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

    <uses-feature android:name="android.hardware.camera" /><!-- 拍照的功能 -->

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

 <activity

            android:name=".MainActivity"

            android:label="@string/app_name"

            android:screenOrientation="landscape"><!-- 写死横屏 -->

            <intent-filter>

                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

 </activity>

<?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>

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 {

    public static final String TAG = "camera";

    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.

        //获取surfaceview的控制器

        mHolder = getHolder();

        //创建侦听

        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 {

            //设置摄像头预览界面在holder对应的那个surfaceview

            mCamera.setPreviewDisplay(holder);

            //开始预览

            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());

        }

    }

}

import java.io.File;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

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.os.Bundle;

import android.util.Log;

import android.view.View;

import android.widget.Button;

import android.widget.FrameLayout;

public class MainActivity extends Activity {

    private Camera mCamera;

    private CameraPreview mPreview;

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        if(checkCameraHardware(this)){

            // Create an instance of Camera

            //创建摄像头实例

            mCamera = getCameraInstance();

        } else {

            return;

        }

        // Create our Preview view and set it as the content of our activity.

        //创建预览类的对象

        mPreview = new CameraPreview(this, mCamera);

        FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);

        //把预览类设置为帧布局的子节点

        preview.addView(mPreview);

        //给按钮设置监听

        Button captureButton = (Button) findViewById(R.id.button_capture);

        captureButton.setOnClickListener(

            new View.OnClickListener() {

                @Override

                public void onClick(View v) {

                    //设置聚焦

                    mCamera.autoFocus(new AutoFocusCallback() {

                        @Override

                        public void onAutoFocus(boolean success, Camera camera) {

                             //进行拍照

                            mCamera.takePicture(null, null, mPicture);

                        }

                    });

                }

            }

        );

    }

    /** 检测手机是否有摄像头 */

    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;

        }

    }

    /** 一个获取摄像头对象的安全实例 */

    public static Camera getCameraInstance(){

        Camera c = null;

        try {

            c = Camera.open(); //获取第一个后置摄像头的实例

        }

        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() {

        //拍照时会调用此方法

        //data：照片的字节数组

        @Override

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

            try {

                File pictureFile = new File("sdcard/mr.jpg");

                FileOutputStream fos = new FileOutputStream(pictureFile);

                fos.write(data);

                fos.close();

            } catch (FileNotFoundException e) {

                Log.d(CameraPreview.TAG, "File not found: " + e.getMessage());

            } catch (IOException e) {

                Log.d(CameraPreview.TAG, "Error accessing file: " + e.getMessage());

            } finally {

                //拍照完成后重新进入预览

                camera.startPreview();

            }

        }

    };

}