小编Amr*_* A.的帖子

我正在尝试编写我的第一个Android应用程序,这将涉及拍照并用它做事.

我在网上查看了几个教程之后编写了一些代码,但是只要点击按钮就会得到以下NullPointerException:

10-03 14:48:00.284 26310-26310/org.broadinstitute.jsnap E/MainActivity: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.XmlResourceParser android.content.pm.ProviderInfo.loadXmlMetaData(android.content.pm.PackageManager, java.lang.String)' on a null object reference
10-03 14:48:00.293 26310-26310/org.broadinstitute.jsnap E/MYAPP: exception
                                                                 java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.XmlResourceParser android.content.pm.ProviderInfo.loadXmlMetaData(android.content.pm.PackageManager, java.lang.String)' on a null object reference
                                                                     at android.support.v4.content.FileProvider.parsePathStrategy(FileProvider.java:583)
                                                                     at android.support.v4.content.FileProvider.getPathStrategy(FileProvider.java:557)
                                                                     at android.support.v4.content.FileProvider.getUriForFile(FileProvider.java:399)
                                                                     at org.broadinstitute.jsnap.MainActivity.takePhoto(MainActivity.java:54)
                                                                     at org.broadinstitute.jsnap.MainActivity.access$000(MainActivity.java:24)
                                                                     at org.broadinstitute.jsnap.MainActivity$1.onClick(MainActivity.java:43)
                                                                     at android.view.View.performClick(View.java:6205)
                                                                     at android.widget.TextView.performClick(TextView.java:11103)
                                                                     at android.view.View$PerformClick.run(View.java:23653)
                                                                     at android.os.Handler.handleCallback(Handler.java:751)
                                                                     at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                     at android.os.Looper.loop(Looper.java:154)
                                                                     at android.app.ActivityThread.main(ActivityThread.java:6682)
                                                                     at java.lang.reflect.Method.invoke(Native Method)
                                                                     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1520)
                                                                     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1410)

我不太清楚如何解决.这是我的相关代码:

表现:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="org.broadinstitute.jsnap"> …

我有两个具有相同数量和类型的元素的Scala列表,如下所示:

val x = List("a", "b", "c")
val y = List("1", "2", "3")

我想要的结果如下:

List("a1", "b2", "c3")

如何在Scala中完成？我可以使用可变结构来解决这个问题,但我认为这对于Scala来说是不同寻常的.