I have a custom view written in Kotlin using JvmOverloads that I could have default value.
class MyView @JvmOverloads constructor(
context: Context,
attrs: AttributeSet? = null,
defStyle: Int = 0,
defStyleRes: Int = 0
) : LinearLayout(context, attrs, defStyle, defStyleRes)
All works fine in Android 5.1 and above.
However it crashes in 4.4, since the constructor in 4.4 doesn't have defStyleRes
. How could I have that supported that in 5.1 and above I could have defStyleRes
but not in 4.4, without need to explicitly having 4 constructors defined like we did in Java?
Note: The below would works fine in 4.4, but then we loose the defStyleRes
.
class MyView @JvmOverloads constructor(
context: Context,
attrs: AttributeSet? = null,
defStyle: Int = 0
) : LinearLayout(context, attrs, defStyle)
I got a way of doing so. Just overload the first 3 functions will do, leave the 4th one for Lollipop and above wrap with @TargetApi.
class MyView : LinearLayout {
@JvmOverloads
constructor(context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0)
: super(context, attrs, defStyleAttr)
@TargetApi(Build.VERSION_CODES.LOLLIPOP)
constructor(context: Context, attrs: AttributeSet?, defStyleAttr: Int, defStyleRes: Int)
: super(context, attrs, defStyleAttr, defStyleRes)
}
Best way is to have your class this way.
class MyView : LinearLayout {
@JvmOverloads constructor(context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0) : super(context, attrs, defStyleAttr)
@TargetApi(Build.VERSION_CODES.LOLLIPOP) constructor(context: Context, attrs: AttributeSet?, defStyleAttr: Int, defStyleRes: Int) : super(context, attrs, defStyleAttr, defStyleRes)
}
Just define the constructors like this:
constructor(context: Context) : super(context)
constructor(context: Context, attrs: AttributeSet) : super(context, attrs)
constructor(context: Context, attrs: AttributeSet, defStyleAttr: Int) : super(context, attrs, defStyleAttr)
@TargetApi(21)
constructor(context: Context, attrs: AttributeSet, defStyleAttr: Int, defStyleRes: Int) : super(context, attrs, defStyleAttr, defStyleRes)
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