Question

您好我正在编写应用程序并使用firebase登录后获取用户的显示名称但是我只在api 27 java.lang.String com.google.firebase.auth.FirebaseUser.getDisplayName()' on a null object reference

上收到此错误

用户在发生这种情况时登录

我的代码是

String displayname =  FirebaseAuth.getInstance().getCurrentUser().getDisplayName().toString();

    Toast.makeText(getApplicationContext(),"Logged in as "+ displayname, Toast.LENGTH_LONG).show();

Answer 1

当没有用户登录时，

FirebaseAuth.getInstance().getCurrentUser()会返回空的FirebaseUser。您在该空引用上调用<div style="background-color:black"> <div class="dropdown1"> <button class="dropbtn1">REFRIGERANTS</button> <div id="myDropdown1" class="dropdown1-content" style="text-align:left;"> <a href="#">Refrigerants</a><br> <a href="#">Lubricants</a><br> <a href="#">Treatments</a><br> <a href="#">R-134A Products</a><br> </div> </div> <div class="dropdown1"> <button class="dropbtn1">FLUIDS</button> <div id="myDropdown2" class="dropdown1-content" style="text-align:left"> <a href="#">Brake Fluid</a><br> <a href="#">Automatic Transmission Fluid</a><br> <a href="#">Power Steering Fluid</a><br> </div> </div> <div class="dropdown1"> <button class="dropbtn1">ADDITIVES</button> <div id="myDropdown3" class="dropdown1-content" style="text-align:left"> <a href="#">Fuel Additives</a><br> <a href="#">Oil Additives</a> </div> </div> <div class="dropdown1"> <button class="dropbtn1">CLEANERS</button> <div id="myDropdown4" class="dropdown1-content" style="text-align:left"> <a href="#">Brake Parts Cleaner</a><br> <a href="#">Carb & Air Intake Cleaners</a><br> <a href="#">General Cleaners</a><br> <a href="#">Battery Cleaners</a><br> </div> </div> <div class="dropdown1"> <button class="dropbtn1">WINTER DRIVING</button> <div id="myDropdown5" class="dropdown1-content" text-align="left"> <a href="#">Link 1</a><br> <a href="#">Link 2</a><br> <a href="#">Link 3</a><br> </div> </div> <div class="dropdown1"> <button class="dropbtn1">LUBIRICANTS</button> <div id="myDropdown6" class="dropdown1-content" text-align="left"> <a href="#">Link 1</a><br> <a href="#">Link 2</a><br> <a href="#">Link 3</a><br> </div> </div> <div class="dropdown1"> <button class="dropbtn1">OTHER PRODUCTS</button> <div id="myDropdown7" class="dropdown1-content" text-align="left"> <a href="#">Link 1</a><br> <a href="#">Link 2</a><br> <a href="#">Link 3</a><br> </div> </div> </div>，这会导致错误。你应该在那里检查null，看看在User对象上调用方法是否安全。

Firebase Auth，java.lang.String com.google.firebase.auth.FirebaseUser.getDisplayName（）＆＃39;在null对象引用上

1 个答案: