switch case statement error: case expressions must be constant expression

Question

In a regular Android project, constants in the resource R class are declared like this:

public static final int main=0x7f030004;

However, as of ADT 14, in a library project, they will be declared like this:

public static int main=0x7f030004;

In other words, the constants are not final in a library project. Therefore your code would no longer compile.

The solution for this is simple: Convert the switch statement into an if-else statement.

public void onClick(View src)
{
    int id = src.getId();
    if (id == R.id.playbtn){
        checkwificonnection();
    } else if (id == R.id.stopbtn){
        Log.d(TAG, "onClick: stopping srvice");
        Playbutton.setImageResource(R.drawable.playbtn1);
        Playbutton.setVisibility(0); //visible
        Stopbutton.setVisibility(4); //invisible
        stopService(new Intent(RakistaRadio.this,myservice.class));
        clearstatusbar();
        timer.cancel();
        Title.setText(" ");
        Artist.setText(" ");
    } else if (id == R.id.btnmenu){
        openOptionsMenu();
    }
}

http://tools.android.com/tips/non-constant-fields

You can quickly convert a switch statement to an if-else statement using the following:

In Eclipse
Move your cursor to the switch keyword and press Ctrl + 1 then select

Convert 'switch' to 'if-else'.

In Android Studio
Move your cursor to the switch keyword and press Alt + Enter then select

Replace 'switch' with 'if'.

Unchecking "Is Library" in the project Properties worked for me.

Solution can be done be this way:

1. Just assign the value to Integer
2. Make variable to final

Example:

public static final int cameraRequestCode = 999;

Hope this will help you.

R.id.*, since ADT 14 are not more declared as final static int so you can not use in switch case construct. You could use if else clause instead.

Simple solution for this problem is :

Click on the switch and then press CTL+1, It will change your switch to if-else block statement, and will resolve your problem

How about this other solution to keep the nice switch instead of an if-else:

private enum LayoutElement {
    NONE(-1),
    PLAY_BUTTON(R.id.playbtn),
    STOP_BUTTON(R.id.stopbtn),
    MENU_BUTTON(R.id.btnmenu);

    private static class _ {
        static SparseArray<LayoutElement> elements = new SparseArray<LayoutElement>();
    }

    LayoutElement(int id) {
        _.elements.put(id, this);
    }

    public static LayoutElement from(View view) {
        return _.elements.get(view.getId(), NONE);
    }

}

So in your code you can do this:

public void onClick(View src) {
    switch(LayoutElement.from(src)) {
    case PLAY_BUTTTON:
        checkwificonnection();
        break;

    case STOP_BUTTON:
        Log.d(TAG, "onClick: stopping srvice");
        Playbutton.setImageResource(R.drawable.playbtn1);
        Playbutton.setVisibility(0); //visible
        Stopbutton.setVisibility(4); //invisible
        stopService(new Intent(RakistaRadio.this,myservice.class));
        clearstatusbar();
        timer.cancel();
        Title.setText(" ");
        Artist.setText(" ");
        break;

    case MENU_BUTTON:
        openOptionsMenu();
        break;
    }
}

Enums are static so this will have very limited impact. The only window for concern would be the double lookup involved (first on the internal SparseArray and later on the switch table)

That said, this enum can also be utilised to fetch the items in a fluent manner, if needed by keeping a reference to the id... but that's a story for some other time.

It was throwing me this error when I using switch in a function with variables declared in my class:

private void ShowCalendar(final Activity context, Point p, int type) 
{
    switch (type) {
        case type_cat:
            break;

        case type_region:
            break;

        case type_city:
            break;

        default:
            //sth
            break;
    }
}

The problem was solved when I declared final to the variables in the start of the class:

final int type_cat=1, type_region=2, type_city=3;