如何在android中打开前置摄像头预览?

时间:2012-12-15 08:46:03

标签: android xml android-manifest

现在我正在开发相机应用程序,因为我需要同时使用前后摄像头。我的要求是当我首先打开我的应用程序时它将显示后面的表面视图,当我按下一个按钮它还会切换到前置摄像头时我有一个按钮表面视图,当我第二次按下按钮时,它将再次切换到后置摄像头,我写了这段代码。

        import android.app.Activity;
        import android.app.AlertDialog;
        import android.content.Context;
        import android.hardware.Camera;
        import android.hardware.Camera.CameraInfo;
        import android.hardware.Camera.Size;
        import android.os.Bundle;
        import android.util.Log;
        import android.view.Menu;
        import android.view.MenuInflater;
        import android.view.MenuItem;
        import android.view.SurfaceHolder;
        import android.view.SurfaceView;
        import android.view.View;
        import android.view.ViewGroup;
        import android.view.Window;
        import android.view.WindowManager;

        import java.io.IOException;
        import java.util.List;

        import com.example.R;

        public class MainActivity extends Activity {
             private Preview mPreview;
                Camera mCamera;
                int numberOfCameras;
                int cameraCurrentlyLocked;

                // The first rear facing camera
                int defaultCameraId;

            protected void onCreate(Bundle savedInstanceState) 
              {
                super.onCreate(savedInstanceState);
                // Hide the window title.
                requestWindowFeature(Window.FEATURE_NO_TITLE);
                getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);

                // Create a RelativeLayout container that will hold a SurfaceView,
                // and set it as the content of our activity.
                mPreview = new Preview(this);
                setContentView(mPreview);

                // Find the total number of cameras available
                numberOfCameras = Camera.getNumberOfCameras();

                // Find the ID of the default camera
                CameraInfo cameraInfo = new CameraInfo();
                    for (int i = 0; i < numberOfCameras; i++)
                   {
                        Camera.getCameraInfo(i, cameraInfo);
                        if (cameraInfo.facing == CameraInfo.CAMERA_FACING_BACK)
                        {
                            defaultCameraId = i;
                        }
                    }
            }

            @Override
            protected void onResume() {
                super.onResume();

                // Open the default i.e. the first rear facing camera.
                mCamera = Camera.open();
                cameraCurrentlyLocked = defaultCameraId;
                mPreview.setCamera(mCamera);
            }

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

                // Because the Camera object is a shared resource, it's very
                // important to release it when the activity is paused.
                if (mCamera != null) {
                    mPreview.setCamera(null);
                    mCamera.release();
                    mCamera = null;
                }
            }

            @Override
            public boolean onCreateOptionsMenu(Menu menu) {

                // Inflate our menu which can gather user input for switching camera
                MenuInflater inflater = getMenuInflater();
                inflater.inflate(R.menu.camera_menu, menu);
                return true;
            }

            @Override
            public boolean onOptionsItemSelected(MenuItem item) {
                // Handle item selection
                switch (item.getItemId()) {
                case R.id.switch_cam:
                    // check for availability of multiple cameras
                    if (numberOfCameras == 1) {
                        AlertDialog.Builder builder = new AlertDialog.Builder(this);
                        builder.setMessage("camera_alert")
                               .setNeutralButton("Close", null);
                        AlertDialog alert = builder.create();
                        alert.show();
                        return true;
                    }

                    // OK, we have multiple cameras.
                    // Release this camera -> cameraCurrentlyLocked
                    if (mCamera != null) {
                        mCamera.stopPreview();
                        mPreview.setCamera(null);
                        mCamera.release();
                        mCamera = null;
                    }

                    // Acquire the next camera and request Preview to reconfigure
                    // parameters.
                    mCamera = Camera
                            .open((cameraCurrentlyLocked + 1) % numberOfCameras);
                    cameraCurrentlyLocked = (cameraCurrentlyLocked + 1)
                            % numberOfCameras;
                    mPreview.switchCamera(mCamera);

                    // Start the preview
                    mCamera.startPreview();
                    return true;
                default:
                    return super.onOptionsItemSelected(item);
                }
            }

            class Preview extends ViewGroup implements SurfaceHolder.Callback {
                private final String TAG = "Preview";

                SurfaceView mSurfaceView;
                SurfaceHolder mHolder;
                Size mPreviewSize;
                List<Size> mSupportedPreviewSizes;
                Camera mCamera;

                Preview(Context context) {
                    super(context);

                    mSurfaceView = new SurfaceView(context);
                    addView(mSurfaceView);

                    // Install a SurfaceHolder.Callback so we get notified when the
                    // underlying surface is created and destroyed.
                    mHolder = mSurfaceView.getHolder();
                    mHolder.addCallback(this);
                    mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
                }

                public void setCamera(Camera camera) {
                    mCamera = camera;
                    if (mCamera != null) {
                        mSupportedPreviewSizes = mCamera.getParameters().getSupportedPreviewSizes();
                        requestLayout();
                    }
                }

                public void switchCamera(Camera camera) {
                   setCamera(camera);
                   try {
                       camera.setPreviewDisplay(mHolder);
                   } catch (IOException exception) {
                       Log.e(TAG, "IOException caused by setPreviewDisplay()", exception);
                   }
                   Camera.Parameters parameters = camera.getParameters();
                   parameters.setPreviewSize(mPreviewSize.width, mPreviewSize.height);
                   requestLayout();

                   camera.setParameters(parameters);
                }

                @Override
                protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
                    // We purposely disregard child measurements because act as a
                    // wrapper to a SurfaceView that centers the camera preview instead
                    // of stretching it.
                    final int width = resolveSize(getSuggestedMinimumWidth(), widthMeasureSpec);
                    final int height = resolveSize(getSuggestedMinimumHeight(), heightMeasureSpec);
                    setMeasuredDimension(width, height);

                    if (mSupportedPreviewSizes != null) {
                        mPreviewSize = getOptimalPreviewSize(mSupportedPreviewSizes, width, height);
                    }
                }

                @Override
                protected void onLayout(boolean changed, int l, int t, int r, int b) {
                    if (changed && getChildCount() > 0) {
                        final View child = getChildAt(0);

                        final int width = r - l;
                        final int height = b - t;

                        int previewWidth = width;
                        int previewHeight = height;
                        if (mPreviewSize != null) {
                            previewWidth = mPreviewSize.width;
                            previewHeight = mPreviewSize.height;
                        }

                        // Center the child SurfaceView within the parent.
                        if (width * previewHeight > height * previewWidth) {
                            final int scaledChildWidth = previewWidth * height / previewHeight;
                            child.layout((width - scaledChildWidth) / 2, 0,
                                    (width + scaledChildWidth) / 2, height);
                        } else {
                            final int scaledChildHeight = previewHeight * width / previewWidth;
                            child.layout(0, (height - scaledChildHeight) / 2,
                                    width, (height + scaledChildHeight) / 2);
                        }
                    }
                }

                public void surfaceCreated(SurfaceHolder holder) {
                    // The Surface has been created, acquire the camera and tell it where
                    // to draw.
                    try {
                        if (mCamera != null) {
                            mCamera.setPreviewDisplay(holder);
                        }
                    } catch (IOException exception) {
                        Log.e(TAG, "IOException caused by setPreviewDisplay()", exception);
                    }
                }

                public void surfaceDestroyed(SurfaceHolder holder) {
                    // Surface will be destroyed when we return, so stop the preview.
                    if (mCamera != null) {
                        mCamera.stopPreview();
                    }
                }


                private Size getOptimalPreviewSize(List<Size> sizes, int w, int h) {
                    final double ASPECT_TOLERANCE = 0.1;
                    double targetRatio = (double) w / h;
                    if (sizes == null) return null;

                    Size optimalSize = null;
                    double minDiff = Double.MAX_VALUE;

                    int targetHeight = h;

                    // Try to find an size match aspect ratio and size
                    for (Size size : sizes) {
                        double ratio = (double) size.width / size.height;
                        if (Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE) continue;
                        if (Math.abs(size.height - targetHeight) < minDiff) {
                            optimalSize = size;
                            minDiff = Math.abs(size.height - targetHeight);
                        }
                    }

                    // Cannot find the one match the aspect ratio, ignore the requirement
                    if (optimalSize == null) {
                        minDiff = Double.MAX_VALUE;
                        for (Size size : sizes) {
                            if (Math.abs(size.height - targetHeight) < minDiff) {
                                optimalSize = size;
                                minDiff = Math.abs(size.height - targetHeight);
                            }
                        }
                    }
                    return optimalSize;
                }

                public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
                    // Now that the size is known, set up the camera parameters and begin
                    // the preview.
                    Camera.Parameters parameters = mCamera.getParameters();
                    parameters.setPreviewSize(mPreviewSize.width, mPreviewSize.height);
                    requestLayout();

                    mCamera.setParameters(parameters);
                    mCamera.startPreview();
                }

            }
        }

        and my menu.xml
        <?xml version="1.0" encoding="utf-8"?>
        <menu xmlns:android="http://schemas.android.com/apk/res/android">
            <item android:id="@+id/switch_cam"
                  android:title="@string/switch_cam" />
        </menu>

        when i write this code i get error

        menu cannot be resolved or is not a field and 
        switch_cam cannot be resolved or is not a field
        pleae help me

2 个答案:

答案 0 :(得分:0)

if(valueofcam.equalsIgnoreCase("front")){
            // Find the ID of the default camera
            CameraInfo cameraInfo = new CameraInfo();
                for (int i = 0; i < numberOfCameras; i++) {
                    Camera.getCameraInfo(i, cameraInfo);
                    if (cameraInfo.facing == CameraInfo.CAMERA_FACING_FRONT) {
                        defaultCameraId = i;
//                      Toast.makeText(getApplicationContext(), "front", Toast.LENGTH_LONG).show();
                    }
                    else if (cameraInfo.facing == CameraInfo.CAMERA_FACING_BACK) {
                        defaultCameraId = i;
//                      Toast.makeText(getApplicationContext(), ""+defaultCameraId, Toast.LENGTH_LONG).show();
                    }
                }
    }

    camera = Camera.open(defaultCameraId);

答案 1 :(得分:0)

使用Google的cameraview,并在activity_main.xml中调整此对象:

        <com.google.android.cameraview.CameraView
            android:id="@+id/camera"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:adjustViewBounds="true"
            app:autoFocus="true"
            app:aspectRatio="4:3"
            app:facing="front"
            app:flash="off"
            android:background="@android:color/black" />

网址:https://github.com/google/cameraview