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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