如何使用彩色按钮作为用户选择从第二个活动更改我的 MainActivity 的背景颜色？

Question

I have a program with more than one activity. From my MainActivity I can click a button which will send the user to the ThirdActivity_ColorPicker. In the third activity I have three buttons, named colors, when clicked should change the background color of the MainActivity. Except, it is not changing the background color.

In MainActivity I have an Intent which switches me to the third activity.

private View.OnClickListener changeToColorPickerActivity = new View.OnClickListener() {
    @Override
    public void onClick(View view) {
      Intent goToThirdActivityColorPicker = new Intent(getApplication(), ThirdActivity_ColorPicker.class);
      startActivityForResult(goToThirdActivityColorPicker, COLOR_PICKER_REQUEST);
    }
  };

In my third activity I have the three buttons, red, blue, and green, which when clicked should change the MainActivity background color to the selected color.

  private View.OnClickListener changeMainActivityToBlue = new View.OnClickListener() {
    @Override
    public void onClick(View view) {
      Intent intentBlue = new Intent();
      setResult(RESULT_CODE_BLUE, intentBlue);
      finish();
    }
  };

Back in MainActivity I have an onActivityResult to receive data from the thrid activity

  @Override
  protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    thirdAct = new ThirdActivity_ColorPicker();

    if(requestCode == RESULT_OK && resultCode == thirdAct.RESULT_CODE_RED){
      constraintLayout.findViewById(R.id.main_layout).setBackgroundColor(getColor(R.color.redBackground));
    }else if(requestCode == RESULT_OK && resultCode == thirdAct.RESULT_CODE_GREEN){
      constraintLayout.findViewById(R.id.main_layout).setBackgroundColor(getColor(R.color.greenBackground));
    }else if(requestCode == RESULT_OK && resultCode == thirdAct.RESULT_CODE_BLUE){
      constraintLayout.setBackgroundColor(getColor(R.color.blueBackground));
    }
  }

Result I would like is for the background color to change with the code above, but used correctly because I know I am doing something wrong somewhere. Thank you.

Answer 1

In your ThirdActivity_ColorPicker , change the code on each of your color button click, that is (Red, Green, Blue, etc), as below. This will set the Bundle data and result for the previous activity.

 Intent intentRed = new Intent();
 intentRed.putExtra(COLOR_CODE, 
 getApplicationContext().getResources().getColor(R.color.redBackground));
 setResult(Activity.RESULT_OK, intentRed);
 finish();

Then, in your MainActivity , in onActivityResult , make below changes:

 if (requestCode == COLOR_PICKER_REQUEST && resultCode == RESULT_OK) {
   if (data != null && data.getExtras() != null) {
      Bundle bundle = data.getExtras();
      int colorBg = bundle.getInt(COLOR_CODE);
      findViewById(R.id.mainBg).setBackgroundColor(colorBg);
    }
 }

COLOR_PICKER_REQUEST is the int , which you set for the startActivityForResult and COLOR_CODE is any String for the bundle key.