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android - Firebase firestore 空文档路径

问题描述

null由于具有来自 firestore 数据库的文档路径，我无法启动活动。我不知道怎么了，你的帮助很重要。

以下是代码：-

DocumentReference documentReference2 = fStore.collection("users").document(userID)
                .collection("Values").document("DabaCount");
        documentReference2.addSnapshotListener(this, new EventListener<DocumentSnapshot>() {
            @Override
            public void onEvent(@Nullable DocumentSnapshot value, @Nullable FirebaseFirestoreException error) {
                num = String.valueOf(value.getString("Count"));
            }
        });

        int numnum = Integer.parseInt(num);

        int ii = 1;

        if (numnum > ii){
            ii = 1;
        }

        String ci = String.valueOf(ii);
        String DabaPattern = "Daba" + ci;

        DocumentReference documentReference3 = fStore.collection("users").document(userID)
                .collection("DabaSet").document(DabaPattern);
        documentReference3.addSnapshotListener(this, new EventListener<DocumentSnapshot>() {
            @Override
            public void onEvent(@Nullable DocumentSnapshot value, @Nullable FirebaseFirestoreException error) {
                DabaKey = String.valueOf(value.getString("DabaID"));
            }
        });

        FirebaseDatabase database = FirebaseDatabase.getInstance();
        DatabaseReference myRef = database.getReference(DabaKey);
        myRef.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                String value = dataSnapshot.getValue(String.class);
                Weight = value;
                Toast.makeText(GetDaba.this, Weight, Toast.LENGTH_SHORT).show();
            }
            @Override
            public void onCancelled(DatabaseError error) {}
        });

这是输出错误：-

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.smartdaba, PID: 6733
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.smartdaba/com.example.smartdaba.GetDaba}: java.lang.NullPointerException: Provided document path must not be null.
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3449)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7656)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
     Caused by: java.lang.NullPointerException: Provided document path must not be null.
        at com.google.firebase.firestore.util.Preconditions.checkNotNull(Preconditions.java:147)
        at com.google.firebase.firestore.CollectionReference.document(CollectionReference.java:103)
        at com.example.smartdaba.GetDaba.onCreate(GetDaba.java:75)
        at android.app.Activity.performCreate(Activity.java:8000)
        at android.app.Activity.performCreate(Activity.java:7984)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3422)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:223) 
        at android.app.ActivityThread.main(ActivityThread.java:7656) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947) 

标签： androidfirebasegoogle-cloud-firestore

解决方案

  1. 似乎您正在尝试document从代码中的空访问数据。请确保firebase firestore您的集合或文档的名称与您的代码中编写的名称相对应。
  2. 从上面的代码中，您已经声明了一个集合引用变量，但是您缺少一个get()用于从云 Firestore 中检索信息的方法。这是一个例子：-

从 Cloud Firestore 中检索信息的错误方式，

            documentReference.addSnapshotListener(this, new EventListener<DocumentSnapshot>() {
                @Override
                public void onEvent(@Nullable DocumentSnapshot value, @Nullable FirebaseFirestoreException error) {
                    //Firebase data manipulation
                }
            });

从 Cloud Firestore 中检索信息的正确方法，

        documentReference.get().addSnapshotListener(this, new EventListener<DocumentSnapshot>() {
            @Override
            public void onEvent(@Nullable DocumentSnapshot value, @Nullable FirebaseFirestoreException error) {
                //Firebase data manipulation
            }
        });

尽量确保get()从云火库获取数据时不会错过该方法。

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