现在大部分的手机都具备自动对焦的拍摄功能，这意味着这些手机可以具备条码扫描的功能，手机具备条码扫描的功能，可以优化购物流程，快速存储电子名片(Android二维码)等。
本文使用ZXing 1.6实现条码/二维码识别。ZXing是个很经典的条码/二维码识别的开源类库，很早就有开发者在J2ME上使用ZXing了，不过要支持JSR-234规范(自动对焦)的手机才能发挥其威力，而目前已经有不少Android手机具备自动对焦的功能。
本文代码运行的结果如下，使用91手机助手截图时，无法截取SurfaceView的实时图像：
本文使用了ZXing1.6的core，即把/zxing-1.6/core/下的src复制覆盖工程的src；另外还要使用到/zxing-1.6/android/下的PlanarYUVLuminanceSource.java。
PS：/zxing-1.6/android/ 是BarcodeScanner的源码，本文程序相当于BarcodeScanner的精简版，只保留最基本的识别功能。
源码目录结果如下图，ChecksumException.java下面还有很多源文件，截图尚未列出：
本文例子必须要开摄像头和自动对焦的权限，不然启动时会报异常，所需权限如下：
<uses-permission android:name="android.permission.CAMERA"></uses-permission>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>
<uses-feature android:name="android.hardware.camera" />
<uses-feature android:name="android.hardware.camera.autofocus" />
main.xml源码如下，main.xml必须要用到FrameLayout才能重叠控件实现 范围框 的效果：
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/FrameLayout01"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<SurfaceView
android:id="@+id/sfvCamera"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
</SurfaceView>
<RelativeLayout
android:id="@+id/RelativeLayout01"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<ImageView
android:id="@+id/ImageView01"
android:layout_width="160dip"
android:layout_height="100dip">
</ImageView>
<View
android:id="@+id/centerView"
android:layout_centerVertical="true"
android:layout_centerHorizontal="true"
android:layout_width="300dip"
android:layout_height="180dip"
android:background="#55FF6666">
</View>
<TextView
android:id="@+id/txtScanResult"
android:layout_centerHorizontal="true"
android:layout_below="@+id/centerView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Scanning..."
android:textColor="#FF000000">
</TextView>
</RelativeLayout>
</FrameLayout>
testCamera.java是主类，负责控制Camera和对图像做解码，源码如下：
package com.testCamera;
import java.util.Timer;
import java.util.TimerTask;
import com.google.zxing.BinaryBitmap;
import com.google.zxing.MultiFormatReader;
import com.google.zxing.Result;
import com.google.zxing.Android.PlanarYUVLuminanceSource;
import com.google.zxing.common.HybridBinarizer;
import android.app.Activity;
import android.graphics.Bitmap;
import android.hardware.Camera;
import android.os.Bundle;
import android.view.SurfaceView;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;
public class testCamera extends Activity {
/** Called when the activity is first created. */
private SurfaceView sfvCamera;
private SFHCamera sfhCamera;
private ImageView imgView;
private View centerView;
private TextView txtScanResult;
private Timer mTimer;
private MyTimerTask mTimerTask;
// 按照标准HVGA
final static int width = 480;
final static int height = 320;
int dstLeft, dstTop, dstWidth, dstHeight;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
this.setTitle("Android条码/二维码识别Demo-----hellogv");
imgView = (ImageView) this.findViewById(R.id.ImageView01);
centerView = (View) this.findViewById(R.id.centerView);
sfvCamera = (SurfaceView) this.findViewById(R.id.sfvCamera);
sfhCamera = new SFHCamera(sfvCamera.getHolder(), width, height,
previewCallback);
txtScanResult = (TextView) this.findViewById(R.id.txtScanResult);
// 初始化定时器
mTimer = new Timer();
mTimerTask = new MyTimerTask();
mTimer.schedule(mTimerTask, 0, 80);
}
class MyTimerTask extends TimerTask {
@Override
public void run() {
if (dstLeft == 0) {// 只赋值一次
dstLeft = centerView.getLeft() * width
/ getWindowManager().getDefaultDisplay().getWidth();
dstTop = centerView.getTop() * height
/ getWindowManager().getDefaultDisplay().getHeight();
dstWidth = (centerView.getRight() - centerView.getLeft())
* width
/ getWindowManager().getDefaultDisplay().getWidth();
dstHeight = (centerView.getBottom() - centerView.getTop())
* height
/ getWindowManager().getDefaultDisplay().getHeight();
}
sfhCamera.AutoFocusAndPreviewCallback();
}
}
/**
* 自动对焦后输出图片
*/
private Camera.PreviewCallback previewCallback = new Camera.PreviewCallback() {
@Override
public void onPreviewFrame(byte[] data, Camera arg1) {
// 取得指定范围的帧的数据
PlanarYUVLuminanceSource source = new PlanarYUVLuminanceSource(
data, width, height, dstLeft, dstTop, dstWidth, dstHeight);
// 取得灰度图
Bitmap mBitmap = source.renderCroppedGreyscaleBitmap();
// 显示灰度图
imgView.setImageBitmap(mBitmap);
BinaryBitmap bitmap = new BinaryBitmap(new HybridBinarizer(source));
MultiFormatReader reader = new MultiFormatReader();
try {
Result result = reader.decode(bitmap);
String strResult = "BarcodeFormat:"
+ result.getBarcodeFormat().toString() + " text:"
+ result.getText();
txtScanResult.setText(strResult);
} catch (Exception e) {
txtScanResult.setText("Scanning");
}
}
};
}
SFHCamera.java是Camera控制类，源码如下：
package com.testCamera;
import java.io.IOException;
import android.graphics.PixelFormat;
import android.hardware.Camera;
import android.util.Log;
import android.view.SurfaceHolder;
public class SFHCamera implements SurfaceHolder.Callback {
private SurfaceHolder holder = null;
private Camera mCamera;
private int width, height;
private Camera.PreviewCallback previewCallback;
public SFHCamera(SurfaceHolder holder, int w, int h,
Camera.PreviewCallback previewCallback) {
this.holder = holder;
this.holder.addCallback(this);
this.holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
width = w;
height = h;
this.previewCallback = previewCallback;
}
@Override
public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) {
Camera.Parameters parameters = mCamera.getParameters();
parameters.setPreviewSize(width, height);// 设置尺寸
parameters.setPictureFormat(PixelFormat.JPEG);
mCamera.setParameters(parameters);
mCamera.startPreview();// 开始预览
Log.e("Camera", "surfaceChanged");
}
@Override
public void surfaceCreated(SurfaceHolder arg0) {
mCamera = Camera.open();// 启动服务
try {
mCamera.setPreviewDisplay(holder);// 设置预览
Log.e("Camera", "surfaceCreated");
} catch (IOException e) {
mCamera.release();// 释放
mCamera = null;
}
}
@Override
public void surfaceDestroyed(SurfaceHolder arg0) {
mCamera.setPreviewCallback(null);
mCamera.stopPreview();// 停止预览
mCamera = null;
Log.e("Camera", "surfaceDestroyed");
}
/**
* 自动对焦并回调Camera.PreviewCallback
*/
public void AutoFocusAndPreviewCallback() {
if (mCamera != null)
mCamera.autoFocus(mAutoFocusCallBack);
}
/**
* 自动对焦
*/
private Camera.AutoFocusCallback mAutoFocusCallBack = new Camera.AutoFocusCallback() {
@Override
public void onAutoFocus(boolean success, Camera camera) {
if (success) { // 对焦成功，回调Camera.PreviewCallback
mCamera.setOneShotPreviewCallback(previewCallback);
}
}
};
}
其中testCamera.java的Camera.PreviewCallback previewCallback 是整个程序的逻辑核心，作为回调函数给SFHCamera.java的内部Camera类调用。
