Test2.java

// find TextInputLayout
TextInputLayout textInputLayout = findViewById(R.id.textInputLayout);

// 隨意設定一個 startIcon
textInputLayout.setStartIconDrawable(R.drawable.ic_check);

// 從 textInputLayout 找出 icon 後隱藏
CheckableImageButton icon = textInputLayout.findViewById(R.id.text_input_start_icon);
icon.setVisibility(View.GONE);

// 自訂文字
TextView tv = new TextView(this);
tv.setText("手機電話");
tv.setTextColor(Color.BLACK);

// 從 textInputLayout 找出主布局: inputFrame
FrameLayout inputFrame = ((FrameLayout) textInputLayout.getChildAt(0));

// 再從 inputFrame 找出顯示 startIcon 的 LinearLayout: startLayout
LinearLayout startLayout = (LinearLayout) inputFrame.getChildAt(inputFrame.getChildCount() - 2);
startLayout.setVerticalGravity(Gravity.CENTER);
startLayout.addView(tv,0);