写一个Qt c++调用java操作安卓手机进行扫描二维码的程序

好的，下面是一个简单的示例程序：

首先，我们需要在Qt中使用Java Native Interface（JNI）来调用Java代码。在Qt中，我们可以使用QAndroidJniObject类来实现这一点。

接下来，我们需要使用Android SDK中的ZXing库来实现二维码扫描。为了使用ZXing，我们需要在Qt中导入ZXing库的Java代码。

因此，我们需要在Qt工程中添加以下文件：

1. ZXing Android库文件

将ZXing库的Android代码导入到Qt工程中。这可以通过将zxing-core-3.3.3.jar文件（或最新版本）复制到Qt工程的android/libs目录中来实现。

2. Java代码

package com.example.qrcode;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.DecodeHintType;
import com.google.zxing.Result;
import com.google.zxing.client.android.BeepManager;
import com.google.zxing.client.android.CaptureActivityHandler;
import com.google.zxing.client.android.DecodeFormatManager;
import com.google.zxing.client.android.DecodeHintManager;
import com.google.zxing.client.android.InactivityTimer;
import com.google.zxing.client.android.IntentSource;
import com.google.zxing.client.android.PreferencesActivity;
import com.google.zxing.client.android.ResultHandler;
import com.google.zxing.client.android.ResultHandlerFactory;
import com.google.zxing.client.android.camera.CameraManager;
import com.google.zxing.client.android.result.ResultHandler;
import com.google.zxing.client.android.result.ResultHandlerFactory;

import java.io.IOException;
import java.util.ArrayList;
import java.util.EnumMap;
import java.util.List;
import java.util.Map;

public class ScanActivity extends Activity implements SurfaceHolder.Callback {
    private static final String TAG = ScanActivity.class.getSimpleName();

    private CaptureActivityHandler handler;
    private CameraManager cameraManager;
    private Result savedResultToShow;
    private ViewfinderView viewfinderView;
    private TextView statusView;
    private Button buttonBack;
    private BeepManager beepManager;
    private InactivityTimer inactivityTimer;
    private List<BarcodeFormat> decodeFormats;
    private Map<DecodeHintType, ?> decodeHints;
    private String characterSet;
    private IntentSource source;

    /**
     * 当活动首次创建时调用。
     */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_scan);

        // 初始化相机管理器
        cameraManager = new CameraManager(getApplication());

        viewfinderView = (ViewfinderView) findViewById(R.id.viewfinder_view);
        statusView = (TextView) findViewById(R.id.status_view);
        buttonBack = (Button) findViewById(R.id.button_back);

        beepManager = new BeepManager(this);
        inactivityTimer = new InactivityTimer(this);

        // 显示返回按钮
        buttonBack.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                finish();
            }
        });
    }

    /**
     * 当活动已经可见时调用。
     */
    @Override
    public void onResume() {
        super.onResume();

        handler = null;
        savedResultToShow = null;

        // 初始化相机视图
        SurfaceView surfaceView = (SurfaceView) findViewById(R.id.preview_view);
        SurfaceHolder surfaceHolder = surfaceView.getHolder();
        if (surfaceHolder == null) {
            throw new IllegalStateException("No SurfaceHolder?");
        }

        if (cameraManager.isOpen()) {
            Log.w(TAG, "initCamera() while already open -- late SurfaceView callback?");
            return;
        }

        try {
            cameraManager.openDriver(surfaceHolder);
            // 创建捕获活动处理程序
            if (handler == null) {
                handler = new CaptureActivityHandler(this, decodeFormats, decodeHints, characterSet, cameraManager);
            }
            decodeOrStoreSavedBitmap(null, null);
        } catch (IOException ioe) {
            Log.w(TAG, ioe);
            displayFrameworkBugMessageAndExit();
        } catch (RuntimeException e) {
            Log.w(TAG, "Unexpected error initializing camera", e);
            displayFrameworkBugMessageAndExit();
        }

        // 启动电源管理器和闪光灯
        beepManager.updatePrefs();
        inactivityTimer.onResume();
        source = IntentSource.NONE;
        decodeFormats = null;
        characterSet = null;
    }

    /**
     * 当活动不再可见时调用。
     */
    @Override
    public void onPause() {
        if (handler != null) {
            handler.quitSynchronously();
            handler = null;
        }
        inactivityTimer.onPause();
        beepManager.close();
        cameraManager.closeDriver();
        if (!hasSurface) {
            SurfaceView surfaceView = (SurfaceView) findViewById(R.id.preview_view);
            SurfaceHolder surfaceHolder = surfaceView.getHolder();
            surfaceHolder.removeCallback(this);
        }
        super.onPause();
    }

    /**
     * 当活动被销毁时调用。
     */
    @Override
    public void onDestroy() {
        inactivityTimer.shutdown();
        super.onDestroy();
    }

    /**
     * 处理扫描结果。
     *
     * @param rawResult 扫描结果
     * @param barcode   扫描结果的位图
     */
    public void handleDecode(Result rawResult, com.google.zxing.Result barcode) {
        inactivityTimer.onActivity();
        beepManager.playBeepSoundAndVibrate();
        String result = barcode.getText();

        Toast.makeText(this, result, Toast.LENGTH_SHORT).show();

        // 在状态视图中显示结果
        statusView.setText(barcode.getText());

        // 将结果保存并显示
        savedResultToShow = rawResult;
        ResultHandler resultHandler = ResultHandlerFactory.makeResultHandler(this, barcode);
        String displayContents = resultHandler.getDisplayContents();
        if (displayContents != null) {
            statusView.setText(displayContents);
        }

        // 将扫描结果返回给Qt应用
        QAndroidJniObject jResult = QAndroidJniObject::fromString(result);
        QAndroidJniObject::callStaticMethod<void>("com/example/qrcode/ScanActivity", "onScanResult", "(Ljava/lang/String;)V", jResult.object<jstring>());
    }

    /**
     * 在UI线程上显示有关框架错误的消息，并退出应用程序。
     */
    private void displayFrameworkBugMessageAndExit() {
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle(getString(R.string.app_name));
        builder.setMessage(getString(R.string.msg_camera_framework_bug));
        builder.setPositiveButton(R.string.button_ok, new FinishListener(this));
        builder.setOnCancelListener(new FinishListener(this));
        builder.show();
    }

    /**
     * 将扫描结果返回给Qt应用。
     */
    public static void onScanResult(QString result) {
        emit scanResult(result);
    }
}

3. Qt代码

#include <QtAndroidExtras>
#include <QAndroidJniObject>
#include <QDebug>

...

// 在Android上扫描二维码
void MainWindow::scanQRCode() {
    QAndroidJniObject::callStaticMethod<void>("com/example/qrcode/ScanActivity", "startScan", "()V");
}

// 处理扫描结果
void MainWindow::onScanResult(QString result) {
    qDebug() << "Scan result:" << result;
}

// 处理扫描结果信号
void MainWindow::handleScanResult() {
    QAndroidJniEnvironment env;
    if (env->ExceptionCheck()) {
        env->ExceptionClear();
        return;
    }

    QAndroidJniObject jResult = QAndroidJniObject::callStaticObjectMethod("com/example/qrcode/ScanActivity", "getResult", "()Ljava/lang/String;");
    QString result = jResult.toString();

    if (result.isEmpty()) {
        return;
    }

    onScanResult(result);
}

...

// 连接到扫描结果信号
connect(this, SIGNAL(scanResult(QString)), this, SLOT(onScanResult(QString)));

// 请求获取Android权限
QtAndroid::PermissionResultCallback callback = [](const QtAndroid::PermissionResult &result) {
    if (result == QtAndroid::PermissionResult::Granted) {
        // 已授权
        scanQRCode();
    } else {
        // 未授权
        qDebug() << "Permission denied!";
    }
};

QtAndroid::requestPermissionsSync(QStringList() << "android.permission.CAMERA", callback);

...

这个程序将会请求获取相机权限，然后启动扫描二维码的Activity。扫描结果将被传递回Qt应用程序中的槽函数中。