Question

One situation, three different approaches.

One (variables are declared at the top of the activity as private):

radioGroup = (RadioGroup) findViewById(R.id.RadioGroup);

radioButton1 = (RadioButton) findViewById(R.id.RadioButton1);
radioButton2 = (RadioButton) findViewById(R.id.RadioButton2);

radioGroup.setOnCheckedChangeListener(new OnCheckedChangeListener() {

    @Override
    public void onCheckedChanged(RadioGroup group, int checkedId) {
        if (radioButton1.isChecked()) {
            // do something
        } else if (radioButton2.isChecked()) {
            // do something
        }
    }
});

Two:

final RadioGroup radioGroup = (RadioGroup) findViewById(R.id.RadioGroup);

final RadioButton radioButton1 = (RadioButton) findViewById(R.id.RadioButton1);
final RadioButton radioButton2 = (RadioButton) findViewById(R.id.RadioButton2);

radioGroup.setOnCheckedChangeListener(new OnCheckedChangeListener() {

    @Override
    public void onCheckedChanged(RadioGroup group, int checkedId) {
        if (radioButton1.isChecked()) {
            // do something
        } else if (radioButton2.isChecked()) {
            // do something
        }
    }
});

Three:

((RadioGroup) findViewById(R.id.RadioGroup)).setOnCheckedChangeListener(new OnCheckedChangeListener() {

    @Override
    public void onCheckedChanged(RadioGroup group, int checkedId) {
        if (((RadioButton) findViewById(R.id.RadioButton1)).isChecked()) {
            // do something
        } else if (((RadioButton) findViewById(R.id.RadioButton2)).isChecked()) {
            // do something
        }
    }
});

Which one is the “best” approach or it doesn’t mind?

Answer 1

I don’t think there is any difference between one and two. Three however, will suffer a performance penalty, because every time onCheckedChanged is fired, it will have to call findViewById for each radio button. The other methods are “caching” a reference to the RadioButton.