空白环绕Android相机预览

Question

This is first exposure to Android I am having issues with my preview being surrounded by whitespace on both the top and bottom and I'm not sure what could be causing it. Any help is greatly appreciated.

activity_main:

<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:orientation="vertical"
tools:context="com.baltimorehackathon.MainActivity" >

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

</RelativeLayout>

Preview:

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

import android.content.Context;
import android.hardware.Camera;
import android.hardware.Camera.Size;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.view.ViewGroup;

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

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

    private boolean cameraConfigured;

    public 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) {
        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) {
        try {
            if (mCamera != null) {
                mCamera.setPreviewDisplay(holder);
            }
        } catch (IOException exception) {
            Log.e(TAG, "IOException caused by setPreviewDisplay()", exception);
        }
    }

    public void surfaceDestroyed(SurfaceHolder holder) {
        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;
    }

    private Camera.Size getBestPreviewSize(int width, int height)
    {
            Camera.Size result=null;    
            Camera.Parameters p = mCamera.getParameters();
            for (Camera.Size size : p.getSupportedPreviewSizes()) {
                if (size.width<=width && size.height<=height) {
                    if (result==null) {
                        result=size;
                    } else {
                        int resultArea=result.width*result.height;
                        int newArea=size.width*size.height;

                        if (newArea>resultArea) {
                            result=size;
                        }
                    }
                }
            }
        return result;

    }

    public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
        if(mCamera != null){
            if (!cameraConfigured ) {
                Camera.Parameters parameters=mCamera.getParameters();
                Camera.Size size = getBestPreviewSize(w,h);
                if (size != null) {
                    parameters.setPreviewSize(size.width, size.height);
                    mCamera.setDisplayOrientation(90);
                    mCamera.setParameters(parameters);
                    cameraConfigured=true;
                }
                mCamera.startPreview();
            }
        }

    }
}

Main Activity:

 import android.app.Activity;
import android.hardware.Camera;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;

public class MainActivity extends Activity {

    private Preview mPreview;
    Camera mCamera;
    int numberOfCameras;
    int cameraCurrentlyLocked;
    int defaultCameraId;
    boolean cameraConfigured;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mPreview = new Preview(this);
        setContentView(mPreview);

        mPreview.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                mCamera.autoFocus(null);
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

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

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

Answer 1

That's because your Preview class finds the best fitting aspect ratio for the camera and it just happens not to fit the screen nicely.

You could change the color of the background to something else:

public Preview(Context context) {
    super(context);
    setBackgroundColor(Color.BLACK);
    ...
}

Or don't use this Preview class at all:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    SurfaceView surfaceView = new SurfaceView(this);
    setContentView(surfaceView);

    SurfaceHolder surfaceHolder = surfaceView.getHolder();
    surfaceHolder.addCallback(new SurfaceHolder.Callback() {
        @Override
        public void surfaceDestroyed(SurfaceHolder holder) {
            mCamera.stopPreview();
            mCamera.release();
            mCamera = null;
        }

        @Override
        public void surfaceCreated(SurfaceHolder holder) {
            mCamera = Camera.open(0);
            try {
                mCamera.setPreviewDisplay(holder);
            } catch (IOException exception) {
                mCamera.release();
                mCamera = null;
            }
        }

        @Override
        public void surfaceChanged(SurfaceHolder holder, int format, int width,
                                   int height) {
            mCamera.startPreview();
        }
    });
}

Answer 2

It ended up being an orientation issue on my camera. The camera orientation is separate from the view. A simple camera.setDisplayOrientation(90) did the trick.