Is my method to set up android apps dimensions correct?

Issue

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?

Solution

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));
    }

}

Answered By - manfcas