Android在线音乐播放器

Question

我尝试建立Android在线音乐播放器，在下载和播放歌曲的同时，用户可以在下载时间(完成下载之前)听到音乐。我使用下面的download类和MediaPlayer来启动音乐，但是这个类只在下载完成时工作，如果用户在下载完成之前单击播放，使用NullpointExption下载应用程序崩溃，有什么解决方案...！？

Download Class (可恢复)：

public class downloader {
private static boolean Stopdownloader = false;//use for stop download


public static void Stop(boolean status) {
    Stopdownloader = status;
}


public static void dl(final String downloadPath, final String filePath, final Ondownloadprogress lisener) {
    Thread thread = new Thread(new Runnable() {

        @Override
        public void run() {
            try {
                int downloadedSize = 0;
                int fileLength = 0;
                URL url = new URL(downloadPath);
                HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                File file = new File(filePath);
                if (file.exists()) {
                    connection.setRequestProperty("Range", "bytes=" + file.length() + "-");
                    downloadedSize = (int) file.length();
                }
                connection.setRequestMethod("GET");
                connection.setDoInput(true);
                final int FILE_SIZE = connection.getContentLength();
                connection.connect();
                fileLength = connection.getContentLength() + downloadedSize;
                BufferedInputStream input = new BufferedInputStream(connection.getInputStream());
                RandomAccessFile output = new RandomAccessFile(file, "rw");
                output.seek(downloadedSize);

                byte data[] = new byte[1024];
                int count = 0;
                int progress = 0;

                while ((count = input.read(data, 0, 1024)) != -1
                        && progress != 100)
                {
                    if (Stopdownloader) {
                        break;
                    }
                    downloadedSize += count;
                    output.write(data, 0, count);
                    progress = (int) ((downloadedSize * 100) / fileLength);
                    final int ss = (int) ((downloadedSize * 100) / fileLength);
                    final float persent = ((float) progress / FILE_SIZE) * 100;
                    if (lisener != null) {
                        final int finalProgres = progress;
                        G.HANDLER.post(new Runnable() {

                            @Override
                            public void run() {
                                lisener.ondownload((int) ss, finalProgres, FILE_SIZE);
                            }
                        });

                    }
                }

                output.close();
                input.close();
            }
            catch (MalformedURLException e) {}
            catch (IOException e) {}
            finally {}
        }
    });

    thread.start();

}}

在MainActivity中：

    play.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View arg0) {
            downloader.dl("http://MUSIC-URL","/temp.mp3", null);
            downloader.Stop(false);
            MediaPlayer Music = MediaPlayer.create(G.context, Uri.parse("/temp.mp3"));
            Music.start();
            Music.prepare();
        }
    });

Answer 1

您需要在start()之前执行prepare()

android参考资料写得很好：http://developer.android.com/reference/android/media/MediaPlayer.html

看看这篇教程，http://sapandiwakar.in/tutorial-how-to-manually-create-android-media-player-controls/，我认为它也应该能让你前进一点。