用android写一个音乐播放器，包括xml和java文件

以下是一个简单的 Android 音乐播放器的 XML 和 Java 文件示例：

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ListView
        android:id="@+id/listView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_above="@+id/bottomLayout" />

    <LinearLayout
        android:id="@+id/bottomLayout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:background="#FFFFFF"
        android:orientation="horizontal"
        android:padding="10dp">

        <ImageView
            android:id="@+id/prevButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@drawable/prev" />

        <ImageView
            android:id="@+id/playButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@drawable/play" />

        <ImageView
            android:id="@+id/nextButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@drawable/next" />

        <SeekBar
            android:id="@+id/seekBar"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1" />

        <TextView
            android:id="@+id/timeTextView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="0:00/0:00" />
    </LinearLayout>
</RelativeLayout>

MainActivity.java:

import android.media.MediaPlayer;
import android.os.Bundle;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.SeekBar;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.concurrent.TimeUnit;

public class MainActivity extends AppCompatActivity {

    private ListView listView;
    private ImageView prevButton;
    private ImageView playButton;
    private ImageView nextButton;
    private SeekBar seekBar;
    private TextView timeTextView;

    private MediaPlayer mediaPlayer;
    private Handler handler = new Handler();

    private ArrayList<String> songsList = new ArrayList<>();

    private int currentIndex = 0;

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

        // Initialize views
        listView = findViewById(R.id.listView);
        prevButton = findViewById(R.id.prevButton);
        playButton = findViewById(R.id.playButton);
        nextButton = findViewById(R.id.nextButton);
        seekBar = findViewById(R.id.seekBar);
        timeTextView = findViewById(R.id.timeTextView);

        // Add some songs to the list
        songsList.add("song1.mp3");
        songsList.add("song2.mp3");
        songsList.add("song3.mp3");

        // Set up the media player
        mediaPlayer = MediaPlayer.create(this, R.raw.song1);
        mediaPlayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
            @Override
            public void onCompletion(MediaPlayer mediaPlayer) {
                playNextSong();
            }
        });

        // Set up the seek bar
        seekBar.setMax(mediaPlayer.getDuration());
        seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
                if (fromUser) {
                    mediaPlayer.seekTo(progress);
                }
                updateTimeTextView();
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {

            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {

            }
        });

        // Set up the list view
        SongAdapter songAdapter = new SongAdapter(this, songsList);
        listView.setAdapter(songAdapter);

        // Set up the play button
        playButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (mediaPlayer.isPlaying()) {
                    mediaPlayer.pause();
                    playButton.setImageResource(R.drawable.play);
                } else {
                    mediaPlayer.start();
                    playButton.setImageResource(R.drawable.pause);
                    handler.postDelayed(updateSeekBarRunnable, 0);
                }
            }
        });

        // Set up the previous button
        prevButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                playPreviousSong();
            }
        });

        // Set up the next button
        nextButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                playNextSong();
            }
        });
    }

    private void playNextSong() {
        currentIndex++;
        if (currentIndex >= songsList.size()) {
            currentIndex = 0;
        }
        playSongAtIndex(currentIndex);
    }

    private void playPreviousSong() {
        currentIndex--;
        if (currentIndex < 0) {
            currentIndex = songsList.size() - 1;
        }
        playSongAtIndex(currentIndex);
    }

    private void playSongAtIndex(int index) {
        mediaPlayer.reset();
        int resourceId = getResources().getIdentifier(songsList.get(index), "raw", getPackageName());
        mediaPlayer = MediaPlayer.create(this, resourceId);
        mediaPlayer.start();
        playButton.setImageResource(R.drawable.pause);
        seekBar.setMax(mediaPlayer.getDuration());
        handler.postDelayed(updateSeekBarRunnable, 0);
    }

    private Runnable updateSeekBarRunnable = new Runnable() {
        @Override
        public void run() {
            seekBar.setProgress(mediaPlayer.getCurrentPosition());
            updateTimeTextView();
            handler.postDelayed(this, 100);
        }
    };

    private void updateTimeTextView() {
        long minutes = TimeUnit.MILLISECONDS.toMinutes(mediaPlayer.getCurrentPosition());
        long seconds = TimeUnit.MILLISECONDS.toSeconds(mediaPlayer.getCurrentPosition()) -
                TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes(mediaPlayer.getCurrentPosition()));
        String currentTimeString = String.format("%d:%02d", minutes, seconds);
        minutes = TimeUnit.MILLISECONDS.toMinutes(mediaPlayer.getDuration());
        seconds = TimeUnit.MILLISECONDS.toSeconds(mediaPlayer.getDuration()) -
                TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes(mediaPlayer.getDuration()));
        String durationString = String.format("%d:%02d", minutes, seconds);
        timeTextView.setText(currentTimeString + "/" + durationString);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        mediaPlayer.stop();
        mediaPlayer.release();
    }
}

这个示例包括一个简单的界面，一个播放列表，播放、暂停、上一首、下一首和进度条控件，以及如何使用 MediaPlayer 控件播放音乐。注意，这只是一个简单的示例，可以根据自己的需求进行修改和扩展。