##Building Apps with Multimedia
-
Managing Audio Playback
-
控制音量和播放 + Audio Stream：安卓系统为不同的用途维护了不同的audio stream，便于用户控制不同类型声音的音量
- music
- alarm
- notification
- 来电话
- system sound
- 打电话过程中的声音
- DTMF tones
+ 通过设置
setVolumeControlStream()，系统将在Activity/Fragment仍在界面上时，自动响应设备的音量操作键，增大或减小设置类型媒体的音量 + 当用户通过耳机等外设，按下播放控制按键时，例如：播放/暂停、上一曲/下一曲，系统将发送一个action为android.intent.action.MEDIA_BUTTON的广播，如下BroadcastReceiver可以响应处理这一广播（需要在AndroidManifest.xml中声明）：java public class RemoteControlReceiver extends BroadcastReceiver { @Override public void onReceive(Context context, Intent intent) { if (Intent.ACTION_MEDIA_BUTTON.equals(intent.getAction())) { KeyEvent event = (KeyEvent)intent.getParcelableExtra(Intent.EXTRA_KEY_EVENT); if (KeyEvent.KEYCODE_MEDIA_PLAY == event.getKeyCode()) { // Handle key press. } } } }
-
Managing Audio Focus + 请求/释放audio focus ```java AudioManager am = mContext.getSystemService(Context.AUDIO_SERVICE); ...
// Request audio focus for playback int result = am.requestAudioFocus(afChangeListener, // Use the music stream. AudioManager.STREAM_MUSIC, // Request permanent focus. AudioManager.AUDIOFOCUS_GAIN);
if (result == AudioManager.AUDIOFOCUS_REQUEST_GRANTED) { am.registerMediaButtonEventReceiver(RemoteControlReceiver); // Start playback. }
... // Abandon audio focus when playback complete
am.abandonAudioFocus(afChangeListener); ``` -
requestAudioFocus的最后一个参数可以设为AudioManager.AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK，用于请求短暂的audio focus，允许其他app在失去audio focus时继续播放音乐（但应该降低音量） -
监听audio focus状态改变
OnAudioFocusChangeListener afChangeListener = new OnAudioFocusChangeListener() {
public void onAudioFocusChange(int focusChange) {
if (focusChange == AUDIOFOCUS_LOSS_TRANSIENT
// Pause playback
} else if (focusChange == AudioManager.AUDIOFOCUS_GAIN) {
// Resume playback
} else if (focusChange == AudioManager.AUDIOFOCUS_LOSS) {
am.unregisterMediaButtonEventReceiver(RemoteControlReceiver);
am.abandonAudioFocus(afChangeListener);
// Stop playback
}
}
};- 响应临时失焦且允许重音的情形
OnAudioFocusChangeListener afChangeListener = new OnAudioFocusChangeListener() {
public void onAudioFocusChange(int focusChange) {
if (focusChange == AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK) {
// Lower the volume
} else if (focusChange == AudioManager.AUDIOFOCUS_GAIN) {
// Raise it back to normal
}
}
};- 检查声音播放设备
if (audioManager.isBluetoothA2dpOn()) {
// A2DP audio routing to the Bluetooth headset
} else if (audioManager.isSpeakerphoneOn()) {
// Adjust output for Speakerphone.
} else if (audioManager.isWiredHeadsetOn()) {
// Adjust output for headsets
} else if (audioManager.isBluetoothScoOn()) {
// SCO is used for communications
} else {
// If audio plays and noone can hear it, is it still playing?
}- 一旦耳机/蓝牙耳机断开连接，系统将继续使用默认设备（扬声器）播放，同时系统会发送一个
AudioManager.ACTION_AUDIO_BECOMING_NOISY广播，可以通过以下代码进行响应
private class BroadcastReceiver myNoisyAudioStreamReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
if (AudioManager.ACTION_AUDIO_BECOMING_NOISY.equals(intent.getAction())) {
// Pause the playback
}
}
};
private void startPlayback() {
registerReceiver(myNoisyAudioStreamReceiver, new IntentFilter(AudioManager.ACTION_AUDIO_BECOMING_NOISY));
}
private void stopPlayback() {
unregisterReceiver(myNoisyAudioStreamReceiver);
}-
Capturing Photos
-
使用已有相机APP拍照 + 声明使用相机的feature，注意，并非权限，便于google play等应用商店确定设备是否可以安装本应用
xml <manifest ... > <uses-feature android:name="android.hardware.camera" android:required="true" /> ... </manifest>+ 也可以设置required为false，手动检查设备是否有相机：packageManager.hasSystemFeature(PackageManager.FEATURE_CAMERA)+ 发送Intent调起已有相机APP拍照，发送Intent之前需要检查是否有其他APP可以响应此Intent，如没有却调用了startActivity，将会抛出异常 ```java static final int REQUEST_IMAGE_CAPTURE = 1;private void dispatchTakePictureIntent() { Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE); if (takePictureIntent.resolveActivity(getPackageManager()) != null) { startActivityForResult(takePictureIntent, REQUEST_IMAGE_CAPTURE); } }
在发送takePictureIntent之前，可以手动设置要照片要保存的位置`takePictureIntent.putExtra(android.provider.MediaStore.EXTRA_OUTPUT, imageFileUri);`，拍照成功返回之后，可以直接访问该uri。 + 获取拍照结果缩略图java @Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { if (requestCode == REQUEST_IMAGE_CAPTURE && resultCode == RESULT_OK) { Bundle extras = data.getExtras(); Bitmap imageBitmap = (Bitmap) extras.get("data"); mImageView.setImageBitmap(imageBitmap); } }+ 获取完整照片 照片保存在外置存储卡的公开区域，需要声明权限，`WRITE_EXTERNAL_STORAGE`包含了`READ_EXTERNAL_STORAGE`权限，目录路径通过`Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES)`函数获得xml <manifest ...> ...如果要保存在APP私有目录下，API 18之后，将不用声明该权限，目录路径通过`context.getExternalFilesDir(Environment.DIRECTORY_PICTURES)`函数获得，app访问自己对应的该目录，从API 19起，将不需要任何权限，但是访问其他APP对应的目录时，需要`WRITE_EXTERNAL_STORAGE`/`READ_EXTERNAL_STORAGE`权限，该目录不一定任何时候都可以访问，也不具备安全性xml <manifest ...> ...拍照设置保存文件java String mCurrentPhotoPath;private File createImageFile() throws IOException { // Create an image file name String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date()); String imageFileName = "JPEG_" + timeStamp + "_"; File storageDir = Environment.getExternalStoragePublicDirectory( Environment.DIRECTORY_PICTURES); File image = File.createTempFile( imageFileName, /* prefix / ".jpg", / suffix / storageDir / directory */ );
// Save a file: path for use with ACTION_VIEW intents mCurrentPhotoPath = "file:" + image.getAbsolutePath(); return image;}
static final int REQUEST_TAKE_PHOTO = 1;
private void dispatchTakePictureIntent() { Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE); // Ensure that there's a camera activity to handle the intent if (takePictureIntent.resolveActivity(getPackageManager()) != null) { // Create the File where the photo should go File photoFile = null; try { photoFile = createImageFile(); } catch (IOException ex) { // Error occurred while creating the File ... } // Continue only if the File was successfully created if (photoFile != null) { takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(photoFile)); startActivityForResult(takePictureIntent, REQUEST_TAKE_PHOTO); } } }
+ 加入Gallery，当保存路径设为`context.getExternalFilesDir(type)`时，将无法加入Galleryjava private void galleryAddPic() { Intent mediaScanIntent = new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE); File f = new File(mCurrentPhotoPath); Uri contentUri = Uri.fromFile(f); mediaScanIntent.setData(contentUri); this.sendBroadcast(mediaScanIntent); }+ 获取压缩后的图片，用于显示在ImageView上java private void setPic() { // Get the dimensions of the View int targetW = mImageView.getWidth(); int targetH = mImageView.getHeight();// Get the dimensions of the bitmap BitmapFactory.Options bmOptions = new BitmapFactory.Options(); bmOptions.inJustDecodeBounds = true; BitmapFactory.decodeFile(mCurrentPhotoPath, bmOptions); int photoW = bmOptions.outWidth; int photoH = bmOptions.outHeight; // Determine how much to scale down the image int scaleFactor = Math.min(photoW/targetW, photoH/targetH); // Decode the image file into a Bitmap sized to fill the View bmOptions.inJustDecodeBounds = false; bmOptions.inSampleSize = scaleFactor; bmOptions.inPurgeable = true; Bitmap bitmap = BitmapFactory.decodeFile(mCurrentPhotoPath, bmOptions); mImageView.setImageBitmap(bitmap);} ```
-
使用已有相机应用录制视频，与拍照类似，需要发送的Intent初始化为
Intent takeVideoIntent = new Intent(MediaStore.ACTION_VIDEO_CAPTURE);，onActivityResult返回的intent的data数据，就是录制视频的Uri，intent.getData()。 -
直接使用相机 + Camera API
- 权限
<uses-permission android:name="android.permission.CAMERA" /> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> <uses-feature android:name="android.hardware.camera" android:required="true" />
- 在onResume中inflate SurfaceView，动态添加到layout中，在onPause中停止预览，移除SurfaceView，以解决界面onPause后再onResume就无法预览的问题。在SurfaceView的
surfaceCreated回调中打开相机，开始预览
@Override public void surfaceCreated(SurfaceHolder holder) { mSurfaceHolder = holder; initPreview(holder); } @Override public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) { } @Override public void surfaceDestroyed(SurfaceHolder holder) { releaseResources(); } @Override protected void onResume() { mSurfaceView = (SurfaceView) LayoutInflater.from(getActivity()) .inflate(R.layout.ui_surface_view, null); flContainer.addView(mSurfaceView, 0); isPreview = true; SurfaceHolder mSurfaceHolder = mSurfaceView.getHolder(); mSurfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS); mSurfaceHolder.setKeepScreenOn(true); mSurfaceHolder.addCallback(this); }
- 打开相机，开始预览
private boolean initPreview(SurfaceHolder holder) { int mSupportVideoFormat[] = {ImageFormat.NV21, ImageFormat.YV12}; try { cameraid = getCameraId(isFrontCamera); mCamera = Camera.open(cameraid); } catch (Exception e) { e.printStackTrace(); return false; } if (mCamera == null) { ToastUtils.toastResId(R.string.error_init_player_fail); return false; } // change to portrait record setCameraDisplayOrientation(cameraid, mCamera); try { mCamera.setPreviewDisplay(holder); } catch (IOException e) { ToastUtils.toastResId(R.string.error_IO_error); e.printStackTrace(); return false; } Camera.Parameters parameters = mCamera.getParameters(); parameters.setPreviewSize(width, height); parameters.setPictureSize(width, height); if (isLightOn) { parameters.setFlashMode(Camera.Parameters.FLASH_MODE_TORCH); } int actualFormat = 0; List<Integer> list = parameters.getSupportedPreviewFormats(); for (int format : mSupportVideoFormat) { for (Integer i : list) { Timber.i("startVideoCapture " + "suport format:" + i); if (format == i.intValue()) { actualFormat = format; break; } } if (actualFormat != 0) { break; } } if (actualFormat == 0) { Timber.e("startVideoCapture" + " no suport format be found"); return false; } parameters.setPreviewFormat(actualFormat);// ImageFormat.YV12 try { mCamera.setParameters(parameters); mCamera.startPreview(); } catch (Exception e) { e.printStackTrace(); return false; } return true; }
+ [Google Camera2 Sample](https://github.com/googlesamples/android-Camera2Basic/blob/241c6fac81/Application%2Fsrc%2Fmain%2Fjava%2Fcom%2Fexample%2Fandroid%2Fcamera2basic%2FCamera2BasicFragment.java)，[简版](http://blog.csdn.net/torvalbill/article/details/40378539)
+ 权限
```xml
<uses-sdk
android:minSdkVersion="21"
android:targetSdkVersion="21" />
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-feature android:name="android.hardware.camera2.full" />
```
+ layout
```xml
<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:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.camera2te.MainActivity" >
<TextureView
android:id="@+id/texture"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true" />
</RelativeLayout>
```
+ 设置TextureView回调，在`onSurfaceTextureAvailable`回调中打开相机
```java
private TextureView.SurfaceTextureListener mSurfaceTextureListener = new TextureView.SurfaceTextureListener(){
@Override
public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
Log.e(TAG, "onSurfaceTextureAvailable, width="+width+",height="+height);
openCamera();
}
@Override
public void onSurfaceTextureSizeChanged(SurfaceTexture surface,
int width, int height) {
}
@Override
public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {
return false;
}
@Override
public void onSurfaceTextureUpdated(SurfaceTexture surface) {
}
};
@Override
protected void onResume() {
...
mTextureView.setSurfaceTextureListener(mSurfaceTextureListener);
...
}
```
+ 打开相机，在相机回调中开始预览
```java
private void openCamera() {
CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
try {
String cameraId = manager.getCameraIdList()[0];
CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);
StreamConfigurationMap map = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
mPreviewSize = map.getOutputSizes(SurfaceTexture.class)[0];
manager.openCamera(cameraId, mStateCallback, null);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
private CameraDevice.StateCallback mStateCallback = new CameraDevice.StateCallback() {
@Override
public void onOpened(CameraDevice camera) {
mCameraDevice = camera;
startPreview();
}
@Override
public void onDisconnected(CameraDevice camera) {
}
@Override
public void onError(CameraDevice camera, int error) {
}
};
```
+ 开启预览
```java
protected void startPreview() {
if(null == mCameraDevice || !mTextureView.isAvailable() || null == mPreviewSize) {
Log.e(TAG, "startPreview fail, return");
return;
}
SurfaceTexture texture = mTextureView.getSurfaceTexture();
if(null == texture) {
Log.e(TAG,"texture is null, return");
return;
}
texture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());
Surface surface = new Surface(texture);
try {
mPreviewBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
} catch (CameraAccessException e) {
e.printStackTrace();
}
mPreviewBuilder.addTarget(surface);
try {
mCameraDevice.createCaptureSession(Arrays.asList(surface), new CameraCaptureSession.StateCallback() {
@Override
public void onConfigured(CameraCaptureSession session) {
mPreviewSession = session;
updatePreview();
}
@Override
public void onConfigureFailed(CameraCaptureSession session) {
Toast.makeText(MainActivity.this, "onConfigureFailed", Toast.LENGTH_LONG).show();
}
}, null);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
protected void updatePreview() {
if(null == mCameraDevice) {
Log.e(TAG, "updatePreview error, return");
}
mPreviewBuilder.set(CaptureRequest.CONTROL_MODE, CameraMetadata.CONTROL_MODE_AUTO);
HandlerThread thread = new HandlerThread("CameraPreview");
thread.start();
Handler backgroundHandler = new Handler(thread.getLooper());
try {
mPreviewSession.setRepeatingRequest(mPreviewBuilder.build(), null, backgroundHandler);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
```
- Printing Content, >= API 19
- 打印图片
PrintHelper photoPrinter = new PrintHelper(getActivity());
photoPrinter.setScaleMode(PrintHelper.SCALE_MODE_FIT);
Bitmap bitmap = BitmapFactory.decodeResource(getResources(),
R.drawable.droids);
photoPrinter.printBitmap("droids.jpg - test print", bitmap);- ScaleMode + SCALE_MODE_FIT：等比例缩放图片，使之可以在打印区域内显示 + SCALE_MODE_FILL：充满打印区域，上下/左右可能会有部分内容无法打印
- 打印HTML文档
private WebView mWebView;
private void doWebViewPrint() {
// Create a WebView object specifically for printing
WebView webView = new WebView(getActivity());
webView.setWebViewClient(new WebViewClient() {
public boolean shouldOverrideUrlLoading(WebView view, String url) {
return false;
}
@Override
public void onPageFinished(WebView view, String url) {
Log.i(TAG, "page finished loading " + url);
createWebPrintJob(view);
mWebView = null;
}
});
// Generate an HTML document on the fly:
String htmlDocument = "<html><body><h1>Test Content</h1><p>Testing, " +
"testing, testing...</p></body></html>";
webView.loadDataWithBaseURL(null, htmlDocument, "text/HTML", "UTF-8", null);
// Keep a reference to WebView object until you pass the PrintDocumentAdapter
// to the PrintManager
mWebView = webView;
}
private void createWebPrintJob(WebView webView) {
// Get a PrintManager instance
PrintManager printManager = (PrintManager) getActivity()
.getSystemService(Context.PRINT_SERVICE);
// Get a print adapter instance
PrintDocumentAdapter printAdapter = webView.createPrintDocumentAdapter();
// Create a print job with name and adapter instance
String jobName = getString(R.string.app_name) + " Document";
PrintJob printJob = printManager.print(jobName, printAdapter,
new PrintAttributes.Builder().build());
// Save the job object for later status checking
mPrintJobs.add(printJob);
}- 自定义文档（内容）打印： + 可以先把View画到bitmap中，然后打印bitmap + 也可以实现PrintDocumentAdapter，打印自定义内容