"尝试在空对象引用上读取字段'int android.content.pm.ApplicationInfo.targetSdkVersion'"异常

Question

在使用Mockito运行Espresso测试时,我目前遇到此问题,"Attempt to read from the field 'int android.content.pm.ApplicationInfo.targetSdkVersion' on a null object reference"在主Activity启动后,异常会随机出现.

这是主Activity的init部分:

private MainActivity subject;
SingleActivityFactory<MainActivity> activityFactory =
    new SingleActivityFactory<MainActivity>(MainActivity.class) {
        @Override
        protected MainActivity create(Intent intent) {
            subject = spy(getActivityClassToIntercept());
            return subject;
        }
    };

@Rule public ActivityTestRule<MainActivity> mainActivityRule =
    new ActivityTestRule<>(activityFactory, true, false);

@Before
public void init() {
    mainActivityRule.launchActivity(null);
}

这是例外:

java.lang.NullPointerException: Attempt to read from field 'int 
android.content.pm.ApplicationInfo.targetSdkVersion' on a null object 
reference
at android.view.View.getLayoutDirection(View.java:10277)
at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:446)
at android.view.View.measure(View.java:23169)
at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:1059)
at android.view.View.measure(View.java:23169)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6749)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:141)
at android.view.View.measure(View.java:23169)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6749)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1535
Test running failed: Instrumentation run failed due to 'Process crashed.'

另外,崩溃的logcat:

2018-11-06 15:34:50.391 3299-3299/com.application.android E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.application.android, PID: 3299
java.lang.NullPointerException: Attempt to read from field 'int android.content.pm.ApplicationInfo.targetSdkVersion' on a null object reference
    at android.view.View.getLayoutDirection(View.java:10277)
    at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:446)
    at android.view.View.measure(View.java:23169)
    at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:1059)
    at android.view.View.measure(View.java:23169)
    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6749)
    at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)

这里的问题是这个问题不一致 - 失败率约为40%.有没有人对这个问题有任何见解？此外,我应该提一下,如果在没有使用Mockito监视活动的情况下启动活动,则不会出现此问题.

更新:

通过在View.java类中引入更改来解决此问题:

@ResolvedLayoutDir
public int getLayoutDirection() {
    //added check if ApplicationInfo is not null
    if(getContext().getApplicationInfo() == null){
            View v = this;
            Log.i("View id: ", getContext().getString(v.getId()));
            Log.e("Main error", "Bug catched");
    }
    else {
        final int targetSdkVersion = getContext().getApplicationInfo().targetSdkVersion;
        if (targetSdkVersion < Build.VERSION_CODES.JELLY_BEAN_MR1) {
            mPrivateFlags2 |= PFLAG2_LAYOUT_DIRECTION_RESOLVED;
            return LAYOUT_DIRECTION_RESOLVED_DEFAULT;
        }
    }
    return ((mPrivateFlags2 & PFLAG2_LAYOUT_DIRECTION_RESOLVED_RTL) ==
            PFLAG2_LAYOUT_DIRECTION_RESOLVED_RTL) ? LAYOUT_DIRECTION_RTL : LAYOUT_DIRECTION_LTR;
}

如果不修改系统类,是否可以实现类似的结果？

Answer 1

我认为你的问题与上一个问题有关，

使用方法时会产生类似的行为getFragmentManager()，

解决方案是：

改为使用getSupportFragmentManager() 并从 v4.app.Fragment 类扩展