現在Android智能手機的像素都會提供照相的功能，大部分的手機的攝像頭的像素都在1000萬以上的像素，有的甚至會更高。它們大多都會支持光學變焦、曝光以及快門等等。
下面的程序Demo實例示范了使用Camera v2來進行拍照，當用戶按下拍照鍵時，該應用會自動對焦，當對焦成功時拍下照片。
layout/activity_main.xml界面布局代碼如下：
<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.fukaimei.camerav2test"> <!-- 授予該程序使用攝像頭的權限 --> <uses-permission android:name="android.permission.CAMERA" /> <application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:roundIcon="@mipmap/ic_launcher_round" android:supportsRtl="true" android:theme="@style/AppTheme"> <activity android:name=".MainActivity"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application></manifest>
上面的程序的界面提供了一個自定義TextureView來顯示預覽取景，十分簡單。該自定義TextureView類的代碼如下：
AutoFitTextureView.java邏輯代碼如下：
package com.fukaimei.camerav2test;import android.content.Context;import android.util.AttributeSet;import android.view.TextureView;/** * Created by FuKaimei on 2017/9/29. */public class AutoFitTextureView extends TextureView { private int mRatioWidth = 0; private int mRatioHeight = 0; public AutoFitTextureView(Context context, AttributeSet attrs) { super(context, attrs); } public void setAspectRatio(int width, int height) { mRatioWidth = width; mRatioHeight = height; requestLayout(); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); int width = MeasureSpec.getSize(widthMeasureSpec); int height = MeasureSpec.getSize(heightMeasureSpec); if (0 == mRatioWidth || 0 == mRatioHeight) { setMeasuredDimension(width, height); } else { if (width < height * mRatioWidth / mRatioHeight) { setMeasuredDimension(width, width * mRatioHeight / mRatioWidth); } else { setMeasuredDimension(height * mRatioWidth / mRatioHeight, height); } } }}接來了的MainActivity.java程序將會使用CameraManager來打開CameraDevice，并通過CameraDevice創建CameraCaptureSession，然后即可通過CameraCaptureSession進行預覽或拍照了。
MainActivity.java邏輯代碼如下：
package com.fukaimei.camerav2test;import android.Manifest;import android.app.Activity;import android.content.Context;import android.content.pm.PackageManager;import android.content.res.Configuration;import android.graphics.ImageFormat;import android.graphics.SurfaceTexture;import android.hardware.camera2.CameraAccessException;import android.hardware.camera2.CameraCaptureSession;import android.hardware.camera2.CameraCharacteristics;import android.hardware.camera2.CameraDevice;import android.hardware.camera2.CameraManager;import android.hardware.camera2.CameraMetadata;import android.hardware.camera2.CaptureRequest;import android.hardware.camera2.TotalCaptureResult;import android.hardware.camera2.params.StreamConfigurationMap;import android.media.Image;import android.media.ImageReader;import android.os.Build;import android.os.Bundle;import android.support.annotation.RequiresApi;import android.support.v4.app.ActivityCompat;import android.util.Log;import android.util.Size;import android.util.SparseIntArray;import android.view.Surface;import android.view.TextureView;import android.view.View;import android.widget.Toast;import java.io.File;import java.io.FileOutputStream;import java.nio.ByteBuffer;import java.util.ArrayList;import java.util.Arrays;import java.util.Collections;import java.util.Comparator;import java.util.List;@RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)public class MainActivity extends Activity implements View.OnClickListener { private static final SparseIntArray ORIENTATIONS = new SparseIntArray(); private static final String TAG = "MainActivity"; static { ORIENTATIONS.append(Surface.ROTATION_0, 90); ORIENTATIONS.append(Surface.ROTATION_90, 0); ORIENTATIONS.append(Surface.ROTATION_180, 270); ORIENTATIONS.append(Surface.ROTATION_270, 180); } private AutoFitTextureView textureView; // 攝像頭ID（通常0代表后置攝像頭，1代表前置攝像頭） private String mCameraId = "0"; // 定義代表攝像頭的成員變量 private CameraDevice cameraDevice; // 預覽尺寸 private Size previewSize; private CaptureRequest.Builder previewRequestBuilder; // 定義用于預覽照片的捕獲請求 private CaptureRequest previewRequest; // 定義CameraCaptureSession成員變量 private CameraCaptureSession captureSession; private ImageReader imageReader; private final TextureView.SurfaceTextureListener mSurfaceTextureListener = new TextureView.SurfaceTextureListener() { @Override public void onSurfaceTextureAvailable(SurfaceTexture texture , int width, int height) { // 當TextureView可用時，打開攝像頭 openCamera(width, height); } @Override public void onSurfaceTextureSizeChanged(SurfaceTexture texture , int width, int height) { } @Override public boolean onSurfaceTextureDestroyed(SurfaceTexture texture) { return true; } @Override public void onSurfaceTextureUpdated(SurfaceTexture texture) { } }; private final CameraDevice.StateCallback stateCallback = new CameraDevice.StateCallback() { // 攝像頭被打開時激發該方法 @Override public void onOpened(CameraDevice cameraDevice) { MainActivity.this.cameraDevice = cameraDevice; // 開始預覽 createCameraPreviewSession(); // ② } // 攝像頭斷開連接時激發該方法 @Override public void onDisconnected(CameraDevice cameraDevice) { cameraDevice.close(); MainActivity.this.cameraDevice = null; } // 打開攝像頭出現錯誤時激發該方法 @Override public void onError(CameraDevice cameraDevice, int error) { cameraDevice.close(); MainActivity.this.cameraDevice = null; MainActivity.this.finish(); } }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); textureView = (AutoFitTextureView) findViewById(R.id.texture); // 為該組件設置監聽器 textureView.setSurfaceTextureListener(mSurfaceTextureListener); findViewById(R.id.capture).setOnClickListener(this); } @Override public void onClick(View view) { captureStillPicture(); } private void captureStillPicture() { try { if (cameraDevice == null) { return; } // 創建作為拍照的CaptureRequest.Builder final CaptureRequest.Builder captureRequestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE); // 將imageReader的surface作為CaptureRequest.Builder的目標 captureRequestBuilder.addTarget(imageReader.getSurface()); // 設置自動對焦模式 captureRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE); // 設置自動曝光模式 captureRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH); // 獲取設備方向 int rotation = getWindowManager().getDefaultDisplay().getRotation(); // 根據設備方向計算設置照片的方向 captureRequestBuilder.set(CaptureRequest.JPEG_ORIENTATION , ORIENTATIONS.get(rotation)); // 停止連續取景 captureSession.stopRepeating(); // 捕獲靜態圖像 captureSession.capture(captureRequestBuilder.build() , new CameraCaptureSession.CaptureCallback() // ⑤ { // 拍照完成時激發該方法 @Override public void onCaptureCompleted(CameraCaptureSession session , CaptureRequest request, TotalCaptureResult result) { try { // 重設自動對焦模式 previewRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER, CameraMetadata.CONTROL_AF_TRIGGER_CANCEL); // 設置自動曝光模式 previewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH); // 打開連續取景模式 captureSession.setRepeatingRequest(previewRequest, null, null); } catch (CameraAccessException e) { e.printStackTrace(); } } }, null); } catch (CameraAccessException e) { e.printStackTrace(); } } // 打開攝像頭 private void openCamera(int width, int height) { setUpCameraOutputs(width, height); CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE); try { // 打開攝像頭 if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) { // TODO: Consider calling // ActivityCompat#requestPermissions // here to request the missing permissions, and then overriding // public void onRequestPermissionsResult(int requestCode, String[] permissions, // int[] grantResults) // to handle the case where the user grants the permission. See the documentation // for ActivityCompat#requestPermissions for more details. return; } manager.openCamera(mCameraId, stateCallback, null); // ① } catch (CameraAccessException e) { e.printStackTrace(); } } private void createCameraPreviewSession() { try { SurfaceTexture texture = textureView.getSurfaceTexture(); texture.setDefaultBufferSize(previewSize.getWidth(), previewSize.getHeight()); Surface surface = new Surface(texture); // 創建作為預覽的CaptureRequest.Builder previewRequestBuilder = cameraDevice .createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW); // 將textureView的surface作為CaptureRequest.Builder的目標 previewRequestBuilder.addTarget(new Surface(texture)); // 創建CameraCaptureSession，該對象負責管理處理預覽請求和拍照請求 cameraDevice.createCaptureSession(Arrays.asList(surface , imageReader.getSurface()), new CameraCaptureSession.StateCallback() // ③ { @Override public void onConfigured(CameraCaptureSession cameraCaptureSession) { // 如果攝像頭為null，直接結束方法 if (null == cameraDevice) { return; } // 當攝像頭已經準備好時，開始顯示預覽 captureSession = cameraCaptureSession; try { // 設置自動對焦模式 previewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE); // 設置自動曝光模式 previewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH); // 開始顯示相機預覽 previewRequest = previewRequestBuilder.build(); // 設置預覽時連續捕獲圖像數據 captureSession.setRepeatingRequest(previewRequest, null, null); // ④ } catch (CameraAccessException e) { e.printStackTrace(); } } @Override public void onConfigureFailed(CameraCaptureSession cameraCaptureSession) { Toast.makeText(MainActivity.this, "配置失敗！" , Toast.LENGTH_SHORT).show(); } }, null ); } catch (CameraAccessException e) { e.printStackTrace(); } } private void setUpCameraOutputs(int width, int height) { CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE); try { // 獲取指定攝像頭的特性 CameraCharacteristics characteristics = manager.getCameraCharacteristics(mCameraId); // 獲取攝像頭支持的配置屬性 StreamConfigurationMap map = characteristics.get( CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP); // 獲取攝像頭支持的最大尺寸 Size largest = Collections.max( Arrays.asList(map.getOutputSizes(ImageFormat.JPEG)), new CompareSizesByArea()); // 創建一個ImageReader對象，用于獲取攝像頭的圖像數據 imageReader = ImageReader.newInstance(largest.getWidth(), largest.getHeight(), ImageFormat.JPEG, 2); imageReader.setOnImageAvailableListener( new ImageReader.OnImageAvailableListener() { // 當照片數據可用時激發該方法 @Override public void onImageAvailable(ImageReader reader) { // 獲取捕獲的照片數據 Image image = reader.acquireNextImage(); ByteBuffer buffer = image.getPlanes()[0].getBuffer(); byte[] bytes = new byte[buffer.remaining()]; // 使用IO流將照片寫入指定文件 File file = new File(getExternalFilesDir(null), "pic.jpg"); buffer.get(bytes); try ( FileOutputStream output = new FileOutputStream(file)) { output.write(bytes); Toast.makeText(MainActivity.this, "保存: " + file, Toast.LENGTH_LONG).show(); } catch (Exception e) { e.printStackTrace(); } finally { image.close(); } } }, null); // 獲取最佳的預覽尺寸 previewSize = chooseOptimalSize(map.getOutputSizes( SurfaceTexture.class), width, height, largest); // 根據選中的預覽尺寸來調整預覽組件（TextureView的）的長寬比 int orientation = getResources().getConfiguration().orientation; if (orientation == Configuration.ORIENTATION_LANDSCAPE) { textureView.setAspectRatio( previewSize.getWidth(), previewSize.getHeight()); } else { textureView.setAspectRatio( previewSize.getHeight(), previewSize.getWidth()); } } catch (CameraAccessException e) { e.printStackTrace(); } catch (NullPointerException e) { Log.d(TAG, "出現錯誤"); } } private static Size chooseOptimalSize(Size[] choices , int width, int height, Size aspectRatio) { // 收集攝像頭支持的打過預覽Surface的分辨率 List<Size> bigEnough = new ArrayList<>(); int w = aspectRatio.getWidth(); int h = aspectRatio.getHeight(); for (Size option : choices) { if (option.getHeight() == option.getWidth() * h / w && option.getWidth() >= width && option.getHeight() >= height) { bigEnough.add(option); } } // 如果找到多個預覽尺寸，獲取其中面積最小的。 if (bigEnough.size() > 0) { return Collections.min(bigEnough, new CompareSizesByArea()); } else { System.out.println("找不到合適的預覽尺寸！！！"); return choices[0]; } } // 為Size定義一個比較器Comparator static class CompareSizesByArea implements Comparator<Size> { @Override public int compare(Size lhs, Size rhs) { // 強轉為long保證不會發生溢出 return Long.signum((long) lhs.getWidth() * lhs.getHeight() - (long) rhs.getWidth() * rhs.getHeight()); } }}上面的程序中序號①的代碼是用于打開系統攝像頭，openCamera()方法的第一個參數代表請求打開的攝像頭ID，此處傳入的攝像頭ID為“0”，這代表打開設備后置攝像頭；如果需要打開設備指定攝像頭（比如前置攝像頭），可以在調用openCamera()方法時傳入相應的攝像頭ID。
注意：由于該程序需要使用手機的攝像頭，因此還需要在清單文件AndroidManifest.xml文件中授權相應的權限：
<!-- 授予該程序使用攝像頭的權限 --> <uses-permission android:name="android.permission.CAMERA" />
Demo程序運行效果界面截圖如下：
Demo程序源碼下載地址
以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持VEVB武林網。
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