Adding Google Play Services and checking for Google Play Services before attempting GCM implementation

app/build.gradle

@@ -24,4 +24,5 @@ dependencies {
     compile 'com.github.bumptech.glide:glide:3.5.2'
     compile 'com.android.support:appcompat-v7:21.0.2'
     compile 'com.android.support:support-annotations:22.0.0'
+    compile 'com.google.android.gms:play-services-gcm:7.0.0'
 }

app/src/main/java/com/example/android/sunshine/app/MainActivity.java

@@ -19,15 +19,19 @@ import android.content.Intent;
 import android.net.Uri;
 import android.os.Bundle;
 import android.support.v7.app.ActionBarActivity;
+import android.util.Log;
 import android.view.Menu;
 import android.view.MenuItem;
 
 import com.example.android.sunshine.app.sync.SunshineSyncAdapter;
+import com.google.android.gms.common.ConnectionResult;
+import com.google.android.gms.common.GooglePlayServicesUtil;
 
 public class MainActivity extends ActionBarActivity implements ForecastFragment.Callback {
 
     private final String LOG_TAG = MainActivity.class.getSimpleName();
     private static final String DETAILFRAGMENT_TAG = "DFTAG";
+    private final static int PLAY_SERVICES_RESOLUTION_REQUEST = 9000;
 
     private boolean mTwoPane;
     private String mLocation;
@@ -61,6 +65,13 @@ public class MainActivity extends ActionBarActivity implements ForecastFragment.
         forecastFragment.setUseTodayLayout(!mTwoPane);
 
         SunshineSyncAdapter.initializeSyncAdapter(this);
+
+        if (!checkPlayServices()) {
+            // this is where we could either prompt a user that they should install
+            // the latest version of Google Play Services, or add an error snackbar
+            // that some features won't be available.
+        }
+
     }
 
     @Override
@@ -82,16 +93,22 @@ public class MainActivity extends ActionBarActivity implements ForecastFragment.
             startActivity(new Intent(this, SettingsActivity.class));
             return true;
         }
-
         return super.onOptionsItemSelected(item);
     }
 
     @Override
     protected void onResume() {
         super.onResume();
-        String location = Utility.getPreferredLocation( this );
+
+        // If Google Play Services is not available, some features, such as GCM-powered weather
+        // alerts, will not be available.
+        if (!checkPlayServices()) {
+            // Store regID as null
+        }
+
+        String location = Utility.getPreferredLocation(this);
         // update the location in our second pane using the fragment manager
-            if (location != null && !location.equals(mLocation)) {
+        if (location != null && !location.equals(mLocation)) {
             ForecastFragment ff = (ForecastFragment)getSupportFragmentManager().findFragmentById(R.id.fragment_forecast);
             if ( null != ff ) {
                 ff.onLocationChanged();
@@ -125,4 +142,24 @@ public class MainActivity extends ActionBarActivity implements ForecastFragment.
             startActivity(intent);
         }
     }
+
+    /**
+     * Check the device to make sure it has the Google Play Services APK. If
+     * it doesn't, display a dialog that allows users to download the APK from
+     * the Google Play Store or enable it in the device's system settings.
+     */
+    private boolean checkPlayServices() {
+        int resultCode = GooglePlayServicesUtil.isGooglePlayServicesAvailable(this);
+        if (resultCode != ConnectionResult.SUCCESS) {
+            if (GooglePlayServicesUtil.isUserRecoverableError(resultCode)) {
+                GooglePlayServicesUtil.getErrorDialog(resultCode, this,
+                        PLAY_SERVICES_RESOLUTION_REQUEST).show();
+            } else {
+                Log.i(LOG_TAG, "This device is not supported.");
+                finish();
+            }
+            return false;
+        }
+        return true;
+    }
 }