java - 回调监听器无法正常工作

Question

我正在使用Realm library对于我的应用程序。我做了一个异步请求来获取这样的对象:

    public static void getMissions(final List<StatutMission> listStatus, final SListener<List<RMission>> listener) {

    final String[] statesCode = new String[listStatus.size()];

    for (int i = 0; i < listStatus.size(); i++) {
        statesCode[i] = listStatus.get(i).getStateCode();
    }


    final RealmResults<RMission> results = Realm.getDefaultInstance().where(RMission.class).in("state", statesCode).findAllAsync();
    results.addChangeListener(new RealmChangeListener<RealmResults<RMission>>() {
        @Override
        public void onChange(RealmResults<RMission> element) {

            Log.d(TAG, element.size() + " mission(s) found in database with states " + StringUtils.arrayToString(statesCode, ","));
            listener.onResponse(Realm.getDefaultInstance().copyFromRealm(element));
            results.removeChangeListener(this);

        }
    });

}

监听器类:

public interface SListener<T> {

void onResponse(@Nullable T result);

}

我在多个设备中测试了我的代码，但仅在一台设备(三星平板电脑)上出现了问题。

问题代码:

   MissionManager.getMissions(listStatus, new SListener<List<RMission>>() {
        @Override
        public void onResponse(List<RMission> result) {

谁能帮我解决这个问题吗？

提前致谢。

Answer 1

1.) Realm.getDefaultInstance().where(... 和 Realm.getDefaultInstance().copyFromRealm(...) 您正在打开 Realm 实例将永远无法关闭，请阅读 the docs

2.) 您没有将 RealmResults 保留为字段引用，因此终结器将在评估异步查询之前销毁它，因此不会调用回调，请阅读文档 here和 here

From javadoc:

Registering a change listener will not prevent the underlying RealmResults from being garbage collected. If the RealmResults is garbage collected, the change listener will stop being triggered. To avoid this, keep a strong reference for as long as appropriate e.g. in a class variable.

public class MyActivity extends Activity {

    private RealmResults<Person> results; // Strong reference to keep listeners alive

    @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         results = realm.where(Person.class).findAllAsync();
         results.addChangeListener(new RealmChangeListener<RealmResults<Person>>() {
           @Override
           public void onChange(RealmResults<Person> persons) {
               // React to change
           }
       });
     }
     // remove change listeners, and close Realm in onDestroy()
 }

3.) 如果您在 UI 线程上急切地复制惰性求值 RealmResults 中的每个惰性求值元素，那么异步求值查询的所有麻烦都毫无意义，所以你应该重新评估你的逻辑，特别是在你读完the relevant docs on how Realm queries work之后.

All fetches (including queries) are lazy in Realm, and the data is never copied.

由于数据永远不会被复制，因此您没有理由使用 copyFromRealm()。