Android, get resource id by string?

Question

Is there a better way to do this:

 int drawable; switch(mSignalStrength) { case 0: drawable = R.drawable.signal_0; break; case 1: drawable = R.drawable.signal_1; break; case 2: drawable = R.drawable.signal_2; break; case 3: drawable = R.drawable.signal_3; break; case 4: drawable = R.drawable.signal_4; break; case 5: drawable = R.drawable.signal_5; break; default: drawable = -1; }

I'm trying to replace the switch statement with some int getDrawableIdByString("signal_" + mSignalStrength) function.

Use reflection: getIdentifier(). You can return the resource id by passing its name. — Phantômaxx
– Phantômaxx, Commented Nov 2, 2015 at 9:40
@warlock I've got the same code repeated 6 times, for different values of signal strength. That's ugly. — fadedbee
– fadedbee, Commented Nov 2, 2015 at 10:14
@chrisdew, this is just a switch case , this will run on behalf of the value provided in mSignalStrength, In that case of repeating you should post the complete problem, what you are trying to achieve and how — Lakhwinder Singh
– Lakhwinder Singh, Commented Nov 2, 2015 at 10:17

Marko · Accepted Answer · 2015-11-02 10:31:47Z

As someone mentioned in the comments, you can use the

getIdentifier(String name, String defType, String defPackage)

For you case, like this

int resId = getResources().getIdentifier("signal_" + mSignalStrength, "drawable", getPackageName());

Phantômaxx · Accepted Answer · 2015-11-02 11:17:19Z

By using reflection, you can return the resource id by passing its name.
This is what I use when I need something like that:

1 - Add this method to your code:

protected final static int getResourceID (final String resName, final String resType, final Context ctx) { final int ResourceID = ctx.getResources().getIdentifier(resName, resType, ctx.getApplicationInfo().packageName); if (ResourceID == 0) { throw new IllegalArgumentException ( "No resource string found with name " + resName ); } else { return ResourceID; } }

2 - Use it like this:

int myID = getResourceID("your_resource_name", "drawable", getApplicationContext());

Note (1): no path (and no extension, in case of images).
Note (2): use "drawable" for drawables, "string" for strings, ...

JoeyJubb · Accepted Answer · 2015-11-02 11:12:48Z

The way you're doing it is the most readable and robust way.

It allows you to add / remove items later down the line and doesn't tie you in to a specific naming convention.

It's easier to read because you can just click through to the drawable resource from the code and see for yourself exactly which drawable matches which case -- something that becomes a bit harder when you're generating the id this way.

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