Html.fromHtml keeps throwing NullPointerException

Question

Say I have a String that I have formatted to contain bold letters. But at some point I need to be able to strip the formatting. Below is what I have tried but keep getting NullPointerException

Here is my method

public String stripFormatting(String input){
    return Html.fromHtml(input).toString();
}

Here is a call

stripFormatting("<b>0</b>")

The error trace is not saying much, but here

java.lang.NullPointerException
at com.mypkg.utils.MyClassTest.stripFormatting(MyClassTest.java:111)
at com.mypkg.utils.MyClassTest.testLessThan100_000(MyClassTest.java:53)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:234)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:74)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)

Answer 1

I see you're trying to run this from a unit test - calling Html.fromHtml will not work as intended because unit tests can't use Android dependent code.

According to Building Local Unit Tests https://developer.android.com/training/testing/unit-testing/local-unit-tests.html under Mock Android Dependencies -

By default, the Android Plug-in for Gradle executes your local unit tests against a modified version of the android.jar library, which does not contain any actual code. Instead, method calls to Android classes from your unit test throw an exception. This is to make sure you test only your code and do not depend on any particular behavior of the Android platform (that you have not explicitly mocked).

It's easily fixed, though - just change your test from a unit test to an instrumentation test (ie, under the androidTest directory, which will actually use the full android.jar rather than a stub like for unit tests). It'll be a little slower to run but should at least execute correctly.

Certain things are mockable (eg, getString from context s via Mockito as described in the above link) but that doesn't work for static methods. I suspect if you're testing HTML stripping you'll want to actually test that it's doing what you expect, so an instrumentation test is the way to go.