Android Firestore 搜索集合，其中文档是唯一 ID

您将需要一个名称查询：

var peopleRef = db.collection("users");
// there may multiple users if there are more then one `John Doe`
peopleRef.where("name", "==", "John Doe")
.get()
.then(function(querySnapshot) {
    querySnapshot.forEach(function(doc) {
        //Here below will list all people who's name = "John Doe", If only one then this John Doe's  id no: doc.id as fallow:
        console.log(doc.id, " => ", doc.data());
    });
})
.catch(function(error) {
    console.log("Error getting documents: ", error);
});