Unable to instantiate activity problem while debuging

Rishav Raina :

when i try to open my app.It crash all code are below of activity that crash!

2020-04-02 13:11:45.102 8088-8088/comviewappisome.google.sites.watchandearn E/AndroidRuntime: FATAL EXCEPTION: main Process: comviewappisome.google.sites.watchandearn, PID: 8088 java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{comviewappisome.google.sites.watchandearn/comviewappisome.google.sites.watchandearn.login}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.Window$Callback android.view.Window.getCallback()' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2876) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3081) at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1831) at android.os.Handler.dispatchMessage(Handler.java:106) at android.os.Looper.loop(Looper.java:201) at android.app.ActivityThread.main(ActivityThread.java:6826) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:873) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.Window$Callback android.view.Window.getCallback()' on a null object reference at android.support.v7.app.AppCompatDelegateImplBase.(AppCompatDelegateImplBase.java:117) at android.support.v7.app.AppCompatDelegateImplV9.(AppCompatDelegateImplV9.java:149) at android.support.v7.app.AppCompatDelegateImplV14.(AppCompatDelegateImplV14.java:56) at android.support.v7.app.AppCompatDelegateImplV23.(AppCompatDelegateImplV23.java:31) at android.support.v7.app.AppCompatDelegateImplN.(AppCompatDelegateImplN.java:31) at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:198) at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:183) at android.support.v7.app.AppCompatActivity.getDelegate(AppCompatActivity.java:519) at android.support.v7.app.AppCompatActivity.findViewById(AppCompatActivity.java:190) at comviewappisome.google.sites.watchandearn.login.(login.java:14) at java.lang.Class.newInstance(Native Method) at android.app.AppComponentFactory.instantiateActivity(AppComponentFactory.java:69) at android.app.Instrumentation.newActivity(Instrumentation.java:1216) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2864) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3081) at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1831) at android.os.Handler.dispatchMessage(Handler.java:106) at android.os.Looper.loop(Looper.java:201) at android.app.ActivityThread.main(ActivityThread.java:6826) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:873) 2020-04-02 13:11:45.109 451-451/? E/SELinux: avc: denied { find } for service=miui.mqsas.MQSService pid=8088 uid=10263 scontext=u:r:untrusted_app_27:s0:c512,c768 tcontext=u:object_r:mqs_service:s0 tclass=service_manager permissive=0

package comviewappisome.google.sites.watchandearn;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.LinearLayout;

import static comviewappisome.google.sites.watchandearn.SharedPreferences.PREFS_NAME;


public class login extends AppCompatActivity {

    LinearLayout guestlogin = (LinearLayout )findViewById(R.id.guest);

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);

        guestlogin.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                SharedPreferences settings = getSharedPreferences(comviewappisome.google.sites.watchandearn.SharedPreferences.PREFS_NAME, 0); // 0 - for private mode
                SharedPreferences.Editor editor = settings.edit();

                //Set "hasLoggedIn" to true
                editor.putBoolean("hasLoggedIn", true);

                // Commit the edits!
                editor.commit();
                Intent i = new Intent(login.this, ChoiceSelection.class);
                startActivity(i);
            }
        });

    }

}

jo3rn :

You need to call findViewById after setContentView

LinearLayout guestlogin; // do not instantiate here

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
        guestlogin = (LinearLayout) findViewById(R.id.guest);

        guestlogin.setOnClickListener (...)