<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

     android:layout_width="match_parent"

     android:layout_height="match_parent"

     android:layout_margin="20dp"

     android:orientation="vertical">

     <android.support.design.widget.TextInputLayout

         android:id="@+id/textInput"

         android:layout_width="match_parent"

         android:layout_height="wrap_content">

         <EditText

             android:layout_width="match_parent"

             android:layout_height="wrap_content" />

     </android.support.design.widget.TextInputLayout>

 </LinearLayout>

TextInputLayout textInput = (TextInputLayout) this.findViewById(R.id.textInput);

textInput.setHint("请输入用户名");

         final TextInputLayout textInput = (TextInputLayout) this.findViewById(R.id.textInput);

         textInput.setHint("请输入用户名");

         EditText editText = textInput.getEditText();

         editText.addTextChangedListener(new TextWatcher() {

             @Override

             public void beforeTextChanged(CharSequence s, int start, int count, int after) {}

             @Override

             public void onTextChanged(CharSequence s, int start, int before, int count) {

                 if (s.length() > 10) {

                     textInput.setError("用户名不能超过10位");

                     textInput.setErrorEnabled(true);

                 } else {

                     textInput.setErrorEnabled(false);

                 }

             }

             @Override

             public void afterTextChanged(Editable s) {}

         });