当团队准备着手做 APP 时,我们把目标对准了 Flutter,尤其近期 Flutter 的使用热度一直不断攀升。由于第一次使用 Flutter,就想通过自己的实践去提升自己的能力。
在做 APP 时,我们用到了视频播放器,当前使用官方提供的插件「video_player」https://github.com/flutter/plugins/tree/master/packages/video_player,可能该插件在国外没什么问题,但国内很多视频播放器做的很精良,自定义功能很齐全。
举一个例子:国内的 APP 全屏播放视频时,几乎都是横向全屏的,但官方提供的插件在 iOS 端是竖向直播的,效果很不好。
因此萌生了自己想做一个视频播放插件:
要求
- Android 和 iOS 端都是使用原生开发,体验效果好;
- 尽可能使用 GitHub Star 靠前的第三方开源插件,减轻自己的开发工作量;
根据以上的「2」要求,我主要找到了 lipangit/JiaoZiVideoPlayer
和 newyjp/JPVideoPlayer
好了,所有铺垫都做好了,我们开始一步步实现插件开发吧~
1. 创建插件
flutter create --org com.***.test --template=plugin bms_video_player
2. 创建关联类
在 lib/bms_video_player.dart
文件中创建 BmsVideoPlayerController
类,用于和原生代码关联:
class BmsVideoPlayerController {
MethodChannel _channel;
BmsVideoPlayerController.init(int id) {
_channel = new MethodChannel('bms_video_player_$id');
}
Future<void> loadUrl(String url) async {
assert(url != null);
return _channel.invokeMethod('loadUrl', url);
}
}
这里存在的 MethodChannel
有待于下一次好好研究研究。
3. 创建 Callback
typedef void BmsVideoPlayerCreatedCallback(BmsVideoPlayerController controller);
4. 创建 Widget 布局
创建 Widget,用于添加原生布局:
class BmsVideoPlayer extends StatefulWidget {
final BmsVideoPlayerCreatedCallback onCreated;
final x;
final y;
final width;
final height;
BmsVideoPlayer({
Key key,
@required this.onCreated,
@required this.x,
@required this.y,
@required this.width,
@required this.height,
});
@override
State<StatefulWidget> createState() => _VideoPlayerState();
}
class _VideoPlayerState extends State<BmsVideoPlayer> {
@override
void initState() {
super.initState();
}
@override
Widget build(BuildContext context) {
return GestureDetector(
behavior: HitTestBehavior.opaque,
child: nativeView(),
onHorizontalDragStart: (DragStartDetails details) {
print("onHorizontalDragStart: ${details.globalPosition}");
// if (!controller.value.initialized) {
// return;
// }
// _controllerWasPlaying = controller.value.isPlaying;
// if (_controllerWasPlaying) {
// controller.pause();
// }
},
onHorizontalDragUpdate: (DragUpdateDetails details) {
print("onHorizontalDragUpdate: ${details.globalPosition}");
print(details.globalPosition);
// if (!controller.value.initialized) {
// return;
// }
// seekToRelativePosition(details.globalPosition);
},
onHorizontalDragEnd: (DragEndDetails details) {
print("onHorizontalDragEnd");
// if (_controllerWasPlaying) {
// controller.play();
// }
},
onTapDown: (TapDownDetails details) {
print("onTapDown: ${details.globalPosition}");
},
);
}
nativeView() {
if (defaultTargetPlatform == TargetPlatform.android) {
return AndroidView(
viewType: 'plugins.bms_video_player/view',
onPlatformViewCreated: onPlatformViewCreated,
creationParams: <String,dynamic>{
"x": widget.x,
"y": widget.y,
"width": widget.width,
"height": widget.height,
},
creationParamsCodec: const StandardMessageCodec(),
);
} else {
return UiKitView(
viewType: 'plugins.bms_video_player/view',
onPlatformViewCreated: onPlatformViewCreated,
creationParams: <String,dynamic>{
"x": widget.x,
"y": widget.y,
"width": widget.width,
"height": widget.height,
},
creationParamsCodec: const StandardMessageCodec(),
);
}
}
Future<void> onPlatformViewCreated(id) async {
if (widget.onCreated == null) {
return;
}
widget.onCreated(new BmsVideoPlayerController.init(id));
}
}
这里的 AndroidView
和 UiKitView
字如其意,不同的系统使用不同的 widget。
其中,AndroidView
和 UiKitView
都自带几个参数,如:
- viewType:用于区分不同的插件名称和来源;
- onPlatformViewCreated:用于在 widget 创建后,调用其函数 (
onPlatformViewCreated
); - creationParams:用于将参数传递给原生控件。
下面开始,根据 iOS 和 Android 分别注册插件和实现功能,首先是 Android。
5.1 注册 ViewFactory
在 BmsVideoPlayerPlugin
类中注册 ViewFactory
:new VideoViewFactory(registrar)
,并命名为 「plugins.bms_video_player/view」:
public static void registerWith(Registrar registrar) {
registrar.platformViewRegistry()
.registerViewFactory("plugins.bms_video_player/view", new VideoViewFactory(registrar));
}
5.2 创建 VideoViewFactory
该 VideoViewFactory
类需要集成类 PlatformViewFactory
,实现函数:create(Context context, int viewId, Object args)
:
public class VideoViewFactory extends PlatformViewFactory {
private final Registrar registrar;
public VideoViewFactory(Registrar registrar) {
super(StandardMessageCodec.INSTANCE);
this.registrar = registrar;
}
@Override
public PlatformView create(Context context, int viewId, Object args) {
return new VideoView(context, viewId, args, this.registrar);
}
}
开始我们的正餐了,创建实现类 VideoView
。
5.3 VideoView
public class VideoView implements PlatformView, MethodCallHandler {
private final JzvdStd jzvdStd;
private final MethodChannel methodChannel;
private final Registrar registrar;
VideoView(Context context, int viewId, Object args, Registrar registrar) {
this.registrar = registrar;
this.jzvdStd = getJzvStd(registrar, args);
this.methodChannel = new MethodChannel(registrar.messenger(), "bms_video_player_" + viewId);
this.methodChannel.setMethodCallHandler(this);
}
@Override
public View getView() {
return jzvdStd;
}
@Override
public void onMethodCall(MethodCall methodCall, MethodChannel.Result result) {
switch (methodCall.method) {
case "loadUrl":
String url = methodCall.arguments.toString();
jzvdStd.setUp(url, "", Jzvd.SCREEN_NORMAL);
break;
default:
result.notImplemented();
}
}
@Override
public void dispose() {}
private JzvdStd getJzvStd(Registrar registrar, Object args) {
JzvdStd view = (JzvdStd) LayoutInflater.from(registrar.activity()).inflate(R.layout.jz_video, null);
return view;
}
}
直接分析代码:
- 实现接口:PlatformView 和 MethodCallHandler,第一个接口「PlatformView」,用于
return
原生 View,也就是我们使用的第三方插件:JzvdStd。第二个接口「MethodCallHandler」,用于处理从 Dart 发过来的请求函数,如本文创建的函数:loadUrl
- 这里
return
的JzvdStd
,使用 xml:
<?xml version="1.0" encoding="utf-8"?>
<cn.jzvd.JzvdStd
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/jz_video"
android:layout_width="match_parent"
android:layout_height="match_parent" />
5.4 引入第三方插件
当然,我们需要在 build.gradle
最后加入插件:
dependencies {
implementation 'cn.jzvd:jiaozivideoplayer:7.0_preview'
}
至此,我们的 Android 端就算完成了,接下来看看 iOS 端。
6.1 注册 ViewFactory
同样的,在类 BmsVideoPlayerPlugin
中注册 VideoViewFactory
+ (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar>*)registrar {
VideoViewFactory* factory =
[[VideoViewFactory alloc] initWithMessenger:registrar.messenger];
[registrar registerViewFactory:factory withId:@"plugins.bms_video_player/view"];
}
6.2 创建 VideoViewFactory
#import "VideoViewFactory.h"
#import "BMSVideoPlayerViewController.h"
@implementation VideoViewFactory {
NSObject<FlutterBinaryMessenger>* _messenger;
}
- (instancetype)initWithMessenger:(NSObject<FlutterBinaryMessenger>*)messenger {
self = [super init];
if (self) {
_messenger = messenger;
}
return self;
}
- (NSObject<FlutterMessageCodec>*)createArgsCodec {
return [FlutterStandardMessageCodec sharedInstance];
}
- (nonnull NSObject<FlutterPlatformView> *)createWithFrame:(CGRect)frame
viewIdentifier:(int64_t)viewId
arguments:(id _Nullable)args {
BMSVideoPlayerViewController* viewController =
[[BMSVideoPlayerViewController alloc] initWithWithFrame:frame
viewIdentifier:viewId
arguments:args
binaryMessenger:_messenger];
return viewController;
}
@end
代码还是很简单,重点往下看 BMSVideoPlayerViewController
6.3 BMSVideoPlayerViewController
#import "BMSVideoPlayerViewController.h"
#import <JPVideoPlayer/JPVideoPlayerKit.h>
@interface BMSVideoPlayerViewController ()<JPVideoPlayerDelegate>
@end
@implementation BMSVideoPlayerViewController {
UIView * _videoView;
int64_t _viewId;
FlutterMethodChannel* _channel;
}
#pragma mark - life cycle
- (instancetype)initWithWithFrame:(CGRect)frame
viewIdentifier:(int64_t)viewId
arguments:(id _Nullable)args
binaryMessenger:(NSObject<FlutterBinaryMessenger>*)messenger {
if ([super init]) {
_viewId = viewId;
_videoView = [UIView new];
_videoView.backgroundColor = [UIColor greenColor];
NSDictionary *dic = args;
CGFloat x = [dic[@"x"] floatValue];
CGFloat y = [dic[@"y"] floatValue];
CGFloat width = [dic[@"width"] floatValue];
CGFloat height = [dic[@"height"] floatValue];
_videoView.frame = CGRectMake(x, y, width, height);
_videoView.jp_videoPlayerDelegate = self;
NSString* channelName = [NSString stringWithFormat:@"bms_video_player_%lld", viewId];
_channel = [FlutterMethodChannel methodChannelWithName:channelName binaryMessenger:messenger];
__weak __typeof__(self) weakSelf = self;
[_channel setMethodCallHandler:^(FlutterMethodCall* call, FlutterResult result) {
[weakSelf onMethodCall:call result:result];
}];
}
return self;
}
- (nonnull UIView *)view {
return _videoView;
}
- (void)onMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result {
if ([[call method] isEqualToString:@"loadUrl"]) {
[self onLoadUrl:call result:result];
} else {
result(FlutterMethodNotImplemented);
}
}
- (void)onLoadUrl:(FlutterMethodCall*)call result:(FlutterResult)result {
NSString* url = [call arguments];
if (![self loadUrl:url]) {
result([FlutterError errorWithCode:@"loadUrl_failed"
message:@"Failed parsing the URL"
details:[NSString stringWithFormat:@"URL was: '%@'", url]]);
} else {
result(nil);
}
}
- (bool)loadUrl:(NSString*)url {
NSURL* nsUrl = [NSURL URLWithString:url];
if (!nsUrl) {
return false;
}
[_videoView jp_playVideoWithURL:nsUrl
bufferingIndicator:nil
controlView:nil
progressView:nil
configuration:^(UIView *view, JPVideoPlayerModel *playerModel) {
// self.muteSwitch.on = ![self.videoContainer jp_muted];
}];
return true;
}
#pragma mark - JPVideoPlayerDelegate
- (BOOL)shouldAutoReplayForURL:(nonnull NSURL *)videoURL {
return true;
}
@end
其实,代码实现都很简单,唯一和 Android 端不一样的就是控件的创建不一样,Android 的我直接用 xml,iOS 的主要是需要定义 Frame 大小,我尝试使用函数传递的 frame 值,貌似不管用。如果有人知道问题所在,欢迎告知我!
最后,和 Android 一样,引入我们使用的第三方插件:
6.4 引入 JPVideoPlayer
在文件 bms_video_player.podspec
引入:
s.dependency 'JPVideoPlayer'
7. 链接调用
看「4」的创建 widget 后的回调函数:
Future<void> onPlatformViewCreated(id) async {
if (widget.onCreated == null) {
return;
}
widget.onCreated(new BmsVideoPlayerController.init(id));
}
直接 new BmsVideoPlayerController.init(id)
,即创建了 channel
:
MethodChannel _channel;
BmsVideoPlayerController.init(int id) {
_channel = new MethodChannel('bms_video_player_$id');
}
Future<void> loadUrl(String url) async {
assert(url != null);
return _channel.invokeMethod('loadUrl', url);
}
有了 channel
自然和原生代码串联起来了,同时创建 loadUrl
函数供外界调用。
8. 测试使用
藉此,我们的插件实现了基本功能了,写个 demo,测试下效果:
import 'package:flutter/material.dart';
import 'package:bms_video_player/bms_video_player.dart';
void main() => runApp(MyApp());
class MyApp extends StatefulWidget {
@override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
var viewPlayerController;
@override
void initState() {
super.initState();
}
@override
Widget build(BuildContext context) {
var x = 0.0;
var y = 0.0;
var width = 400.0;
var height = width * 9.0 / 16.0;
BmsVideoPlayer videoPlayer = new BmsVideoPlayer(
onCreated: onViewPlayerCreated,
x: x,
y: y,
width: width,
height: height
);
return MaterialApp(
home: Scaffold(
appBar: AppBar(
title: const Text('Plugin example app'),
),
body: Container(
child: videoPlayer,
width: width,
height: height
)
),
);
}
void onViewPlayerCreated(viewPlayerController) {
this.viewPlayerController = viewPlayerController;
this.viewPlayerController.loadUrl("https://www.****.com/****.mp4");
}
}
相信这代码不用多解释了,引入我们的插件 widget,然后调用 loadUrl
函数,传入我们的视频链接,即可开始播放了。
iOS 效果
Android 效果
总结
第一次使用 Flutter,第一次实现基本的插件功能,写的比较粗糙,但相信基本的写法都在里面了。接下来就是实现播放视频的所有功能,如:暂停/播放,小窗口播放、全屏播放、缓存、静音等。
还有,就是如何实现 Dart 和原生代码进行通讯的。
未完待续,敬请期待
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