当 Logcat 不显示任何类时如何查找错误？

Question

使用 Android Studio 开发我的应用时，我遇到了运行时错误，但 Logcat 没有在我的任何类中显示该错误。

发生这种情况时如何确定问题出在哪里/哪段代码失败了？

例子：

09-17 13:29:23.420  17656-17656/com.mycompany.android.app E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.NullPointerException
        at android.support.v4.app.Fragment.setUserVisibleHint(Fragment.java:860)
        at android.support.v4.app.FragmentStatePagerAdapter.setPrimaryItem(FragmentStatePagerAdapter.java:152)
        at android.support.v4.view.ViewPager.populate(ViewPager.java:1103)
        at android.support.v4.view.ViewPager.populate(ViewPager.java:951)
        at android.support.v4.view.ViewPager.onTouchEvent(ViewPager.java:2041)
        at android.view.View.dispatchTouchEvent(View.java:7320)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2179)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1914)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2185)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1886)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2185)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1886)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2185)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1886)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2185)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1886)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2185)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1886)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2185)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1886)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2038)
        at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1490)
        at android.app.Activity.dispatchTouchEvent(Activity.java:2471)
        at android.support.v7.internal.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:59)
        at android.support.v7.internal.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:59)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1986)
        at android.view.View.dispatchPointerEvent(View.java:7514)
        at android.view.ViewRootImpl.deliverPointerEvent(ViewRootImpl.java:3679)
        at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:3623)
        at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:4798)
        at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:4777)
        at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:4873)
        at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:208)
        at android.os.MessageQueue.nativePollOnce(Native Method)
        at android.os.MessageQueue.next(MessageQueue.java:125)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5751)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1083)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:850)
        at dalvik.system.NativeStart.main(Native Method)

Answer 1

我建议将代码封装在 isVisible() 方法中的片段中。例如，

//do something 

到

if(isVisible()) {
    //do something
}