使用它们中的任何一个如此简单和容易... 你喜欢哪种方式
ValueEventListener responseListener = new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
// Do stuff
} else {
// Do stuff
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
};
FirebaseUtil.getResponsesRef().child(postKey).addValueEventListener(responseListener);
function go() {
var userId = prompt('Username?', 'Guest');
checkIfUserExists(userId);
}
var USERS_LOCATION = 'https://SampleChat.firebaseIO-demo.com/users';
function userExistsCallback(userId, exists) {
if (exists) {
alert('user ' + userId + ' exists!');
} else {
alert('user ' + userId + ' does not exist!');
}
}
// Tests to see if /users/<userId> has any data.
function checkIfUserExists(userId) {
var usersRef = new Firebase(USERS_LOCATION);
usersRef.child(userId).once('value', function(snapshot) {
var exists = (snapshot.val() !== null);
userExistsCallback(userId, exists);
});
}
Firebase userRef= new Firebase(USERS_LOCATION);
userRef.child(userId).addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot snapshot) {
if (snapshot.getValue() !== null) {
//user exists, do something
} else {
//user does not exist, do something else
}
}
@Override
public void onCancelled(FirebaseError arg0) {
}
});
@yahoo我将如何访问它?我无法看到它在Swift文档中的位置。 – Hidden14
请参阅此。 https://gist.github.com/anantn/4323949 –