我使用代码段访问包含APK文件的Zip文件。它在调试模式下工作正常，但在发布模式下抛出异常。
ZipFile zip = new ZipFile(file);
ZipEntry mft = zip.getEntry("AndroidManifest.xml");
is = zip.getInputStream(mft);
如果在调试模式下发布，它不会产生任何问题。但是，在发布模式下，应用程序崩溃了。
W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0x418c6c08)
************ 29072016 ************
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.vxeed.xnap/com.vxeed.xnap.forms.MainMenu}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2413)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2471)
at android.app.ActivityThread.access$900(ActivityThread.java:175)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1308)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:146)
at android.app.ActivityThread.main(ActivityThread.java:5602)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.vxeed.xnap.common.ay.a(Unknown Source)
at com.vxeed.xnap.forms.MainMenu.onCreate(Unknown Source)
at android.app.Activity.performCreate(Activity.java:5451)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2377)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2471)
at android.app.ActivityThread.access$900(ActivityThread.java:175)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1308)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:146)
at android.app.ActivityThread.main(ActivityThread.java:5602)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
at dalvik.system.NativeStart.main(Native Method)
如果我摆脱这种方法，它工作正常。我是否需要在proguard规则中添加额外的内容？请指教。提前致谢