Sound recording and playback is really simple using the MediaRecorder and MediaPlayer classes .. see the example below ..

• First some layout .. a button to start/stop recording and a button to play the recorded stuff (main.xml):

  <?xml version="1.0" encoding="utf-8"?>
  <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:orientation="vertical"
      android:layout_width="fill_parent"
      android:layout_height="fill_parent"
      >
  <TextView
  	android:id="@+id/output"
      android:layout_width="fill_parent"
      android:layout_height="wrap_content"
      android:text=""
      />
  <Button android:text="@+string/record" android:id="@+id/btRecord" android:layout_width="wrap_content" android:layout_height="wrap_content"></Button>
  <Button android:text="@+string/play" android:id="@+id/btPlay" android:layout_width="wrap_content" android:layout_height="wrap_content"></Button>
  </LinearLayout>

• Adjusting the externalized strings in the strings.xml

  <?xml version="1.0" encoding="utf-8"?>
  <resources>
      <string name="app_name">Soundrecorder Tutorial</string>
  	<string name="record">Record!</string>
  	<string name="play">Play</string>
  </resources>

• Set permissions needed in the AndroidManifest.xml

  <?xml version="1.0" encoding="utf-8"?>
  <manifest xmlns:android="http://schemas.android.com/apk/res/android"
        package="com.hascode.android"
        android:versionCode="1"
        android:versionName="1.0">
      <application android:icon="@drawable/icon" android:label="@string/app_name">
          <activity android:name=".RecorderActivity"
                    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>
      <uses-sdk android:minSdkVersion="7" />
   
  <uses-permission android:name="android.permission.RECORD_AUDIO"></uses-permission>
  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>
  </manifest>

• Now the activity to bring in some action .. RecorderActivity.java

  package com.hascode.android;
   
  import java.io.File;
  import java.io.IOException;
   
  import android.app.Activity;
  import android.media.MediaPlayer;
  import android.media.MediaRecorder;
  import android.os.Bundle;
  import android.os.Environment;
  import android.util.Log;
  import android.view.View;
  import android.view.View.OnClickListener;
  import android.widget.Button;
  import android.widget.TextView;
   
  public class RecorderActivity extends Activity {
  	private static final String APP_TAG = "com.hascode.android.soundrecorder";
   
  	private MediaRecorder recorder = new MediaRecorder();
  	private MediaPlayer player = new MediaPlayer();
   
  	private Button btRecord;
  	private Button btPlay;
  	private TextView resultView;
   
  	private boolean recording = false;
  	private boolean playing = false;
  	private File outfile = null;
   
  	@Override
  	public void onCreate(Bundle savedInstanceState) {
  		super.onCreate(savedInstanceState);
  		setContentView(R.layout.main);
  		resultView = (TextView) findViewById(R.id.output);
   
  		try {
  			// the soundfile
  			File storageDir = new File(Environment
  					.getExternalStorageDirectory(), "com.hascode.recorder");
  			storageDir.mkdir();
  			Log.d(APP_TAG, "Storage directory set to " + storageDir);
  			outfile = File.createTempFile("hascode", ".3gp", storageDir);
   
  			// init recorder
  			recorder.setAudioSource(MediaRecorder.AudioSource.MIC);
  			recorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
  			recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
  			recorder.setOutputFile(outfile.getAbsolutePath());
   
  			// init player
  			player.setDataSource(outfile.getAbsolutePath());
  		} catch (IOException e) {
  			Log.w(APP_TAG, "File not accessible ", e);
  		} catch (IllegalArgumentException e) {
  			Log.w(APP_TAG, "Illegal argument ", e);
  		} catch (IllegalStateException e) {
  			Log.w(APP_TAG, "Illegal state, call reset/restore", e);
  		}
   
  		btRecord = (Button) findViewById(R.id.btRecord);
  		btRecord.setOnClickListener(handleRecordClick);
   
  		btPlay = (Button) findViewById(R.id.btPlay);
  		btPlay.setOnClickListener(handlePlayClick);
   
  	}
   
  	private final OnClickListener handleRecordClick = new OnClickListener() {
  		@Override
  		public void onClick(View view) {
  			if (!recording) {
  				startRecord();
  			} else {
  				stopRecord();
  			}
  		}
  	};
   
  	private final OnClickListener handlePlayClick = new OnClickListener() {
  		@Override
  		public void onClick(View view) {
  			if (!playing) {
  				startPlay();
  			} else {
  				stopPlay();
  			}
  		}
  	};
   
  	private void startRecord() {
  		Log.d(APP_TAG, "start recording..");
  		printResult("start recording..");
  		try {
  			recorder.prepare();
  			recorder.start();
  			recording = true;
  		} catch (IllegalStateException e) {
  			Log
  					.w(APP_TAG,
  							"Invalid recorder state .. reset/release should have been called");
  		} catch (IOException e) {
  			Log.w(APP_TAG, "Could not write to sd card");
  		}
  	}
   
  	private void stopRecord() {
  		Log.d(APP_TAG, "stop recording..");
  		printResult("stop recording..");
  		recorder.stop();
  		recorder.reset();
  		recorder.release();
  		recording = false;
  	}
   
  	private void startPlay() {
  		Log.d(APP_TAG, "starting playback..");
  		printResult("start playing..");
  		try {
  			playing = true;
  			player.prepare();
  			player.start();
  		} catch (IllegalStateException e) {
  			Log.w(APP_TAG, "illegal state .. player should be reset");
  		} catch (IOException e) {
  			Log.w(APP_TAG, "Could not write to sd card");
  		}
  	}
   
  	private void stopPlay() {
  		Log.d(APP_TAG, "stopping playback..");
  		printResult("stop playing..");
  		player.stop();
  		player.reset();
  		player.release();
  		playing = false;
  	}
   
  	private void printResult(String result) {
  		resultView.setText(result);
  	}
  }

• Finally the app looks like this on my emulator
  

  The Application in the Android Emulator

• Now play around with the recorder

• A SD Card is created using the android tool or the mksdcard tool

  android create avd -n <youravd> -t <targetID> -c <size>[K|M]
  or:
  mksdcard <size> <file>

• Start the emulator with the param -sdcard /path/to/sdcard.img
• More information is available at the Android Developers Website

• In general use the logcat tool from the Android Debugging Bridge to look for debugging messages, exceptions, strack traces ..

  # adb -s emulator-5554 shell
  logcat
  I/ActivityManager(   52): Displayed activity com.hascode.android/.RecorderActivity:
  I/ARMAssembler(   52): generated scanline__00000077:03545404_00000A04_00000000 [ 29
  I/ARMAssembler(   52): generated scanline__00000177:03515104_00001A01_00000000 [ 73
  D/com.hascode.android.soundrecorder(  198): start recording..
  W/com.hascode.android.soundrecorder(  198): Could not write to sd card

• W/com.hascode.android.soundrecorder(  209): File not accessible – Check the permissions set for the directory you are trying to save the files to – more information is available at the Android Developers Website – also take a look in your AndroidManifest.xml and check if the permission WRITE_EXTERNAL_STORAGE is set:

  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>

• Using the Android Debugging Bridge it is possible to check the user permissions set in the emulator

  adb -s emulator-5554 shell
  # ls -l sdcard
  d---rwxr-x system   sdcard_rw          2010-05-02 14:50 LOST.DIR
  # ls -l sdcard/com.hascode.recorder
  ----rwxr-x system   sdcard_rw        0 2010-05-02 15:33 hascode44433.3gp

• If you need a GUI – try the the Dalvik Debug Monitor Service by running ddms – screenshots below:
  

  Debugging in DDMS

  

  File System

• IBM.com: Tapping into Android’s sensors
• MediaRecorder API
• Android Developers: Audio and Video
• Android Developers: SD Card Emulation
• Android Developers: SD Card Creation
• Android Developers: User Id’s and file access

• 2015-03-03: Table of contents and image captions added.

Tags: Android, ddms, media, player, recorder, sensor

This entry was posted on Sunday, May 2nd, 2010 at 5:36 pm and is filed under Android, Snippet. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.