Firebase 错误无法为 child() 中的参数“pathString”传递 null

Question

I try to make a Database Reference in firebase but after run the program it showed java.lang.NullPointerException: Can't pass null for argument 'path string' in the child() Please tell me the proper solution

String receiverUid, senderUid;
DatabaseReference reference;
FirebaseDatabase database = FirebaseDatabase.getInstance();


reference = database.getReference("vcResponse").child(senderUid).child(receiverUid);

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.griffindor.postapp/com.griffindor.postapp.activities.calling.InCallingActivity}: java.lang.NullPointerException: Can't pass null for argument 'pathString' in child()
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3175)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3312)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:113)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:71)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2038)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:226)
        at android.app.ActivityThread.main(ActivityThread.java:7178)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:503)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:942)
     Caused by: java.lang.NullPointerException: Can't pass null for argument 'pathString' in child()
        at com.google.firebase.database.DatabaseReference.child(DatabaseReference.java:96)
        at com.griffindor.postapp.activities.calling.InCallingActivity.onCreate(InCallingActivity.java:74)
        at android.app.Activity.performCreate(Activity.java:7383)
        at android.app.Activity.performCreate(Activity.java:7374)

Answer 1

首先你需要保证receiverUid, senderUid是非空的

First, you need to ensure that the receiverUid and senderUid are non empty