我读了很多关于onActivityResult
的问题,但似乎没有一个描述的问题适合我,比如在startActivityForResult
中放一个负的requestCode或其他东西。
我正在玩我的活动中的摄像头,它将其预览流传输到SurfaceView。拍完照片后,我关闭了摄像头,释放了它的资源,调用了setResult(RESULT_OK, DataIntent)
,并希望在我的父级中触发onActivityResult
。
如果我在子活动的onCreate
中设置了一个结果,并在onCreate中完成子活动,则结果不会传递给onActivityResult。
什么可能的原因是onActivityResult
没有触发?我会写下我的一些来源,以便理解我在做什么……
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;
}
}
发布于 2011-02-18 18:27:07
现在我自己解决了这个问题。
在放弃让onActivityResult
触发之后,我决定通过从MainActivity向CaptureActivity传递一个静态引用来“破解”Android的封装,即使我知道这不是一个好主意。
在finish()
调用之后,用Context.RESULT_CANCELLED
神奇地触发了onActivityResult
...不出所料,因为我不再调用setResult
。
让onActivityResult
被触发我调查了为什么它现在能工作。我发现,这与传递给一个意图的位图有关。如果我将一个Parcellable
位图放入我的resultIntent onActivityResult
中,它永远不会被解雇。
因此,在上面的代码中删除以下代码行将会起作用:
intent.putExtra(Config.SCAN_RESULT_BMP, barcode);
这对我来说没问题,因为我在其他活动中并不需要BitMap。这与其说是一种需求,不如说是一种“特性”。
如果你们中的一些人想要将大数据传递到像Bitmap
这样的Intent
中,可以考虑将其存储在SD上的某个地方,在ParentActivity (How to take a photo by Intent)中从SD读取此Bitmap
时,在Intent中传递路径。
正如here所述,Parcelable
的限制是1MB,因此传递给Intent
的任何更大的内容都将导致内部 TransactionTooLargeException
,并将静默失败
发布于 2014-10-02 21:39:44
确保传递给startActivityForResult(...)
的number参数(requestCode
)为>=0
发布于 2011-05-14 22:16:51
也有同样的问题。检查您的清单,确保您使用的不是单个实例:
android:launchMode="singleInstance"
https://stackoverflow.com/questions/5019711
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