demo 跑不起来

[jiangkaiying]

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.iigo.keystore/com.iigo.keystore.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.security.PrivateKey java.security.KeyStore$PrivateKeyEntry.getPrivateKey()' on a null object reference
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2514)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2574)
    at android.app.ActivityThread.access$1000(ActivityThread.java:166)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1411)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:148)
    at android.app.ActivityThread.main(ActivityThread.java:5563)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:853)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:737)
 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.security.PrivateKey java.security.KeyStore$PrivateKeyEntry.getPrivateKey()' on a null object reference
    at com.iigo.keystore.KeyStoreUtil.sign(KeyStoreUtil.java:246)
    at com.iigo.keystore.MainActivity.onCreate(MainActivity.java:45)
    at android.app.Activity.performCreate(Activity.java:6309)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1114)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2467)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2574) 
    at android.app.ActivityThread.access$1000(ActivityThread.java:166) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1411) 
    at android.os.Handler.dispatchMessage(Handler.java:102) 
    at android.os.Looper.loop(Looper.java:148) 
    at android.app.ActivityThread.main(ActivityThread.java:5563) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:853) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:737) 

[MaosanDao]

me too