Android url MP3实现播放，暂停，上一首，下一首，渐变色进度条和时间点

实现播放、暂停、上一首、下一首、渐变色进度条和时间点可以通过MediaPlayer和SeekBar组合实现。具体步骤如下：

1. 在布局文件中添加MediaPlayer和SeekBar组件，如下所示：

<SeekBar
    android:id="@+id/seekBar"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:padding="16dp"
    android:progressDrawable="@drawable/custom_seekbar_progress"
    android:thumb="@drawable/custom_seekbar_thumb" />

<Button
    android:id="@+id/btnPrevious"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Previous" />

<Button
    android:id="@+id/btnPlayPause"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Play" />

<Button
    android:id="@+id/btnNext"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Next" />

2. 在Activity中实例化MediaPlayer和SeekBar组件，并设置监听器，如下所示：

private MediaPlayer mediaPlayer;
private SeekBar seekBar;

private int[] musicList = {R.raw.music1, R.raw.music2, R.raw.music3};
private int currentTrack = 0;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    mediaPlayer = MediaPlayer.create(this, musicList[currentTrack]);
    mediaPlayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
        @Override
        public void onCompletion(MediaPlayer mp) {
            playNextTrack();
        }
    });

    seekBar = findViewById(R.id.seekBar);
    seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
        @Override
        public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
            if (fromUser) {
                mediaPlayer.seekTo(progress);
            }
        }

        @Override
        public void onStartTrackingTouch(SeekBar seekBar) {

        }

        @Override
        public void onStopTrackingTouch(SeekBar seekBar) {

        }
    });

    Button btnPrevious = findViewById(R.id.btnPrevious);
    btnPrevious.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            playPreviousTrack();
        }
    });

    Button btnPlayPause = findViewById(R.id.btnPlayPause);
    btnPlayPause.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (mediaPlayer.isPlaying()) {
                pauseTrack();
            } else {
                playTrack();
            }
        }
    });

    Button btnNext = findViewById(R.id.btnNext);
    btnNext.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            playNextTrack();
        }
    });
}

3. 实现播放、暂停、上一首、下一首功能，如下所示：

private void playTrack() {
    mediaPlayer.start();
    updateSeekBar();
    Button btnPlayPause = findViewById(R.id.btnPlayPause);
    btnPlayPause.setText("Pause");
}

private void pauseTrack() {
    mediaPlayer.pause();
    Button btnPlayPause = findViewById(R.id.btnPlayPause);
    btnPlayPause.setText("Play");
}

private void playPreviousTrack() {
    if (currentTrack > 0) {
        currentTrack--;
    } else {
        currentTrack = musicList.length - 1;
    }
    mediaPlayer.stop();
    mediaPlayer = MediaPlayer.create(this, musicList[currentTrack]);
    playTrack();
}

private void playNextTrack() {
    if (currentTrack < musicList.length - 1) {
        currentTrack++;
    } else {
        currentTrack = 0;
    }
    mediaPlayer.stop();
    mediaPlayer = MediaPlayer.create(this, musicList[currentTrack]);
    playTrack();
}

4. 实现渐变色进度条和时间点功能，如下所示：

private void updateSeekBar() {
    seekBar.setMax(mediaPlayer.getDuration());
    new Handler().postDelayed(new Runnable() {
        @Override
        public void run() {
            seekBar.setProgress(mediaPlayer.getCurrentPosition());
            updateSeekBar();
        }
    }, 1000);

    int minutes = (mediaPlayer.getCurrentPosition() / 1000) / 60;
    int seconds = (mediaPlayer.getCurrentPosition() / 1000) % 60;
    String time = String.format("%d:%02d", minutes, seconds);

    TextView txtTime = findViewById(R.id.txtTime);
    txtTime.setText(time);
}

5. 最后，添加自定义SeekBar的样式，如下所示：

<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:id="@android:id/background">
        <color android:color="#BDBDBD" />
    </item>
    <item android:id="@android:id/progress">
        <clip>
            <shape>
                <corners android:radius="4dp" />
                <gradient
                    android:angle="0"
                    android:endColor="#FF4081"
                    android:startColor="#3F51B5" />
            </shape>
        </clip>
    </item>
    <item android:id="@android:id/secondaryProgress">
        <clip>
            <shape>
                <corners android:radius="4dp" />
                <gradient
                    android:angle="0"
                    android:endColor="#FF4081"
                    android:startColor="#3F51B5" />
            </shape>
        </clip>
    </item>
</layer-list>

至此，实现了Android url MP3实现播放、暂停、上一首、下一首、渐变色进度条和时间点的功能。