NullPointer由于数据库不包含数据

Question

07-08 17:04:34.978: E/AndroidRuntime(322): FATAL EXCEPTION: main 
07-08 17:04:34.978: E/AndroidRuntime(322): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.gurpswu.gurps/com.gurpswu.gurps.Home}: java.lang.NullPointerException 
07-08 17:04:34.978: E/AndroidRuntime(322): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647) 
07-08 17:04:34.978: E/AndroidRuntime(322): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663) 
07-08 17:04:34.978: E/AndroidRuntime(322): at android.app.ActivityThread.access$1500(ActivityThread.java:117) 
07-08 17:04:34.978: E/AndroidRuntime(322): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931) 
07-08 17:04:34.978: E/AndroidRuntime(322): at android.os.Handler.dispatchMessage(Handler.java:99) 
07-08 17:04:34.978: E/AndroidRuntime(322): at android.os.Looper.loop(Looper.java:123) 
07-08 17:04:34.978: E/AndroidRuntime(322): at android.app.ActivityThread.main(ActivityThread.java:3683) 
07-08 17:04:34.978: E/AndroidRuntime(322): at java.lang.reflect.Method.invokeNative(Native Method) 
07-08 17:04:34.978: E/AndroidRuntime(322): at java.lang.reflect.Method.invoke(Method.java:507) 
07-08 17:04:34.978: E/AndroidRuntime(322): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 
07-08 17:04:34.978: E/AndroidRuntime(322): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 
07-08 17:04:34.978: E/AndroidRuntime(322): at dalvik.system.NativeStart.main(Native Method) 
07-08 17:04:34.978: E/AndroidRuntime(322): Caused by: java.lang.NullPointerException 
07-08 17:04:34.978: E/AndroidRuntime(322): at com.gurpswu.gurps.Player.getIntField(Player.java:153) 
07-08 17:04:34.978: E/AndroidRuntime(322): at com.gurpswu.gurps.Home.hudSetup(Home.java:102) 
07-08 17:04:34.978: E/AndroidRuntime(322): at com.gurpswu.gurps.Home.onCreate(Home.java:25) 
07-08 17:04:34.978: E/AndroidRuntime(322): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 
07-08 17:04:34.978: E/AndroidRuntime(322): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611) 
07-08 17:04:34.978: E/AndroidRuntime(322): ... 11 more 

我有一个游戏。当用户第一次打开应用程序并按下继续游戏按钮时，游戏将尝试使用下面的代码从数据库中检索值。

  stats.open(); 
    playerId = stats.getIntField(stats.KEY_ROWID); 
    String playerName = stats.getStringField(stats.KEY_NAME); 
    String playerCity = stats.getStringField(stats.KEY_CITY); 
    playerHealth = stats.getIntField(stats.KEY_HEALTH); 
    playerEnergy = stats.getIntField(stats.KEY_ENERGY); 
    playerRank = stats.getIntField(stats.KEY_RANK); 
    playerCash = stats.getIntField(stats.KEY_CASH); 
    stats.close(); 

然而，这些数据库字段都填充...如何安装check..so，如果数据库存在此代码只运行。如果它不存在，那么它会要求玩家开始一个新的游戏。

Answer 1

在做stats.open()之后必须检查stats，你应该调用返回行数的东西。你可以把一个条件，如果行是0

，或者你可以尝试捕捉与NullPExe

try{ 
    stats.open(); 
    playerId = stats.getIntField(stats.KEY_ROWID); 
    String playerName = stats.getStringField(stats.KEY_NAME); 
    String playerCity = stats.getStringField(stats.KEY_CITY); 
    playerHealth = stats.getIntField(stats.KEY_HEALTH); 
    playerEnergy = stats.getIntField(stats.KEY_ENERGY); 
    playerRank = stats.getIntField(stats.KEY_RANK); 
    playerCash = stats.getIntField(stats.KEY_CASH); 
    stats.close(); 
} catch(NullPointerException e) { .. do needful or return null }