System.arraycopy does not do a deep copy. I just tried it. But it is very fast. <grin>
I setup the timing test. I did 5000 passes over the copy loops; 522 ms for (i=0; i<3; i++) a[i] = b[i].clone(); 453 ms for(i=3; i-->0;) a[i] = b[i].clone(); 447 ms int pos = 0; for(type x; b) a[pos++] = x.clone(); I had written a type.clone() to make the deep copy for each array element. I was surprised that the for_each version did so well. I won't put much faith in the timing differences between it and the subtraction version. Rud http://mysticlakesoftware.blogspot.com/ On Aug 25, 8:00 am, Peli <peli0...@googlemail.com> wrote: > To deep copy an array, you can use > System.arraycopy(..)http://developer.android.com/reference/java/lang/System.html#arraycop... > > System.arraycopy(b, 0, a, 0, 3); > > but for a float array of length 3, you can simply write > a[0]=b[0]; > a[1]=b[1]; > a[2]=b[2]; > > or > for (i=0; i<3; i++) a[i] = b[i]; > > I've never tried to profile which of the 3 ways is actually the > fastest on a real Android device. If someone has the time, please try > all 3 in a tight loop and report back :-) > > (there is also > for(i=3; i-->0;) a[i] = b[i]; > which may be even faster?) > > Note: all assume that you have initialized a already beforehand, > a = new float[3]; > > Peli > > On Aug 25, 8:24 am, Rud <rudmerr...@gmail.com> wrote: > > > > > Hi, > > > The code is originally from my Blog. The reason for the clone is > > explained there. > > > I admit to not having worked with Java enough to have the deep > > understanding of how containers deal with objects. In my application I > > ran into a problem trying to make a copy of an array and had to write > > my own copy. > > > I had a set of data that gets consumed while the app runs. I wanted to > > reset that data at times. I put the data in an array and then cloned > > it to the working array. I was surprised when the original data got > > changed when the cloned data was changed. I also realized that the > > sensor code wasn't doing what I thought it was but haven't taken the > > time to adjust it. > > > How in Java do you actually make a deep copy of an array? > > > Rudhttp://mysticlakesoftware.blogspot.com/ > > > On Aug 21, 7:07 am, Peli <peli0...@googlemail.com> wrote: > > > > > .... = event.values.clone(); > > > > Note that this creates new objects constantly that have to be garbage > > > collected later. Depending on the kind of application, it may be > > > better to just copy the values into a persisting array. > > > > Peliwww.openintents.org > > > > On Aug 21, 4:06 am, mscwd01 <mscw...@gmail.com> wrote: > > > > > Heres my code, which works: > > > > > public void onSensorChanged(SensorEvent event) { > > > > > Sensor sensor = event.sensor; > > > > int type = sensor.getType(); > > > > switch (type) { > > > > case Sensor.TYPE_MAGNETIC_FIELD: > > > > mags = event.values.clone(); > > > > isReady = true; > > > > break; > > > > case Sensor.TYPE_ACCELEROMETER: > > > > accels = event.values.clone(); > > > > break; > > > > case Sensor.TYPE_ORIENTATION: > > > > orients = event.values.clone(); > > > > break; > > > > } > > > > > if (mags != null && accels != null && isReady) { > > > > isReady = false; > > > > > SensorManager.getRotationMatrix(R, I, accels, mags); > > > > SensorManager.remapCoordinateSystem(R, > > > > SensorManager.AXIS_Y, SensorManager.AXIS_MINUS_X, outR); > > > > SensorManager.getOrientation(outR, values); > > > > > azimuth = > > > > getAzimuth(-convert.radToDeg(values[0])); > > > > pitch= convert.radToDeg(values[1]); > > > > roll = -convert.radToDeg(values[2]); > > > > > } > > > > > } > > > > > On Aug 21, 2:39 am, Mike Collins <mike.d.coll...@gmail.com> wrote: > > > > > > I have a sensor event handler that gets fired and I have no problem > > > > > getting and processing acceleration readings. However this code > > > > > always fails. > > > > > > if (event.sensor.getType() == > > > > > Sensor.TYPE_ACCELEROMETER) > > > > > { > > > > > float[] geomagnetic = new float[3]; > > > > > geomagnetic[0] = geomagnetic[1] = > > > > > geomagnetic[2] = 0; > > > > > > float[] r = new float[9]; > > > > > float[] I = new float[9]; > > > > > boolean b = > > > > > SensorManager.getRotationMatrix(r, I, event.values.clone > > > > > (), event.values.clone()); > > > > > if ( ! b) > > > > > { > > > > > Log.e(LOG_TAG, "getRotationMatrix > > > > > failed"); > > > > > return; > > > > > } > > > > > ... > > > > > > tia, > > > > > mike- Hide quoted text - > > > > - Show quoted text -- Hide quoted text - > > - Show quoted text - --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en -~----------~----~----~----~------~----~------~--~---
