在第 57 节我们使用 MediaPlayer 实现了一个 mp3 播放器,除了播放 Android 还提供了 MediaRecorder 用于录音。Android 设备基本都会有一个麦克风,通过 MediaRecorder 可以打开麦克风进行语音采集,这一节我们就来学习如何在 Android 系统上实现一个录音功能。
1. MediaRecorder 常用接口
- setAudioSource():
设置录制的音频源 - setVideoSource():
设置录制的视频源 - setOutputFormat():
设置输出格式 - setAudioEncoder():
设置音频编码器 - setOutputFile():
配置录制的音频存储文件路径 - stop():
停止录制 - release():
释放 MediaRecorder 实例,回收其所占资源
2. MediaRecorder 的使用步骤
- 创建 MediaRecorder
直接通过无参构造器创建即可:
MediaRecorder myAudioRecorder = new MediaRecorder();
- 配置录音参数
创建好之后,再对 MediaRecorder 实例进行参数配置,配置项有很多,一般需要设置音频输入源、音频输出格式、音频编码方式以及输出文件目录,如下:
myAudioRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
myAudioRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
myAudioRecorder.setAudioEncoder(MediaRecorder.OutputFormat.AMR_NB);
myAudioRecorder.setOutputFile(outputFile);
- 开始录音
在确定了录音配置和输出目录之后,我们就可以调用一下两个方法开始录音了:
myAudioRecorder.prepare();
myAudioRecorder.start();
- 停止录音
录音结束调用stop()
停止录制,如果不再使用还要记得调用release()
释放 MediaRecorder 所占用的资源
3. 录音示例
本节使用 MediaRecorder 实现一个录音机:
3.1 MediaRecorder 控制逻辑
作为一个完整的录音功能,当然在录音结束之后也得要能回放录音。所以整个的控制要分为录音控制和播放控制,我们按照上一小节讲述的步骤用 MediaRecorder 完成录音,然后调用 MediaPlayer 来完成录音回放:
package com.emercy.myapplication;import android.app.Activity;
import android.content.pm.PackageManager;
import android.media.MediaPlayer;
import android.media.MediaRecorder;
import android.os.Build;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;import java.io.IOException;
import java.util.Random;import static android.Manifest.permission.RECORD_AUDIO;
import static android.Manifest.permission.WRITE_EXTERNAL_STORAGE;public class MainActivity extends Activity {Button buttonStart, buttonStop, buttonPlayLastRecordAudio,buttonStopPlayingRecording;String AudioSavePathInDevice = null;MediaRecorder mediaRecorder;Random random;String RandomAudioFileName = "emercy";public static final int RequestPermissionCode = 1;MediaPlayer mediaPlayer;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);buttonStart = findViewById(R.id.button);buttonStop = findViewById(R.id.button2);buttonPlayLastRecordAudio = findViewById(R.id.button3);buttonStopPlayingRecording = findViewById(R.id.button4);buttonStop.setEnabled(false);buttonPlayLastRecordAudio.setEnabled(false);buttonStopPlayingRecording.setEnabled(false);random = new Random();buttonStart.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {if (checkPermission()) {AudioSavePathInDevice =Environment.getExternalStorageDirectory().getAbsolutePath() + "/" +CreateRandomAudioFileName(5) + "AudioRecording.3gp";MediaRecorderReady();try {mediaRecorder.prepare();mediaRecorder.start();} catch (IllegalStateException | IOException e) {e.printStackTrace();}buttonStart.setEnabled(false);buttonStop.setEnabled(true);Toast.makeText(MainActivity.this, "Recording started",Toast.LENGTH_LONG).show();} else {requestPermission();}}});buttonStop.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {mediaRecorder.stop();buttonStop.setEnabled(false);buttonPlayLastRecordAudio.setEnabled(true);buttonStart.setEnabled(true);buttonStopPlayingRecording.setEnabled(false);Toast.makeText(MainActivity.this, "Recording Completed", Toast.LENGTH_LONG).show();}});buttonPlayLastRecordAudio.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) throws IllegalArgumentException,SecurityException, IllegalStateException {buttonStop.setEnabled(false);buttonStart.setEnabled(false);buttonStopPlayingRecording.setEnabled(true);mediaPlayer = new MediaPlayer();try {mediaPlayer.setDataSource(AudioSavePathInDevice);mediaPlayer.prepare();} catch (IOException e) {e.printStackTrace();}mediaPlayer.start();Toast.makeText(MainActivity.this, "录音完毕", Toast.LENGTH_LONG).show();}});buttonStopPlayingRecording.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {buttonStop.setEnabled(false);buttonStart.setEnabled(true);buttonStopPlayingRecording.setEnabled(false);buttonPlayLastRecordAudio.setEnabled(true);if (mediaPlayer != null) {mediaPlayer.stop();mediaPlayer.release();MediaRecorderReady();}}});}public void MediaRecorderReady() {mediaRecorder = new MediaRecorder();mediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);mediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);mediaRecorder.setAudioEncoder(MediaRecorder.OutputFormat.AMR_NB);mediaRecorder.setOutputFile(AudioSavePathInDevice);}public String CreateRandomAudioFileName(int string) {StringBuilder stringBuilder = new StringBuilder(string);int i = 0;while (i < string) {stringBuilder.append(RandomAudioFileName.charAt(random.nextInt(RandomAudioFileName.length())));i++;}return stringBuilder.toString();}private void requestPermission() {if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {requestPermissions(new String[]{WRITE_EXTERNAL_STORAGE, RECORD_AUDIO}, RequestPermissionCode);}}@Overridepublic void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {if (requestCode == RequestPermissionCode) {if (grantResults.length > 0) {boolean StoragePermission = grantResults[0] ==PackageManager.PERMISSION_GRANTED;boolean RecordPermission = grantResults[1] ==PackageManager.PERMISSION_GRANTED;if (StoragePermission && RecordPermission) {Toast.makeText(MainActivity.this, "Permission Granted", Toast.LENGTH_LONG).show();} else {Toast.makeText(MainActivity.this, "Permission Denied", Toast.LENGTH_LONG).show();}}}}public boolean checkPermission() {int storagePermission = 0;int recordPermission = 0;if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.M) {storagePermission = checkSelfPermission(WRITE_EXTERNAL_STORAGE);recordPermission = checkSelfPermission(RECORD_AUDIO);}return storagePermission == PackageManager.PERMISSION_GRANTED &&recordPermission == PackageManager.PERMISSION_GRANTED;}
}
和拍照一样,录音也需要获取权限(注意 Android 6.0 以上还需要动态获取权限),除此之外只需要按照步骤进行录音就可以实现功能了。
3.2 录音布局
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"android:padding="30dp"><Buttonandroid:id="@+id/button"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_alignParentStart="true"android:layout_marginTop="37dp"android:text="录音" /><Buttonandroid:id="@+id/button2"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_alignTop="@+id/button"android:layout_centerHorizontal="true"android:text="停止" /><Buttonandroid:id="@+id/button3"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_alignTop="@+id/button2"android:layout_alignParentEnd="true"android:layout_alignParentRight="true"android:text="回放" /><Buttonandroid:id="@+id/button4"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_below="@+id/button2"android:layout_centerHorizontal="true"android:layout_marginTop="10dp"android:text="结束回放" />
</RelativeLayout>
对于两大功能:“录音”和“回放”,各提供两个按键控制,分别对应开始和结束。
最终编译效果:
4. 小结
MediaRecorder 很多时候都是配合 MediaPlayer 或者其他播放器一起使用,而两者之间也有很多相似之处。当然本节提到的只是最基本的录音及音频输出功能,如果需要进一步研究音视频相关的内容就得深入到底层编解码原理。不过对于大多数非专业音视频制作 App 而言已经足够。