Android example source code file (CameraPreview.java)

This example Android source code file (CameraPreview.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

activity, android, aspect_tolerance, camera, camerapreview, content, hardware, ioexception, list, os, override, preview, size, surfaceholder, surfaceview, ui, view

The CameraPreview.java Android example source code

/*
 * Copyright (C) 2007 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.apis.graphics;

import android.app.Activity;
import android.content.Context;
import android.hardware.Camera;
import android.hardware.Camera.Size;
import android.os.Bundle;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.Window;

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

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

public class CameraPreview extends Activity {
    private Preview mPreview;

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

        // Hide the window title.
        requestWindowFeature(Window.FEATURE_NO_TITLE);

        // Create our Preview view and set it as the content of our activity.
        mPreview = new Preview(this);
        setContentView(mPreview);
    }

}

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

class Preview extends SurfaceView implements SurfaceHolder.Callback {
    SurfaceHolder mHolder;
    Camera mCamera;

    Preview(Context context) {
        super(context);

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

    public void surfaceCreated(SurfaceHolder holder) {
        // The Surface has been created, acquire the camera and tell it where
        // to draw.
        mCamera = Camera.open();
        try {
           mCamera.setPreviewDisplay(holder);
        } catch (IOException exception) {
            mCamera.release();
            mCamera = null;
            // TODO: add more exception handling logic here
        }
    }

    public void surfaceDestroyed(SurfaceHolder holder) {
        // Surface will be destroyed when we return, so stop the preview.
        // Because the CameraDevice object is not a shared resource, it's very
        // important to release it when the activity is paused.
        mCamera.stopPreview();
        mCamera.release();
        mCamera = null;
    }


    private Size getOptimalPreviewSize(List<Size> sizes, int w, int h) {
        final double ASPECT_TOLERANCE = 0.05;
        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();

        List<Size> sizes = parameters.getSupportedPreviewSizes();
        Size optimalSize = getOptimalPreviewSize(sizes, w, h);
        parameters.setPreviewSize(optimalSize.width, optimalSize.height);

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

}