Question

I am getting back to work on an app I worked on a while ago, when I had everything built around Android 2.2 Froyo.

I have updated my SDK for the latest APIs and noticed that the ClipboardManager features I was using are deprecated. I updated the code to use the newer ClipData model and tried it out on my Froyo phone and, of course, I get a NoClassDefFoundError in the new code.

I’ve had a look around SO and haven’t found any real discussions of general strategy for maintaining backwards compatibility.

I’m not entirely sure how I should handle this and other situations where the API differs, because I want users of all versions to be able to use my app.

Should I be doing a check as follows?

if(version == old){
   use old API;
} else {
   use new API;
}

If so, I have deprecated code in my class and Eclipse will have the warning there forever.

On the other hand, I could just build against an old version of the API and hope that new versions will handle it okay. But then I run the risk of building against buggy or low-performance code when a better alternative is available.

What is the best way to deal with this?

Answer 1

You can do that (checking the API version).

You can also use reflection to call the newer classes.

I wouldn’t worry about using deprecated methods as all Android versions are backwards compatible, saying that you want to watch when things are for 3.0 Honeycomb as these are a little different.

Here’s an explanation of how to use reflection: (yes it’s been on SO before, so maybe search for reflection)

http://www.youtube.com/watch?v=zNmohaZYvPw&feature=player_detailpage#t=2087s

I’m looking at making the project this is in available but until then here’s some code:

(You could do this in a class that extends Application i.e. one time setup)

 public static Method getExternalFilesDir;

    static {
            try {
                    Class<?> partypes[] = new Class[1];
                    partypes[0] = String.class;
                    getExternalFilesDir = Context.class.getMethod("getExternalFilesDir", partypes);
            } catch (NoSuchMethodException e) {
                    Log.e(TAG, "getExternalFilesDir isn't available in this devices api");
            }
    } 

Now getExternalFilesDir() is only available on API level 8 or above, so I want to use this if they have (Froyo), but otherwise I need another method.

Now I have my test for the method I can go ahead and attempt to use it:

  if(ClassThatExtendsApplication.getExternalFilesDir != null){
            Object arglist[] = new Object[1];
            arglist[0] = null;  
            File path = (File) ClassThatExtendsApplication.getExternalFilesDir.invoke(context, arglist);
           // etc etc
  } else {
      // Not available do something else (like your deprecated methods / or load a different class / or notify they should get a newer version of Android to enhance your app ;-))
  }

Hope that helps and shortcuts a lot of googling 🙂

P.S. if in the else you want to use your deprectated methods still, just add the @SuppressWarnings("deprecation") annotation above it, This will get rid of the warning and you have done it for the right reasons as you are using the latest API’s when possible.