Android 创建自己的Camera App

在sdk中找到/sdk/docs/guide/topics/media/camera.html#custom-camera，里面有详细的api参考

在清单文件中添加相应的权限：

    
    <uses-permission android:name="android.permission.CAMERA" />
    <uses-feature android:name="android.hardware.camera" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.RECORD_AUDIO" />
    

按照官方文档，分为下面几步：

• Detect and Access Camera - Create code to check for the existence of cameras and request access.
• Create a Preview Class - Create a camera preview class that extends SurfaceView and implements theSurfaceHolder interface. This class previews the live images from the camera.
• Build a Preview Layout - Once you have the camera preview class, create a view layout that incorporates the preview and the user interface controls you want.
• Setup Listeners for Capture - Connect listeners for your interface controls to start image or video capture in response to user actions, such as pressing a button.
• Capture and Save Files - Setup the code for capturing pictures or videos and saving the output.
• Release the Camera - After using the camera, your application must properly release it for use by other applications.

接下来分别实现：

1、检查设备是否有照相机

    /** 检查设备是否存在照相机 */
    private boolean checkCameraHardware(Context context) {
        if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA)){
            // this device has a camera
            return true;
        } else {
            // no camera on this device
            return false;
        }
    }
    

2、得到一个照相机

 /** 一种安全的方式获取Cameer对象的实例. */
    public static Camera getCameraInstance(){
        Camera c = null;
        try {
            c = Camera.open(); // attempt to get a Camera instance
        }
        catch (Exception e){
            // Camera is not available (in use or does not exist)
        }
        return c; // returns null if camera is unavailable
    }

3、新建一个名为CameraPreview的类

package com.wuyudong.mycamera;

import java.io.IOException;

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

/** A basic Camera preview class */
public class CameraPreview extends SurfaceView implements
        SurfaceHolder.Callback {
    private static final String TAG = "CameraPreview";
    private SurfaceHolder mHolder;
    private Camera mCamera;

    public CameraPreview(Context context, Camera camera) {
        super(context);
        mCamera = camera;

        // Install a SurfaceHolder.Callback so we get notified when the
        // underlying surface is created and destroyed.
        mHolder = getHolder();
        mHolder.addCallback(this);
        // deprecated setting, but required on Android versions prior to 3.0
        mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }

    public void surfaceCreated(SurfaceHolder holder) {
        // The Surface has been created, now tell the camera where to draw the
        // preview.
        try {
            mCamera.setPreviewDisplay(holder);
            mCamera.startPreview();
        } catch (IOException e) {
            Log.d(TAG, "Error setting camera preview: " + e.getMessage());
        }
    }

    public void surfaceDestroyed(SurfaceHolder holder) {
        // empty. Take care of releasing the Camera preview in your activity.
    }

    public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
        // If your preview can change or rotate, take care of those events here.
        // Make sure to stop the preview before resizing or reformatting it.

        if (mHolder.getSurface() == null) {
            // preview surface does not exist
            return;
        }

        // stop preview before making changes
        try {
            mCamera.stopPreview();
        } catch (Exception e) {
            // ignore: tried to stop a non-existent preview
        }

        // set preview size and make any resize, rotate or
        // reformatting changes here

        // start preview with new settings
        try {
            mCamera.setPreviewDisplay(mHolder);
            mCamera.startPreview();

        } catch (Exception e) {
            Log.d(TAG, "Error starting camera preview: " + e.getMessage());
        }
    }
}

4、设置一个预览功能的layout，将原来布局文件中的内容替换成下面的代码

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
  <FrameLayout
    android:id="@+id/camera_preview"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_weight="1"
    />

  <Button
    android:id="@+id/button_capture"
    android:text="Capture"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    />
</LinearLayout>

5、在清单文件中加入 android:screenOrientation="landscape" 调整相机为横向拍摄

6、在MainActivity中添加

public class MainActivity extends Activity {

    private Camera mCamera;
    private CameraPreview mPreview;

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

        // Create an instance of Camera
        mCamera = getCameraInstance();

        // Create our Preview view and set it as the content of our activity.
        mPreview = new CameraPreview(this, mCamera);
        FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
        preview.addView(mPreview);
    }
}

7、实现拍摄按钮的功能

（1）添加拍照回调方法

    private PictureCallback mPicture = new PictureCallback() {

        @Override
        public void onPictureTaken(byte[] data, Camera camera) {

            File pictureFile = new File("/sdcard/" + System.currentTimeMillis()+".jpg");
            try {
                FileOutputStream fos = new FileOutputStream(pictureFile);
                fos.write(data);
                fos.close();
            } catch (IOException e) {
                Log.d("TAG", "Error accessing file: " + e.getMessage());
            }
        }
    };

给拍照按钮添加注册事件：

        // Add a listener to the Capture button
        Button captureButton = (Button) findViewById(R.id.button_capture);
        captureButton.setOnClickListener(
            new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    // get an image from the camera
                    mCamera.takePicture(null, null, mPicture);
                }
            }
        );

完整的代码如下：

package com.wuyudong.mycamera;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.sql.Date;

import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.content.pm.PackageManager;
import android.hardware.Camera;
import android.hardware.Camera.AutoFocusCallback;
import android.hardware.Camera.PictureCallback;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.FrameLayout;

public class MainActivity extends Activity {

    private Camera mCamera;
    private CameraPreview mPreview;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // 创建一个 Camera 的实例
        mCamera = getCameraInstance();

        // 创建一个预览界面
        mPreview = new CameraPreview(this, mCamera);
        FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
        preview.addView(mPreview);
        
        // Add a listener to the Capture button
        Button captureButton = (Button) findViewById(R.id.button_capture);
        captureButton.setOnClickListener(
            new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    mCamera.autoFocus(new AutoFocusCallback() {  // 对焦
                        
                        @Override
                        public void onAutoFocus(boolean success, Camera camera) {
                            // get an image from the camera
                            mCamera.takePicture(null, null, mPicture);
                            
                        }
                    });
                    
                }
            }
        );
    }

    /** 检查设备是否存在照相机 */
    private boolean checkCameraHardware(Context context) {
        if (context.getPackageManager().hasSystemFeature(
                PackageManager.FEATURE_CAMERA)) {
            // this device has a camera
            return true;
        } else {
            // no camera on this device
            return false;
        }
    }

    /** 一种安全的方式获取Cameer对象的实例. */
    public static Camera getCameraInstance() {
        Camera c = null;
        try {
            c = Camera.open(); // attempt to get a Camera instance
        } catch (Exception e) {
            // Camera is not available (in use or does not exist)
        }
        return c; // returns null if camera is unavailable
    }
    
    private PictureCallback mPicture = new PictureCallback() {

        @Override
        public void onPictureTaken(byte[] data, Camera camera) {

            File pictureFile = new File("/sdcard/" + System.currentTimeMillis()+".jpg");
            try {
                FileOutputStream fos = new FileOutputStream(pictureFile);
                fos.write(data);
                fos.close();
            } catch (IOException e) {
                Log.d("TAG", "Error accessing file: " + e.getMessage());
            }
        }
    };
    
    protected void onDestory() {
        if(mCamera != null) {    //释放资源
            mCamera.release();
            mCamera = null;
        }
    }

}