How to close custom dialog which itself is an activity and get data from it?

I have created custom dialog and I want to close it on Cancel button click. I searched on google, most of the people are using Dialog or AlertDialog but I am not using anything like that. This is my TextDialogActivity which is loading on button click in my app. From MainActivity I am just rendering another activity as custom dialog. When I click Save button on the dialog I want to access data in parent activity, which is stored in a variable textData in child activity.

  public class TextDialogActivity extends AppCompatActivity {
  TabHost tabHost;
  private static final int FILE_SELECT_CODE = 0;
  private String textData;

  private Button browse;
  private Button cancel_button1;
  private Button cancel_button2;
  private TextView text_preview;

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

      browse = findViewById(R.id.browse_file_button);
      text_preview = findViewById(R.id.text_preview);
      cancel_button1 = findViewById(R.id.cancel_button);
      cancel_button2 = findViewById(R.id.cancel_button2);

      tabHost = findViewById(R.id.tabHost);
      tabHost.setup();

      TabHost.TabSpec spec=tabHost.newTabSpec("tag1");

      spec.setContent(R.id.encode_dialog_text_tab);
      spec.setIndicator("Edit Text");
      tabHost.addTab(spec);

      spec=tabHost.newTabSpec("tag2");
      spec.setContent(R.id.encode_dialog_browse_tab);
      spec.setIndicator("Browse");
      tabHost.addTab(spec);

      browse.setOnClickListener(new View.OnClickListener() {
          @Override
          public void onClick(View v) {
              showFileChooser();
          }
      });

      cancel_button1.setOnClickListener(new View.OnClickListener() {
          @Override
          public void onClick(View v) {
                // close dialog
          }
      });

      cancel_button2.setOnClickListener(new View.OnClickListener() {
          @Override
          public void onClick(View v) {
                 // close dialog
          }
      });

   }
 }

I added @style/Theme.AppCompat.Dialog to my AndroidManifest.xml to make my dialog.

 <activity
        android:name=".activity.TextDialogActivity"
        android:theme="@style/Theme.AppCompat.Dialog"
        android:label="Secret Message">
 </activity>

This is the screenshot.

My custom dialog/popup is an activity itself. I am not using Dialog or AlertDialog. For closing this dialog on Cancel button click, this is what I did:

 cancel_button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            finish();  // Call this method to close the dialog
        }
 });

And for accessing data from child activity(TextDialogActivity) to parent(MainActivity) activity, I did the same as @Kemo suggested here in answers. This is the code:

// From Parent activity(MainActivity) opening popup on button click
popUpButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent=new Intent(getContext(), TextDialogActivity.class);
            startActivityForResult(intent, TEXTFILE);
        }
});

// From Child activity(TextDialogActivity) sending data to parent activity
save_button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if(!secretText.isEmpty()) {
              Intent intent = new Intent();
              intent.putExtra("popup_data", secretText);
              setResult(RESULT_OK, intent);
              finish();
            }
        }
});

Now I want the result from child activity to parent activity for that I did this in onActivityResult method:

// In parent activity get data on onActivityResult
if (requestCode == TEXTFILE && resultCode == getActivity().RESULT_OK){
     secretText = data.getExtras().getString("popup_data", "");
}