java– 由于null对象引用,无法向RealmList添加新对象

概述我必须使用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.类我在哪

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.

类我在哪里尝试添加新对象

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<Contact> contacts = new RealmList<>();public ContactBook() {}public RealmList<Contact> getContacts() {    return contacts;}public voID setContacts(RealmList<Contact> 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.access0(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.access0(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)

解决方法:

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RealmLists,因为它必须首先转换为正确(或托管)的Realm对象.但错误信息肯定会更好.

总结

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