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如何检查对象关系是否为空？

2014-12-06 78 views
2 
ParseObject current; 
... 
ParseQuery<ParseObject> query = ParseQuery.getQuery("Primary"); 
    try{ 
     if(current == null){ 
      System.out.println("current is NULL");     //prints properly 
      System.out.println("Initial query: " + query.count()); //prints 'Initial Query: 90' 
      query.whereDoesNotExist("Parent4"); 
      System.out.println("Test1");        //prints properly 
      System.out.println("Query Count: " + query.count());  //seems to cause nullpointer 
      List<ParseObject> list = query.find(); 
      System.out.println("Test2"); 
      for(ParseObject p: list){ 
       listItems.add((String)p.get("Title")); //listItems used to populate listview when listview is generated 

...(closing brackets,else statement, exception catching, rest of program)

我试图搜索我的解析数据库标题为“主要”的所有在“Parent4”（关系）字段中具有空关系的项目，并将它们显示到我的字符串列表（listItems）中添加到listView创建时。我知道我的数据库中的两个对象没有任何关系，所以我希望显示这两个对象的标题。我之前有一个有点工作的版本之前，这工作得很好，除了我检查列表中的每个对象的标题，而不是对象本身导致后来在我的程序中，当两个对象具有相同的标题，这是什么这在我的程序中应该是可以接受的。如何检查对象关系是否为空？

任何想法为什么行“query.whereDoesNotExist（”Parent4“）;”当我想要打印查询的计数时，似乎导致空指针异常？或者任何想法，我可以如何处理这个呢？

这里的日志：

12-06 18:20:50.030: I/Process(2469): Sending signal. PID: 2469 SIG: 9 
12-06 18:20:57.740: I/System.out(2517): current is NULL 
12-06 18:20:58.159: I/System.out(2517): Initial query: 92 
12-06 18:20:58.159: I/System.out(2517): Test1 
12-06 18:20:58.378: D/AndroidRuntime(2517): Shutting down VM 
12-06 18:20:58.379: E/AndroidRuntime(2517): FATAL EXCEPTION: main 
12-06 18:20:58.379: E/AndroidRuntime(2517): Process: com.parse.starter, PID: 2517 
12-06 18:20:58.379: E/AndroidRuntime(2517): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.parse.starter/com.parse.starter.ParseStarterProjectActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'int org.json.JSONObject.optInt(java.lang.String)' on a null object reference 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at android.app.ActivityThread.access$800(ActivityThread.java:144) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at android.os.Handler.dispatchMessage(Handler.java:102) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at android.os.Looper.loop(Looper.java:135) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at android.app.ActivityThread.main(ActivityThread.java:5221) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at java.lang.reflect.Method.invoke(Native Method) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at java.lang.reflect.Method.invoke(Method.java:372) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) 
12-06 18:20:58.379: E/AndroidRuntime(2517): Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int org.json.JSONObject.optInt(java.lang.String)' on a null object reference 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at com.parse.ParseQuery$18.then(ParseQuery.java:1014) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at com.parse.ParseQuery$18.then(ParseQuery.java:1011) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$9.run(Task.java:444) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.BoltsExecutors$ImmediateExecutor.execute(BoltsExecutors.java:97) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task.completeImmediately(Task.java:440) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task.access$100(Task.java:27) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$5.then(Task.java:307) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$5.then(Task.java:304) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task.runContinuations(Task.java:506) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task.access$600(Task.java:27) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$TaskCompletionSource.trySetError(Task.java:577) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$TaskCompletionSource.setError(Task.java:604) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$10$1.then(Task.java:487) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$10$1.then(Task.java:481) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$9.run(Task.java:444) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.BoltsExecutors$ImmediateExecutor.execute(BoltsExecutors.java:97) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task.completeImmediately(Task.java:440) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task.continueWith(Task.java:314) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task.continueWith(Task.java:325) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$10.run(Task.java:481) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.BoltsExecutors$ImmediateExecutor.execute(BoltsExecutors.java:97) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task.completeAfterTask(Task.java:473) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task.access$200(Task.java:27) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$6.then(Task.java:342) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$6.then(Task.java:339) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task.runContinuations(Task.java:506) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task.access$600(Task.java:27) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$TaskCompletionSource.trySetError(Task.java:577) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at com.parse.ParseRequest$4.then(ParseRequest.java:350) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at com.parse.ParseRequest$4.then(ParseRequest.java:344) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$10.run(Task.java:477) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.BoltsExecutors$ImmediateExecutor.execute(BoltsExecutors.java:97) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task.completeAfterTask(Task.java:473) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task.access$200(Task.java:27) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$6.then(Task.java:342) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$6.then(Task.java:339) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task.runContinuations(Task.java:506) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task.access$600(Task.java:27) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$TaskCompletionSource.trySetError(Task.java:577) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$TaskCompletionSource.setError(Task.java:604) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$10$1.then(Task.java:487) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$10$1.then(Task.java:481) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$9.run(Task.java:444) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.BoltsExecutors$ImmediateExecutor.execute(BoltsExecutors.java:97) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task.completeImmediately(Task.java:440) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task.continueWith(Task.java:314) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task.continueWith(Task.java:325) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$10.run(Task.java:481) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.BoltsExecutors$ImmediateExecutor.execute(BoltsExecutors.java:97) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task.completeAfterTask(Task.java:473) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task.access$200(Task.java:27) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$6.then(Task.java:342) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$6.then(Task.java:339) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task.runContinuations(Task.java:506) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task.access$600(Task.java:27) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$TaskCompletionSource.trySetResult(Task.java:561) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$TaskCompletionSource.setResult(Task.java:595) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$10$1.then(Task.java:489) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$10$1.then(Task.java:481) 
12-06 18:20:58.379: E/AndroidRuntime(2517):  at bolts.Task$9.ru 
12-06 18:20:58.379: D/Error(2517): ERR: exClass=java.lang.NullPointerException 
12-06 18:20:58.379: D/Error(2517): ERR: exMsg=Attempt to invoke virtual method 'int org.json.JSONObject.optInt(java.lang.String)' on a null object reference 
12-06 18:20:58.379: D/Error(2517): ERR: file=ParseQuery.java 
12-06 18:20:58.379: D/Error(2517): ERR: class=com.parse.ParseQuery$18 
12-06 18:20:58.379: D/Error(2517): ERR: method=then line=1014 
12-06 18:20:58.379: D/Error(2517): ERR: stack=java.lang.RuntimeException: Unable to start activity ComponentInfo{com.parse.starter/com.parse.starter.ParseStarterProjectActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'int org.json.JSONObject.optInt(java.lang.String)' on a null object reference 
12-06 18:20:58.379: D/Error(2517): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298) 
12-06 18:20:58.379: D/Error(2517): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360) 
12-06 18:20:58.379: D/Error(2517): at android.app.ActivityThread.access$800(ActivityThread.java:144) 
12-06 18:20:58.379: D/Error(2517): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278) 
12-06 18:20:58.379: D/Error(2517): at android.os.Handler.dispatchMessage(Handler.java:102) 
12-06 18:20:58.379: D/Error(2517): at android.os.Looper.loop(Looper.java:135) 
12-06 18:20:58.379: D/Error(2517): at android.app.ActivityThread.main(ActivityThread.java:5221) 
12-06 18:20:58.379: D/Error(2517): at java.lang.reflect.Method.invoke(Native Method) 
12-06 18:20:58.379: D/Error(2517): at java.lang.reflect.Method.invoke(Method.java:372) 
12-06 18:20:58.379: D/Error(2517): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) 
12-06 18:20:58.379: D/Error(2517): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) 
12-06 18:20:58.379: D/Error(2517): Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int org.json.JSONObject.optInt(java.lang.String)' on a null object reference 
12-06 18:20:58.379: D/Error(2517): at com.parse.ParseQuery$18.then(ParseQuery.java:1014) 
12-06 18:20:58.379: D/Error(2517): at com.parse.ParseQuery$18.then(ParseQuery.java:1011) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$9.run(Task.java:444) 
12-06 18:20:58.379: D/Error(2517): at bolts.BoltsExecutors$ImmediateExecutor.execute(BoltsExecutors.java:97) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task.completeImmediately(Task.java:440) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task.access$100(Task.java:27) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$5.then(Task.java:307) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$5.then(Task.java:304) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task.runContinuations(Task.java:506) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task.access$600(Task.java:27) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$TaskCompletionSource.trySetError(Task.java:577) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$TaskCompletionSource.setError(Task.java:604) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$10$1.then(Task.java:487) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$10$1.then(Task.java:481) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$9.run(Task.java:444) 
12-06 18:20:58.379: D/Error(2517): at bolts.BoltsExecutors$ImmediateExecutor.execute(BoltsExecutors.java:97) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task.completeImmediately(Task.java:440) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task.continueWith(Task.java:314) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task.continueWith(Task.java:325) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$10.run(Task.java:481) 
12-06 18:20:58.379: D/Error(2517): at bolts.BoltsExecutors$ImmediateExecutor.execute(BoltsExecutors.java:97) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task.completeAfterTask(Task.java:473) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task.access$200(Task.java:27) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$6.then(Task.java:342) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$6.then(Task.java:339) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task.runContinuations(Task.java:506) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task.access$600(Task.java:27) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$TaskCompletionSource.trySetError(Task.java:577) 
12-06 18:20:58.379: D/Error(2517): at com.parse.ParseRequest$4.then(ParseRequest.java:350) 
12-06 18:20:58.379: D/Error(2517): at com.parse.ParseRequest$4.then(ParseRequest.java:344) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$10.run(Task.java:477) 
12-06 18:20:58.379: D/Error(2517): at bolts.BoltsExecutors$ImmediateExecutor.execute(BoltsExecutors.java:97) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task.completeAfterTask(Task.java:473) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task.access$200(Task.java:27) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$6.then(Task.java:342) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$6.then(Task.java:339) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task.runContinuations(Task.java:506) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task.access$600(Task.java:27) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$TaskCompletionSource.trySetError(Task.java:577) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$TaskCompletionSource.setError(Task.java:604) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$10$1.then(Task.java:487) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$10$1.then(Task.java:481) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$9.run(Task.java:444) 
12-06 18:20:58.379: D/Error(2517): at bolts.BoltsExecutors$ImmediateExecutor.execute(BoltsExecutors.java:97) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task.completeImmediately(Task.java:440) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task.continueWith(Task.java:314) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task.continueWith(Task.java:325) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$10.run(Task.java:481) 
12-06 18:20:58.379: D/Error(2517): at bolts.BoltsExecutors$ImmediateExecutor.execute(BoltsExecutors.java:97) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task.completeAfterTask(Task.java:473) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task.access$200(Task.java:27) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$6.then(Task.java:342) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$6.then(Task.java:339) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task.runContinuations(Task.java:506) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task.access$600(Task.java:27) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$TaskCompletionSource.trySetResult(Task.java:561) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$TaskCompletionSource.setResult(Task.java:595) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$10$1.then(Task.java:489) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$10$1.then(Task.java:481) 
12-06 18:20:58.379: D/Error(2517): at bolts.Task$9.run(Task.java:444) 
12-06 18:20:58.379: D/Error(2517): at bolts.BoltsExecutors$ImmediateExecuto 
12-06 18:20:58.379: D/Error(2517): ERR: TOTAL BYTES WRITTEN: 13252

来源

2014-12-06 user4333097

+0

问：你能澄清你所说的 “query.whereDoesNotExist（” Parent4" ）的意思; “当我想要打印查询的计数时，似乎导致空指针异常？ “在哪一行是被调用的异常？'whereDoesNotExist'或'count（）'后面的 – cjds 2014-12-07 00:08:25

+0

不幸的是我不确定。我的eclipse日志似乎并没有说12-06 18：09：41.636：D/AndroidRuntime （2121）：---------开始崩溃 12-06 18：09：41.659：E/AndroidRuntime（2121）：致命例外：主要 12-06 18：09：41.659：E/AndroidRuntime （2121）：进程：com.parse.starter，PID：2121 12-06 18：09：41.659：E/AndroidRuntime（2121）：java.lang.RuntimeException：无法启动活动ComponentInfo {com.parse.starter/com.parse.starter.ParseStarterProjectActivity}：java.lang.NullPointerException：尝试在空对象引用 – user4333097 2014-12-07 00:13:31

+0

上调用虚拟方法'int org.json.JSONObject.optInt（java.lang.String）'您是否也可以发布错误日志？ – cjds 2014-12-07 00:15:38

回答

1

更新时间： 你可以做到这一点通过另一个方法

ParseQuery<RelationParse> innerQuery = ParseQuery.getQuery("Primary"); 
ParseQuery<TestParse> query = ParseQuery.getQuery("Primary"); 
query.whereDoesNotMatchQuery("Parent4", innerQuery); 
List<TestParse> listWithEmptyRelations = query.find();

来源

2014-12-07 08:22:36 gio

+0

Parent4在Primary类中，它是指主类，所以我不认为at'll工作。还有像这样的简单解决方案吗？ – user4333097 2014-12-07 19:40:41

+0

然后，您还需要在内部查询中使用“主要”。 – gio 2014-12-07 21:48:46

+0

什么是RelationParse和TestParse？ – user4333097 2014-12-07 23:10:27

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