我的项目中需要有一个 QR 扫描仪。我使用 ZBar 来完成这项任务。主要是我对 ZBar git example 给出的示例代码做了一个非常小的改动来完成这项工作。我需要在浏览器（如果是 url）或对话框中（如果是正常信息）显示扫描结果。
除非我在浏览器中扫描二维码后尝试显示 url，否则我的代码在下面给出的每件事都可以正常工作。当我从浏览器返回我的应用程序时，相机视口变黑并保持非活动状态。我试图让相机恢复活动以扫描另一个二维码，但我失败了。我试图在我的 onResume() 函数中重新打开相机，但这会导致错误并强制退出应用程序。请在那个问题上帮助我。
package com.myapp;
import net.sourceforge.zbar.Config;
import net.sourceforge.zbar.Image;
import net.sourceforge.zbar.ImageScanner;
import net.sourceforge.zbar.Symbol;
import net.sourceforge.zbar.SymbolSet;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.ActivityInfo;
import android.hardware.Camera;
import android.hardware.Camera.AutoFocusCallback;
import android.hardware.Camera.PreviewCallback;
import android.hardware.Camera.Size;
import android.net.Uri;
import android.os.Bundle;
import android.os.Handler;
import android.webkit.URLUtil;
import android.widget.FrameLayout;
import com.myapp.CameraPreview;
/* Import ZBar Class files */
public class QRScannerActivity extends Activity
{
private Camera mCamera;
private CameraPreview mPreview;
private Handler autoFocusHandler;
ImageScanner scanner;
private boolean barcodeScanned = false;
private boolean previewing = true;
static {
System.loadLibrary("iconv");
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.qr_scanner_main);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
autoFocusHandler = new Handler();
mCamera = getCameraInstance();
/* Instance barcode scanner */
scanner = new ImageScanner();
scanner.setConfig(0, Config.X_DENSITY, 3);
scanner.setConfig(0, Config.Y_DENSITY, 3);
mPreview = new CameraPreview(this, mCamera, previewCb, autoFocusCB);
FrameLayout preview = (FrameLayout)findViewById(R.id.cameraPreview);
preview.addView(mPreview);
}
@Override
protected void onPause() {
super.onPause();
releaseCamera();
//finish();
}
/** A safe way to get an instance of the Camera object. */
public static Camera getCameraInstance(){
Camera c = null;
try {
c = Camera.open();
} catch (Exception e){
}
return c;
}
private void releaseCamera() {
//Toast.makeText(QRScannerActivity.this, "Paused State", Toast.LENGTH_SHORT).show();
if (mCamera != null) {
previewing = false;
mCamera.setPreviewCallback(null);
mPreview.getHolder().removeCallback(mPreview);
mCamera.release();
mCamera = null;
}
}
private Runnable doAutoFocus = new Runnable() {
public void run() {
if (previewing)
mCamera.autoFocus(autoFocusCB);
}
};
PreviewCallback previewCb = new PreviewCallback() {
public void onPreviewFrame(byte[] data, Camera camera) {
Camera.Parameters parameters = camera.getParameters();
Size size = parameters.getPreviewSize();
Image barcode = new Image(size.width, size.height, "Y800");
barcode.setData(data);
int result = scanner.scanImage(barcode);
String QRScannerResult;
if (result != 0) {
previewing = false;
mCamera.setPreviewCallback(null);
mCamera.stopPreview();
SymbolSet syms = scanner.getResults();
for (Symbol sym : syms) {
QRScannerResult = sym.getData();
showResultAction(QRScannerResult);
barcodeScanned = true;
}
}
}
};
// Mimic continuous auto-focusing
AutoFocusCallback autoFocusCB = new AutoFocusCallback() {
public void onAutoFocus(boolean success, Camera camera) {
autoFocusHandler.postDelayed(doAutoFocus, 1000);
}
};
private void showResultAction(String QRScannerResult){
if (URLUtil.isValidUrl(QRScannerResult)) {
if (barcodeScanned) {
barcodeScanned = false;
mCamera.setPreviewCallback(previewCb);
mCamera.startPreview();
previewing = true;
mCamera.autoFocus(autoFocusCB);
}
Intent i = new Intent(Intent.ACTION_VIEW);
i.setData(Uri.parse(QRScannerResult));
startActivity(i);
}else {
new AlertDialog.Builder(this)
.setTitle("QR Data")
.setMessage(QRScannerResult)
.setPositiveButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
if (barcodeScanned) {
barcodeScanned = false;
mCamera.setPreviewCallback(previewCb);
mCamera.startPreview();
previewing = true;
mCamera.autoFocus(autoFocusCB);
}
}
})
.show();
}
}
}
提前致谢。萨基布