Why do I get
Cannot resolve symbol 'R' ?
Most likely you have some kind of error in an XML file, e g
activity_main.xml. Fix this problem and rebuild the project:
- Build->Clean project
- Build->Rebuild project
Most likely you in your Java code are referring to a view you think is defined in an XML file, e g
If your Java code looks like this:
EditText et = findViewById(R.id.textField); Button barilla = findViewById(R.id.button); Button b = (Button) view;
And you get a compilation error saying
Cannot resolve symbol 'button' associated with the highlighted line. Then make sure your layout has defined
<Button android:id="@+id/button" android:layout_width="wrap_content" android:layout_height="wrap_content" android:onClick="helloPressed" android:text="ManUtd loosers" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintLeft_toLeftOf="parent" app:layout_constraintRight_toRightOf="parent" app:layout_constraintTop_toTopOf="parent" />
Run time problems
Could not find method ... mean?
Most likely you've added an OnClickListener, using either XML or the Design view, to a Button and at the same time forgotten to the actual method which will be called by Android when clicking (in runtime).
Check out the exercise [Android:Exercises_Android_basics#Add_an_action_to_the_view Add an action to the view] and the ones following that.
It simply means you're doing a typecast which, in runtime, did not work since the object you're casting is not of the type you're casting to. As an exmaple you can't cast a Spinner to a Button.
This is usually caused by looking up, using
findViewById using the wrong id.