[英]Translate Kotlin code into Java - Understanding the Syntax
I am looking to try to us this piece of code which thanks to Azimuth reading changes to opposite when user holds the phone upright I need to use this code to experiment in Java however i am unsure of how to translate the code below in to Java:我正在尝试向我们尝试这段代码,这要归功于当用户直立手机时方位角读数会发生变化
override fun onSensorChanged(event: SensorEvent) {
if (event.sensor.type != Sensor.TYPE_ROTATION_VECTOR) return
SensorManager.getRotationMatrixFromVector(rotationMatrix, event.values)
val (matrixColumn, sense) = when (val rotation =
activity.windowManager.defaultDisplay.rotation
) {
Surface.ROTATION_0 -> Pair(0, 1)
Surface.ROTATION_90 -> Pair(1, -1)
Surface.ROTATION_180 -> Pair(0, -1)
Surface.ROTATION_270 -> Pair(1, 1)
else -> error("Invalid screen rotation value: $rotation")
}
val x = sense * rotationMatrix[matrixColumn]
val y = sense * rotationMatrix[matrixColumn + 3]
azimuthChanged(-atan2(y, x))
}
If any one could help understand and translate this to Java that would be a big help, it looks fairly simple but i am unsure on the syntax of these lines:如果有人可以帮助理解并将其翻译为 Java 这将是一个很大的帮助,它看起来相当简单,但我不确定这些行的语法:
val (matrixColumn, sense) = when (val rotation =
activity.windowManager.defaultDisplay.rotation
) {
Surface.ROTATION_0 -> Pair(0, 1)
Surface.ROTATION_90 -> Pair(1, -1)
Surface.ROTATION_180 -> Pair(0, -1)
Surface.ROTATION_270 -> Pair(1, 1)
else -> error("Invalid screen rotation value: $rotation")
}
Thanks if you can help.谢谢,如果你能帮忙。
This is using a destructuring declaration, which isn't available in Java, so instead you have to declare two variables and then assign them in a switch
statement, which is analogous to a Kotlin when
statement.这是使用解构声明,这在 Java 中不可用,因此您必须声明两个变量,然后在
switch
语句中分配它们,这类似于 Kotlin when
语句。
int matrixColumn;
int sense;
switch(getActivity().getWindowManager().getDefaultDisplay.getRotation()) {
case Surface.ROTATION_0:
matrixColumn = 0;
sense = 1;
break;
case Surface.ROTATION_90:
matrixColumn = 1;
sense = -1;
break;
case Surface.ROTATION_180:
matrixColumn = 0;
sense = -1;
break;
default: // Surface.ROTATION_270:
matrixColumn = 1;
sense = 1;
break;
}
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