[camera] Enable camera plugin to compile with earlier android apis with custom AndroidManifest settings

packages/camera/CHANGELOG.md

@@ -1,3 +1,10 @@
+## 0.5.1
+
+* Can now be compiled with earlier Android sdks below 21 when
+`<uses-sdk tools:overrideLibrary="io.flutter.plugins.camera"/>` has been added to the project
+`AndroidManifest.xml`. For sdks below 21, the plugin won't be registered and calls to it will throw
+a `MissingPluginException.`
+
 ## 0.5.0
 
 * **Breaking Change** This plugin no longer handles closing and opening the camera on Android

packages/camera/android/src/main/java/io/flutter/plugins/camera/CameraPlugin.java

@@ -82,11 +82,13 @@ public void onOrientationChanged(int i) {
   }
 
   public static void registerWith(Registrar registrar) {
-    if (registrar.activity() == null) {
+    if (registrar.activity() == null || Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
       // When a background flutter view tries to register the plugin, the registrar has no activity.
-      // We stop the registration process as this plugin is foreground only.
+      // We stop the registration process as this plugin is foreground only. Also, if the sdk is
+      // less than 21 (min sdk for Camera2) we don't register the plugin.
       return;
     }
+
     final MethodChannel channel =
         new MethodChannel(registrar.messenger(), "plugins.flutter.io/camera");
 
@@ -126,8 +128,8 @@ public void onMethodCall(MethodCall call, final Result result) {
             cameras.add(details);
           }
           result.success(cameras);
-        } catch (CameraAccessException e) {
-          result.error("cameraAccess", e.getMessage(), null);
+        } catch (Exception e) {
+          handleException(e, result);
         }
         break;
       case "initialize":
@@ -168,8 +170,8 @@ public void onMethodCall(MethodCall call, final Result result) {
           try {
             camera.startPreviewWithImageStream();
             result.success(null);
-          } catch (CameraAccessException e) {
-            result.error("CameraAccess", e.getMessage(), null);
+          } catch (Exception e) {
+            handleException(e, result);
           }
           break;
         }
@@ -178,8 +180,8 @@ public void onMethodCall(MethodCall call, final Result result) {
           try {
             camera.startPreview();
             result.success(null);
-          } catch (CameraAccessException e) {
-            result.error("CameraAccess", e.getMessage(), null);
+          } catch (Exception e) {
+            handleException(e, result);
           }
           break;
         }
@@ -198,6 +200,18 @@ public void onMethodCall(MethodCall call, final Result result) {
     }
   }
 
+  // We move catching CameraAccessException out of onMethodCall because it causes a crash
+  // on plugin registration for sdks incompatible with Camera2 (< 21). We want this plugin to
+  // to be able to compile with <21 sdks for apps that want the camera and support earlier version.
+  @SuppressWarnings("ConstantConditions")
+  private void handleException(Exception exception, Result result) {
+    if (exception instanceof CameraAccessException) {
+      result.error("CameraAccess", exception.getMessage(), null);
+    }
+
+    throw (RuntimeException) exception;
+  }
+
   private static class CompareSizesByArea implements Comparator<Size> {
     @Override
     public int compare(Size lhs, Size rhs) {

packages/camera/pubspec.yaml

@@ -2,7 +2,7 @@ name: camera
 description: A Flutter plugin for getting information about and controlling the
   camera on Android and iOS. Supports previewing the camera feed, capturing images, capturing video,
   and streaming image buffers to dart.
-version: 0.5.0
+version: 0.5.1
 authors:
   - Flutter Team <flutter-dev@googlegroups.com>
   - Luigi Agosti <luigi@tengio.com>