Android Studio从单选按钮获取值并在其他地方使用它

Question

I've got the code below, to use a radio button and get the value and return it as a string for a function. Hoping that I could use it elsewhere in the main program. However, it doesn't. it would allow me to use the variable btn and if, I did the atl-enter suggestion by declaring it to final string [] , it'll return null. Most online tutorial and stackoverflow previous question only includes toasting text from whichever button chosen, within onCheckedChanged .

public String listeneronbutton() {
        String btn;
        radioGroup = (RadioGroup) findViewById(R.id.radioGroup);

        radioGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup radioGroup, int checkedID) {
                int selectedId = radioGroup.getCheckedRadioButtonId();
                radioButton = (RadioButton) findViewById(checkedID);
                Toast.makeText(getApplicationContext(), radioButton.getText(), Toast.LENGTH_SHORT).show();
                btn = String.valueOf(radioButton.getText());      //(error here: variable 'btn' is accessed from within inner class, needs to be declared final)
            }
        });
        return btn;
}

How do I get the function listeneronbutton() properly being able to get and return btn value?

Answer 1

you cannot have a method which adds the OnCheckedChangeListener and gets the String , at the same time (because separation of duties & the one method only should run once, the other method more often). alike this you can add method instanceRadioGroup() to onCreate() or onCreateView() and then get the current value with method getButtonText() .

also, the variable int checkedId is already being passed into the scope, so one can use that.

/** the handle for the {@link RadioGroup} */
private RadioGroup mRadioGroup = null;

/** this field holds the button's text */
private String mButtonText = null;

/** the setter for the field */
protected void setButtonText(@Nullable String value) {
    this.mButtonText = value;
}

/** the getter for the field */
protected String getButtonText() {
    return this.mButtonText;
}

/** it sets mButtonText by checkedId */
protected void updateButtonText(int checkedId) {
    if ((checkedId == -1)) {
        this.setButtonText(null);
    } else {
        RadioButton radioButton = (RadioButton) this.mRadioGroup.findViewById(checkedId);
        this.setButtonText(radioButton.getText());
    }
}

/** this code should only run once, onCreate() or onCreateView() */
protected void instanceRadioGroup() {

    /* setting the handle for the {@link RadioGroup} */
    this.mRadioGroup = (RadioGroup) findViewById(R.id.radioGroup);

    /* update the field with the text of the default selection */
    int checkedId = this.mRadioGroup.getCheckedRadioButtonId();
    this.updateButtonText(checkedId);

    /* and also add an onCheckedChange listener */
    this.mRadioGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
        @Override
        public void onCheckedChanged(RadioGroup radioGroup, int checkedId) {
            updateButtonText(checkedId);
        }
    });
}

Answer 2

Change your method like this :

public String listeneronbutton() {
    String btn;
    RadioGroup radioGroup =(RadioGroup)findViewById(R.id.radioGroup);
    int selectedId = radioGroup.getCheckedRadioButtonId();
    radioButton = (RadioButton) findViewById(checkedID);
    Toast.makeText(getApplicationContext(), radioButton.getText(), Toast.LENGTH_SHORT).show();
    btn = String.valueOf(radioButton.getText());      

    return btn;
}

Answer 3

Declare String btn as field. Thus you can access anywhere inside class.

public class Test{
    String btn;
    public String listeneronbutton(){

        return btn;
    }
}