使用Android Service切換歌曲

1.AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.app"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="15"
        android:targetSdkVersion="15" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.app.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <service
            android:name=".MusicService"
            android:exported="true" />
    </application>

</manifest>

2.activity_main.xml

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

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="音樂播放" />

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >

        <Button
            android:id="@+id/previous"
            android:layout_width="wrap_content"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="上一首" />

        <Button
            android:id="@+id/play"
            android:layout_width="wrap_content"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="播放" />

        <Button
            android:id="@+id/next"
            android:layout_width="wrap_content"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="下一首" />

        <Button
            android:id="@+id/pause"
            android:layout_width="wrap_content"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="暫停" />
    </LinearLayout>

</LinearLayout>

3.MusicService.java

import java.io.IOException;

import android.app.Service;

import android.content.Intent;

import android.database.Cursor;

import android.media.MediaPlayer;

import android.net.Uri;

import android.os.IBinder;

import android.provider.MediaStore;

import android.widget.Toast;

public class MusicService extends Service {

String[] mCursorCols = new String[] {

"audio._id AS _id", // index must match IDCOLIDX below

MediaStore.Audio.Media.ARTIST, MediaStore.Audio.Media.ALBUM,

MediaStore.Audio.Media.TITLE, MediaStore.Audio.Media.DATA,

MediaStore.Audio.Media.MIME_TYPE, MediaStore.Audio.Media.ALBUM_ID,

MediaStore.Audio.Media.ARTIST_ID, MediaStore.Audio.Media.DURATION };

private MediaPlayer mMediaPlayer;

private Cursor mCursor;

private int mPlayPosition = 0;

public static final String PLAY_ACTION = "com.app.PLAY_ACTION";

public static final String PAUSE_ACTION = "com.app.PAUSE_ACTION";

public static final String NEXT_ACTION = "com.app.NEXT_ACTION";

public static final String PREVIOUS_ACTION = "com.app.PREVIOUS_ACTION";

@Override

public IBinder onBind(Intent arg0) {

// TODO Auto-generated method stub

return null;

}

@Override

public void onCreate() {

super.onCreate();

mMediaPlayer = new MediaPlayer();

// 透過一個URI 可以取得所有音頻檔

Uri MUSIC_URL = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;

// 這裏過濾了一下，因為有些音頻檔很短，這裏作了處理，過濾大於10 秒的歌

mCursor = getContentResolver().query(MUSIC_URL, mCursorCols,

"duration > 10000", null, null);

}

@Override

public void onStart(Intent intent, int startId) {

super.onStart(intent, startId);

String action = intent.getAction();

if (action.equals(PLAY_ACTION)) {

play();

} else if (action.equals(PAUSE_ACTION)) {

pause();

} else if (action.equals(NEXT_ACTION)) {

next();

} else if (action.equals(PREVIOUS_ACTION)) {

previous();

}

}

// play the music

public void play() {

init();

}

// 暫停時，結束服務

public void pause() {

this.stopSelf();

}

// 上一首

public void previous() {

mPlayPosition--;

if (mPlayPosition < 0) {

mPlayPosition = mCursor.getCount() - 1;

}

init();

}

public void next() {

mPlayPosition++;

if (mPlayPosition == mCursor.getCount()) {

mPlayPosition = 0;

}

init();

}

public void init() {

mMediaPlayer.reset();

String dataSource = getDateByPosition(mCursor, mPlayPosition);

String info = getInfoByPosition(mCursor, mPlayPosition);

// 用Toast 顯示歌曲資訊

Toast.makeText(getApplicationContext(), info, Toast.LENGTH_SHORT)

.show();

try {

mMediaPlayer.setDataSource(dataSource);

mMediaPlayer.prepare();

mMediaPlayer.start();

} catch (IllegalArgumentException e1) {

e1.printStackTrace();

} catch (IllegalStateException e1) {

e1.printStackTrace();

} catch (IOException e1) {

e1.printStackTrace();

}

}

// 根據位置來取得歌曲位置

public String getDateByPosition(Cursor c, int position) {

c.moveToPosition(position);

int dataColumn = c.getColumnIndex(MediaStore.Audio.Media.DATA);

String data = c.getString(dataColumn);

return data;

}

// 取得當前播放歌曲演唱者及歌名

public String getInfoByPosition(Cursor c, int position) {

c.moveToPosition(position);

int titleColumn = c.getColumnIndex(MediaStore.Audio.Media.TITLE);

int artistColumn = c.getColumnIndex(MediaStore.Audio.Media.ARTIST);

String info = c.getString(artistColumn) + " "

+ c.getString(titleColumn);

return info;

}

// 服務結束時要釋放MediaPlayer

public void onDestroy() {

super.onDestroy();

mMediaPlayer.release();

}

}

4.MainActivity.java

import android.app.Activity;

import android.content.ComponentName;

import android.content.Intent;

import android.os.Bundle;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

public class MainActivity extends Activity implements OnClickListener {

private Button mPrevious, mPlay, mNext, mPause;

private ComponentName component;

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

setupViews();

}

// 初始化一些工作

// 將畫面按鈕取出存入物件變數內

public void setupViews() {

component = new ComponentName(this, MusicService.class);

mPrevious = (Button) findViewById(R.id.previous);

mPlay = (Button) findViewById(R.id.play);

mNext = (Button) findViewById(R.id.next);

mPause = (Button) findViewById(R.id.pause);

// 註冊按鈕發生事件

mPrevious.setOnClickListener(this);

mPlay.setOnClickListener(this);

mNext.setOnClickListener(this);

mPause.setOnClickListener(this);

}

// 按鈕點擊事件回應

public void onClick(View v) {

if (v == mPrevious) {

Intent mIntent = new Intent(MusicService.PREVIOUS_ACTION);

mIntent.setComponent(component);

// 執行服務

startService(mIntent);

} else if (v == mPlay) {

Intent mIntent = new Intent(MusicService.PLAY_ACTION);

mIntent.setComponent(component);

startService(mIntent);

} else if (v == mNext) {

Intent mIntent = new Intent(MusicService.NEXT_ACTION);

mIntent.setComponent(component);

startService(mIntent);

} else {

Intent mIntent = new Intent(MusicService.PAUSE_ACTION);

mIntent.setComponent(component);

startService(mIntent);

}

}

}