android 音频播放 以及 二维码模块中音频播放和震动(vibrate)的实现

参考：《第一行代码》第8章

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在Android中播放音频文件一般都是使用MediaPlayer类来实现，它对多种格式的音频文件提供了非常全面的控制方法，从而使得播放音乐的工作变得非常简单。

常用MediaPlayer类的控制方法：

1.setDataSource()：设置要播放的音频文件的位置

2.prepare()：在开始播放之前调用这个方法完成准备工作

3.start()：开始或继续播放音频

4.pause()：暂停播放音频

5.reset()：将MediaPlayer对象重置到刚刚创建的状态

6.seekTo()：从指定的位置开始播放音频

7.stop()：停止播放音频。调用这个方法后的MediaPlayer无法再播放音频

8.release()：释放与MediaPlayer对象相关的资源

9.isPlaying()：判断当前MediaPlayer是否正在播放音频

10.getDuration()：获取载入的音频文件的时长

简单的工作流程：首先需要创建出一个MediaPlayer对象，然后调用setDataSource()方法来设置音频文件的路径，再调用prepare()方法使MediaPlayer进入到准备状态，接下来调用start()方法就可以开始播放音频，调用pause()方法就会暂停播放，调用reset()方法就会停止播放。

新建项目AudioTest

MainActivity.java：

package com.zj.audiotest;import android.app.Activity;import android.media.MediaPlayer;import android.os.Bundle;import android.os.Environment;import android.view.View;import android.widget.Button;import java.io.File;public class MainActivity extends Activity implements View.OnClickListener {    private Button play;    private Button pause;    private Button stop;    private MediaPlayer mediaPlayer = new MediaPlayer();    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        play = (Button)findViewById(R.id.play);        pause = (Button)findViewById(R.id.pause);        stop = (Button)findViewById(R.id.stop);        play.setOnClickListener(this);        pause.setOnClickListener(this);        stop.setOnClickListener(this);        initMediaPlayer(); //initialize    }    private void initMediaPlayer() {        try {            File file = new File(Environment.getExternalStorageDirectory(), "music.mp3");            mediaPlayer.setDataSource(file.getPath()); //Specify the path for the audio file            mediaPlayer.prepare(); //Let MediaPlayer enter the ready state        } catch (Exception e) {            e.printStackTrace();        }    }    @Override    public void onClick(View v) {        switch (v.getId()) {            case R.id.play:                if (!mediaPlayer.isPlaying()) {                    mediaPlayer.start(); //start playing                }                break;            case R.id.pause:                if (mediaPlayer.isPlaying()) {                    mediaPlayer.pause(); //pause playback                }                break;            case R.id.stop:                if (mediaPlayer.isPlaying()) {                    mediaPlayer.reset(); //stop playing and return to the state of the uninialization                    initMediaPlayer(); //initialize                }                break;            default:                break;        }    }    @Override    protected void onDestroy() {        super.onDestroy();        if (mediaPlayer != null) {            mediaPlayer.stop();            mediaPlayer.release();        }    }}

activity_main.xml：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent">    <Button        android:id="@+id/play"        android:layout_width="0dp"        android:layout_height="wrap_content"        android:layout_weight="1"        android:text="Play"        />    <Button        android:id="@+id/pause"        android:layout_width="0dp"        android:layout_height="wrap_content"        android:layout_weight="1"        android:text="Pause"        />    <Button        android:id="@+id/stop"        android:layout_width="0dp"        android:layout_height="wrap_content"        android:layout_weight="1"        android:text="Stop"        /></LinearLayout>

访问外部存储需要读权限

在AndroidManifest.xml上加入:

<!-- 访问外部存储的权限 -->    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

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震动VIBRATE：

                    long VIBRATE_DURATIN = 200L;                    Vibrator vibrate = (Vibrator)getSystemService(VIBRATOR_SERVICE);                    vibrate.vibrate(VIBRATE_DURATIN);

需要权限：

    <!-- permission to vibrate -->    <uses-permission android:name="android.permission.VIBRATE" />

函数解析：

    /**     * Use with {@link #getSystemService} to retrieve a {@link     * android.os.Vibrator} for interacting with the vibration hardware.     *     * @see #getSystemService     * @see android.os.Vibrator     */    public static final String VIBRATOR_SERVICE = "vibrator";

使用函数getSystemService去检索一个震动功能，为了和震动硬件交互

    /**     * Vibrate constantly for the specified period of time.     * <p>This method requires the caller to hold the permission     * {@link android.Manifest.permission#VIBRATE}.     *     * @param milliseconds The number of milliseconds to vibrate.     */    public void vibrate(long milliseconds) {        vibrate(milliseconds, null);    }

在指定时间内不断的震动。此方法需要拥有权限

android.permission.VIBRATE

参数milliseconds表示振动的毫秒数

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二维码模块的音频播放和震动:

修改上面AudioTest项目：

MainActivity.java如下：

package com.zj.audiotest;import android.app.Activity;import android.content.res.AssetFileDescriptor;import android.media.AudioManager;import android.media.MediaPlayer;import android.os.Bundle;import android.os.Vibrator;import android.view.View;import android.widget.Button;import java.io.IOException;public class MainActivity extends Activity implements View.OnClickListener {    private MediaPlayer mediaPlayer;    private boolean playBeep;    private static final float BEEP_VOLUME = 0.10f;    private boolean vibrate;    private Button btnVibrate;    private static final long VIBRATE_DURATION = 200L;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        btnVibrate = (Button)findViewById(R.id.vibrate);        btnVibrate.setOnClickListener(this);        playBeep = true;        AudioManager audioService = (AudioManager) getSystemService(AUDIO_SERVICE);        if (audioService.getRingerMode() != AudioManager.RINGER_MODE_NORMAL) {            playBeep = false;        }        initBeepSound();        vibrate = true;    }    private void initBeepSound() {        if (playBeep && mediaPlayer == null) {            // The volume on STREAM_SYSTEM is not adjustable, and users found it            // too loud,            // so we now play on the music stream.            setVolumeControlStream(AudioManager.STREAM_MUSIC);            mediaPlayer = new MediaPlayer();            mediaPlayer.setAudioStreamType(AudioManager.STREAM_ALARM);            mediaPlayer.setOnCompletionListener(beepListener);            AssetFileDescriptor file = getResources().openRawResourceFd(R.raw.beep);            try {                mediaPlayer.setDataSource(file.getFileDescriptor(),                        file.getStartOffset(), file.getLength());                file.close();                mediaPlayer.setVolume(BEEP_VOLUME, BEEP_VOLUME);                mediaPlayer.prepare();            } catch (IOException e) {                mediaPlayer = null;            }        }    }    /**     * When the beep has finished playing, rewind to queue up another one.     */    private final MediaPlayer.OnCompletionListener beepListener = new MediaPlayer.OnCompletionListener() {        public void onCompletion(MediaPlayer mediaPlayer) {            mediaPlayer.seekTo(0);        }    };    @Override    public void onClick(View v) {        switch (v.getId()) {            case R.id.vibrate:                playBeepSoundAndVibrate();                break;            default:                break;        }    }    public void playBeepSoundAndVibrate() {        if (playBeep && mediaPlayer != null) {            mediaPlayer.start();        }        if (vibrate) {            Vibrator vibrator = (Vibrator) getSystemService(VIBRATOR_SERVICE);            vibrator.vibrate(VIBRATE_DURATION);        }    }    @Override    protected void onDestroy() {        super.onDestroy();        if (mediaPlayer != null) {            mediaPlayer.stop();            mediaPlayer.release();        }    }}

activity_main.xml如下：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent">    <Button        android:id="@+id/vibrate"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="Vib"        /></LinearLayout>

需要加上震动的权限，故AndroidManifest.xml如下：

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"    package="com.zj.audiotest" >    <application        android:allowBackup="true"        android:icon="@mipmap/ic_launcher"        android:label="@string/app_name"        android:theme="@style/AppTheme" >        <activity            android:name=".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>    </application>    <!-- 访问外部存储的权限 -->    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />    <!-- permission to vibrate -->    <uses-permission android:name="android.permission.VIBRATE" /></manifest>

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