Is my method to set up android apps dimensions correct?

Question

I use Android studio as a development environment and My method to set up android apps dimensions is like that:

1- I create a layout for hdpi devices basing on Nexus S offered by Android Studio.

2- I put all dimensions (using dp and sp units) in the values-hdpi folder.

3- I make 9 copies from this folder and rename them as the following:

1. values-420dpi
2. values-560dpi
3. values-ldpi
4. values-mdpi
5. values-sw480dp
6. values-sw600dp
7. values-sw720dp
8. values-xhdpi
9. values-xxhdpi

4- After that, I open the layout file that I want to configure its dimensions and I select the following:

1. Nexus 5X FOR 420dpi
2. Nexus 6P FOR 560dpi
3. 2.7" QVGA FOR ldpi
4. 3.2" QVGA FOR mdpi
5. 5.4" FWVGA FOR sw480dp
6. Nexus 7 FOR sw600dp
7. Nexus 9 FOR sw720dp
8. Nexus 4 FOR xhdpi
9. Nexus 5 FOR xxhdpi

5- I start changing the dimensions in each file until layout fit within the selected device.

This was my method to set up android apps dimensions, and I want to know if it is correct? and if it exists another way to do the same thing but easily?

Answer 1

You should use only one type of selector. For example, in your case:

1. values-sw420dp
2. values-sw480dp
3. values-sw560dp
4. values-sw600dp
5. values-sw720dp

should be enough (but obviously that depends on the requirements of the app and the device you want to fully support). Why are you using also density-based selectors (like values-mdpi)? As you probably know, dp and sp dimensions are density independent.

It's worth adding that, if you design your layout carefully, you can reduce a lot the number of dimensions you need to explicitly declare. For example, you can use LinearLayouts with weighed children.

In complex projects, when I want the app to scale with the screen size, I usually use a script to generate all the dimens files starting from a reference one, applying the desired multiplier to every screen class. The actual code depends a lot on your specific needs, but an example in Java could be:

public class GenerateDimens {

    public static void main(String[] args) throws Exception {
        String resFolder = "app/src/main/res/";
        String dimensFileName = "dimens.xml";
        File source = new File(resFolder + "values-sw800dp", dimensFileName);
        File target = new File(resFolder + "values-sw0dp", dimensFileName);
        DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
        Document document = builder.parse(source);
        NodeList nodeList = document.getElementsByTagName("dimen");
        Pattern pattern = Pattern.compile("(\\d+).*");
        for (int i = 0; i < nodeList.getLength(); i++) {
            Node dimen = nodeList.item(i);
            String textContent = dimen.getTextContent();
            Matcher matcher = pattern.matcher(textContent);
            if (matcher.find()) {
                String oldValue = matcher.group(1);
                String newValue = String.valueOf((int) (Integer.parseInt(oldValue) / 1.33));
                dimen.setTextContent(textContent.replaceFirst(oldValue, newValue));
            }
        }
        TransformerFactory transformerFactory = TransformerFactory.newInstance();
        Transformer transformer = transformerFactory.newTransformer();
        transformer.setOutputProperty(OutputKeys.INDENT, "yes");
        transformer.setOutputProperty(OutputKeys.DOCTYPE_PUBLIC, "yes");
        document.setXmlStandalone(true);
        transformer.transform(new DOMSource(document), new StreamResult(target));
    }

}