AndroidDropdownPicker and AndroidDialogPicker (facebook#22999)

Summary:
Changelog:
----------

[Android] [Changed] - As mentioned in facebook#22990, I have moved native components required by PickerAndroid.android.js into separate files and added Flow Typing.
Pull Request resolved: facebook#22999

Differential Revision: D13697130

Pulled By: TheSavior

fbshipit-source-id: 42da73d82cca45fefa066871eed5a637811643c8

Libraries/Components/Picker/AndroidDialogPickerNativeComponent.js

@@ -0,0 +1,47 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow
+ */
+
+'use strict';
+
+const requireNativeComponent = require('requireNativeComponent');
+
+import type {SyntheticEvent} from 'CoreEventTypes';
+import type {TextStyleProp} from 'StyleSheet';
+import type {NativeComponent} from 'ReactNative';
+
+type PickerAndroidChangeEvent = SyntheticEvent<
+  $ReadOnly<{|
+    position: number,
+  |}>,
+>;
+
+type Item = $ReadOnly<{|
+  label: string,
+  value: ?(number | string),
+  color?: ?number,
+|}>;
+
+type NativeProps = $ReadOnly<{|
+  enabled?: ?boolean,
+  items: $ReadOnlyArray<Item>,
+  mode?: ?('dialog' | 'dropdown'),
+  onSelect?: (event: PickerAndroidChangeEvent) => void,
+  selected: number,
+  prompt?: ?string,
+  testID?: string,
+  style?: ?TextStyleProp,
+  accessibilityLabel?: ?string,
+|}>;
+
+type DialogPickerNativeType = Class<NativeComponent<NativeProps>>;
+
+module.exports = ((requireNativeComponent(
+  'AndroidDialogPicker',
+): any): DialogPickerNativeType);

Libraries/Components/Picker/AndroidDropdownPickerNativeComponent.js

@@ -0,0 +1,47 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow
+ */
+
+'use strict';
+
+const requireNativeComponent = require('requireNativeComponent');
+
+import type {SyntheticEvent} from 'CoreEventTypes';
+import type {TextStyleProp} from 'StyleSheet';
+import type {NativeComponent} from 'ReactNative';
+
+type PickerAndroidChangeEvent = SyntheticEvent<
+  $ReadOnly<{|
+    position: number,
+  |}>,
+>;
+
+type Item = $ReadOnly<{|
+  label: string,
+  value: ?(number | string),
+  color?: ?number,
+|}>;
+
+type NativeProps = $ReadOnly<{|
+  enabled?: ?boolean,
+  items: $ReadOnlyArray<Item>,
+  mode?: ?('dialog' | 'dropdown'),
+  onSelect?: (event: PickerAndroidChangeEvent) => void,
+  selected: number,
+  prompt?: ?string,
+  testID?: string,
+  style?: ?TextStyleProp,
+  accessibilityLabel?: ?string,
+|}>;
+
+type DropdownPickerNativeType = Class<NativeComponent<NativeProps>>;
+
+module.exports = ((requireNativeComponent(
+  'AndroidDropdownPicker',
+): any): DropdownPickerNativeType);

Libraries/Components/Picker/PickerAndroid.android.js

@@ -10,14 +10,12 @@
 
 'use strict';
 
+const AndroidDropdownPickerNativeComponent = require('AndroidDropdownPickerNativeComponent');
+const AndroidDialogPickerNativeComponent = require('AndroidDialogPickerNativeComponent');
 const React = require('React');
 const StyleSheet = require('StyleSheet');
 
 const processColor = require('processColor');
-const requireNativeComponent = require('requireNativeComponent');
-
-const DropdownPicker = requireNativeComponent('AndroidDropdownPicker');
-const DialogPicker = requireNativeComponent('AndroidDialogPicker');
 
 const REF_PICKER = 'picker';
 const MODE_DROPDOWN = 'dropdown';
@@ -103,7 +101,9 @@ class PickerAndroid extends React.Component<
 
   render() {
     const Picker =
-      this.props.mode === MODE_DROPDOWN ? DropdownPicker : DialogPicker;
+      this.props.mode === MODE_DROPDOWN
+        ? AndroidDropdownPickerNativeComponent
+        : AndroidDialogPickerNativeComponent;
 
     const nativeProps = {
       enabled: this.props.enabled,