控制音量和播放
- Audio Stream：安卓系統(tǒng)為不同的用途維護(hù)了不同的audio stream，便于用戶(hù)控制不同類(lèi)型聲音的音量
  - music
  - alarm
  - notification
  - 來(lái)電話(huà)
  - system sound
  - 打電話(huà)過(guò)程中的聲音
  - DTMF tones
- 通過(guò)設(shè)置setVolumeControlStream()，系統(tǒng)將在Activity/Fragment仍在界面上時(shí)，自動(dòng)響應(yīng)設(shè)備的音量操作鍵，增大或減小設(shè)置類(lèi)型媒體的音量
- 當(dāng)用戶(hù)通過(guò)耳機(jī)等外設(shè)，按下播放控制按鍵時(shí)，例如：播放/暫停、上一曲/下一曲，系統(tǒng)將發(fā)送一個(gè)action為android.intent.action.MEDIA_BUTTON的廣播，如下BroadcastReceiver可以響應(yīng)處理這一廣播（需要在AndroidManifest.xml中聲明）：
```
  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

請(qǐng)求/釋放audio focus

  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的最后一個(gè)參數(shù)可以設(shè)為AudioManager.AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK，用于請(qǐng)求短暫的audio focus，允許其他app在失去audio focus時(shí)繼續(xù)播放音樂(lè)（但應(yīng)該降低音量）

監(jiān)聽(tīng)audio focus狀態(tài)改變

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
        }
    }
};

響應(yīng)臨時(shí)失焦且允許重音的情形

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
        }
    }
};

檢查聲音播放設(shè)備

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?
}

一旦耳機(jī)/藍(lán)牙耳機(jī)斷開(kāi)連接，系統(tǒng)將繼續(xù)使用默認(rèn)設(shè)備（揚(yáng)聲器）播放，同時(shí)系統(tǒng)會(huì)發(fā)送一個(gè)AudioManager.ACTION_AUDIO_BECOMING_NOISY廣播，可以通過(guò)以下代碼進(jìn)行響應(yīng)

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

使用已有相機(jī)APP拍照

聲明使用相機(jī)的feature，注意，并非權(quán)限，便于google play等應(yīng)用商店確定設(shè)備是否可以安裝本應(yīng)用
```
  <manifest ... >
      <uses-feature android:name="android.hardware.camera" android:required="true" />
      ...
  </manifest>
```
也可以設(shè)置required為false，手動(dòng)檢查設(shè)備是否有相機(jī)：packageManager.hasSystemFeature(PackageManager.FEATURE_CAMERA)
發(fā)送Intent調(diào)起已有相機(jī)APP拍照，發(fā)送Intent之前需要檢查是否有其他APP可以響應(yīng)此Intent，如沒(méi)有卻調(diào)用了startActivity，將會(huì)拋出異常
```
  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);
      }
  }
```
在發(fā)送takePictureIntent之前，可以手動(dòng)設(shè)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，可以直接訪(fǎng)問(wèn)該uri。

獲取拍照結(jié)果縮略圖

  @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);
      }
  }

獲取完整照片
照片保存在外置存儲(chǔ)卡的公開(kāi)區(qū)域，需要聲明權(quán)限，WRITE_EXTERNAL_STORAGE包含了READ_EXTERNAL_STORAGE權(quán)限，目錄路徑通過(guò)Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES)函數(shù)獲得

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

如果要保存在APP私有目錄下，API 18之后，將不用聲明該權(quán)限，目錄路徑通過(guò)context.getExternalFilesDir(Environment.DIRECTORY_PICTURES)函數(shù)獲得，app訪(fǎng)問(wèn)自己對(duì)應(yīng)的該目錄，從API 19起，將不需要任何權(quán)限，但是訪(fǎng)問(wèn)其他APP對(duì)應(yīng)的目錄時(shí)，需要WRITE_EXTERNAL_STORAGE/READ_EXTERNAL_STORAGE權(quán)限，該目錄不一定任何時(shí)候都可以訪(fǎng)問(wèn)，也不具備安全性

  <manifest ...>
      <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"
                      android:maxSdkVersion="18" />
      ...
  </manifest>

拍照設(shè)置保存文件

  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，當(dāng)保存路徑設(shè)為context.getExternalFilesDir(type)時(shí)，將無(wú)法加入Gallery

  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);
  }

獲取壓縮后的圖片，用于顯示在ImageView上

  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);
  }

使用已有相機(jī)應(yīng)用錄制視頻，與拍照類(lèi)似，需要發(fā)送的Intent初始化為Intent takeVideoIntent = new Intent(MediaStore.ACTION_VIDEO_CAPTURE);，onActivityResult返回的intent的data數(shù)據(jù)，就是錄制視頻的Uri，intent.getData()。

直接使用相機(jī)

Camera API

權(quán)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，動(dòng)態(tài)添加到layout中，在onPause中停止預(yù)覽，移除SurfaceView，以解決界面onPause后再onResume就無(wú)法預(yù)覽的問(wèn)題。在SurfaceView的surfaceCreated回調(diào)中打開(kāi)相機(jī)，開(kāi)始預(yù)覽

@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);
}

打開(kāi)相機(jī)，開(kāi)始預(yù)覽

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，簡(jiǎn)版

權(quán)限

<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

<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>

設(shè)置TextureView回調(diào)，在onSurfaceTextureAvailable回調(diào)中打開(kāi)相機(jī)

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);
    ...
}

打開(kāi)相機(jī)，在相機(jī)回調(diào)中開(kāi)始預(yù)覽

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) {  

    }  

};

開(kāi)啟預(yù)覽

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

打印圖片

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：等比例縮放圖片，使之可以在打印區(qū)域內(nèi)顯示
- SCALE_MODE_FILL：充滿(mǎn)打印區(qū)域，上下/左右可能會(huì)有部分內(nèi)容無(wú)法打印

打印HTML文檔

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);
}

自定義文檔（內(nèi)容）打?。?
- 可以先把View畫(huà)到bitmap中，然后打印bitmap
- 也可以實(shí)現(xiàn)PrintDocumentAdapter，打印自定義內(nèi)容

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