android/hcgallery/CameraFragment.java

/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.hcgallery;

import android.app.ActionBar;
import android.app.Activity;
import android.app.Fragment;
import android.content.Context;
import android.content.Intent;
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.LayoutInflater;
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 java.io.IOException;
import java.util.List;

public class CameraFragment extends Fragment {

    private Preview mPreview;
    Camera mCamera;
    int mNumberOfCameras;
    int mCurrentCamera;  // Camera ID currently chosen
    int mCameraCurrentlyLocked;  // Camera ID that's actually acquired

    // The first rear facing camera
    int mDefaultCameraId;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Create a container that will hold a SurfaceView for camera previews
        mPreview = new Preview(this.getActivity());

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

        // Find the ID of the rear-facing ("default") camera
        CameraInfo cameraInfo = new CameraInfo();
        for (int i = 0; i < mNumberOfCameras; i++) {
            Camera.getCameraInfo(i, cameraInfo);
            if (cameraInfo.facing == CameraInfo.CAMERA_FACING_BACK) {
                mCurrentCamera = mDefaultCameraId = i;
            }
        }
        setHasOptionsMenu(mNumberOfCameras > 1);
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        // Add an up arrow to the "home" button, indicating that the button will go "up"
        // one activity in the app's Activity heirarchy.
        // Calls to getActionBar() aren't guaranteed to return the ActionBar when called
        // from within the Fragment's onCreate method, because the Window's decor hasn't been
        // initialized yet.  Either call for the ActionBar reference in Activity.onCreate()
        // (after the setContentView(...) call), or in the Fragment's onActivityCreated method.
        Activity activity = this.getActivity();
        ActionBar actionBar = activity.getActionBar();
        actionBar.setDisplayHomeAsUpEnabled(true);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        return mPreview;
    }

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

        // Use mCurrentCamera to select the camera desired to safely restore
        // the fragment after the camera has been changed
        mCamera = Camera.open(mCurrentCamera);
        mCameraCurrentlyLocked = mCurrentCamera;
        mPreview.setCamera(mCamera);
    }

    @Override
    public 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 void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
        if (mNumberOfCameras > 1) {
            // Inflate our menu which can gather user input for switching camera
            inflater.inflate(R.menu.camera_menu, menu);
        } else {
            super.onCreateOptionsMenu(menu, inflater);
        }
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle item selection
        switch (item.getItemId()) {
        case R.id.menu_switch_cam:
            // Release this camera -> mCameraCurrentlyLocked
            if (mCamera != null) {
                mCamera.stopPreview();
                mPreview.setCamera(null);
                mCamera.release();
                mCamera = null;
            }

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

            // Start the preview
            mCamera.startPreview();
            return true;
        case android.R.id.home:
            Intent intent = new Intent(this.getActivity(), MainActivity.class);
            intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP|Intent.FLAG_ACTIVITY_SINGLE_TOP);
            startActivity(intent);
            return true;

        default:
            return super.onOptionsItemSelected(item);
        }
    }
}

// ----------------------------------------------------------------------

/**
 * A simple wrapper around a Camera and a SurfaceView that renders a centered
 * preview of the Camera to the surface. We need to center the SurfaceView
 * because not all devices have cameras that support preview sizes at the same
 * aspect ratio as the device's display.
 */
class Preview extends ViewGroup implements SurfaceHolder.Callback {
    private final String TAG = "Preview";

    SurfaceView mSurfaceView;
    SurfaceHolder mHolder;
    Size mPreviewSize;
    List<Size> mSupportedPreviewSizes;
    Camera mCamera;
    boolean mSurfaceCreated = false;

    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();
            if (mSurfaceCreated) requestLayout();
        }
    }

    public void switchCamera(Camera camera) {
        setCamera(camera);
        try {
            camera.setPreviewDisplay(mHolder);
        } catch (IOException exception) {
            Log.e(TAG, "IOException caused by setPreviewDisplay()", exception);
        }
    }

    @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);
        }

        if (mCamera != null) {
          Camera.Parameters parameters = mCamera.getParameters();
          parameters.setPreviewSize(mPreviewSize.width, mPreviewSize.height);

          mCamera.setParameters(parameters);
        }
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        if (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);
        }
        if (mPreviewSize == null) requestLayout();
        mSurfaceCreated = true;
    }

    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();
    }

}