Problems running my app, java.lang.RuntimeException

Question

today I have tried running my app, but and have a problem, that i don't know it is. Yesterday worked correctly.

If I comment the indicated line the application runs perfectly

Thanks for your help.

This is the error:

FATAL EXCEPTION: main
Process: com.example.tribuum_app_2022, PID: 7542
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.tribuum_app_2022/com.example.tribuum_app_2022.ui.view.MainActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2646)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707)

at android.app.ActivityThread.- wrap12(ActivityThread.java)

at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460)

at android.os.Handler.dispatchMessage(Handler.java:102)

at android.os.Looper.loop(Looper.java:154)

at android.app.ActivityThread.main(ActivityThread.java:6077)

at java.lang.reflect.Method.invoke(Native Method)

at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)

at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)
Caused by: java.lang.NullPointerException
at com.example.tribuum_app_2022.ui.view.MainActivity.validateUserLogin(MainActivity.kt:37)
at com.example.tribuum_app_2022.ui.view.MainActivity.onCreate(MainActivity.kt:30)

at android.app.Activity.performCreate(Activity.java:6662)

at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)

at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2599)

at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707)

at android.app.ActivityThread.- wrap12(ActivityThread.java)

at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460)

at android.os.Handler.dispatchMessage(Handler.java:102)

at android.os.Looper.loop(Looper.java:154)

at android.app.ActivityThread.main(ActivityThread.java:6077)

at java.lang.reflect.Method.invoke(Native Method)

at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)

at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)

The line where the mistake exist

private fun validateUserLogin(){
        val guardarEnXml = getSharedPreferences("datos_usuario_login", MODE_PRIVATE)
        txtUserLoginIdShare = guardarEnXml.getString("id", null)
        txtUserLoginPassShare = guardarEnXml.getString("pass", null)
Line 37: userLogin = UserLogin(txtUserLoginIdShare!!,txtUserLoginPassShare!!)
        userViewModel.loginUser(userLogin)
    }

The class of the object:

package com.example.app_2022.domain.model
import com.example.app_2022.data.model.UserLoginModel

data class UserLogin(var id: String?, var pass: String?)
fun UserLoginModel.toDomain() = UserLogin(id,pass)

The other class that change the type of the object:

package com.example.app_2022.data.model
import com.example.app_2022.domain.model.UserLogin
import com.google.gson.annotations.SerializedName

data class UserLoginModel(
    @SerializedName("idUsuario") var id: String?,
    @SerializedName("contrasena") val pass: String?
)

fun UserLogin.toDatabase() = UserLoginModel(id = id, pass = pass)

Answer 1

The logcat is saying there is a NullPointerException in line 37. So there txtUserLoginIdShare and txtUserLoginPassShare can be null. Because all the values from SharedPreferences can be null. So you should check it before use, instead of forcing it to NotNull by using !!.