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[translated] 20150616 XBMC--build a remote control
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XBMC: build a remote control
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================================================================================
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**Take control of your home media player with a custom remote control running on your Android phone.**
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**XBMC** is a great piece of software, and can turn almost can computer into a media centre. It can play music and videos, display pictures, and even fetch a weather forecast. To make it easy to use in a home theatre setup, you can control it via mobile phone apps that access a server running on the XBMC machine via Wi-Fi. There are loads of these available for almost all smartphone systems.
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> ### Kodi ###
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>
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> By the time you read this, **XBMC** may be no more. The project team have decided to rename it **Kodi** for legal reasons (and because **XBMC**, or X**-Box Media Centre**, refers to older hardware that is no longer supported). Other than the name, though, nothing has changed. Or at least nothing other than the usual raft of improvements you’d expect from a new release. This shouldn’t affect the remote software though, and it should work on both existing **XBMC** systems, and newer Kodi systems.
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We’ve recently set up an **XBMC** system for playing music, and none of the XBMC remotes we found really excel at this task, especially when the TV attached to the media centre is turned off. They were all a bit too complex, as they packed too much functionality into small screens. We wanted a system designed from the ground up to just access a music library and a radio addon, so we decided to build one ourselves. It didn’t need to be able to access the full capabilities of XBMC, because for tasks other than music, we’d simply switch back to a general-purpose XBMC remote control. Our test system was a Raspberry Pi running the RaspBMC distribution, but nothing here is specific to either the Pi or that distro, and it should work on any Linux-based XBMC system provided the appropriate packages are available.
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The first thing a remote control needs is a user interface. Many XBMC remote controls are written as standalone apps. However, this is just for our music, and we want to be accessible to guests without them having to install anything. The obvious solution is to make a web interface. XBMC does have a built-in web server, but to give us more control, we decided to use a separate web framework. There’s no problem running more than one web server on a computer at a time, but they can’t run on the same port.
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There are quite a few web frameworks available. We’ve used Bottle because it’s a simple, fast framework, and we don’t need any complex functions. Bottle is a Python module, so that’s the language in which we’ll write the server.
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You’ll probably find Bottle in your package manager. In Debian-based systems (including Raspbmc), you can grab it with:
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sudo apt-get install python-bottle
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A remote control is really just a layer that connects the user to a system. Bottle provides what we need to interact with the user, and we’ll interact with **XBMC** using its JSON API. This enables us to control the media player by sending JSON-encoded information.
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We’re going to use a simple wrapper around the XBMC JSON API called xbmcjson. It’s just enough to allow you send requests without having to worry about the actual JSON formatting or any of the banalities of communicating with a server. It’s not included in the PIP package manager, so you need to install it straight from **GitHub**:
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git clone https://github.com/jcsaaddupuy/python-xbmc.git
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cd python-xbmc
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sudo python setup.py install
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This is everything you need, so let’s get coding.
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#### Get started with Bottle ####
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The basic structure of our program is:
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from xbmcjson import XBMC
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from bottle import route, run, template, redirect, static_file, request
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import os
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xbmc = XBMC(“http://192.168.0.5/jsonrpc”, “xbmc”, “xbmc”)
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@route(‘/hello/<name>’)
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def index(name):
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return template(‘<h1>Hello {{name}}!</h1>’, name=name)
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run(host=”0.0.0.0”, port=8000)
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This connects to **XBMC** (though doesn’t actually use it); then Bottle starts serving up the website. In this case, it listens on host 0.0.0.0 (which is every hostname), and port 8000. It only has one site, which is /hello/XXXX where XXXX can be anything. Whatever XXXX is gets passed to index() as the parameter name. This then passes it to the template, which substitutes it into the HTML.
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You can try this out by entering the above into a file (we’ve called it remote.py), and starting it with:
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python remote.py
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You can then point your browser to localhost:8000/hello/world to see the template in action.
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@route() sets up a path in the web server, and the function index() returns the data for that path. Usually, this means returning HTML that’s generated via a template, but it doesn’t have to be (as we’ll see later).
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As we go on, we’ll add more routes to the application to make it a fully-featured XBMC remote control, but it will still be structured in the same way.
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The XBMC JSON API can be accessed by any computer on the same network as the XBMC machine. This means that you can develop it on your desktop, then deploy it to your media centre rather than fiddle round uploading every change to your home theatre PC.
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Templates – like the simple one in the previous example – are a way of combining Python and HTML to control the output. In principal, they can do quite a bit of processing, but they can get messy. We’ll use them just to format the data correctly. Before we can do that, though, we have to have some data.
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> ### Paste ###
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>
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> Bottle includes its own web server, which is what we’ve been using for testing the remote control. However, we found that it didn’t always perform well. When we put the remote into action, we wanted something that could deliver pages a bit quicker. Bottle can work with quite a few different web servers, and we found Paste worked quite well. In order to use this, just install it (in the package python-paste on Debian), and change the run call to:
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>
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> run(host=hostname, port=hostport, server=”paste”)
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>
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> You can see details of how to use other servers at [http://bottlepy.org/docs/dev/deployment.html][1].
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#### Getting data from XBMC ####
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The XBMC JSON API is split up into 14 namespaces: JSONRPC, Player, Playlist, Files, AudioLibrary, VideoLibrary, Input, Application, System, Favourites, Profiles, Settings, Textures and XBMC. Each of these is available from an XBMC object in Python (apart from Favourites, in an apparent oversight). In each of these namespaces there are methods that you can use to control the application. For example, Playlist.GetItems() can be used to get the items on a particular playlist. The server returns data to us in JSON, but the xbmcjson module converts it to a Python dictionary for us.
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There are two items in XBMC that we need to use to control playback: players and playlists. Players hold a playlist and move through it item by item as each song finishes. In order to see what’s currently playing, we need to get the ID of the active player, and through that find out the ID of the current playlist. We’ve done this with the following function:
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def get_playlistid():
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player = xbmc.Player.GetActivePlayers()
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if len(player[‘result’]) > 0:
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playlist_data = xbmc.Player.GetProperties({“playerid”:0, “properties”:[“playlistid”]})
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if len(playlist_data[‘result’]) > 0 and “playlistid” in playlist_data[‘result’].keys():
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return playlist_data[‘result’][‘playlistid’]
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return -1
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If there isn’t a currently active player (that is, if the length of the results section in the returned data is 0), or if the current player has no playlist, this will return -1. Otherwise, it will return the numeric ID of the current playlist.
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Once we’ve got the ID of the current playlist, we can get the details of it. For our purposes, two things are important: the list of items in the playlist, and the position we are in the playlist (items aren’t removed from the playlist after they’ve been played; the current position just marches on).
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def get_playlist():
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playlistid = get_playlistid()
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if playlistid >= 0:
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data = xbmc.Playlist.GetItems({“playlistid”:playlistid, “properties”: [“title”, “album”, “artist”, “file”]})
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position_data = xbmc.Player.GetProperties({“playerid”:0, ‘properties’:[“position”]})
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position = int(position_data[‘result’][‘position’])
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return data[‘result’][‘items’][position:], position
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return [], -1
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This returns the current playlist starting with the item that’s currently playing (since we don’t care about stuff that’s finished), and it also includes the position as this is needed for removing items from the playlist.
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The API is documented at [http://wiki.xbmc.org/?title=JSON-RPC_API/v6][2]. It lists all the available functions, but it a little short on details of how to use them.
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> ### JSON ###
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>
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> JSON stands for JavaScript Object Notation, and was originally designed as a way of serialising JavaScript Objects. It still is used for that, but it’s also a useful way of encoding all sorts of data.
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>
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> JSON objects always have the form:
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>
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> {property1:value1, property2:value2, property3:value3}
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>
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> For an arbitrary number of property/value pairs. To Python programmers, this all looks suspiciously similar to dictionaries, and the two are very similar.
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>
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> As with dictionaries, the value can itself be another JSON object, or a list, so the following is perfectly valid:
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>
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> {“name”:“Ben”, “jobs”:[“cook”, “bottle-washer”], “appearance”: {“height”:195, “skin”:“fair”}}
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>
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> JSON is often used in web services to send data back and fourth, and it’s well supported by most programming languages, so if Python’s not your thing, you should easily be able to use the same functions to control XBMC from software written in the language of your choice.
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#### Bringing them together ####
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The code to link the previous functions to a HTML page is simply:
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@route(‘/juke’)
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def index():
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current_playlist, position = get_playlist()
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return template(‘list’, playlist=current_playlist, offset = position)
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This only has to grab the playlist (using the function we defined above), and pass it to a template that handles the display.
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The main part of the template that handles the display of this data is:
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<h2>Currently Playing:</h2>
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% if playlist is not None:
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% position = offset
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% for song in playlist:
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<strong> {{song[‘title’]}} </strong>
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% if song[‘type’] == ‘unknown’:
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Radio
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% else:
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{{song[‘artist’][0]}}
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% end
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% if position != offset:
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<a href=”/remove/{{position}}”>remove</a>
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% else:
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<a href=”/skip/{{position}}”>skip</a>
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% end
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<br>
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% position += 1
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% end
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As you can see, templates are mostly written in HTML, but with a few extra bits to control output. Variables enclosed by double parenthesise are output in place (as we saw in the first ‘hello world’ example). You can also include Python code on lines starting with a percentage sign. Since indents aren’t used, you need a % end to close any code block (such as a loop or if statement).
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This template first checks that the playlist isn’t empty, then loops through every item on the playlist. Each item is displayed as the song title in bold, then the name of the artist, then a link to either skip it (if it’s the currently playing song), or remove it from the playlist. All songs have a type of ‘song’, so if the type is ‘unknown’, then it isn’t a song, but a radio station.
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The /remove/ and /skip/ routes are simple wrappers around XBMC controls that reload /juke after the change has taken effect:
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@route(‘/skip/<position>’)
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def index(position):
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print xbmc.Player.GoTo({‘playerid’:0, ‘to’:’next’})
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redirect(“/juke”)
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@route(‘/remove/<position>’)
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def index(position):
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playlistid = get_playlistid()
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if playlistid >= 0:
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xbmc.Playlist.Remove({‘playlistid’:int(playlistid), ‘position’:int(position)})
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redirect(“/juke”)
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Of course, it’s no good being able to manage your playlist if you can’t add music to it.
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This is complicated slightly by the fact that once a playlist finishes, it disappears, so you need to create a new one. Rather confusingly, playlists are created by calling the Playlist.Clear() method. This can also be used to kill a playlist that is currently playing a radio station (where the type is unknown). The other complication is that radio streams sit in the playlist and never leave, so if there’s currently a radio station playing, we need to clear the playlist as well.
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These pages include a link to play the songs, which points to /play/<songid>. This page is handled by:
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@route(‘/play/<id>’)
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def index(id):
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playlistid = get_playlistid()
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playlist, not_needed= get_playlist()
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if playlistid < 0 or playlist[0][‘type’] == ‘unknown’:
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xbmc.Playlist.Clear({“playlistid”:0})
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xbmc.Playlist.Add({“playlistid”:0, “item”:{“songid”:int(id)}})
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xbmc.Player.open({“item”:{“playlistid”:0}})
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playlistid = 0
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else:
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xbmc.Playlist.Add({“playlistid”:playlistid, “item”:{“songid”:int(id)}})
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remove_duplicates(playlistid)
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redirect(“/juke”)
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The final thing here is a call to remove_duplicates. This isn’t essential – and some people may not like it – but it makes sure that no song appears in the playlist more than once.
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We also have pages that list all the artists in the collection, and list the songs and albums by particular artists. These are quite straightforward, and work in the same basic way as /juke.
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The UI still needs a bit of attention, but it’s working.
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> ### Logging ###
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>
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> It’s not always clear how to do something using the XBMC JSON API, and the documentation is sometimes a little opaque. One way of finding out how to do something is seeing how other remote controls do it. If you turn on logging, you can see what API calls are being performed as you use another remote control, then incorporate these into your code.
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>
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> To turn on logging, hook your XBMC media centre up to a display and go to Settings > System > Debugging, and turn on Enable Debug Logging. With logging turned on, you need to access the XBMC machine (eg via SSH), then you can view the log. Its location should be displayed in the top-left corner of the XBMC display. In RaspBMC, it’s at /home/pi/.xbmc/temp/xbmc.log. You can then keep an eye on what API calls are being performed in real time using:
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>
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> cd /home/pi/.xbmc/temp
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> tail -f xbmc.log | grep “JSON”
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#### Adding functionality ####
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The above code all works with songs in the XBMC library, but we also wanted to be able to play radio stations. Addons each have their own plugin URL that can be used to pull information out of them using the usual XBMC JSON commands. For example, to get the selected stations from the radio plugin, we use:
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@route(‘/radio/’)
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def index():
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my_stations = xbmc.Files.GetDirectory({“directory”:”plugin://plugin.audio.radio_de/stations/my/”, “properties”:
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[“title”,”thumbnail”,”playcount”,”artist”,”album”,”episode”,”season”,”showtitle”]})
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if ‘result’ in my_stations.keys():
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return template(‘radio’, stations=my_stations[‘result’][‘files’])
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else:
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return template(‘error’, error=’radio’)
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This includes a file that can be added to a playlist just as any song can be. However, these files never finish playing, so (as we saw before) you need to recreate the playlist before adding any songs to it.
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#### Sharing songs ####
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As well as serving up templates, Bottle can serve static files. These are useful whenever you need things that don’t change based on the user input. That could be a CSS file, an image or an MP3. In our simple controller there’s not (yet) any CSS or images to make things look pretty, but we have added a way to download the songs. This lets the media centre act as a sort of NAS box for songs. If you’re transferring large amounts of data, it’s probably best to use something like Samba, but serving static files is a good way of grabbing a couple of tunes on your phone.
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The Bottle code to download a song by its ID is :
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@route(‘/download/<id>’)
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def index(id):
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data = xbmc.AudioLibrary.GetSongDetails({“songid”:int(id), “properties”:[“file”]})
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full_filename = data[‘result’][‘songdetails’][‘file’]
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path, filename = os.path.split(full_filename)
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return static_file(filename, root=path, download=True)
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To use this, we just put a link to the appropriate ID in the /songsby/ page.
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We’ve gone through all the mechanics of the code, but there are a few more bits that just tie it all together. You can see for yourself at the GitHub page:[https://github.com/ben-ev/xbmc-remote][3].
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> ### Setting up ###
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>
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> Once you’ve developed your remote control, you’ll need a way of ensuring that it starts every time you turn on your media centre. There are a few ways of doing this, but the easiest is just to add a command launching it to /etc/rc.local. We installed our file to /opt/xbmc-remote/remote.py with all the other files alongside it. We then added the following line to /etc/rc.local before the final exit 0 line.
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>
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> cd /opt/xbmc-remote && python remote.py &
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> ### GitHub ###
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>
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> This project is quite bare-bones at the moment, but – the business of running a magazine means we don’t have as much time as we’d like to program. However, we’ve set up a GitHub project where we hope to keep working on it, and if you think you’d benefit from the project as well, we’d love your input.
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>
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> To see what’s going on, head over to [https://github.com/ben-ev/xbmc-remote][4] and take a look at what state it’s in. You can get a copy of the latest code from that web page, or clone it from the command line.
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>
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> If you want to improve it, you can fork the project to develop in your own branch, and then send a pull request when your features are working. For more information on working with GitHub, head to [https://github.com/features][5].
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--------------------------------------------------------------------------------
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via: http://www.linuxvoice.com/xbmc-build-a-remote-control/
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作者：[Ben Everard][a]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]:http://www.linuxvoice.com/author/ben_everard/
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[1]:http://bottlepy.org/docs/dev/deployment.html
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[2]:http://wiki.xbmc.org/?title=JSON-RPC_API/v6
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[3]:https://github.com/ben-ev/xbmc-remote
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[4]:https://github.com/ben-ev/xbmc-remote
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[5]:https://github.com/features
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XBMC：自制遥控
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================================================================================
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**通过运行在 Android 手机上的自制遥控器来控制你的家庭媒体播放器。**
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**XBMC** 一款很优秀的软件，能够将几乎所有电脑变身成媒体中心。它可以播放音乐和视频，显示图片，甚至还能显示天气预报。为了在配置成家庭影院后方便使用，你可以通过手机 app 访问运行在已连接到 Wi-Fi 的 XBMC 机器上的服务来控制它。可以找到很多这种工具，几乎覆盖所有智能手机系统。
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> ### Kodi ###
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>
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> 在你阅读这篇文章的时候，**XBMC** 可能已经成为历史。因为法律原因（因为名字 **XBMC** 或 X**-Box Media Center** 里引用了不再支持的过时硬件）项目组决定使用新的名字 **Kodi**。不过，除了名字，其他的都会保持原样。或者说除开通常新版本中所期待的大量新改进。这一般不会影响到遥控软件，它应该能在已有的 **XBMC** 系统和新的 Kodi 系统上都能工作。
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我们目前配置了一个 **XBMC** 系统用于播放音乐，不过我们找到的所有 XBMC 遥控没一个好用的，特别是和媒体中心连接的电视没打开的时候。它们都有点太复杂了，集成了太多功能在手机的小屏幕上。我们希望能有这样的系统，从最开始就是设计成只用于访问音乐库和电台插件，所以我们决定自己实现一个。它不需要用到 XBMC 的所有功能，因为除了音乐以外的任务，我们可以简单地切换使用通用的 XBMC 遥控。我们的测试系统是一个刷了 RaspBMC 发行版的树莓派，但是我们要做的工具并不受限于树莓派或那个发行版，它应该可以匹配任何安装了相关插件的基于 Linux 的 XBMC 系统。
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|
||||
首先，遥控程序需要一个用户界面。大多数 XBMC 遥控程序都是独立的 app。不过对于我们要做的这个音乐控制程序，我们希望用户可以不用安装任何东西就可以使用。显然我们需要使用网页界面。XBMC 本身自带网页服务器，但是为了获得更多权限，我们还是使用了独立的网页框架。在同一台电脑上跑两个以上网页服务器没有问题，只不过它们不能使用相同的端口。
|
||||
|
||||
有几个网页框架可以使用。而我们选用 Bottle 是因为它是一个简单高效的框架，而且我们也确实用不到任何高级功能。Bottle 是一个 Python 模块，所以这也将是我们编写服务器模块的语言。
|
||||
|
||||
你应该能在软件包管理器里找到 Bottle。在基于 Debian 的系统（包括 RaspBMC）里，你可以通过下面的命令安装：
|
||||
|
||||
sudo apt-get install python-bottle
|
||||
|
||||
遥控程序实际上只是连接用户和系统的中间层。Bottle 提供了和用户交互的方式，而我们将通过 JSON API 来和 **XBMC** 交互。这样可以让我们通过发送 JSON 格式消息的方式去控制媒体播放器。
|
||||
|
||||
我们将用到一个叫做 xbmcjson 的简单 XBMC JASON API 封装。足够用来发送控制请求，而不需要关心实际的 JSON 格式以及和服务器通讯的无聊事。它没有包含在 PIP 包管理中，所以你得直接从 **GitHub** 安装：
|
||||
|
||||
git clone https://github.com/jcsaaddupuy/python-xbmc.git
|
||||
cd python-xbmc
|
||||
sudo python setup.py install
|
||||
|
||||
万事俱备，只欠代码。
|
||||
|
||||
#### 先从 Bottle 开始 ####
|
||||
|
||||
我们程序的基本结构：
|
||||
|
||||
from xbmcjson import XBMC
|
||||
from bottle import route, run, template, redirect, static_file, request
|
||||
import os
|
||||
xbmc = XBMC(“http://192.168.0.5/jsonrpc”, “xbmc”, “xbmc”)
|
||||
@route(‘/hello/<name>’)
|
||||
def index(name):
|
||||
return template(‘<h1>Hello {{name}}!</h1>’, name=name)
|
||||
run(host=”0.0.0.0”, port=8000)
|
||||
|
||||
这样程序将连接到 **XBMC**（不过实际上用不到）；然后 Bottle 会开始伺服网站。在我们的代码里，它将监听主机 0.0.0.0（意味着允许所有主机连接）的端口 8000。它只设定了一个站点，就是 /hello/XXXX，这里的 XXXX 可以是任何内容。不管 XXXX 是什么都将作为参数名传递给 index()。然后再替换进去 HTML 网页模版。
|
||||
|
||||
你可以先试着把上面内容写到一个文件（我们取的名字是 remote.py），然后用下面的命令启动：
|
||||
|
||||
python remote.py
|
||||
|
||||
然后你可以在浏览器里访问 localhost:8000/hello/world 看看模版生效的效果。
|
||||
|
||||
@route() 用来设定网页服务器的路径，而函数 index() 会返回该路径的数据。通常是返回由模版生成的 HTML 页面，但是并不是说只能这样（后面会看到）。
|
||||
|
||||
随后，我们将给应用添加更多页面入口，让它变成一个全功能的 XBMC 遥控，但仍将采用相同代码结构。
|
||||
|
||||
XBMC JSON API 接口可以从和 XBMC 机器同网段的任意电脑上访问。也就是说你可以在自己的笔记本上开发，然后再布置到媒体中心上，而不需要浪费时间上传每次改动。
|
||||
|
||||
模版 - 比如前面例子里的那个简单模版 - 是一种结合 Python 和 HTML 来控制输出的方式。理论上，这俩能做很多很多事，但是会非常混乱。我们将只是用它们来生成正确格式的数据。不过，在开始动手之前，我们先得准备点数据。
|
||||
|
||||
> ### Paste ###
|
||||
>
|
||||
> Bottle 自带网页服务器，就是我们用来测试遥控程序的。不过，我们发现它性能有时不够好。当我们的遥控程序正式上线时，我们希望页面能更快一点显示出来。Bottle 可以和很多不同的网页服务器配合工作，而我们发现 Paste 用起来非常不错。而要使用的话，只要简单地安装（Debian 系统里的 python-paste 包），然后修改一下代码里的 run 调用：
|
||||
>
|
||||
> run(host=hostname, port=hostport, server=”paste”)
|
||||
>
|
||||
> 你可以在 [http://bottlepy.org/docs/dev/deployment.html][1] 找到如何使用其他服务器的相关细节。
|
||||
|
||||
#### 从 XBMC 获取数据 ####
|
||||
|
||||
XBMC JSON API 分成 14 个命名空间：JSONRPC, Player, Playlist, Files, AudioLibrary, VideoLibrary, Input, Application, System, Favourites, Profiles, Settings, Textures 和 XBMC。每个都可以通过 Python 的 XBMC 对象访问（Favourites 除外，明显是个疏忽）。每个命名空间都包含许多方法用于对程序的控制。例如，Playlist.GetItems() 可以用来获取某个特定播放列表的内容。服务器会返回给我们 JSON 格式的数据，但 xbmcjson 模块会为我们转化成 Python 词典。
|
||||
|
||||
我们需要用到 XBMC 里的两个组件来控制播放：播放器和播放列表。播放器带有播放列表并在每首歌结束时从列表里取下一首。为了查看当前正在播放的内容，我们需要获取正在工作的播放器的 ID，然后根据它找到当前播放列表的 ID。这个可以通过下面的代码来实现：
|
||||
|
||||
def get_playlistid():
|
||||
player = xbmc.Player.GetActivePlayers()
|
||||
if len(player[‘result’]) > 0:
|
||||
playlist_data = xbmc.Player.GetProperties({“playerid”:0, “properties”:[“playlistid”]})
|
||||
if len(playlist_data[‘result’]) > 0 and “playlistid” in playlist_data[‘result’].keys():
|
||||
return playlist_data[‘result’][‘playlistid’]
|
||||
return -1
|
||||
|
||||
如果当前没有播放器在工作（就是说，返回数据的结果部分的长度是 0），或者当前播放器不带播放列表，这样的话函数会返回 -1。其他时候，它会返回当前播放列表的数字 ID。
|
||||
|
||||
当我们拿到当前播放列表的 ID 后，就可以获取列表的细节内容。按照我们的需求，有两个重要的地方：播放列表里包含的项，以及当前播放所处的位置（已经播放过的项并不会从播放列表移除，只是移动当前播放位置）。
|
||||
|
||||
def get_playlist():
|
||||
playlistid = get_playlistid()
|
||||
if playlistid >= 0:
|
||||
data = xbmc.Playlist.GetItems({“playlistid”:playlistid, “properties”: [“title”, “album”, “artist”, “file”]})
|
||||
position_data = xbmc.Player.GetProperties({“playerid”:0, ‘properties’:[“position”]})
|
||||
position = int(position_data[‘result’][‘position’])
|
||||
return data[‘result’][‘items’][position:], position
|
||||
return [], -1
|
||||
|
||||
这样可以返回以正在播放的项开始的列表（因为我们并不关心已经播放过的内容），而且也包含了位置信息用来从列表里移除项。
|
||||
|
||||
|
||||
|
||||
API 文档在这里：[http://wiki.xbmc.org/?title=JSON-RPC_API/v6][2]。它列出了所有支持的函数，但是关于具体如何使用的描述有点太简单了。
|
||||
|
||||
> ### JSON ###
|
||||
>
|
||||
> JSON 是 JavaScript Object Notation 的缩写，开始设计用于 JavaScript 对象的序列化。目前仍然起到这个作用，但是它也是用来编码任意数据的一种很好用的方式。
|
||||
>
|
||||
> JSON 对象都是这样的格式：
|
||||
>
|
||||
> {property1:value1, property2:value2, property3:value3}
|
||||
>
|
||||
> 支持任意数目的属性/值配对。对 Python 程序员来说，看上去和字典数据结构很相似，不过这两个确实很像。
|
||||
>
|
||||
> 在字典数据结构里，值本身可以是另一个 JSON 对象，或者一个列表，所以下面的格式也是正确的：
|
||||
>
|
||||
> {“name”:“Ben”, “jobs”:[“cook”, “bottle-washer”], “appearance”: {“height”:195, “skin”:“fair”}}
|
||||
>
|
||||
> JSON 通常在网络服务中用来发送和接收数据，并且大多数编程语言都能很好地支持，所以如果你熟悉 Python 的话，你应该可以使用你熟悉的编程语言调用相同的接口来轻松地控制 XBMC。
|
||||
|
||||
#### 整合到一起 ####
|
||||
|
||||
把之前的功能连接到 HTML 页面很简单：
|
||||
|
||||
@route(‘/juke’)
|
||||
def index():
|
||||
current_playlist, position = get_playlist()
|
||||
return template(‘list’, playlist=current_playlist, offset = position)
|
||||
|
||||
只需要抓取播放列表（调用我们之前定义的函数），然后将结果传递给负责显示的模版。
|
||||
|
||||
负责显示列表数据的模版的主要部分是：
|
||||
|
||||
<h2>Currently Playing:</h2>
|
||||
% if playlist is not None:
|
||||
% position = offset
|
||||
% for song in playlist:
|
||||
<strong> {{song[‘title’]}} </strong>
|
||||
% if song[‘type’] == ‘unknown’:
|
||||
Radio
|
||||
% else:
|
||||
{{song[‘artist’][0]}}
|
||||
% end
|
||||
% if position != offset:
|
||||
<a href=”/remove/{{position}}”>remove</a>
|
||||
% else:
|
||||
<a href=”/skip/{{position}}”>skip</a>
|
||||
% end
|
||||
<br>
|
||||
% position += 1
|
||||
% end
|
||||
|
||||
可以看到，模版大部分是用 HTML 写的，只有一小部分用来控制输出的其他代码。用两个括号括起来的变量是输出位置（像我们在第一个 ‘hello world’ 例子里看到的）。你也可以嵌入以百分号开头的 Python 代码。因为没有缩进，你需要用一个 % end 来结束当前的代码块（就像循环或 if 语句）。
|
||||
|
||||
这个模版首先检查列表是否为空，然后遍历里面的每一项。每一项会用粗体显示歌曲名字，然后是艺术家名字，然后是一个是否跳过（如果是当前正在播的歌曲）或从列表移除的链接。所有歌曲的类型都是 ‘song’，如果类型是 ‘unknown’，那就不是歌曲而是网络电台。
|
||||
|
||||
/remove/ 和 /skip/ 路径只是简单地封装了 XBMC 控制功能，在改动生效后重新加载 /juke：
|
||||
|
||||
@route(‘/skip/<position>’)
|
||||
def index(position):
|
||||
print xbmc.Player.GoTo({‘playerid’:0, ‘to’:’next’})
|
||||
redirect(“/juke”)
|
||||
@route(‘/remove/<position>’)
|
||||
def index(position):
|
||||
playlistid = get_playlistid()
|
||||
if playlistid >= 0:
|
||||
xbmc.Playlist.Remove({‘playlistid’:int(playlistid), ‘position’:int(position)})
|
||||
redirect(“/juke”)
|
||||
|
||||
当然，如果不能往列表里添加歌曲的话那这个列表管理功能也不行。
|
||||
|
||||
因为一旦播放列表结束，它就消失了，所以你需要重新创建一个，这会让事情复杂一些。而且有点让人迷惑的是，播放列表是通过调用 Playlist.Clear() 方法来创建的。这个方法也还用来删除包含网络电台（类型是 unknown）的播放列表。另一个麻烦的地方是列表里的网络电台开始播放后就不会停，所以如果当前在播网络电台，也会需要清除播放列表。
|
||||
|
||||
这些页面包含了指向 /play/<songid> 的链接来播放歌曲。通过下面的代码处理：
|
||||
|
||||
@route(‘/play/<id>’)
|
||||
def index(id):
|
||||
playlistid = get_playlistid()
|
||||
playlist, not_needed= get_playlist()
|
||||
if playlistid < 0 or playlist[0][‘type’] == ‘unknown’:
|
||||
xbmc.Playlist.Clear({“playlistid”:0})
|
||||
xbmc.Playlist.Add({“playlistid”:0, “item”:{“songid”:int(id)}})
|
||||
xbmc.Player.open({“item”:{“playlistid”:0}})
|
||||
playlistid = 0
|
||||
else:
|
||||
xbmc.Playlist.Add({“playlistid”:playlistid, “item”:{“songid”:int(id)}})
|
||||
remove_duplicates(playlistid)
|
||||
redirect(“/juke”)
|
||||
|
||||
最后一件事情是实现 remove_duplicates 调用。这并不是必须的 - 而且还有人并不喜欢这个 - 不过可以保证同一首歌不会多次出现在播放列表里。
|
||||
|
||||
我们也实现了一些页面用来列出收藏歌曲里所有艺术家，以及列出指定艺术家的歌曲和专辑。这些都非常简单，和 /juke 页面基本类似。
|
||||
|
||||
|
||||
|
||||
还需要处理一下 UI，不过功能已经有了。
|
||||
|
||||
> ### 日志 ###
|
||||
>
|
||||
> 通常拿到 XBMC JSON API 并不清楚能用来做什么，而且它的文档也有点模糊。找出如何使用的一种方式是看别的遥控程序是怎么做的。如果打开日志功能，就可以在使用其他遥控程序的时候看到哪个 API 被调用了，然后就可以应用到在自己的代码里。
|
||||
>
|
||||
> 要打开日志功能，把 XBMC 媒体中心 接到显示器上，再依次进入设置 > 系统 > 调试，打开允许调试日志。在打开日志功能后，还需要登录到 XBMC 机器上（比如通过 SSH），然后就可以查看日志了。日志文件的位置应该显示在 XBMC 界面左上角。在 RaspBMC 系统里，文件位置是 /home/pi/.xbmc/temp/xbmc.log。你可以通过下面的命令实时监视哪个 API 接口被调用了：
|
||||
>
|
||||
> cd /home/pi/.xbmc/temp
|
||||
> tail -f xbmc.log | grep “JSON”
|
||||
|
||||
#### 增加功能 ####
|
||||
|
||||
上面的代码都是用来播放 XBMC 媒体库里的歌曲的，但我们还希望能播放网络电台。每个插件都有自己的独立 URL 可以通过普通的 XBMC JSON 命令来获取信息。举个例子，要从电台插件里获取选中的电台，可以使用；
|
||||
|
||||
@route(‘/radio/’)
|
||||
def index():
|
||||
my_stations = xbmc.Files.GetDirectory({“directory”:”plugin://plugin.audio.radio_de/stations/my/”, “properties”:
|
||||
[“title”,”thumbnail”,”playcount”,”artist”,”album”,”episode”,”season”,”showtitle”]})
|
||||
if ‘result’ in my_stations.keys():
|
||||
return template(‘radio’, stations=my_stations[‘result’][‘files’])
|
||||
else:
|
||||
return template(‘error’, error=’radio’)
|
||||
|
||||
这样可以返回一个可以和歌曲一样能添加到播放列表的文件。不过，这些文件能一直播下去，所以（之前说过）在添加其他歌曲的时候需要重新创建列表。
|
||||
|
||||
#### 共享歌曲 ####
|
||||
|
||||
除了伺服页面模版，Bottle 还支持静态文件。方便用于那些不会因为用户输入而改变的内容。可以是 CSS 文件，一张图片或是一首 MP3 歌曲。在我们的简单遥控程序里（目前）还没有任何用来美化的 CSS 或图片，不过我们增加了一个下载歌曲的途径。这个可以让媒体中心变成一个存放歌曲的 NAS 盒子。在需要传输大量数据的时候，最好还是用类似 Samba 的功能，但只是下几首歌到手机上的话使用静态文件也是很好的方式。
|
||||
|
||||
通过歌曲 ID 来下载的 Bottle 代码：
|
||||
|
||||
@route(‘/download/<id>’)
|
||||
def index(id):
|
||||
data = xbmc.AudioLibrary.GetSongDetails({“songid”:int(id), “properties”:[“file”]})
|
||||
full_filename = data[‘result’][‘songdetails’][‘file’]
|
||||
path, filename = os.path.split(full_filename)
|
||||
return static_file(filename, root=path, download=True)
|
||||
|
||||
应用的时候，只需要为 /songsby/ 页面里的相应 ID 加个链接。
|
||||
|
||||
我们已经把所有的代码过了一遍，不过还需要一点工作来把它们集合到一起。可以自己去 GitHub 页面 [https://github.com/ben-ev/xbmc-remote][3] 看下。
|
||||
|
||||
> ### 设置 ###
|
||||
>
|
||||
> 我们的遥控程序已经开发完成，还需要保证让它在媒体中心每次开机的时候都能启动。有几种方式，最简单的是在 /etc/rc.local 里增加一行命令来启动。我们的文件位置在 /opt/xbmc-remote/remote.py，其他文件也和它一起。然后在 /etc/rc.local 最后的 exit 0 之前增加了下面一行。
|
||||
>
|
||||
> cd /opt/xbmc-remote && python remote.py &
|
||||
|
||||
> ### GitHub ###
|
||||
>
|
||||
> 这个项目目前还只是个架子，但是 - 我们运营杂志就意味着没有太多自由时间来编程。不过，我们启动了一个 GitHub 项目，希望能持续完善， 而如果你觉得这个项目有用的话，欢迎做出贡献。
|
||||
>
|
||||
> 要查看最新的进展，请访问 [https://github.com/ben-ev/xbmc-remote][4] 看看所处的状态。你可以从页面里获取最新的代码，或者通过命令行复制。
|
||||
>
|
||||
> 如果你希望改善它，可以复制项目到你自己的分支开发，然后在功能完成后发起合并请求。关于如何使用 GitHub 的更多信息，请访问 [https://github.com/features][5]。
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: http://www.linuxvoice.com/xbmc-build-a-remote-control/
|
||||
|
||||
作者：[Ben Everard][a]
|
||||
译者：[zpl1025](https://github.com/zpl1025)
|
||||
校对：[校对者ID](https://github.com/校对者ID)
|
||||
|
||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]:http://www.linuxvoice.com/author/ben_everard/
|
||||
[1]:http://bottlepy.org/docs/dev/deployment.html
|
||||
[2]:http://wiki.xbmc.org/?title=JSON-RPC_API/v6
|
||||
[3]:https://github.com/ben-ev/xbmc-remote
|
||||
[4]:https://github.com/ben-ev/xbmc-remote
|
||||
[5]:https://github.com/features
|
||||
Loading…
Reference in New Issue
Block a user