Android中怎么利用SurfaceView顯示Camera圖像

# Android中怎么利用SurfaceView顯示Camera圖像

## 一、SurfaceView與Camera概述

在Android應用開發中，實時顯示攝像頭圖像是常見需求。`SurfaceView`作為專門用于高效繪制動態內容的視圖組件，配合`Camera` API可以實現這一功能。其核心優勢在于：

1. **獨立繪制線程**：SurfaceView擁有獨立的Surface，可在非UI線程渲染
2. **雙緩沖機制**：減少畫面閃爍
3. **硬件加速支持**：適合視頻/3D等高性能場景

## 二、實現步驟詳解

### 1. 添加權限和特性聲明

```xml
<!-- AndroidManifest.xml -->
<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera" />

<!-- 適配Android 9+ -->
<uses-permission android:name="android.permission.RECORD_AUDIO" 
                 android:required="false" />

2. 布局文件配置

<SurfaceView
    android:id="@+id/camera_preview"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

3. 核心代碼實現

初始化SurfaceHolder

public class CameraActivity extends AppCompatActivity 
    implements SurfaceHolder.Callback {

    private Camera mCamera;
    private SurfaceView mSurfaceView;
    private SurfaceHolder mHolder;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_camera);

        mSurfaceView = findViewById(R.id.camera_preview);
        mHolder = mSurfaceView.getHolder();
        mHolder.addCallback(this);
        // 設置Surface類型
        mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }
}

實現SurfaceHolder.Callback

@Override
public void surfaceCreated(SurfaceHolder holder) {
    try {
        // 打開后置攝像頭
        mCamera = Camera.open();
        // 設置預覽方向（解決畫面旋轉問題）
        mCamera.setDisplayOrientation(90);
        // 綁定SurfaceView
        mCamera.setPreviewDisplay(holder);
        mCamera.startPreview();
    } catch (IOException e) {
        Log.e("Camera", "Error setting preview: " + e.getMessage());
    }
}

@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
    // Surface尺寸變化時重新設置參數
    if (mHolder.getSurface() == null) return;
    
    try {
        mCamera.stopPreview();
        Camera.Parameters params = mCamera.getParameters();
        // 設置預覽尺寸（需選擇設備支持的尺寸）
        List<Camera.Size> sizes = params.getSupportedPreviewSizes();
        Camera.Size optimalSize = getOptimalSize(sizes, width, height);
        params.setPreviewSize(optimalSize.width, optimalSize.height);
        mCamera.setParameters(params);
        mCamera.setPreviewDisplay(mHolder);
        mCamera.startPreview();
    } catch (Exception e) {
        Log.e("Camera", "Error restarting preview: " + e.getMessage());
    }
}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {
    releaseCamera();
}

相機資源釋放

private void releaseCamera() {
    if (mCamera != null) {
        mCamera.stopPreview();
        mCamera.release();
        mCamera = null;
    }
}

@Override
protected void onPause() {
    super.onPause();
    releaseCamera();
}

4. 最佳預覽尺寸計算

private Camera.Size getOptimalSize(List<Camera.Size> sizes, int w, int h) {
    final double ASPECT_TOLERANCE = 0.1;
    double targetRatio = (double) h / w;
    
    Camera.Size optimalSize = null;
    double minDiff = Double.MAX_VALUE;

    for (Camera.Size size : sizes) {
        double ratio = (double) size.width / size.height;
        if (Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE) continue;
        
        double diff = Math.abs(size.height - h) + Math.abs(size.width - w);
        if (diff < minDiff) {
            optimalSize = size;
            minDiff = diff;
        }
    }
    
    return optimalSize != null ? optimalSize : sizes.get(sizes.size() - 1);
}

三、注意事項

1. 權限處理：Android 6.0+需要運行時權限申請

   if (checkSelfPermission(Manifest.permission.CAMERA) 
      != PackageManager.PERMISSION_GRANTED) {
      requestPermissions(new String[]{Manifest.permission.CAMERA}, 100);
   }
   

2. 方向適配：不同設備可能需要特殊處理預覽方向

3. 新API遷移：Android 5.0+建議使用Camera2 API，但SurfaceView仍適用

4. 性能優化：

   • 避免頻繁修改相機參數
   • 使用TextureView替代SurfaceView可實現動畫效果
   • 考慮使用SurfaceTexture進行更靈活的圖像處理

四、完整示例代碼

GitHub示例項目鏈接

通過上述實現，開發者可以構建基礎的相機預覽功能，后續可擴展添加拍照、濾鏡等高級功能。 “`