19、照相机技术

照相机有哪些功能

     Android SDK支持操作Android设备内置的照相机。从Android2.3开始，支持操作多个摄像头（主要指前置摄像头和后置照相机）。通过照相机可以拍照和录像。

编写拍照程序需要考虑哪些方面

是否支持照相机

 

快速拍照和定制拍照

 

存储

照相机涉及到的主要API

Camera

SurfaceView、

MediaRecorder

Intent

拍照和摄像程序可能涉及到的权限和特性

<uses-permission android:name="android.permission.CAMERA" />

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

<uses-permission android:name="android.permission.RECORD_AUDIO" />

<uses-feature android:name="android.hardware.camera" />

DEMO1

拍照Demo

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <Button
        android:id="@+id/btnTakePicture"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="拍照" />

    <ImageView
        android:id="@+id/imageview"
        android:layout_width="320dp"
        android:layout_height="240dp" />

</LinearLayout>

import android.app.Activity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.provider.MediaStore;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;

public class Main extends Activity implements OnClickListener {
    private ImageView imageView;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Button btnTakePicture = (Button) findViewById(R.id.btnTakePicture);
        btnTakePicture.setOnClickListener(this);

        imageView = (ImageView) findViewById(R.id.imageview);
    }

    public void onClick(View view) {
        // 调用系统拍照
        Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
        // 显示拍照窗口
        startActivityForResult(intent, 1);
    }
    
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == 1) {
            if (resultCode == Activity.RESULT_OK) {
                Bitmap cameraBitmap = (Bitmap) data.getExtras().get("data");
                imageView.setImageBitmap(cameraBitmap);
            }
        }
    }

}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="cn.eoe.system.camera" android:versionCode="1"
    android:versionName="1.0">
    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".Main" android:label="@string/app_name">
            <intent-filter>
                  <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>    
    </application>
    <uses-sdk android:minSdkVersion="7" />
</manifest> 

录像Demo

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <Button
        android:id="@+id/btnTakePicture"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="录像" />

    <VideoView
        android:id="@+id/videoview"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</LinearLayout>

import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.MediaController;
import android.widget.VideoView;

public class Main extends Activity implements OnClickListener {
    public VideoView videoView;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        Button btnTakePicture = (Button) findViewById(R.id.btnTakePicture);
        btnTakePicture.setOnClickListener(this);

        videoView = (VideoView) findViewById(R.id.videoview);

    }
    
    public void onClick(View view) {
        Intent intent = new Intent(MediaStore.ACTION_VIDEO_CAPTURE);
        startActivityForResult(intent, 1);
    }

    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == 1) {
            if (resultCode == Activity.RESULT_OK) {
                Uri uri = data.getData();
                Cursor cursor = this.getContentResolver().query(uri, null,
                        null, null, null);

                if (cursor.moveToFirst()) {
                    // 取出路径
                    String videoPath = cursor.getString(cursor
                            .getColumnIndex("_data"));
                    // 加载
                    videoView.setVideoURI(Uri.parse(videoPath));
                    // 设置视频控制控件（停止，快进等）。
                    videoView.setMediaController(new MediaController(this));
                    // 播放。
                    videoView.start();
                }
            }
        }
    }

}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="cn.eoe.record.video" android:versionCode="1"
    android:versionName="1.0">
    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name="Main" android:label="@string/app_name">
            <intent-filter>
                  <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>    
    </application>
    <uses-sdk android:minSdkVersion="7" />
</manifest> 

 

定制拍照程序的步骤

打开照相机：Camera.open

 

创建SurfaceView对象

 

添加回调事件监听器（SurfaceHolder.addCallback）

 

预览（Camera.startPreview）

 

拍照（Camera.takePicture）

检测Android设备是否支持照相机

private boolean checkCameraHardware(Context context) {

    if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA))

    {  return true; }  else  {   return false; }

}

DEMO2

package cn.eoe.custom.camera;

import java.io.File;
import java.io.FileOutputStream;
import java.util.List;

import android.app.Activity;
import android.content.Context;
import android.hardware.Camera;
import android.hardware.Camera.PictureCallback;
import android.hardware.Camera.Size;
import android.os.Bundle;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.view.Window;
import android.view.WindowManager;

public class CustomCameraActivity extends Activity {
    private Camera mCamera;
    private Preview mPreview;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // 设置为全屏
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
        mPreview = new Preview(this);
        setContentView(mPreview);
    }

    protected void onResume() {
        super.onResume();
        // 打开照相机
        mCamera = Camera.open();
        mPreview.setCamera(mCamera);
    }

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

        if (mCamera != null) {
            mCamera.release();
            mCamera = null;
            mPreview.setCamera(null);
        }
    }

    class Preview extends ViewGroup implements SurfaceHolder.Callback,
            OnClickListener {

        SurfaceView mSurfaceView;
        SurfaceHolder mHolder; // 存储事件回掉
        Size mPreviewSize;  // 当前窗口预览尺寸
        List<Size> mSupportedPreviewSizes; // 相机中的预览尺寸
        Camera mCamera;
        Context mContext;  

        public Preview(Context context) {
            super(context);
            mContext = context;
            mSurfaceView = new SurfaceView(context);
            addView(mSurfaceView);
            mHolder = mSurfaceView.getHolder();
            mHolder.addCallback(this);

        }

        public void setCamera(Camera camera) {
            mCamera = camera;
            if (mCamera != null) {
                // 获得当前相机可支持预览的尺寸。
                mSupportedPreviewSizes = mCamera.getParameters()
                        .getSupportedPictureSizes();
                // 调整布局。
                requestLayout();
            }
        }

        private PictureCallback mPictureCallback = new PictureCallback() {

            @Override
            public void onPictureTaken(byte[] data, Camera camera) {
                mCamera.startPreview();
                File pictureFile = new File("/sdcard/image.jpg");
                try {
                    FileOutputStream fos = new FileOutputStream(pictureFile);
                    fos.write(data);
                    fos.close();
                } catch (Exception e) {
                    // TODO: handle exception
                }

            }
        };

        public void onClick(View view) {
            mCamera.takePicture(null, null, mPictureCallback);
        }

        @Override
        public void surfaceChanged(SurfaceHolder holder, int format, int width,
                int height) {
            // 设置预览的尺寸（不支持比如：200 200这种尺寸）。
            Camera.Parameters parameters = mCamera.getParameters();
            parameters.setPreviewSize(mPreviewSize.width, mPreviewSize.height);

            mCamera.setParameters(parameters);
            mCamera.startPreview();  // 预览

        }

        @Override
        public void surfaceCreated(SurfaceHolder holder) {
            try {
                if (mCamera != null) {
                    // 将 Camera和SurfaceView进行一个关联。
                    mCamera.setPreviewDisplay(holder);
                }
            } catch (Exception e) {
                // TODO: handle exception
            }

        }

        @Override
        public void surfaceDestroyed(SurfaceHolder holder) {
            // TODO Auto-generated method stub
            if (mCamera != null) {
                // 停止预览
                mCamera.stopPreview();
            }
        }

        @Override  // 调整预览尺寸。
        protected void onLayout(boolean changed, int l, int t, int r, int b) {
            if (changed && getChildCount() > 0) {  //子视图
                // 获得子视图。
                final View child = getChildAt(0);

                // viewGroup
                int width = r - l;    
                int height = b - t;    

                // 实际窗口尺寸。
                int previewWidth = width;
                int previewHeight = height;

                // mPreviewSize 图像产生的。
                if (mPreviewSize != null) { 
                    // 把前两个初始值覆盖。 
                    previewWidth = mPreviewSize.width;
                    previewHeight = mPreviewSize.height;
                }
                // 手机屏幕的宽高比大于采集图像的宽高比。
                if (width * previewHeight > height * previewWidth) {
                    final int scaledChildWidth = previewWidth * height
                            / previewHeight;
                    // child.layout((width - scaledChildWidth)/2,
                    // 0,(width+scaledChildWidth)/2,height);

                    child.layout(100, 100, 340, 240);
                } else {
                    final int scaledChildHeight = previewHeight * width
                            / previewWidth;
                    child.layout(0, (height - scaledChildHeight) / 2, width,
                            (height + scaledChildHeight) / 2);
                }

            }

        }

        private Size getOptimalPreviewSize(List<Size> sizes, int w, int h) {
            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;

            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);
                }
            }

            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;
        }

        protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
            int width = resolveSize(getSuggestedMinimumWidth(),
                    widthMeasureSpec);
            int height = resolveSize(getSuggestedMinimumHeight(),
                    heightMeasureSpec);

            setMeasuredDimension(width, height);

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

    }

}