleDirection="back_and_forth"
app:sliderAutoCycleEnabled="true"
app:sliderIndicatorAnimationDuration="600"
app:sliderIndicatorGravity="center_horizontal|bottom"
app:sliderIndicatorMargin="15dp"
app:sliderIndicatorOrientation="horizontal"
app:sliderIndicatorPadding="3dp"
app:sliderIndicatorRadius="0.5dp"
app:sliderIndicatorSelectedColor="#5A5A5A"
app:sliderIndicatorUnselectedColor="#FFF"
app:sliderScrollTimeInSec="1"
app:sliderStartAutoCycle="true" />
</androidx.cardview.widget.CardView>

我的适配器没有问题，它可以用于我的其他活动。

Answer 1

如果没有看到logcat错误日志，很难理解这里的问题是什么。然而，我认为我应该提出一些建议，这样你就可以自己调查这个问题了。

您可以考虑从Fragment初始化适配器，如下所示。

SliderImageAdapter adapter = new SliderImageAdapter(getActivity());

此外，请检查您正在使用的布局是否具有ImageSlider属性。如果您在试图膨胀的片段布局中没有布局id，那么它也应该有一个空指针异常。

适配器看起来不错。

更新

从logcat来看，您用于Fragment的布局似乎没有ImageSlider，因此无法初始化sliderView。

从您发布的布局来看，布局id似乎是imageSlider，而不是ImageSlider。布局ID区分大小写。

因此，您应该将以下行修改如下。

view.findViewById(R.id.imageSlider);