java - 从 shoutcast 流中获取元数据

Question

我正在开发一个带有多个 radio 的 radio 应用程序，流媒体播放正常。但我目前正在努力显示艺术家和正在播放的音乐。

这是我用来从 shoutcast 流中获取元数据的类:

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class IcyStreamMeta<Message> {

protected URL streamUrl;
private Map<String, String> metadata;
private boolean isError;

public IcyStreamMeta(URL streamUrl) {
    setStreamUrl(streamUrl);

    isError = false;
}

/**
 * Get artist using stream's title
 *
 * @return String
 * @throws IOException
 */
public String getArtist() throws IOException {
    Map<String, String> data = getMetadata();

    if (!data.containsKey("StreamTitle"))
        return "";

    String streamTitle = data.get("StreamTitle");
    String title = streamTitle.substring(0, streamTitle.indexOf("-"));
    return title.trim();
}

/**
 * Get title using stream's title
 *
 * @return String
 * @throws IOException
 */
public String getTitle() throws IOException {
    Map<String, String> data = getMetadata();

    if (!data.containsKey("StreamTitle"))
        return "";

    String streamTitle = data.get("StreamTitle");
    String artist = streamTitle.substring(streamTitle.indexOf("-")+1);
    return artist.trim();
}

public Map<String, String> getMetadata() throws IOException {
    if (metadata == null) {
        refreshMeta();
    }

    return metadata;
}

public void refreshMeta() throws IOException {
    retreiveMetadata();
}

private void retreiveMetadata() throws IOException {
    URLConnection con = streamUrl.openConnection();
    con.setRequestProperty("Icy-MetaData", "1");
    con.setRequestProperty("Connection", "close");
    con.setRequestProperty("Accept", null);
    con.connect();

    int metaDataOffset = 0;
    Map<String, List<String>> headers = con.getHeaderFields();
    InputStream stream = con.getInputStream();

    if (headers.containsKey("icy-metaint")) {
        // Headers are sent via HTTP
        metaDataOffset = Integer.parseInt(headers.get("icy-metaint").get(0));
    } else {
        // Headers are sent within a stream
        StringBuilder strHeaders = new StringBuilder();
        char c;
        while ((c = (char)stream.read()) != -1) {
            strHeaders.append(c);
            if (strHeaders.length() > 5 && (strHeaders.substring((strHeaders.length() - 4), strHeaders.length()).equals("\r\n\r\n"))) {
                // end of headers
                break;
            }
        }

        // Match headers to get metadata offset within a stream
        Pattern p = Pattern.compile("\\r\\n(icy-metaint):\\s*(.*)\\r\\n");
        Matcher m = p.matcher(strHeaders.toString());
        if (m.find()) {
            metaDataOffset = Integer.parseInt(m.group(2));
        }
    }

    // In case no data was sent
    if (metaDataOffset == 0) {
        isError = true;
        return;
    }

    // Read metadata
    int b;
    int count = 0;
    int metaDataLength = 4080; // 4080 is the max length
    boolean inData = false;
    StringBuilder metaData = new StringBuilder();
    // Stream position should be either at the beginning or right after headers
    while ((b = stream.read()) != -1) {
        count++;

        // Length of the metadata
        if (count == metaDataOffset + 1) {
            metaDataLength = b * 16;
        }

        if (count > metaDataOffset + 1 && count < (metaDataOffset + metaDataLength)) {
            inData = true;
        } else {
            inData = false;
        }
        if (inData) {
            if (b != 0) {
                metaData.append((char)b);
            }
        }
        if (count > (metaDataOffset + metaDataLength)) {
            break;
        }

    }

    // Set the data
    metadata = IcyStreamMeta.parseMetadata(metaData.toString());

    // Close
    stream.close();
}

public boolean isError() {
    return isError;
}

public URL getStreamUrl() {
    return streamUrl;
}

public void setStreamUrl(URL streamUrl) {
    this.metadata = null;
    this.streamUrl = streamUrl;
    this.isError = false;
}

public static Map<String, String> parseMetadata(String metaString) {
    Map<String, String> metadata = new HashMap();
    String[] metaParts = metaString.split(";");
    Pattern p = Pattern.compile("^([a-zA-Z]+)=\\'([^\\']*)\\'$");
    Matcher m;
    for (int i = 0; i < metaParts.length; i++) {
        m = p.matcher(metaParts[i]);
        if (m.find()) {
            metadata.put(m.group(1), m.group(2));
        }
    }

    return metadata;
}
}

以及 MainActivity 上每 10 秒获取元数据的方法

private void getMeta()
    {
    Timer timer = new Timer();
    timer.schedule(new TimerTask() {
        public void run() {
            try {
                IcyStreamMeta icy = new IcyStreamMeta(new URL(RadiophonyService.getRadioURL()));
                final String data = icy.getArtist() + " - " + icy.getTitle();
                final TextView meta = (TextView) findViewById(R.id.now_playing);

                runOnUiThread(new Runnable() {
                    public void run() {
                        meta.setText(data);
                    }
                });
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }, 0, 10000);
}

最初，当我选择一个电台时，它播放但不显示元数据，当我选择另一个电台时，应用程序崩溃并出现此运行时错误:

E/AndroidRuntime:致命异常:Timer-0 进程:com.example.app，PID:23597

java.lang.StringIndexOutOfBoundsException: 长度=0;区域开始=0；区域长度=-1 在 java.lang.String.startEndAndLength(String.java:504) 在 java.lang.String.substring(String.java:1333) 在 com.example.app.utilities.IcyStreamMeta.getArtist(IcyStreamMeta.java:41) 在 com.example.app.activities.MainActivity$8.run(MainActivity.java:306) 在 java.util.Timer$TimerImpl.run(Timer.java:284)

我被困在这个问题上好几天了，我尝试了其他解决方案但没有任何效果!

Answer 1

看起来像这条线

String title = streamTitle.substring(0, streamTitle.indexOf("-"));

是罪魁祸首。

如果 streamTitle 的标题中没有破折号，indexOf() 将返回 -1，而 substring() 令人窒息因为结束索引不能小于起始索引。

也许你需要这样的东西:

int pos = streamTitle.indexOf("-");
String title = (pos == -1) ? streamTitle : streamTitle.substring(0, pos);