Android 音频录制（Audio Capture）

本文是 Android Developer 上官方文档的个人翻译，囿于作者英文水平，可能比较粗糙，原文如下：

原文：http://developer.android.com/intl/zh-cn/guide/topics/media/audio-capture.html

Android 多媒体框架包含了对录制和编码为多种音频格式的支持，因此你可以很简单地将音频集成到自己的应用中。如果设备支持的话，你可以使用 MediaRecorder APIs 来录制音频。

本文档向你展示如何编写一个应用，可以从设备的麦克风录制音频、保存并播放。

注意：Android 模拟器没有录制音频的能力，真机一般都会有这种功能。

执行音频录制（Performing Audio Capture）

音频录制相对音频和视频的播放来说稍微有一点复杂，但仍然相当简单：

1. 创建一个 android.media.MediaRecorder 实例；
2. 使用 MediaRecorder.setAudioSource() 设置音频来源，你有可能会使用 MediaRecorder.AudioSource.MIC ；
3. 使用 MediaRecorder.setOutputFormat() 设置输出文件类型；
4. 使用 MediaRecorder.setOutputFile() 设置输出文件名；
5. 使用 MediaRecorder.setAudioEncoder() 设置音频编码器；
6. 在 MediaRecorder 实例上调用 MediaRecorder.prepare()；
7. 调用 MediaRecorder.start() 开始音频录制；
8. 调用 MediaRecorder.stop() 停止录制；
9. 当你使用完 MediaRecorder 实例，调用它的 MediaRecorder.release() 方法，该方法可以立即释放 MediaRecorder 所占有的资源。

示例：录制音频并播放录制的音频

下面的示例类演示了如何建立、开始和停止音频录制，最后播放录制的音频文件。

/* * The application needs to have the permission to write to external storage * if the output file is written to the external storage, and also the * permission to record audio. These permissions must be set in the * application's AndroidManifest.xml file, with something like: * * <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> * <uses-permission android:name="android.permission.RECORD_AUDIO" /> * */
package com.android.audiorecordtest;

import android.app.Activity;
import android.widget.LinearLayout;
import android.os.Bundle;
import android.os.Environment;
import android.view.ViewGroup;
import android.widget.Button;
import android.view.View;
import android.view.View.OnClickListener;
import android.content.Context;
import android.util.Log;
import android.media.MediaRecorder;
import android.media.MediaPlayer;

import java.io.IOException;


public class AudioRecordTest extends Activity {
    private static final String LOG_TAG = "AudioRecordTest";
    private static String mFileName = null;

    private RecordButton mRecordButton = null;
    private MediaRecorder mRecorder = null;

    private PlayButton   mPlayButton = null;
    private MediaPlayer   mPlayer = null;

    private void onRecord(boolean start) {
        if (start) {
            startRecording();
        } else {
            stopRecording();
        }
    }

    private void onPlay(boolean start) {
        if (start) {
            startPlaying();
        } else {
            stopPlaying();
        }
    }

    private void startPlaying() {
        mPlayer = new MediaPlayer();
        try {
            mPlayer.setDataSource(mFileName);
            mPlayer.prepare();
            mPlayer.start();
        } catch (IOException e) {
            Log.e(LOG_TAG, "prepare() failed");
        }
    }

    private void stopPlaying() {
        mPlayer.release();
        mPlayer = null;
    }

    private void startRecording() {
        mRecorder = new MediaRecorder();
        mRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
        mRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
        mRecorder.setOutputFile(mFileName);
        mRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);

        try {
            mRecorder.prepare();
        } catch (IOException e) {
            Log.e(LOG_TAG, "prepare() failed");
        }

        mRecorder.start();
    }

    private void stopRecording() {
        mRecorder.stop();
        mRecorder.release();
        mRecorder = null;
    }

    class RecordButton extends Button {
        boolean mStartRecording = true;

        OnClickListener clicker = new OnClickListener() {
            public void onClick(View v) {
                onRecord(mStartRecording);
                if (mStartRecording) {
                    setText("Stop recording");
                } else {
                    setText("Start recording");
                }
                mStartRecording = !mStartRecording;
            }
        };

        public RecordButton(Context ctx) {
            super(ctx);
            setText("Start recording");
            setOnClickListener(clicker);
        }
    }

    class PlayButton extends Button {
        boolean mStartPlaying = true;

        OnClickListener clicker = new OnClickListener() {
            public void onClick(View v) {
                onPlay(mStartPlaying);
                if (mStartPlaying) {
                    setText("Stop playing");
                } else {
                    setText("Start playing");
                }
                mStartPlaying = !mStartPlaying;
            }
        };

        public PlayButton(Context ctx) {
            super(ctx);
            setText("Start playing");
            setOnClickListener(clicker);
        }
    }

    public AudioRecordTest() {
        mFileName = Environment.getExternalStorageDirectory().getAbsolutePath();
        mFileName += "/audiorecordtest.3gp";
    }

    @Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);

        LinearLayout ll = new LinearLayout(this);
        mRecordButton = new RecordButton(this);
        ll.addView(mRecordButton,
            new LinearLayout.LayoutParams(
                ViewGroup.LayoutParams.WRAP_CONTENT,
                ViewGroup.LayoutParams.WRAP_CONTENT,
                0));
        mPlayButton = new PlayButton(this);
        ll.addView(mPlayButton,
            new LinearLayout.LayoutParams(
                ViewGroup.LayoutParams.WRAP_CONTENT,
                ViewGroup.LayoutParams.WRAP_CONTENT,
                0));
        setContentView(ll);
    }

    @Override
    public void onPause() {
        super.onPause();
        if (mRecorder != null) {
            mRecorder.release();
            mRecorder = null;
        }

        if (mPlayer != null) {
            mPlayer.release();
            mPlayer = null;
        }
    }
}