cordova-plugin-cszbar-jsg/android/ZBarScannerActivity.java

package org.cloudsky.cordovaPlugins;

import java.io.IOException;

import android.app.Activity;
import android.content.Intent;
import android.content.res.Resources;
import android.hardware.Camera;
import android.hardware.Camera.PreviewCallback;
import android.hardware.Camera.AutoFocusCallback;
import android.os.Bundle;
import android.os.Handler;
import android.view.Gravity;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.ViewGroup;
import android.widget.FrameLayout;
import android.widget.Toast;

import net.sourceforge.zbar.ImageScanner;
import net.sourceforge.zbar.Image;
import net.sourceforge.zbar.Symbol;
import net.sourceforge.zbar.SymbolSet;
import net.sourceforge.zbar.Config;

public class ZBarScannerActivity extends Activity
implements SurfaceHolder.Callback {

    // Config ----------------------------------------------------------
    
    private static int autoFocusInterval = 500; // Interval between AFcallback and next AF attempt.
    
    // Public Constants ------------------------------------------------
    
    public static final String EXTRA_QRVALUE = "qrValue";
    public static final int RESULT_ERROR = RESULT_FIRST_USER + 1;
    
    // State -----------------------------------------------------------
    
    private Camera camera;
    private Handler autoFocusHandler;
    private SurfaceView scannerSurface;
    private SurfaceHolder holder;
    private ImageScanner scanner;
    private int surfW, surfH;

    // For retrieving R.* resources, from the actual app package
    // (we can't use actual.application.package.R.* in our code as we
    // don't know the applciation package name when writing this plugin).
    private String package_name;
    private Resources resources;

    // Static initialisers (class) -------------------------------------
    
    static {
        // Needed by ZBar??
        System.loadLibrary("iconv");
    }
    
    // Activity Lifecycle ----------------------------------------------

    @Override
    public void onCreate (Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);

        // Initiate instance variables
        autoFocusHandler = new Handler();
        scanner = new ImageScanner();
        scanner.setConfig(0, Config.X_DENSITY, 3);
        scanner.setConfig(0, Config.Y_DENSITY, 3);
        
        // Set content view
        setContentView(getResourceId("layout/cszbarscanner"));
        
        // Create preview SurfaceView
        scannerSurface = new SurfaceView (this) {
            @Override
            public void onSizeChanged (int w, int h, int oldW, int oldH) {
                surfW = w;
                surfH = h;
                matchSurfaceToPreviewRatio();
            }
        };
        scannerSurface.setLayoutParams(new FrameLayout.LayoutParams(
            ViewGroup.LayoutParams.MATCH_PARENT,
            ViewGroup.LayoutParams.MATCH_PARENT,
            Gravity.CENTER
        ));
        scannerSurface.getHolder().addCallback(this);
        
        // Add preview SurfaceView to the screen
        ((FrameLayout) findViewById(getResourceId("id/csZbarScannerView"))).addView(scannerSurface);
        findViewById(getResourceId("id/csZbarScannerTitle")).bringToFront();
        findViewById(getResourceId("id/csZbarScannerInstructions")).bringToFront();
    }
    
    @Override
    public void onResume ()
    {
        super.onResume();
        
        try {
            camera = Camera.open();
        } catch (Exception e){
            die("Error: Could not open the camera.");
            return;
        }

        tryStartPreview();
    }
    
    @Override
    public void onPause ()
    {
        releaseCamera();
        super.onPause();
    }
    
    @Override
    public void onDestroy ()
    {
        scanner.destroy();
        super.onDestroy();
    }

    // Event handlers --------------------------------------------------

    @Override
    public void onBackPressed ()
    {
        setResult(RESULT_CANCELED);
        super.onBackPressed();
    }

    // SurfaceHolder.Callback implementation ---------------------------
    
    @Override
    public void surfaceCreated (SurfaceHolder hld)
    {
        tryStopPreview();
        holder = hld;
        tryStartPreview();
    }
    
    @Override
    public void surfaceDestroyed (SurfaceHolder holder)
    {
        // No surface == no preview == no point being in this Activity.
        die("The camera surface was destroyed");
    }
    
    @Override
    public void surfaceChanged (SurfaceHolder hld, int fmt, int w, int h)
    {
        // Sanity check - holder must have a surface...
        if(hld.getSurface() == null) die("There is no camera surface");
        
        surfW = w;
        surfH = h;
        matchSurfaceToPreviewRatio();
        
        tryStopPreview();
        holder = hld;
        tryStartPreview();
    }

    // Continuously auto-focus -----------------------------------------
    
    private AutoFocusCallback autoFocusCb = new AutoFocusCallback()
    {
        public void onAutoFocus(boolean success, Camera camera) {
            autoFocusHandler.postDelayed(doAutoFocus, autoFocusInterval);
        }
    };

    private Runnable doAutoFocus = new Runnable()
    {
        public void run() {
            if(camera != null) camera.autoFocus(autoFocusCb);
        }
    };
    
    // Camera callbacks ------------------------------------------------
    
    // Receives frames from the camera and checks for barcodes.
    private PreviewCallback previewCb = new PreviewCallback()
    {
        public void onPreviewFrame(byte[] data, Camera camera) {
            Camera.Parameters parameters = camera.getParameters();
            Camera.Size size = parameters.getPreviewSize();

            Image barcode = new Image(size.width, size.height, "Y800");
            barcode.setData(data);

            if (scanner.scanImage(barcode) != 0) {
                String qrValue = "";
                
                SymbolSet syms = scanner.getResults();
                for (Symbol sym : syms) {
                    qrValue = sym.getData();
                    
                    // Return 1st found QR code value to the calling Activity.
                    Intent result = new Intent ();
                    result.putExtra(EXTRA_QRVALUE, qrValue);
                    setResult(Activity.RESULT_OK, result);
                    finish();
                }
                
            }
        }
    };
   
    // Misc ------------------------------------------------------------
    
    // finish() due to error
    private void die (String msg)
    {
        setResult(RESULT_ERROR);
        finish();
    }

    private int getResourceId (String typeAndName)
    {
        if(package_name == null) package_name = getApplication().getPackageName();
        if(resources == null) resources = getApplication().getResources();
        return resources.getIdentifier(typeAndName, null, package_name);
    }
    
    // Release the camera resources and state.
    private void releaseCamera ()
    {
        if (camera != null) {
            autoFocusHandler.removeCallbacks(doAutoFocus);
            camera.setPreviewCallback(null);
            camera.release();
            camera = null;
        }
    }
    
    // Match the aspect ratio of the preview SurfaceView with the camera's preview aspect ratio,
    // so that the displayed preview is not stretched/squashed.
    private void matchSurfaceToPreviewRatio () {
        if(camera == null) return;
        if(surfW == 0 || surfH == 0) return;
        
        // Resize SurfaceView to match camera preview ratio (avoid stretching).
        Camera.Parameters params = camera.getParameters();
        Camera.Size size = params.getPreviewSize();
        float previewRatio = (float) size.height / size.width; // swap h and w as the preview is rotated 90 degrees
        float surfaceRatio = (float) surfW / surfH;
        
        if(previewRatio > surfaceRatio) {
            scannerSurface.setLayoutParams(new FrameLayout.LayoutParams(
                surfW,
                Math.round((float) surfW / previewRatio),
                Gravity.CENTER
            ));
        } else if(previewRatio < surfaceRatio) {
            scannerSurface.setLayoutParams(new FrameLayout.LayoutParams(
                Math.round((float) surfH * previewRatio),
                surfH,
                Gravity.CENTER
            ));
        }
    }
    
    // Stop the camera preview safely.
    private void tryStopPreview () {
        // Stop camera preview before making changes.
        try {
            camera.stopPreview();
        } catch (Exception e){
          // Preview was not running. Ignore the error.
        }
    }
    
    // Start the camera preview if possible.
    // If start is attempted but fails, exit with error message.
    private void tryStartPreview () {
        if(holder != null) {
            try {
                // 90 degrees rotation for Portrait orientation Activity.
                camera.setDisplayOrientation(90);
                
                camera.setPreviewDisplay(holder);
                camera.setPreviewCallback(previewCb);
                camera.startPreview();
                camera.autoFocus(autoFocusCb);
            } catch (IOException e) {
                die("Could not start camera preview: " + e.getMessage());
            }
        }
    }
}