前言java
筆者由於項目須要自定義相機,因此瞭解了一下 Android 關於 camera 這塊的 API。Android SDK 21(LOLLIPOP) 開始已經棄用了以前的 Camera 類,提供了 camera2 相關 API,目前網上關於 camera2 API 介紹的資料比較少,筆者蒐集網上資料,結合本身的實踐,在這裏作一個總結。android
流程git
由於 camera2 提供的接口比較多,雖然很靈活,可是也增長了使用的複雜度。首先來大體瞭解一下調用 camera2 的流程,方便咱們理清思路。github
要顯示相機捕捉的畫面,只須要三步:初始化相機,預覽,更新預覽。也就是上圖中左側的部分。要實現這三步,須要用到的主要接口類和它們的做用步驟如上圖右側部分所示。下面就用代碼來詳解一下。ide
案例ui
首先建立一個相機界面:this
activity_camera.xmlspa
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="vertical"> <TextureView android:id="@+id/camera_texture_view" android:layout_width="match_parent" android:layout_height="match_parent" /> <ImageButton android:id="@+id/capture_ib" android:layout_width="60dp" android:layout_height="60dp" android:layout_marginBottom="10dp" android:layout_gravity="bottom|center" android:background="@drawable/send_pres"/> </LinearLayout>
界面很簡單,只有一個 TexureView 和一個按鈕。
接下來在 Activity 中初始化並顯示相機捕捉的畫面。code
首先要解決的一個問題就是畫面拉伸的問題。
要解決這個問題,首先要從 TextureView 下手。xml
CameraActivity.java
mTextureView.setSurfaceTextureListener(new TextureView.SurfaceTextureListener() { @Override public void onSurfaceTextureAvailable(SurfaceTexture surfaceTexture, int width, int height) { mWidth = width; mHeight = height; getCameraId(); openCamera(); } @Override public void onSurfaceTextureSizeChanged(SurfaceTexture surfaceTexture, int i, int i1) { } @Override public boolean onSurfaceTextureDestroyed(SurfaceTexture surfaceTexture) { return false; } @Override public void onSurfaceTextureUpdated(SurfaceTexture surfaceTexture) { } });
在 onSurfaceTextureAvailable 中初始化相機。經過 CameraManager 對象 openCamera,這正是流程圖中 Init 步驟中的第一步。openCamera 有三個參數,第一個是 String 類型的 cameraId,第二個是 CameraDevice.StateCallback,第三個是 Handler。這裏咱們要聲明一個 StateCallback:
private CameraDevice.StateCallback mCameraDeviceStateCallback = new CameraDevice.StateCallback() { @Override public void onOpened(CameraDevice cameraDevice) { mCameraDevice = cameraDevice; createCameraPreview(); } @Override public void onDisconnected(CameraDevice cameraDevice) { mCameraDevice.close(); mCameraDevice = null; } @Override public void onError(CameraDevice cameraDevice, int i) { mCameraDevice.close(); mCameraDevice = null; } };
能夠看到,在 camera 準備完畢以後就能夠建立預覽界面了。解決畫面拉伸的問題就是要爲預覽界面設置一個合適比例的 SurfaceTexture buffer size。
private void createCameraPreview() { try { SurfaceTexture texture = mTextureView.getSurfaceTexture(); assert texture != null; CameraCharacteristics characteristics = mCameraManager.getCameraCharacteristics(mCameraId); StreamConfigurationMap map = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP); int deviceOrientation = getWindowManager().getDefaultDisplay().getOrientation(); int totalRotation = sensorToDeviceRotation(characteristics, deviceOrientation); boolean swapRotation = totalRotation == 90 || totalRotation == 270; int rotatedWidth = mWidth; int rotatedHeight = mHeight; if (swapRotation) { rotatedWidth = mHeight; rotatedHeight = mWidth; } mPreviewSize = getPreferredPreviewSize(map.getOutputSizes(SurfaceTexture.class), rotatedWidth, rotatedHeight); texture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight()); Log.e("CameraActivity", "OptimalSize width: " + mPreviewSize.getWidth() + " height: " + mPreviewSize.getHeight()); ...
這裏根據當前設備及傳感器的旋轉角度來判斷是否交換寬高值,而後經過 CameraCharacteristics 來獲得最適合當前大小比例的寬高,而後把這個寬高設置給 SurfaceTexture 。
private Size getPreferredPreviewSize(Size[] sizes, int width, int height) { List<Size> collectorSizes = new ArrayList<>(); for (Size option : sizes) { if (width > height) { if (option.getWidth() > width && option.getHeight() > height) { collectorSizes.add(option); } } else { if (option.getHeight() > width && option.getWidth() > height) { collectorSizes.add(option); } } } if (collectorSizes.size() > 0) { return Collections.min(collectorSizes, new Comparator<Size>() { @Override public int compare(Size s1, Size s2) { return Long.signum(s1.getWidth() * s1.getHeight() - s2.getWidth() * s2.getHeight()); } }); } return sizes[0]; }
這裏 Sizes 是相機返回的支持的分辨率,從咱們傳遞的參數找找到一個最接近的分辨率。
接下來就要經過 CaptureRequest.Builder以及 CameraCaptureSession.StateCallback 來建立及更新預覽界面:
... Surface surface = new Surface(texture); mBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW); // 設置預覽對象 mBuilder.addTarget(surface); mCameraDevice.createCaptureSession(Arrays.asList(surface), new CameraCaptureSession.StateCallback() { @Override public void onConfigured(CameraCaptureSession cameraCaptureSession) { if (null == mCameraDevice) { return; } mSession = cameraCaptureSession; mBuilder.set(CaptureRequest.CONTROL_MODE, CameraMetadata.CONTROL_MODE_AUTO); try { // 不停地將捕捉的畫面更新到 TextureView mSession.setRepeatingRequest(mBuilder.build(), mSessionCaptureCallback, mBackgroundHandler); } catch (CameraAccessException e) { e.printStackTrace(); } } @Override public void onConfigureFailed(CameraCaptureSession cameraCaptureSession) { Toast.makeText(CameraActivity.this, "Camera configuration change", Toast.LENGTH_SHORT).show(); } }, null); } catch (CameraAccessException e) { e.printStackTrace(); }
這樣就完成了自定義相機第一步。源碼地址請戳這裏。