Android Studio has an automated Java-to-Kotlin converter. On some cases, it doesn't work smoothly, which means some manual work is needed.
Here's an example:
private TextView[] dots;
private void addBottomDots(int currentPage) {
dots = new TextView[layouts.length];
int[] colorsActive = getResources().getIntArray(R.array.array_dot_active);
int[] colorsInactive = getResources().getIntArray(R.array.array_dot_inactive);
dotsLayout.removeAllViews();
for (int i = 0; i < dots.length; i++) {
dots[i] = new TextView(getContext());
dots[i].setText(Html.fromHtml("•"));
dots[i].setTextSize(35);
dots[i].setTextColor(colorsInactive[currentPage]);
dotsLayout.addView(dots[i]);
}
if (dots.length > 0)
dots[currentPage].setTextColor(colorsActive[currentPage]);
}
The result of auto-conversion + manual tweaking is:
private var dots: Array<TextView?>? = null
private fun addBottomDots(currentPage: Int) {
dots = arrayOfNulls(layouts!!.size)
val colorsActive = getResources().getIntArray(R.array.array_dot_active)
val colorsInactive = getResources().getIntArray(R.array.array_dot_inactive)
dotsLayout!!.removeAllViews()
for (i in dots!!.indices) {
dots[i] = TextView(getContext()) // part A
dots!![i].text = Html.fromHtml("•") // part B
dots!![i].textSize = 35f
dots!![i].setTextColor(colorsInactive[currentPage])
dotsLayout!!.addView(dots!![i])
}
if (dots!!.size > 0)
dots!![currentPage].setTextColor(colorsActive[currentPage])
}
At part A, Android studio gives this error message:
Only safe (?.) or non-null asserted (!!.) calls are allowed on a nullable receiver of type TextView?
And at part B:
Smart cast to 'Array' is impossible, because 'dots' is a mutable property that could have been changed by this time.
Another case:
public class MyViewPagerAdapter extends PagerAdapter {
private LayoutInflater layoutInflater;
public MyViewPagerAdapter() {
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
layoutInflater = (LayoutInflater) getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View view = layoutInflater.inflate(layouts[position], container, false);
container.addView(view);
return view;
}
}
which converted into:
inner class MyViewPagerAdapter : PagerAdapter() {
private var layoutInflater: LayoutInflater? = null
override fun instantiateItem(container: ViewGroup, position: Int): Any {
layoutInflater = getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE) // part C
val view = layoutInflater!!.inflate(layouts!![position], container, false)
container.addView(view)
return view
}
At part C:
Type mismatch. Required: LayoutInflater? Found: Any!
How to fix this?
Try the following
private var dots: ArrayList<TestView> = ArrayList()
private fun addBottomDots(currentPage: Int) {
val size = layouts?.size ?: 0
val colorsActive = getResources().getIntArray(R.array.array_dot_active)
val colorsInactive = getResources().getIntArray(R.array.array_dot_inactive)
dotsLayout?.removeAllViews()
for (i in 0 until size) {
val textView = TextView(getContext()) // part A
textView.text = Html.fromHtml("•") // part B
textView.textSize = 35f
textView.setTextColor(colorsInactive[currentPage])
dots.add(textView)
dotsLayout?.addView(dots[i])
}
if (dots.size > 0)
dots[currentPage].setTextColor(colorsActive[currentPage])
}
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