Android：XmlPullParserFactory.newInstance() 创建一个空工厂

Question

我正在尝试让XmlPullParser 工作，因为它比替代方案更有意义。但是，我遇到了第一个障碍，因为XmlPullParserFactory.newInstance() 函数正在返回一个空工厂（由调试器看到）。因此，只要调用 factory.newPullParser()，就会引发异常。

import java.io.IOException;
import java.io.InputStream;
import java.io.StringReader;

import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;
import org.xmlpull.v1.XmlPullParserFactory;

public class XMLParser
{
    public static void getXML(InputStream in)
            throws XmlPullParserException, IOException {
        try {
            XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
            XmlPullParser xpp = factory.newPullParser();

            xpp.setInput(new StringReader("<foo>Hello World!</foo>"));
            int eventType = xpp.getEventType();
            while (eventType != XmlPullParser.END_DOCUMENT) {
                if (eventType == XmlPullParser.START_DOCUMENT) {
                    System.out.println("Start document");
                } else if (eventType == XmlPullParser.START_TAG) {
                    System.out.println("Start tag " + xpp.getName());
                } else if (eventType == XmlPullParser.END_TAG) {
                    System.out.println("End tag " + xpp.getName());
                } else if (eventType == XmlPullParser.TEXT) {
                    System.out.println("Text " + xpp.getText());
                }
                eventType = xpp.next();
            }
            System.out.println("End document");
        } catch (Exception e) {
        }
    }
}

我从单元测试中调用此方法。我真的很困惑这个问题可能是什么，因为我没有发现任何有类似问题的帖子。

跟踪报告： 全线程转储

"main@1" prio=5 tid=0x1 nid=NA runnable
  java.lang.Thread.State: RUNNABLE
  at com.company.app.XMLParser.getXmln(XMLParser.java:40)
  at com.company.app.XMLParserTest.setUp(XMLParserTest.java:36)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(NativeMethodAccessorImpl.java:-1)
  at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  at java.lang.reflect.Method.invoke(Method.java:497)
  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.RunBefores.evaluate(RunBefores.java:24)
  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:78)
  at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:212)
  at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:68)

"Finalizer@836" daemon prio=8 tid=0x3 nid=NA waiting
  java.lang.Thread.State: WAITING
  at java.lang.Object.wait(Object.java:-1)
  at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
  at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:164)
  at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:209)

"Reference Handler@837" daemon prio=10 tid=0x2 nid=NA waiting
  java.lang.Thread.State: WAITING
  at java.lang.Object.wait(Object.java:-1)
  at java.lang.Object.wait(Object.java:502)
  at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:157)

"Attach Listener@834" daemon prio=5 tid=0x5 nid=NA runnable
  java.lang.Thread.State: RUNNABLE

"Signal Dispatcher@835" daemon prio=9 tid=0x4 nid=NA runnable
  java.lang.Thread.State: RUNNABLE

Answer 1

您不能对 Android 的组件进行单元测试。用于编译的 JAR 文件仅包含引发异常的方法存根。为您的问题考虑一个简单的测试用例

public class UnitTest {
    @Test
    public void instanceNotNull() throws Exception {
        assertNotNull(XmlPullParserFactory.newInstance());
    }
}

在没有定义任何配置的情况下运行它，你会得到一个

java.lang.RuntimeException: Method newInstance in org.xmlpull.v1.XmlPullParserFactory not mocked. See http://g.co/androidstudio/not-mocked for details.
    at org.xmlpull.v1.XmlPullParserFactory.newInstance(XmlPullParserFactory.java)
    at ...

添加时

testOptions {
    unitTests.returnDefaultValues = true
}

到你的 gradle android 配置，你会发现测试在断言上失败了。

如果您想使用 android 库进行测试，则需要在带有仪器测试的设备上进行。所以把你的测试用例放在 androidTest 源集中，添加

dependencies {
    testCompile 'junit:junit:4.12'
    androidTestCompile 'com.android.support.test:runner:0.4'
}

到模块的 gradle 文件并在设备上运行它。

有关详细信息，请参阅 Testing Concepts 和 Testing Support Library。

Answer 2

只需将此行添加到您的愿望清单中

                (new Thread() {
                    @Override
                    public void run() {
                        try {
                            XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
                            XmlPullParser xpp = factory.newPullParser();

                            xpp.setInput(new StringReader("<foo>Hello World!</foo>"));
                            int eventType = xpp.getEventType();
                            while (eventType != XmlPullParser.END_DOCUMENT) {
                                if (eventType == XmlPullParser.START_DOCUMENT) {
                                    System.out.println("Start document");
                                } else if (eventType == XmlPullParser.START_TAG) {
                                    System.out.println("Start tag " + xpp.getName());
                                } else if (eventType == XmlPullParser.END_TAG) {
                                    System.out.println("End tag " + xpp.getName());
                                } else if (eventType == XmlPullParser.TEXT) {
                                    System.out.println("Text " + xpp.getText());
                                }
                                eventType = xpp.next();
                            }
                            System.out.println("End document");
                        } catch (Exception e) {
                        }
                    }
                }
                ).start();