Android：带有单选按钮的 IF 语句不起作用

Question

I am trying to make a quiz app, so there are 5 radio buttons with possible answers, and only 1 is correct. Then there's a submit button, which has an onClick="clickMethod" to process the submission.

My clickMethod looks like this:

public void clickMethod(View v){
                RadioGroup group1 = (RadioGroup) findViewById(R.id.radioGroup1);
                int selected = group1.getCheckedRadioButtonId();
                RadioButton button1 = (RadioButton) findViewById(selected);
                if (button1.getText()=="Right Answer")
                    Toast.makeText(this,"Correct!",Toast.LENGTH_SHORT).show();
                else
                    Toast.makeText(this,"Incorrect.",Toast.LENGTH_SHORT).show();
    }

However I can't get the IF statement to work no matter what. If I try to make the toast with "button1.getText()" as parameter it does print the "Right Answer" string, but for some reason inside the IF statement it's not working, and the ELSE is always executed even when I check the right answer.

Does anyone know what might be happening or a better way to do this?

Answer 1

You're not comparing strings correctly.

The == operator is used when we have to compare the String object references. If two String variables point to the same object in memory, the comparison returns true. Otherwise, the comparison returns false. Note that the '==' operator does not compare the content of the text present in the String objects. It only compares the references the 2 Strings are pointing to.

Read here: http://www.javabeginner.com/learn-java/java-string-comparison

Answer 2

You should use the equals String method for String comparison:

public void clickMethod(View v){
    RadioGroup group1 = (RadioGroup) findViewById(R.id.radioGroup1);
    int selected = group1.getCheckedRadioButtonId();
    RadioButton button1 = (RadioButton) findViewById(selected);
    if ("Right Answer".equals(button1.getText())) {
        Toast.makeText(this,"Correct!",Toast.LENGTH_SHORT).show();
    } else {
        Toast.makeText(this,"Incorrect.",Toast.LENGTH_SHORT).show();
    }
}

Answer 3

In Java you can't compare Strings with == you have to use equals() :

if (button1.getText().equals("Right Answer"))

Answer 4

If you want to compare objects in Java you have to use equals() method and not the == operator..

if (button1.getText().toString().equals("Right Answer")) {
 Toast.makeText(this,"Correct!",Toast.LENGTH_SHORT).show();
} else {
 Toast.makeText(this,"Incorrect.",Toast.LENGTH_SHORT).show();
}