为什么我的代码不起作用？

Question

I have the following code to get information from a rating bar and put it into a TextView but it doesn't seem to be working:

public class MainActivity extends Activity {

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

    TextView ratingText = (TextView) findViewById(R.id.ratingText);
    RatingBar rating=(RatingBar)findViewById(R.id.rating);
    rating.setOnRatingBarChangeListener((OnRatingBarChangeListener) this);

}

public void onRatingChanged(RatingBar ratingBar,float rating, boolean fromUser){
    ratingText.setText(""+this.rating.getRating()); 
}

At the second last line of code it is giving me the following error: "rating cannot be resolved or is not a field" and "ratingText cannot be resolved". I am wondering why I am getting these errors and how to fix them. Thanks.

Answer 1

a-) I think your problem is that you need that your class MainActivity implements OnRatingBarChangeListener :

public class MainActivity extends Activity implements OnRatingBarChangeListener {

}

b-) Another possible error is that you need to make sure that you do NOT have this in your imports:

import android.R;

but:

import your.application.packagename.R;

c-) Declare the TextView ratingText and the RatingBar rating outside of the method, as an attribute of the class.

Hope it helps!

Answer 2

Take a look at this for a solution.

r.string error "cannot be resolved or is not a field"

Main idea is to make sure your R reference is correct, and try by deleting the gen files and rebuild the project.

EDIT:: This was incorrect the problem was stated in another answer. by @Marv

Answer 3

It is because you create your ratingText and rating in the onCreate method. This means they are only available inside this method.

Try to do something like this:

private TextView ratingText = null;
private RatingBar rating = null;

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

    ratingText = (TextView) findViewById(R.id.ratingText);
    rating=(RatingBar)findViewById(R.id.rating);
    rating.setOnRatingBarChangeListener((OnRatingBarChangeListener) this);

}

This way they are available in the entire class and you can use them in onRatingChanged .

Answer 4

try this.

public class Test extends Activity implements OnRatingBarChangeListener{

    TextView ratingText;
    RatingBar rating;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
         // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);
        setContentView(R.layout.info);

        ratingText = (TextView) findViewById(R.id.textView_aaa);
        rating=(RatingBar)findViewById(R.id.ratingBar1);
        rating.setOnRatingBarChangeListener((OnRatingBarChangeListener) this);

    }

    @Override
    public void onRatingChanged(RatingBar ratingBar, float rating,
        boolean fromUser) {
        // TODO Auto-generated method stub
        ratingText.setText(""+this.rating.getRating());
    }

}