Open new activity by Clicking button in a Fragment - android-studio

Question

I'm currently working on a mobile app as a final project for my course. I have these two fragments inside a ViewPager2 controlled by a TabLayout. There are buttons inside of these fragments.
The first frag contains 2 buttons. The other frag has only one button. I want them to open an activity but the problem is when I run the app, these buttons won't work. They didn't open the other activity.
Login Fragment
package com.example.biowit;
import android.content.Intent;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import com.blogspot.atifsoftwares.animatoolib.Animatoo;
public class LoginTabFragment extends Fragment {
EditText email, password;
Button btn_login, btn_forpass;
TextView textView;
float v=0;
#Nullable
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
ViewGroup root = (ViewGroup) inflater.inflate(R.layout.login_fragment, container, false);
email = root.findViewById(R.id.input_LI_email);
password = root.findViewById(R.id.input_LI_pass);
btn_forpass = root.findViewById(R.id.btn_FPass);
btn_login = root.findViewById(R.id.btn_LIn);
email.setTranslationX(800);
password.setTranslationX(800);
btn_forpass.setTranslationX(800);
btn_login.setTranslationX(800);
email.setAlpha(v);
password.setAlpha(v);
btn_forpass.setAlpha(v);
btn_login.setAlpha(v);
email.animate().translationX(0).alpha(1).setDuration(800).setStartDelay(300).start();
password.animate().translationX(0).alpha(1).setDuration(800).setStartDelay(300).start();
btn_forpass.animate().translationX(0).alpha(1).setDuration(800).setStartDelay(300).start();
btn_login.animate().translationX(0).alpha(1).setDuration(800).setStartDelay(300).start();
btn_login.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(getActivity(), HomeScreen.class);
startActivity(intent);
Animatoo.animateFade(getActivity());
getActivity().finish();
}
});
return root;
}
}
LoginScreen (where the fragment locates)
package com.example.biowit;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager.widget.ViewPager;
import androidx.viewpager2.widget.ViewPager2;
import android.os.Bundle;
import com.google.android.material.tabs.TabItem;
import com.google.android.material.tabs.TabLayout;
import com.google.android.material.tabs.TabLayoutMediator;
public class
LoginScreen extends AppCompatActivity {
TabLayout tabLayout;
ViewPager2 viewPager;
float v=1;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login_screen);
tabLayout = findViewById(R.id.tab_layout);
viewPager = findViewById(R.id.view_pager);
tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
LoginAdapter login_adapter = new LoginAdapter(this);
viewPager.setAdapter(login_adapter);
new TabLayoutMediator(tabLayout, viewPager,
new TabLayoutMediator.TabConfigurationStrategy() {
#Override
public void onConfigureTab(#NonNull TabLayout.Tab tab, int position) {
switch (position){
case 0:
tab.setText("LOGIN");
break;
case 1:
tab.setText("SIGNUP");
break;
}
}
}).attach();
tabLayout.setAlpha(v);
}
}
Here's the error log(?)
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.biowit, PID: 18551
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.biowit/com.example.biowit.HomeScreen}: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.appcompat.app.ActionBar.hide()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3754)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3912)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2319)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:239)
at android.app.ActivityThread.main(ActivityThread.java:8212)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:626)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1016)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.appcompat.app.ActionBar.hide()' on a null object reference
at com.example.biowit.HomeScreen.onCreate(HomeScreen.java:22)
at android.app.Activity.performCreate(Activity.java:8119)
at android.app.Activity.performCreate(Activity.java:8103)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1359)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3727)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3912) 
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85) 
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2319) 
at android.os.Handler.dispatchMessage(Handler.java:106) 
at android.os.Looper.loop(Looper.java:239) 
at android.app.ActivityThread.main(ActivityThread.java:8212) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:626) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1016) 
HomeScreen (Activity that supposedly open when clicking the button)
package com.example.biowit;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.Window;
import android.view.WindowManager;
import android.widget.Button;
public class HomeScreen extends AppCompatActivity {
Button Chap1_btn, Achieve_btn, HowToPlay_btn, LogOut_btn, Settings_btn;
#Override
protected void onCreate(Bundle savedInstanceState) {
requestWindowFeature(Window.FEATURE_NO_TITLE);
this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);
getSupportActionBar().hide(); // hides the action bar.
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home_screen);
Chap1_btn = findViewById(R.id.btn_Chap1);
Achieve_btn = findViewById(R.id.btn_Achievements);
HowToPlay_btn = findViewById(R.id.btn_HowToPlay);
LogOut_btn = findViewById(R.id.btn_Logout);
Settings_btn = findViewById(R.id.btn_Settings);
Chap1_btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent open_Chap1 = new Intent(getApplicationContext(), LessonScreen.class);
startActivity(open_Chap1);
}
});
Achieve_btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//Intent open_Achievements = new Intent(getApplicationContext(), Achievements.class);
}
});
HowToPlay_btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//Intent open_HowToPlay = new Intent(getApplicationContext().HowToPlay.class);
}
});
LogOut_btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
}
});
Settings_btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent open_Settings = new Intent(getApplicationContext(), Settings.class);
startActivity(open_Settings);
}
});
}
}

Answer 1

getSupportActionBar().hide(); is what's causing the error. You have added it before
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home_screen);
So it's trying to execute it before the activity is initialised.
Add it after the above 2 lines and it should work.