Android: Accessing string.xml using variable name

Question

I want to display a message to the user depending upon a prompt I receive from another part of the program. There can be a number of prompts & they are stored in an enum.

These are my prompts:

Defs.java

public enum Prompt
{
    PromptA,
    PromptB,
    PromptC,
}

I have the externalized strings stored in resources on these lines:

res/values/strings.xml

<string name="PromptA">Error in execution</string>
<string name="PromptB">Process completed successfully</string>
<string name="PromptC">Please try again</string>

Now in my main Activity screen a method is called by some other part:

public void showPrompt(Prompt prompt) {
    String message = getString(R.string.<**what-do-I-put-here?**>);
    //show a dialog box with message
}

I know this can be done with a huge if-else block (there are tons of prompts in the actual application) or a switch statement. It will be really ugly.

Is there a better way to do this?

@OceanBlue: Can't you use a string array resource indexed by prompt.ordinal()? Using ordinal is generally not recommended, as it may be fragile in case you reorder or add an item, but there are many more fragile things when using XML. — maaartinus
– maaartinus, Commented Sep 16, 2012 at 0:30

Femi · Accepted Answer · 2011-05-12 16:00:32Z

24

See Resources.getIdentifier: http://developer.android.com/reference/android/content/res/Resources.html#getIdentifier%28java.lang.String,%20java.lang.String,%20java.lang.String%29 . You can try something like this:

public void showPrompt(Prompt prompt, String label) {
    String message = (String) getResources().getText(getResources().getIdentifier(label, "string", null));
    //show a dialog box with message
}

Try that out and see what that does for you.

EDIT: meh. Try this instead.

public void showPrompt(Prompt prompt, String label) {
    String message = (String) getResources().getText(getResources().getIdentifier(label, "string", "<application package class>"));
    //show a dialog box with message
}

Turns out you have to specify the your package identifier (so if your AndroidManifest.xml has com.blah.blah.blah as the Package put that in the third parameter.

edited May 12, 2011 at 16:00

answered May 12, 2011 at 15:50

Femi

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5 Comments

OceanBlue Over a year ago

Thanks for taking the time to answer. I did notice in the link that you've added: "Note: use of this function is discouraged. It is much more efficient to retrieve resources by identifier than by name." So are the only choices in this fairly common situation, to write inefficient code or ugly, unmaintainable code. :-( Wish Google would add this capability to resources.

Femi Over a year ago

It is discouraged, but not deprecated; driving fast is discouraged as well, but not deprecated :). It is definitely more efficient doing it by resource id, but if you have a few instances where you wish to look up id by string name this is provided for you. If it was not to be used at all it would not have been provided. Or you could write your massive switch statement: your choice.

OceanBlue Over a year ago

Fair enough. At least this is an alternative to using the switch statement.

Greg Over a year ago

Use context.getPackageName() for the package parameter.

Vahid Amiri Over a year ago

This is a pretty good answer. I don't understand why it doesn't have more upvotes.

Leif Andersen · Accepted Answer · 2011-05-12 15:49:33Z

0

What you could do is just enclose the line in a if/else if/else statement, or a switch.

String message;
switch(prompt) {
case PromptA:
    message = getString(R.string.PromptA);
    break;
case PromptB:
    message = getString(R.string.PromptB);
    break;
case PromptC:
    message = getString(R.string.PromptC);
    break;
default:
    message = "";
}

I'm not on the machine I usually develop on, so there may be some silly syntax error in there, but the logic 'should' work.

answered May 12, 2011 at 15:49

Leif Andersen

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1 Comment

OceanBlue Over a year ago

Yes this is exactly what I am doing, but as I mentioned in my question.. this is getting pretty big & ugly since there are so many prompts. Also, in future if a prompt is added, I'd rather not change the code, just the xml.

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