Fixing Compatibility Issues

Let's now go into our activity_settings XML file and see what we need to fix here. 0:00 First, you'll notice that the toolbar has a red error line under it. 0:05 If we hover over the error message, we'll see that the toolbar widget wasn't 0:09 available on the platform in API level 19 and was introduced in API level 21. 0:12 To fix this problem, the AppCompat team created an identical view widget called 0:17 Toolbar that sits in the android.support.v7.widget package. 0:21 So, we'll replace the current toolbar with that now. 0:25 That should take care of the activity_settings.xml file. 0:30 The next thing we'll do is look at the activity files themselves and 0:33 see what needs to change. 0:36 Let's take a look at the SettingsActivity.java file. 0:38 There are a handful of errors we need to take care of here. 0:41 First, you'll see that the toolbar is red. 0:44 Hovering over that, we're told that the toolbar can't be found. 0:47 That's because exactly like the widget in the activitt_setting.xml file, 0:50 toolbar isn't available to use on API level 19. 0:54 We'll change the import statement for the toolbar to use the support toolbar and 0:57 that error message will go away. 1:00 Next, it's very important that we should change all of our activities to extend 1:03 from AppCompatActivity, rather that simply activity. 1:07 One requirement for using AppCompatActivity is that the theme that 1:10 the activity uses must extend from AppCompat. 1:13 Since we already changed that, we're good to go. 1:16 If your theme does not extend from AppCompat, 1:18 your app will crash if you attempt to start an AppCompat activity. 1:20 Lastly, in this file, we need to set up the SupportActionBar, 1:24 rather than simply saying setActionBar. 1:27 Along the same lines, 1:30 we need to change our getActionBar call to use getSupportAcitonBar. 1:31 If we don't, 1:35 we'll get a NullPointerException when that line is executed. 1:35 Now that we've got all this visible errors taken care of in the activity, 1:39 let's run the app and see what happens. 1:42 Before we run the app though, we'll have to revert our hack in the build.gradle 1:44 file that lowered our compile SDK version. 1:47 I'll do that real quick and then bring up an emulator running Android 25 as well as 1:49 an emulator running Android 19 so we can compare any differences. 1:53 Clicking through on the newer emulator, the app looks good. 2:03 Let's check out the emulator running the older version of Android. 2:11 List screen looks good, album screen looks good, but the slider for 2:15 the song playback screen looks different. 2:19 It looks like it belongs on an older version of Android. 2:22 Let's check out the settings activity before going back into Android Studio 2:24 to fix these errors. 2:27 In the settings activity, 2:29 the switches look really weird, they don't seem to fit in with our current theme. 2:30 Let's first go back into the SongPlaybackActivity and 2:34 see what's going on. 2:36 There aren't any errors. 2:40 But we haven't changed this activity or 2:41 the album list or detail activities to extend from AppCompatActivity yet. 2:42 Remember, for a consistent visual look and 2:47 feel, it's important to extend your activities from AppCompatActivity. 2:49 Let's go ahead and do that for the SongPlaybackActivity now and 2:52 run the app again. 2:55 Wonderful, now our song playback activity looks the exact same on 3:03 both versions of Android. 3:06