由于null对象引用，无法向RealmList添加新对象

我必须使用realm对象，一个是带有两个字符串和一个布尔值的基本RealmObject，另一个是该对象的RealmList，以便于访问。 当我尝试从我的ContactBook实例中获取列表并添加新对象时，我尝试在空对象引用上调用虚方法。 但是，我能够获得联系簿的大小，以及联系人的数量，因此这些不是空的。

类我尝试添加新对象的地方

public void viewSetup() { setContentView(R.layout.activity_contacts); ButterKnife.inject(this); Realm.deleteRealmFile(this); realm = Realm.getInstance(this); results = realm.where(ContactBook.class).findAll(); if (toolbar != null) { setSupportActionBar(toolbar); } if (results.size() == 0) { realm.beginTransaction(); ContactBook contactBook = realm.copyToRealm(new ContactBook()); realm.commitTransaction(); } } public void setupCursor() { Cursor cursor = getContentResolver().query(ContactsContract.CommonDataKinds.Phone.CONTENT_URI, null, null, null, null); ContactBook contactBook = results.first(); realm.beginTransaction(); while (cursor.moveToNext()) { String name = cursor.getString(cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME)); String number = cursor.getString(cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER)); if (contactBook.getContacts().where().equalTo("name", name).findAll().size() == 0 && contactBook.getContacts().where().equalTo("number", number).findAll().size() == 0) { contactBook.getContacts().add(new Contact(name, number, false)); } } realm.commitTransaction(); cursor.close(); } 

带有两个字符串的类，以及布尔值

 public class Contact extends RealmObject { private String name; private String number; private boolean allowed; public Contact() { } public Contact(String name, String number, boolean allowed) { this.name = name; this.number = number; this.allowed = allowed; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getNumber() { return number; } public void setNumber(String number) { this.number = number; } public boolean isAllowed() { return allowed; } public void setAllowed(boolean allowed) { this.allowed = allowed; } } 

联系书课

 public class ContactBook extends RealmObject { private RealmList contacts = new RealmList(); public ContactBook() { } public RealmList getContacts() { return contacts; } public void setContacts(RealmList contactBook) { this.contacts = contactBook; } } 

错误日志

  java.lang.RuntimeException: Unable to start activity ComponentInfo{io.github.brady131313.textback/io.github.brady131313.textback.View.ActivityContactSelect}: java.lang.NullPointerException: Attempt to invoke virtual method 'long io.realm.internal.Row.getIndex()' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2661) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726) at android.app.ActivityThread.access$900(ActivityThread.java:172) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1421) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:145) at android.app.ActivityThread.main(ActivityThread.java:5835) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1388) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1183) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'long io.realm.internal.Row.getIndex()' on a null object reference at io.realm.RealmList.add(RealmList.java:122) at io.github.brady131313.textback.View.ActivityContactSelect.setupCursor(ActivityContactSelect.java:69) at io.github.brady131313.textback.View.ActivityContactSelect.onCreate(ActivityContactSelect.java:39) at android.app.Activity.performCreate(Activity.java:6221) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2614)            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)            at android.app.ActivityThread.access$900(ActivityThread.java:172)            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1421)            at android.os.Handler.dispatchMessage(Handler.java:102)            at android.os.Looper.loop(Looper.java:145)            at android.app.ActivityThread.main(ActivityThread.java:5835)            at java.lang.reflect.Method.invoke(Native Method)            at java.lang.reflect.Method.invoke(Method.java:372)            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1388)            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1183) 

Answer 1

这是因为您尝试将非托管对象添加到托管列表。 这段代码在这里：

 if (contactBook.getContacts().where().equalTo("name", name).findAll().size() == 0 && contactBook.getContacts().where().equalTo("number", number).findAll().size() == 0) { contactBook.getContacts().add(new Contact(name, number, false)); } 

应该：

 if (contactBook.getContacts().where().equalTo("name", name).findAll().size() == 0 && contactBook.getContacts().where().equalTo("number", number).findAll().size() == 0) { Contact newContact = realm.copyToRealm(new Contact(name, number, false)); contactBook.getContacts().add(newContact); } 

使用new运算符创建的对象无法在不使用Realm.copyToRealmXXX方法之一的情况下添加到Realm中的Realm.copyToRealmXXX ，因为它必须首先转换为适当的（或托管的）Realm对象。 但错误信息肯定会更好。