android-studio - 无法为接口(interface) retrofit2.http.Url 调用无参数构造函数。为这个类型注册一个Gson的InstanceCreator来解决这个问题

Question

Retrofit 和 Gson 有问题，我不知道为什么？

我的应用在发送登录数据时出错:

Unable to invoke no-args constructor for interface retrofit2.http.Url. Register an InstanceCreator with Gson for this type to fix this problem.

早些时候，我用 Java 制作了这个应用程序，代码完全相同，没有任何错误。但为什么现在使用 Kotlin？

主要事件:

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_main)
            val editText_login_user=findViewById<EditText>(R.id.Login_username)
            val editText_login_password=findViewById<EditText>(R.id.Login_password)
            val button_login=findViewById<Button>(R.id.btn_login)
            button_login.setOnClickListener(View.OnClickListener { Connect_login(editText_login_user.text.toString(),editText_login_password.text.toString()) })
    }
    fun Connect_login(user:String,pass:String):Boolean{
        var client= OkHttpClient()
        var retrofit = Retrofit.Builder()
            .baseUrl("http://sobosha.ir/")
            .client(client)
            .addConverterFactory(GsonConverterFactory.create())
            .build()
        val services=retrofit.create(ApiRet::class.java)
        val call =services.Logindata(user,pass)
        call.enqueue(object : Callback<User_info>{
            override fun onResponse(call: Call<User_info>, response: retrofit2.Response<User_info>) {
                val user: User_info? = response.body()
                Toast.makeText(applicationContext, user?.name,Toast.LENGTH_LONG).show()
            }
            override fun onFailure(call: Call<User_info>, t: Throwable) {
                Toast.makeText(applicationContext, t.message,Toast.LENGTH_LONG).show()
                val editText_login_passwords=findViewById<EditText>(R.id.Login_password)
                editText_login_passwords.setText(t.message)
            }
        })
        return false
    }
}

接口(interface):

public interface ApiRet {

    @FormUrlEncoded
    @POST("/Login.php")
    Call<User_info> Logindata(@Field("username") String user, @Field("password") String pass);
}

和我的用户信息:

class User_info{

    @SerializedName("name")
    var name: String? = null
    @SerializedName("image_url")
    var image_url: Url? = null
    @SerializedName("correct")
    var correct:Boolean ?= null
}

我把界面改成这个

interface Apiservices{

    @FormUrlEncoded
    @POST("Login.php")
    fun Login(@Field("username") user: String, @Field("password") pass: String): Call<User_info>
}

但它并没有改变错误。

Answer 1

首先，你不能使用retrofit2.http.Url。它只是一个注解类。您可以将其更改为 HttpUrl 例如:

class User_info{

    @SerializedName("name")
    var name: String? = null
    @SerializedName("image_url")
    var image_url: HttpUrl? = null
    @SerializedName("correct")
    var correct:Boolean ?= null
}

然后您必须创建并注册自定义 url 反序列化器:

class UrlDeserializer : JsonDeserializer<HttpUrl> {
    override fun deserialize(json: JsonElement, typeOfT: Type?, context: JsonDeserializationContext?): HttpUrl =
        HttpUrl.get(json.asString)

}

val gson = GsonBuilder()
    .registerTypeAdapter(HttpUrl::class.java, UrlDeserializer())
    .create()
var retrofit = Retrofit.Builder()
    .baseUrl("http://sobosha.ir/")
    .client(client)
    .addConverterFactory(GsonConverterFactory.create(gson))
    .build()