fix adapter problem of targetSdkVersion < 23;

lib/src/main/java/com/tbruyelle/rxpermissions2/RxPermissions.java

@@ -41,6 +41,14 @@ public class RxPermissions {
     @VisibleForTesting
     Lazy<RxPermissionsFragment> mRxPermissionsFragment;
 
+    public static RxPermissions with(@NonNull final FragmentActivity activity){
+        return new RxPermissions(activity);
+    }
+
+    public static RxPermissions with(@NonNull final Fragment fragment){
+        return new RxPermissions(fragment);
+    }
+
     public RxPermissions(@NonNull final FragmentActivity activity) {
         mRxPermissionsFragment = getLazySingleton(activity.getSupportFragmentManager());
     }

lib/src/main/java/com/tbruyelle/rxpermissions2/RxPermissionsFragment.java

@@ -2,11 +2,13 @@
 
 import android.annotation.TargetApi;
 import android.content.pm.PackageManager;
+import android.os.Binder;
 import android.os.Build;
 import android.os.Bundle;
 import android.support.annotation.NonNull;
 import android.support.v4.app.Fragment;
 import android.support.v4.app.FragmentActivity;
+import android.support.v4.content.PermissionChecker;
 import android.util.Log;
 
 import java.util.HashMap;
@@ -75,7 +77,21 @@ boolean isGranted(String permission) {
         if (fragmentActivity == null) {
             throw new IllegalStateException("This fragment must be attached to an activity.");
         }
-        return fragmentActivity.checkSelfPermission(permission) == PackageManager.PERMISSION_GRANTED;
+
+        // when targetSdkVersion < Build.VERSION_CODES.M(23), calling like below:
+        // ContextWrapper.checkSelfPermission or Context.checkSelfPermission ,
+        // it will always return PERMISSION_GRANTED
+        boolean permissionGranted;
+        if (fragmentActivity.getApplicationInfo().targetSdkVersion < Build.VERSION_CODES.M) {
+//            permissionGranted = PermissionChecker.checkPermission(fragmentActivity, permission,
+//                    Binder.getCallingPid(), Binder.getCallingUid(), fragmentActivity.getPackageName())
+//                    == PackageManager.PERMISSION_GRANTED;
+            permissionGranted = PermissionChecker.checkSelfPermission(fragmentActivity, permission)
+                    == PackageManager.PERMISSION_GRANTED;
+        } else {
+            permissionGranted = fragmentActivity.checkSelfPermission(permission) == PackageManager.PERMISSION_GRANTED;
+        }
+        return permissionGranted;
     }
 
     @TargetApi(Build.VERSION_CODES.M)