MediaSession.setActionHandler() - Web APIs 编辑

The setActionHandler() method of the MediaSession interface sets a handler for a media session action. These actions let a web app receive notifications when the user engages a device's built-in physical or onscreen media controls, such as play, stop, or seek buttons.

Syntax

navigator.mediaSession.setActionHandler(type, callback)

Parameters

type

A DOMString representing an action type to listen for. It will be one of play, pause, stop, seekbackward,seekforward, seekto, skipad,previoustrack, or nexttrack. Further details on the action types can be found below under Media session actions.

callback

A function to call when the specified action type is invoked. The callback receives no input parameters, and should not return a value.

Return value

undefined.

Description

To remove a previously-established action handler, call setActionHandler() again, specifying null as the callback.

The action handler receives as input a single parameter: an object conforming to the MediaSessionActionDetails dictionary, which provides both the action type (so the same function can handle multiple action types), as well as data needed in order to perform the action.

Examples

This example creates a new media session and assigns action handlers (which don't do anything) to it.

if ('mediaSession' in navigator) {
  navigator.mediaSession.metadata = new MediaMetadata({
    title: 'Unforgettable',
    artist: 'Nat King Cole',
    album: 'The Ultimate Collection (Remastered)',
    artwork: [
      { src: 'https://dummyimage.com/96x96',   sizes: '96x96',   type: 'image/png' },
      { src: 'https://dummyimage.com/128x128', sizes: '128x128', type: 'image/png' },
      { src: 'https://dummyimage.com/192x192', sizes: '192x192', type: 'image/png' },
      { src: 'https://dummyimage.com/256x256', sizes: '256x256', type: 'image/png' },
      { src: 'https://dummyimage.com/384x384', sizes: '384x384', type: 'image/png' },
      { src: 'https://dummyimage.com/512x512', sizes: '512x512', type: 'image/png' },
    ]
  });

  navigator.mediaSession.setActionHandler('play', function() { /* Code excerpted. */ });
  navigator.mediaSession.setActionHandler('pause', function() { /* Code excerpted. */ });
  navigator.mediaSession.setActionHandler('stop', function() { /* Code excerpted. */ });
  navigator.mediaSession.setActionHandler('seekbackward', function() { /* Code excerpted. */ });
  navigator.mediaSession.setActionHandler('seekforward', function() { /* Code excerpted. */ });
  navigator.mediaSession.setActionHandler('seekto', function() { /* Code excerpted. */ });
  navigator.mediaSession.setActionHandler('previoustrack', function() { /* Code excerpted. */ });
  navigator.mediaSession.setActionHandler('nexttrack', function() { /* Code excerpted. */ });
  navigator.mediaSession.setActionHandler('skipad', function() { /* Code excerpted. */ });
}

The following example sets up two functions for playing and pausing, then uses them as callbacks with the relevant action handlers.

const actionHandlers = [
  // play
  [
    'play',
    async function() {
      // play our audio
      await audioEl.play();
      // set playback state
      navigator.mediaSession.playbackState = "playing";
      // update our status element
      updateStatus(allMeta[index], 'Action: play  |  Track is playing...')
    }
  ],
  [
    'pause',
    () => {
      // pause out audio
      audioEl.pause();
      // set playback state
      navigator.mediaSession.playbackState = "paused";
      // update our status element
      updateStatus(allMeta[index], 'Action: pause  |  Track has been paused...');
    }
  ],
]

for (const [action, handler] of actionHandlers) {
  try {
    navigator.mediaSession.setActionHandler(action, handler);
  } catch (error) {
    console.log(`The media session action "${action}" is not supported yet.`);
  }
}

This example uses appropriate action handlers to allow seeking in either direction through the playing media.

let skipTime = 10; // Time to skip in seconds

navigator.mediaSession.setActionHandler('seekbackward', evt => {
 // User clicked "Seek Backward" media notification icon.
 audio.currentTime = Math.max(audio.currentTime - skipTime, 0);
});

navigator.mediaSession.setActionHandler('seekforward', evt => {
 // User clicked "Seek Forward" media notification icon.
 audio.currentTime = Math.min(audio.currentTime + skipTime,
               audio.duration);
});

To remove a media action handler, assign it to null.

navigator.mediaSession.setActionHandler('nexttrack', null);

Supporting multiple actions in one handler function

You can also, if you prefer, use a single function to handle multiple action types, by checking the value of the MediaSessionActionDetails object's action property:

let skipTime = 7;

navigator.mediaSession.setActionHandler("seekforward", handleSeek);
navigator.mediaSession.setActionHandler("seekbackward", handleSeek);

function handleSeek(details) {
  switch(details.action) {
    case "seekforward":
      audio.currentTime = Math.min(audio.currentTime + skipTime,
              audio.duration);
      break;
    case "seekbackward":
      audio.currentTime = Math.max(audio.currentTime - skipTime, 0);
      break;
  }
}

Here, the handleSeek() function handles both seekbackward and seekforward actions.

Specifications

Browser compatibility

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