[코틀린] 공부1

findView..

Toast

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val btn : Button = findViewById(R.id.button)
        val tv : TextView = findViewById(R.id.textView)
        val etv : EditText = findViewById(R.id.editText)

        etv.addTextChangedListener(object : TextWatcher {
            override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {
            }

            override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {
                tv.text = etv.text
                if (etv.text.length >= 6)
                    btn.visibility = View.VISIBLE
                else
                    btn.visibility = View.INVISIBLE
            }

            override fun afterTextChanged(s: Editable?) {
            }

        })

        btn.setOnClickListener {
            Toast.makeText(this, tv.text, Toast.LENGTH_SHORT).show()
        }

    }
}