chemistry formula on Android

Question

I'm developing an android project and I want to render some chemistry formula.

I wrote the following code and I got the following result.

I create a custom string and show it in a textview.

But my question is this: Is this the best way to do this? And is there another way to handle that?

str = new SpannableString(Html.fromHtml("2H<sup>+</sup> + So<sub size = 2>4</sub><sup size = 2>2-</sup> --> H<sub size =2>2</sub>So<sub size = 2>4</sub>"));
ss1.setSpan(new RelativeSizeSpan(0.6f), 2,3, 0); // set size
ss1.setSpan(new RelativeSizeSpan(0.6f), 8,11, 0); // set size
ss1.setSpan(new RelativeSizeSpan(0.6f), 17,18, 0); // set size
ss1.setSpan(new RelativeSizeSpan(0.6f), 20,21, 0); // set size
TempF.setText(ss1,TextView.BufferType.SPANNABLE);

Answer 1

I had a similar problem to solve. I created a simple library by extending WebView and using JavaScript in the background. https://github.com/RanaRanvijaySingh/EquationView

String strChem = "Chemistry: \\(\\ce{CO2 + C -> 2 CO}\\)";
EquationView equationViewChem = findViewById(R.id.equationViewChem);
equationViewChem.setText(strChem);

In your layout file:

<com.rana.equationview.EquationView
 android:id="@+id/equationViewChem"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"/>

Hope this helps someone.

Answer 2

I don't think there is a better way.

Unfortunately Html.fromHtml() ignores <font size="n"> tags, so these spans need to be added manually, as you have done.