Swift
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在前文中,我介绍了如何使用 AVFoundation 框架来制作一个简单的音频播放器(点击查看)。但这个播放器不支持后台播放,程序退到后台时音乐就会停止播放。
本文接着介绍如何实现后台播放功能。
1,效果图
(1)运行程序并播放音乐。这时我们返回桌面或者关闭屏幕,会发现音乐仍然在播放。
(2)在锁屏界面上,会显示当前的歌曲信息、专辑图片、当前进度等。同时还提供相关的控制按钮供我们使用。
(3)同样的,在上拉的音乐控制面板中,也会显示相关信息,并允许我们进行相关操作。
2,实现步骤
(1)为了让播放器能在后台持续播放,我们需要将 Targets -> Capabilities ->BackgroundModes 设为 ON,同时勾选“Audio, AirPlay, and Picture in Picture”。(2)同时还要在 AppDelegate.swift 中注册后台播放。
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import
UIKit
import
AVFoundation
@UIApplicationMain
class
AppDelegate
:
UIResponder
,
UIApplicationDelegate
{
var
window:
UIWindow
?
func
application(_ application:
UIApplication
, didFinishLaunchingWithOptions
launchOptions: [
UIApplicationLaunchOptionsKey
:
Any
]?) ->
Bool
{
// 注册后台播放
let
session =
AVAudioSession
.sharedInstance()
do {
try session.setActive(
true
)
try session.setCategory(
AVAudioSessionCategoryPlayback
)
} catch {
print
(error)
}
return
true
}
func
applicationWillResignActive(_ application:
UIApplication
) {
}
func
applicationDidEnterBackground(_ application:
UIApplication
) {
}
func
applicationWillEnterForeground(_ application:
UIApplication
) {
}
func
applicationDidBecomeActive(_ application:
UIApplication
) {
}
func
applicationWillTerminate(_ application:
UIApplication
) {
}
}
(3)ViewController.swift(主视图代码,黄色部分为新增的代码)
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import
UIKit
import
AVFoundation
import
MediaPlayer
class
ViewController
:
UIViewController
{
//播放按钮
@IBOutlet
weak
var
playButton:
UIButton
!
//可拖动的进度条
@IBOutlet
weak
var
playbackSlider:
UISlider
!
//当前播放时间标签
@IBOutlet
weak
var
playTime:
UILabel
!
//播放器相关
var
playerItem:
AVPlayerItem
?
var
player:
AVPlayer
?
override
func
viewDidLoad() {
super
.viewDidLoad()
//初始化播放器
let
url =
URL
(string:
"http://mxd.766.com/sdo/music/data/3/m10.mp3"
)
playerItem =
AVPlayerItem
(url: url!)
player =
AVPlayer
(playerItem: playerItem!)
//设置进度条相关属性
let
duration :
CMTime
= playerItem!.asset.duration
let
seconds :
Float64
=
CMTimeGetSeconds
(duration)
playbackSlider!.minimumValue = 0
playbackSlider!.maximumValue =
Float
(seconds)
playbackSlider!.isContinuous =
false
//播放过程中动态改变进度条值和时间标签
player!.addPeriodicTimeObserver(forInterval:
CMTimeMakeWithSeconds
(1, 1),
queue:
DispatchQueue
.main) { (
CMTime
) ->
Void
in
if
self
.player!.currentItem?.status == .readyToPlay &&
self
.player?.rate != 0{
//更新进度条进度值
let
currentTime =
CMTimeGetSeconds
(
self
.player!.currentTime())
self
.playbackSlider!.value =
Float
(currentTime)
//一个小算法,来实现00:00这种格式的播放时间
let
all:
Int
=
Int
(currentTime)
let
m:
Int
=all % 60
let
f:
Int
=
Int
(all/60)
var
time:
String
=
""
if
f<10{
time=
"0\(f):"
}
else
{
time=
"\(f)"
}
if
m<10{
time+=
"0\(m)"
}
else
{
time+=
"\(m)"
}
//更新播放时间
self
.playTime!.text=time
//设置后台播放显示信息
self
.setInfoCenterCredentials(playbackState: 1)
}
}
}
//播放按钮点击
@IBAction
func
playButtonTapped(_ sender:
Any
) {
//根据rate属性判断当天是否在播放
if
player?.rate == 0 {
player!.play()
playButton.setTitle(
"暂停"
,
for
: .normal)
}
else
{
player!.pause()
playButton.setTitle(
"播放"
,
for
: .normal)
//后台播放显示信息进度停止
setInfoCenterCredentials(playbackState: 0)
}
}
//拖动进度条改变值时触发
@IBAction
func
playbackSliderValueChanged(_ sender:
Any
) {
let
seconds :
Int64
=
Int64
(playbackSlider.value)
let
targetTime:
CMTime
=
CMTimeMake
(seconds, 1)
//播放器定位到对应的位置
player!.seek(to: targetTime)
//如果当前时暂停状态,则自动播放
if
player!.rate == 0
{
player?.play()
playButton.setTitle(
"暂停"
,
for
: .normal)
}
}
//页面显示时添加相关通知监听
override
func
viewWillAppear(_ animated:
Bool
) {
//播放完毕
NotificationCenter
.
default
.addObserver(
self
, selector: #selector(finishedPlaying),
name:
NSNotification
.
Name
.
AVPlayerItemDidPlayToEndTime
, object: playerItem)
//告诉系统接受远程响应事件,并注册成为第一响应者
UIApplication
.shared.beginReceivingRemoteControlEvents()
self
.becomeFirstResponder()
}
//页面消失时取消歌曲播放结束通知监听
override
func
viewWillDisappear(_ animated:
Bool
) {
NotificationCenter
.
default
.removeObserver(
self
)
//停止接受远程响应事件
UIApplication
.shared.endReceivingRemoteControlEvents()
self
.resignFirstResponder()
}
//歌曲播放完毕
func
finishedPlaying(myNotification:
NSNotification
) {
print
(
"播放完毕!"
)
let
stopedPlayerItem:
AVPlayerItem
= myNotification.object
as
!
AVPlayerItem
stopedPlayerItem.seek(to: kCMTimeZero)
}
//是否能成为第一响应对象
override
var
canBecomeFirstResponder:
Bool
{
return
true
}
// 设置后台播放显示信息
func
setInfoCenterCredentials(playbackState:
Int
) {
let
mpic =
MPNowPlayingInfoCenter
.
default
()
//专辑封面
let
mySize =
CGSize
(width: 400, height: 400)
let
albumArt =
MPMediaItemArtwork
(boundsSize:mySize) { sz
in
return
UIImage
(named:
"cover"
)!
}
//获取进度
let
postion =
Double
(
self
.playbackSlider!.value)
let
duration =
Double
(
self
.playbackSlider!.maximumValue)
mpic.nowPlayingInfo = [
MPMediaItemPropertyTitle
:
"我是歌曲标题"
,
MPMediaItemPropertyArtist
:
"hangge.com"
,
MPMediaItemPropertyArtwork
: albumArt,
MPNowPlayingInfoPropertyElapsedPlaybackTime
: postion,
MPMediaItemPropertyPlaybackDuration
: duration,
MPNowPlayingInfoPropertyPlaybackRate
: playbackState]
}
//后台操作
override
func
remoteControlReceived(with event:
UIEvent
?) {
guard
let
event = event
else
{
print
(
"no event\n"
)
return
}
if
event.type ==
UIEventType
.remoteControl {
switch
event.subtype {
case
.remoteControlTogglePlayPause:
print
(
"暂停/播放"
)
case
.remoteControlPreviousTrack:
print
(
"上一首"
)
case
.remoteControlNextTrack:
print
(
"下一首"
)
case
.remoteControlPlay:
print
(
"播放"
)
player!.play()
case
.remoteControlPause:
print
(
"暂停"
)
player!.pause()
//后台播放显示信息进度停止
setInfoCenterCredentials(playbackState: 0)
default
:
break
}
}
}
override
func
didReceiveMemoryWarning() {
super
.didReceiveMemoryWarning()
}
}
源码下载:hangge_1668.zip
原文出自:www.hangge.com 转载请保留原文链接:http://www.hangge.com/blog/cache/detail_1669.html
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