首页 / ANDROID / android之多媒体篇(二)
android之多媒体篇(二)
内容导读
互联网集市收集整理的这篇技术教程文章主要介绍了android之多媒体篇(二),小编现在分享给大家,供广大互联网技能从业者学习和参考。文章包含11421字,纯文字阅读大概需要17分钟。
内容图文
![android之多媒体篇(二)](/upload/InfoBanner/zyjiaocheng/1212/e92f098954f74d159a0cfbdc44be9160.jpg)
管理音频焦点
情景:当你的app隐退到后台,而其他也有播放能力的app浮现在前台,这个时候,你可能要暂停你原有app的播放功能,和解除监听Media Button,把控制权交给前台的APP。
这就需要监听音频的焦点。
在开始播放之前,请求焦点,使用AudioManager的requestAudioFocus方法。
当你请求音频焦点,你可以指定你要监听的流类型(比如STREAM_MUSIC)和指定你要占有焦点多久。
当然从编程的角度来看,app获取焦点,其它app失去焦点,你应该都需要有所反应。
示例:请求音频焦点
01
|
AudioManager am = (AudioManager)getSystemService(Context.AUDIO_SERVICE);
|
02
|
03
|
// Request audio focus for playback
|
04
|
int
result = am.requestAudioFocus(focusChangeListener,
|
05
|
// Use the music stream.
|
06
|
AudioManager.STREAM_MUSIC,
|
07
|
// Request permanent focus.
|
08
|
AudioManager.AUDIOFOCUS_GAIN);
|
09
|
10
|
if
(result == AudioManager.AUDIOFOCUS_REQUEST_GRANTED) {
|
11
|
mediaPlayer.start();
|
12
|
}
|
应对失去焦点的监听:
01
|
private
OnAudioFocusChangeListener focusChangeListener =
|
02
|
new
OnAudioFocusChangeListener() {
|
03
|
04
|
public
void
onAudioFocusChange(
int
focusChange) {
|
05
|
AudioManager am =
|
06
|
(AudioManager)getSystemService(Context.AUDIO_SERVICE);
|
07
|
08
|
switch
(focusChange) {
|
09
|
case
(AudioManager.AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK) :
|
10
|
// Lower the volume while ducking.
|
11
|
mediaPlayer.setVolume(
0
.2f,
0
.2f);
|
12
|
break
;
|
13
|
14
|
case
(AudioManager.AUDIOFOCUS_LOSS_TRANSIENT) :
|
15
|
pause();
|
16
|
break
;
|
17
|
18
|
case
(AudioManager.AUDIOFOCUS_LOSS) :
|
19
|
stop();
|
20
|
ComponentName component =
|
21
|
new
ComponentName(AudioPlayerActivity.
this
,
|
22
|
MediaControlReceiver.
class
);
|
23
|
am.unregisterMediaButtonEventReceiver(component);
|
24
|
break
;
|
25
|
26
|
case
(AudioManager.AUDIOFOCUS_GAIN) :
|
27
|
// Return the volume to normal and resume if paused.
|
28
|
mediaPlayer.setVolume(1f, 1f);
|
29
|
mediaPlayer.start();
|
30
|
break
;
|
31
|
32
|
default
:
break
;
|
33
|
34
|
}
|
35
|
}
|
36
|
};
|
放弃音频焦点:
1
|
AudioManager am =
|
2
|
(AudioManager)getSystemService(Context.AUDIO_SERVICE);
|
3
|
4
|
am.abandonAudioFocus(focusChangeListener);
|
当你戴上耳机的时候,你可能需要降低音量或者先暂停播放,如何监听这种输出方式的改变呢?
答:
1
|
private
class
NoisyAudioStreamReceiver
extends
BroadcastReceiver {
|
2
|
@Override
|
3
|
public
void
onReceive(Context context, Intent intent) {
|
4
|
if
(AudioManager.ACTION_AUDIO_BECOMING_NOISY.equals
|
5
|
(intent.getAction())) {
|
6
|
pause();
|
7
|
}
|
8
|
}
|
9
|
}
|
录音
使用AudioRecord类去录音。创建一个AudioRecorder,指定资源,频率,通道配置,音频编码,和缓冲区大小。
1
|
int
bufferSize = AudioRecord.getMinBufferSize(frequency,
|
2
|
channelConfiguration,
|
3
|
audioEncoding);
|
4
|
AudioRecord audioRecord =
new
AudioRecord(MediaRecorder.AudioSource.MIC,
|
5
|
frequency, channelConfiguration,
|
6
|
audioEncoding, bufferSize);
|
频率、音频编码、和通道配置会影响录音的大小和质量。
出去私有的考虑,Android需要RECORD_AUDIO权限:
1
|
<
uses-permission
android:name=”android.permission.RECORD_AUDIO”/>
|
当AudioRecorder对象被初始化,然后可以通过startRecording方法去开始异步录音,使用read方法将原始的音频数据放入录音缓冲区:
1
|
audioRecord.startRecording();
|
2
|
while
(isRecording) {
|
3
|
[ ... populate the buffer ... ]
|
4
|
int
bufferReadResult = audioRecord.read(buffer,
0
, bufferSize);
|
5
|
}
|
录下的原始音频数据后,拿什么播放呢?
答:使用AudioTrack去播放该类音频。
录音的例子:
01
|
int
frequency =
11025
;
|
02
|
int
channelConfiguration = AudioFormat.CHANNEL_CONFIGURATION_MONO;
|
03
|
int
audioEncoding = AudioFormat.ENCODING_PCM_16BIT;
|
04
|
05
|
File file =
|
06
|
new
File(Environment.getExternalStorageDirectory(), “raw.pcm”);
|
07
|
08
|
// Create the new file.
|
09
|
try
{
|
10
|
file.createNewFile();
|
11
|
}
catch
(IOException e) {
|
12
|
Log.d(TAG, “IO Exception”, e);
|
13
|
}
|
14
|
15
|
try
{
|
16
|
OutputStream os =
new
FileOutputStream(file);
|
17
|
BufferedOutputStream bos =
new
BufferedOutputStream(os);
|
18
|
DataOutputStream dos =
new
DataOutputStream(bos);
|
19
|
20
|
int
bufferSize = AudioRecord.getMinBufferSize(frequency,
|
21
|
channelConfiguration,
|
22
|
audioEncoding);
|
23
|
short
[] buffer =
new
short
[bufferSize];
|
24
|
25
|
// Create a new AudioRecord object to record the audio.
|
26
|
AudioRecord audioRecord =
|
27
|
new
AudioRecord(MediaRecorder.AudioSource.MIC,
|
28
|
frequency,
|
29
|
channelConfiguration,
|
30
|
audioEncoding, bufferSize);
|
31
|
audioRecord.startRecording();
|
32
|
33
|
while
(isRecording) {
|
34
|
int
bufferReadResult = audioRecord.read(buffer,
0
, bufferSize);
|
35
|
for
(
int
i =
0
; i < bufferReadResult; i++)
|
36
|
dos.writeShort(buffer[i]);
|
37
|
}
|
38
|
39
|
audioRecord.stop();
|
40
|
dos.close();
|
41
|
}
catch
(Throwable t) {
|
42
|
Log.d(TAG, “An error occurred during recording”, t);
|
43
|
}
|
AudioTrack播放声音
1
|
AudioTrack audioTrack =
new
AudioTrack(AudioManager.STREAM_MUSIC,
|
2
|
frequency,
|
3
|
channelConfiguration,
|
4
|
audioEncoding,
|
5
|
audioLength,
|
6
|
AudioTrack.MODE_STREAM);
|
注意前面的参数要与你之前录音的参数一致。
1
|
audioTrack.play();
|
2
|
audioTrack.write(audio,
0
, audioLength);
|
write方法将原始的音频数据加入到播放缓冲区中。
创建Sound Pool
一般用来播放短促的声音,支持多音频同步播放。
直接看例子:
01
|
int
maxStreams =
10
;
|
02
|
SoundPool sp =
new
SoundPool(maxStreams, AudioManager.STREAM_MUSIC,
0
);
|
03
|
04
|
int
track1 = sp.load(
this
, R.raw.track1,
0
);
|
05
|
int
track2 = sp.load(
this
, R.raw.track2,
0
);
|
06
|
int
track3 = sp.load(
this
, R.raw.track3,
0
);
|
07
|
08
|
track1Button.setOnClickListener(
new
OnClickListener() {
|
09
|
public
void
onClick(View v) {
|
10
|
sp.play(track1,
1
,
1
,
0
, -
1
,
1
);
|
11
|
}
|
12
|
});
|
13
|
14
|
track2Button.setOnClickListener(
new
OnClickListener() {
|
15
|
public
void
onClick(View v) {
|
16
|
sp.play(track2,
1
,
1
,
0
,
0
,
1
);
|
17
|
}
|
18
|
});
|
19
|
20
|
track3Button.setOnClickListener(
new
OnClickListener() {
|
21
|
public
void
onClick(View v) {
|
22
|
sp.play(track3,
1
,
1
,
0
,
0
,
0
.5f);
|
23
|
}
|
24
|
});
|
25
|
26
|
stopButton.setOnClickListener(
new
OnClickListener() {
|
27
|
public
void
onClick(View v) {
|
28
|
sp.stop(track1);
|
29
|
sp.stop(track2);
|
30
|
sp.stop(track3);
|
31
|
}
|
32
|
});
|
33
|
34
|
chipmunkButton.setOnClickListener(
new
OnClickListener() {
|
35
|
public
void
onClick(View v) {
|
36
|
sp.setRate(track1, 2f);
|
37
|
}
|
38
|
});
|
Android2.2(Api Level 8)引入两个非常方便的方法,autoPause和autoResume,分别会暂停和运行状态,所有活跃的音频流。
若不再需要这些音频集合,就可以soundPool.release();去释放资源。
照相机拍照
使用Intents去拍照:
1
|
startActivityForResult(
|
2
|
new
Intent(MediaStore.ACTION_IMAGE_CAPTURE), TAKE_PICTURE);
|
当然对应的onActivityResult,默认的返回的照片会以缩略图的形式。
如果想获取完整大小的图片,则需要先指定存储的目标文件,下面例子展示:
01
|
// Create an output file.
|
02
|
File file =
new
File(Environment.getExternalStorageDirectory(),
|
03
|
“test.jpg”);
|
04
|
Uri outputFileUri = Uri.fromFile(file);
|
05
|
06
|
// Generate the Intent.
|
07
|
Intent intent =
new
Intent(MediaStore.ACTION_IMAGE_CAPTURE);
|
08
|
intent.putExtra(MediaStore.EXTRA_OUTPUT, outputFileUri);
|
09
|
10
|
// Launch the camera app.
|
11
|
startActivityForResult(intent, TAKE_PICTURE);
|
注意:一旦你以这种方式启动后,就不会有缩略图返回了,所以所接收到得Intent将为null。
下面这个例子的onActivityResult对这两种情况做了处理:
01
|
@Override
|
02
|
protected
void
onActivityResult(
int
requestCode,
|
03
|
int
resultCode, Intent data) {
|
04
|
if
(requestCode == TAKE_PICTURE) {
|
05
|
// Check if the result includes a thumbnail Bitmap
|
06
|
if
(data !=
null
) {
|
07
|
if
(data.hasExtra(“data”)) {
|
08
|
Bitmap thumbnail = data.getParcelableExtra(“data”);
|
09
|
imageView.setImageBitmap(thumbnail);
|
10
|
}
|
11
|
}
else
{
|
12
|
// If there is no thumbnail image data, the image
|
13
|
// will have been stored in the target output URI.
|
14
|
15
|
// Resize the full image to fit in out image view.
|
16
|
int
width = imageView.getWidth();
|
17
|
int
height = imageView.getHeight();
|
18
|
19
|
BitmapFactory.Options factoryOptions =
new
|
20
|
BitmapFactory.Options();
|
21
|
22
|
factoryOptions.inJustDecodeBounds =
true
;
|
23
|
BitmapFactory.decodeFile(outputFileUri.getPath(),
|
24
|
factoryOptions);
|
25
|
26
|
int
imageWidth = factoryOptions.outWidth;
|
27
|
int
imageHeight = factoryOptions.outHeight;
|
28
|
29
|
// Determine how much to scale down the image
|
30
|
int
scaleFactor = Math.min(imageWidth/width,
|
31
|
imageHeight/height);
|
32
|
33
|
// Decode the image file into a Bitmap sized to fill the View
|
34
|
factoryOptions.inJustDecodeBounds =
false
;
|
35
|
factoryOptions.inSampleSize = scaleFactor;
|
36
|
factoryOptions.inPurgeable =
true
;
|
37
|
38
|
Bitmap bitmap =
|
39
|
BitmapFactory.decodeFile(outputFileUri.getPath(),
|
40
|
factoryOptions);
|
41
|
42
|
imageView.setImageBitmap(bitmap);
|
43
|
}
|
44
|
}
|
45
|
}
|
直接控制照相机
首先这个少不了:
1
|
<
uses-permission
android:name=”android.permission.CAMERA”/>
|
获取Camera通过:
Camera camera = Camera.open();
当你使用完了,记得释放资源哦:
camera.release();
照相机的属性
1
|
Camera.Parameters parameters = camera.getParameters();
|
通过此,你可以找到很多关于照相机的属性,有些参数是基于平台版本的。
你可以获得焦点的长度,还有相对水平和垂直的角度,分别通过getFocalLength和get[Horizontal/Vertical]ViewAngle。
Android 2.3(Api Level
9)引入getFocusDistance方法,你可以用来估计镜头和对象之间的距离,此方法会注入一个浮点数组,包含近、远、最优焦点距离;
01
|
float
[] focusDistances =
new
float
[
3
];
|
02
|
03
|
parameters.getFocusDistances(focusDistances);
|
04
|
05
|
float
near =
|
06
|
focusDistances[Camera.Parameters.FOCUS_DISTANCE_NEAR_INDEX];
|
07
|
float
far =
|
08
|
focusDistances[Camera.Parameters.FOCUS_DISTANCE_FAR_INDEX];
|
09
|
float
optimal =
|
10
|
focusDistances[Camera.Parameters.FOCUS_DISTANCE_OPTIMAL_INDEX];
|
照相机设置和图像参数
设置参数的方法,类似于set*,从而修改Parameter对象,修改完之后:
camera.setParameters(parameters);
具体参数细节就不介绍了。
使用照相机预览
同样SurfaceView又派上用场了。
看段框架代码:
01
|
public
class
CameraActivity
extends
Activity
implements
|
02
|
SurfaceHolder.Callback {
|
03
|
04
|
private
static
final
String TAG = “CameraActivity”;
|
05
|
06
|
private
Camera camera;
|
07
|
08
|
@Override
|
09
|
public
void
onCreate(Bundle savedInstanceState) {
|
10
|
super
.onCreate(savedInstanceState);
|
11
|
setContentView(R.layout.main);
|
12
|
13
|
SurfaceView surface = (SurfaceView)findViewById(R.id.surfaceView);
|
14
|
SurfaceHolder holder = surface.getHolder();
|
15
|
holder.addCallback(
this
);
|
16
|
holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
|
17
|
holder.setFixedSize(
400
,
300
);
|
18
|
}
|
19
|
20
|
public
void
surfaceCreated(SurfaceHolder holder) {
|
21
|
try
{
|
22
|
camera.setPreviewDisplay(holder);
|
23
|
camera.startPreview();
|
24
|
// TODO Draw over the preview if required.
|
25
|
}
catch
(IOException e) {
|
26
|
Log.d(TAG, “IO Exception”, e);
|
27
|
}
|
28
|
}
|
29
|
30
|
31
|
public
void
surfaceDestroyed(SurfaceHolder holder) {
|
32
|
camera.stopPreview();
|
33
|
}
|
34
|
35
|
public
void
surfaceChanged(SurfaceHolder holder,
int
format,
|
36
|
int
width,
int
height) {
|
37
|
}
|
38
|
39
|
@Override
|
40
|
protected
void
onPause() {
|
41
|
super
.onPause();
|
42
|
camera.release();
|
43
|
}
|
44
|
45
|
@Override
|
46
|
protected
void
onResume() {
|
47
|
super
.onResume();
|
48
|
camera = Camera.open();
|
49
|
}
|
50
|
}
|
调用camera的setPreviewCallback方法,传入一个PreviewCallback的实现,重写onPreviewFrame方法。
01
|
camera.setPreviewCallback(
new
PreviewCallback() {
|
02
|
public
void
onPreviewFrame(
byte
[] data, Camera camera) {
|
03
|
int
quality =
60
;
|
04
|
05
|
Size previewSize = camera.getParameters().getPreviewSize();
|
06
|
YuvImage image =
new
YuvImage(data, ImageFormat.NV21,
|
07
|
previewSize.width, previewSize.height,
null
);
|
08
|
ByteArrayOutputStream outputStream =
new
ByteArrayOutputStream();
|
09
|
10
|
image.compressToJpeg(
|
11
|
new
Rect(
0
,
0
,previewSize.width, previewSize.height),
|
12
|
quality, outputStream);
|
13
|
14
|
// TODO Do something with the preview image.
|
15
|
}
|
16
|
});
|
Android 4.0加入了人脸识别的API这里就不多说了。
拍照
前面这些都配置过了,那么如何拍照呢?
答:使用camera对象的takePicture方法,传入一个ShutterCallback和两个PictureCallback实现(一个为了RAW,另外一个为了JPEG编码的图像)。
例子:框架代码,拍照和保存JPEG图像到SD卡:
01
|
private
void
takePicture() {
|
02
|
camera.takePicture(shutterCallback, rawCallback,
jpegCallback);
|
03
|
}
|
04
|
05
|
ShutterCallback shutterCallback =
new
ShutterCallback() {
|
06
|
public
void
onShutter() {
|
07
|
// TODO Do something when the shutter closes.
|
08
|
}
|
09
|
};
|
10
|
11
|
PictureCallback rawCallback =
new
PictureCallback() {
|
12
|
public
void
onPictureTaken(
byte
[] data, Camera camera) {
|
13
|
// TODO Do something with the image RAW data.
|
14
|
}
|
15
|
};
|
16
|
17
|
PictureCallback jpegCallback =
new
PictureCallback() {
|
18
|
public
void
onPictureTaken(
byte
[] data, Camera camera) {
|
19
|
// Save the image JPEG data to the SD card
|
20
|
FileOutputStream outStream =
null
;
|
21
|
try
{
|
22
|
String path = Environment.getExternalStorageDirectory() +
|
23
|
“\test.jpg”;
|
24
|
25
|
outStream =
new
FileOutputStream(path);
|
26
|
outStream.write(data);
|
27
|
outStream.close();
|
28
|
}
catch
(FileNotFoundException e) {
|
29
|
Log.e(TAG, “File Note Found”, e);
|
30
|
}
catch
(IOException
e) {
|
31
|
Log.e(TAG, “IO Exception”, e);
|
32
|
}
|
33
|
}
|
34
|
};
|
原文:http://www.cnblogs.com/Free-Thinker/p/3546412.html
内容总结
以上是互联网集市为您收集整理的android之多媒体篇(二)全部内容,希望文章能够帮你解决android之多媒体篇(二)所遇到的程序开发问题。 如果觉得互联网集市技术教程内容还不错,欢迎将互联网集市网站推荐给程序员好友。
内容备注
版权声明:本文内容由互联网用户自发贡献,该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务,不拥有所有权,不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容, 请发送邮件至 gblab@vip.qq.com 举报,一经查实,本站将立刻删除。
内容手机端
扫描二维码推送至手机访问。