Main Activity

package com.example.activslogs;

import androidx.activity.result.ActivityResult;
import androidx.activity.result.ActivityResultCallback;
import androidx.activity.result.ActivityResultLauncher;
import androidx.activity.result.contract.ActivityResultContract;
import androidx.activity.result.contract.ActivityResultContracts;
import androidx.appcompat.app.AppCompatActivity;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
//все свойства и атрибуты имеют префикс m -member
    // автоматическое дополнение alt+enter
    private TextView tv;
    private EditText et;
    private  TextView mtvRes;
    private ActivityResultLauncher<Intent> mActivityResultLauncher;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d(Common.LOG_TAG, "MainActivity create");
        setContentView(R.layout.activity_main);

        mtvRes = findViewById(R.id.tvRes);

        mActivityResultLauncher =registerForActivityResult(
                new ActivityResultContracts.StartActivityForResult(),
                new ActivityResultCallback<ActivityResult>() {
                    @Override
                    public void onActivityResult(ActivityResult result) {
                        if (result.getResultCode() == Activity.RESULT_OK){
                            Intent intent = result.getData();
                            mtvRes.setText(intent.getStringExtra("param"));
                            Toast.makeText(getApplicationContext(),
                                    "Успешно вернулись",
                                    Toast.LENGTH_SHORT).show();
                        }
                    }
                }
        );

        ((Button) findViewById(R.id.bRes)).setOnClickListener(v->{
            Intent intent = new Intent(MainActivity.this, ThirdActivity.class);
            intent.putExtra("in param", mtvRes.getText());
            mActivityResultLauncher.launch(intent);
        });


        tv = findViewById(R.id.tv);
        et = findViewById(R.id.etInput);
        tv.setText("Доброе утро");

        View.OnClickListener cl = new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                btnClick(view);
            }
        };
        ((Button) findViewById(R.id.button)).setOnClickListener(cl);
        ((TextView) findViewById(R.id.textView4)).setOnClickListener(cl);

        ((Button) findViewById(R.id.btnSecondActivity)).setOnClickListener(v->{
           Intent intent = new Intent(MainActivity.this,SecondActivity.class);
           Bundle bundle = new Bundle();
           bundle.putString("param1","1 параметр от основной активности");
           bundle.putString("title", "запущена из основной активности");
           intent.putExtras(bundle);
           //intent.putExtra("param1", "1 параметр от основной активности");
           startActivity(intent);
        });
    }

    @Override
    protected void onStart() {
        super.onStart();
        Log.d(Common.LOG_TAG, "MainActivity start");
    }

    @Override
    protected void onStop() {
        super.onStop();
        Log.d(Common.LOG_TAG, "MainActivity stop");
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.d(Common.LOG_TAG, "MainActivity destroy");
    }

    @Override
    protected void onPause() {
        super.onPause();
        Log.d(Common.LOG_TAG, "MainActivity pause");
    }

    @Override
    protected void onResume() {
        super.onResume();
        Log.d(Common.LOG_TAG, "MainActivity resume");
    }

    public void btnClick(View view) {
        switch (view.getId()) {
            case R.id.button: {
                String s = et.getText().toString();
                if (TextUtils.isEmpty(s)) {
                    et.setError("Укажите текст");
                    return;
                }
                tv.setText(s);

                break;
            }
            case R.id.textView4: {
                tv.setText("4 февраля. Ура!");
                break;
            }
        }

        tv.setOnLongClickListener(new View.OnLongClickListener() {
            @Override
            public boolean onLongClick(View view) {
                tv.setText("Доброе утро");
                return false;
            }
        });
    }
}