Resume fragment when switching back from a another fragment in android(Java)

Question

I heve read all the answers related this.

I have 2 buttons, both opens different fragment.

when I open a fragment, do something with it, open another fragment and come back to the first fragment then I see all the changes I made are not applied, because fragment restarted. Please help me..

Activity

    package com.example.canvastag;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

import com.example.canvastag.fragments.firstFrag;
import com.example.canvastag.fragments.secondFrag;

public class asking extends AppCompatActivity {
    firstFrag frag1;
    secondFrag frag2;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_asking);
        Button button = findViewById(R.id.frag1button);
        Button button2 = findViewById(R.id.frag2button);
        frag1 = new firstFrag();
        frag2 = new secondFrag();

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                getSupportFragmentManager().beginTransaction().replace(R.id.fragmentContainer, frag1, "").commit();
            }
        });

        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                getSupportFragmentManager().beginTransaction().replace(R.id.fragmentContainer, frag2, "").commit();
            }
        });


    }
}

Fragment 1

public class firstFrag extends Fragment {
View view;
TextView textView;
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        view= inflater.inflate(R.layout.fragment_first, container, false);
        textView=view.findViewById(R.id.textFrag);
        Button button = view.findViewById(R.id.buttonAdd);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                textView.setText("button clicked");
            }
        });

     return view;
    }
}

Fragment 2-

public class secondFrag extends Fragment {
View view;
TextView textView;
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        view= inflater.inflate(R.layout.fragment_second, container, false);
        textView=view.findViewById(R.id.textFrag);
        Button button = view.findViewById(R.id.buttonAdd);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                textView.setText("button seocnd clicked");
            }
        });

     return view;
    }
}

I want to resume fragment when I come back to it, not restart.

OUTPUT-

Thank you so much...

Answer 1

Instead of:

  getSupportFragmentManager().beginTransaction().replace(R.id.fragmentContainer, frag1, "").commit();

Try using:

  getSupportFragmentManager().beginTransaction().add(R.id.fragmentContainer, frag1, "").commit();

Note:

You can add this to the fragment transaction: addToBackStack(null) so your previous state will be added to the backstack allowing you to go back with the back button.