Android onActivityResult 未调用/触发

Question

我阅读了很多关于 onActivityResult 问题的信息，但似乎没有一个所描述的问题适合我，例如在 startActivityForResult 或其他内容中放置一个否定的 requestCode。

我正在使用我的 Activity 中的相机，它将其预览流式传输到 SurfaceView。拍照后，我关闭凸轮释放其资源，调用 setResult(RESULT_OK, DataIntent) 并希望 onActivityResult 在我的 parent 中触发。

但事实并非如此。如果我在子 Activity 的 onCreate 中设置结果并在 onCreate 中完成子，则结果不会传递给 onActivityResult。

onActivityResult 没有被触发的可能原因是什么？我会写下我的一些来源，以了解我在做什么......

public class MainActivity extends Activity {
    Button mButtonScan;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        mButtonScan = (Button)findViewById(R.id.main_btn_scan);
    }

    /**
    * OnClick Event called from main.xml
    * @param v View that called that onClickEvent
    */
    public void btnCaptureClick(View v) {
        Intent intent = new Intent(this, CaptureActivity.class);
        startActivityForResult(intent, Constants.REQUEST_CODE_CAPTURE);
    }

    /**
    * callback for this Activity. Called when an Activity which was started by
    * this.startActivityForResult(intent, requestCode) sets its result and calls finish()
    */
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        String foo = "foo";
        switch (requestCode) {
            case Constants.REQUEST_CODE_CAPTURE:
                switch (resultCode) {
                    case RESULT_FIRST_USER:
                        Toast.makeText(this, data.getStringExtra(Config.SCAN_RESULT_TEXT), Toast.LENGTH_LONG).show();
                        break;
                    case RESULT_CANCELED:
                        break;
                    default:
                        break;
                }
                break;

            default:
                super.onActivityResult(requestCode, resultCode, data);
                break;
        }
    }
}


public class CaptureActivity extends Activity implements ActivityCallback, SurfaceHolder.Callback, PreviewCallback {

    private Preview mPreview;
    private Camera mCam;
    private SurfaceHolder mHolder;
    private Size size;

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.capture);

        mPreview = (Preview)findViewById(R.id.capture_preview); 
    }

    @Override
    public void onValidDecodeResult(Result rawResult, Bitmap barcode) {
        Intent intent = new Intent();
        if (rawResult != null && barcode != null) {
            intent.putExtra(Config.SCAN_RESULT_TEXT, rawResult.getText());
            intent.putExtra(Config.SCAN_RESULT_FORMAT, rawResult.getBarcodeFormat().getName());
            intent.putExtra(Config.SCAN_RESULT_BMP, barcode);
        } else {
            intent.putExtra(Config.SCAN_RESULT_TEXT, "foo");
            intent.putExtra(Config.SCAN_RESULT_FORMAT, "bar");
            intent.putExtra(Config.SCAN_RESULT_BMP, "barcode");
        }
        mPreview = null;
        setResult(Activity.RESULT_FIRST_USER, intent);
        finish();   
    }

    @Override
    public void onPreviewFrame(byte[] data, Camera camera) {
        MultiFormatReader reader = new MultiFormatReader();     
        PlanarYUVLuminanceSource source = new PlanarYUVLuminanceSource(data, size.width, size.height, 160, 60, 480, 360);
        GlobalHistogramBinarizer binarizer = new GlobalHistogramBinarizer(source);
        BinaryBitmap bb = new BinaryBitmap(binarizer);
        Result result = null;
        try {
            result = reader.decode(bb);
        } catch (NotFoundException e) {
            //do NOTHING cause e == null
        } catch (Exception e){
            e.printStackTrace();
        } finally {
            reader.reset();
        }
        if (result != null) {
            mCam.stopPreview();
            releaseCameraResources();
            onValidDecodeResult(result, source.renderCroppedGreyscaleBitmap());
        } else {
            camera.setOneShotPreviewCallback(this);
        }       
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        try {
            mCam = Camera.open();
            mCam.setPreviewDisplay(mPreview.getHolder());
        } catch (IOException e) {
            releaseCameraResources();
            e.printStackTrace();
        }           
    }

    private void releaseCameraResources() {
        mCam.release();
        mCam = null;
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width,
        int height) {
        //begin Preview
        Camera.Parameters parameters = mCam.getParameters();

        List<Size> sizes = parameters.getSupportedPreviewSizes();

        size = getOptimalPreviewSize(sizes, width, height);
        parameters.setPreviewSize(size.width, size.height);

        mCam.setParameters(parameters);
        mCam.startPreview();
        mCam.setOneShotPreviewCallback(this);
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        if (mCam != null) {
            mCam.stopPreview();
            releaseCameraResources();
        }   
    }

    private Size getOptimalPreviewSize(List<Size> sizes, int width, int height) {
        final double ASPECT_TOLERANCE = 0.05;
        double targetRatio = (double) width / height;

        if (sizes == null) return null; 
            Size optimalSize = null;
            double minDiff = Double.MAX_VALUE;

            int targetHeight = height;

            for (Size size: sizes) {
                double ratio = (double) size.width / size.height;
                if(Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE) {
                    continue;
                }

                if (Math.abs(size.height - targetHeight) < minDiff) {
                    optimalSize = size;
                    minDiff = Math.abs(size.height - targetHeight);
                }               
            }

            if (optimalSize == null) {
                //cannot find matching aspect-ratio
                minDiff = Double.MAX_VALUE;
                for (Size size : sizes) {
                    if (Math.abs(size.height - targetHeight) < minDiff) {
                        optimalSize = size;
                        minDiff = Math.abs(size.height - targetHeight);
                }
            }
        }
        return optimalSize;
    }
}

Answer 1

确保传递给 startActivityForResult(...) 的数字参数 (requestCode) 为 >=0