Java firestore快照的视图更改代码

我已经阅读了Firestore的文档：

但在使用相同的代码时，我无法解析DocumentChange、EventListener等符号。 类似地，我无法解析诸如getDocumentChanges、getDocument、addSnapshotListener之类的方法

我已经导入了'com.google.firebase:firebase admin:5.8.0'

build.gradle文件

group 'firestore'
version '1.0-SNAPSHOT'
apply plugin: 'java'
sourceCompatibility = 1.8
repositories {
    mavenCentral()
}
dependencies {
    testCompile group: 'junit', name: 'junit', version: '4.12'
}
dependencies {
  compile 'com.google.firebase:firebase-admin:5.8.0'
}

下面是代码，我正在尝试：

package firestore;

import com.google.api.core.SettableApiFuture;
import com.google.firestore.v1beta1.DocumentChange;
import com.google.cloud.firestore.DocumentChange;
import com.google.cloud.firestore.DocumentChange.Type;
import com.google.cloud.firestore.EventListener;
import com.google.cloud.firestore.ListenerRegistration;
import com.google.cloud.firestore.Firestore;
import com.google.cloud.firestore.FirestoreException;
import com.google.cloud.firestore.Query;
import com.google.cloud.firestore.QuerySnapshot;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.TimeUnit;
import javax.annotation.Nullable;
import static com.google.api.ChangeType.ADDED;
import static com.google.api.ChangeType.MODIFIED;
import static com.google.api.ChangeType.REMOVED;

/**
 * Snippets to demonstrate Firestore 'listen' operations.
 */
@SuppressWarnings("Convert2Lambda")
public class FirestoreChange {
    private static final long TIMEOUT_SECONDS = 5;

    private final Firestore db;

    FirestoreChange(Firestore db) {
        this.db = db;
    }

    /**
     * Listen to a query, returning the list of DocumentChange events in the first snapshot.
     */
    List<DocumentChange> listenForChanges() throws Exception {
        SettableApiFuture<List<DocumentChange>> future = SettableApiFuture.create();

        // [START listen_for_changes]
        db.collection("cities")
                .whereEqualTo("state", "CA")
                .addSnapshotListener(new EventListener<QuerySnapshot>() {
                    @Override
                    public void onEvent(@Nullable QuerySnapshot snapshots,
                                        @Nullable FirestoreException e) {
                        if (e != null) {
                            System.err.println("Listen failed: " + e);
                            return;
                        }

                        for (DocumentChange dc : snapshots.getDocumentChanges()) {
                            switch (dc.getType()) {
                                case ADDED:
                                    System.out.println("New city: " + dc.getDocument().getData());
                                    break;
                                case MODIFIED:
                                    System.out.println("Modified city: " + dc.getDocument().getData());
                                    break;
                                case REMOVED:
                                    System.out.println("Removed city: " + dc.getDocument().getData());
                                    break;
                                default:
                                    break;
                            }
                        }
                        // [START_EXCLUDE silent]
                        if (!future.isDone()) {
                            future.set(snapshots.getDocumentChanges());
                        }
                        // [END_EXCLUDE]
                    }
                });
        // [END listen_for_changes]

        return future.get(TIMEOUT_SECONDS, TimeUnit.SECONDS);
    }

}

---

这是因为您根本没有在build.gradle文件中添加Cloud Firestore依赖项。添加firebase管理员不足以使Firestore正常工作。要解决这个问题，只需添加以下代码行：

compile 'com.google.firebase:firebase-firestore:11.8.0'

---

就在firebase管理依赖项之后。同步您的项目并重试。

请提供包含您的类和build.gradle文件的a。@AlexMamo，Graddle文件：-组“firestore”版本“1.0-SNAPSHOT”应用插件：“java”sourceCompatibility=1.8存储库{mavenCentral}依赖项{testCompile group:'junit'，name:'junit'，version:'4.12'}依赖项{compile'com.google.firebase:firebase admin:5.8.0'}代码是URL中“查看快照之间的更改”部分的代码：请通过添加mcv和build.gradle文件编辑您的问题。@AlexMamo，我已更新了代码，请检查并告知我缺少什么？我更新了buildgradle文件，但仍然无法解决导入问题。请尝试清理您的项目并重新编译再重复一遍。