Android Error Label

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:orientation="vertical"
              android:gravity="center_horizontal"
              android:padding="16dp">

    <com.dd.ui.view.ErrorLabelLayout
            android:id="@+id/nameErrorLayout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content">

        <EditText
                android:id="@+id/editFirsName"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:hint="First name"/>

    </com.dd.ui.view.ErrorLabelLayout>

    <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:gravity="center"
            android:orientation="horizontal">

        <Button
                android:id="@+id/btnError"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginRight="8dp"
                android:text="Show error"/>

        <Button
                android:id="@+id/btnClear"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginLeft="8dp"
                android:text="Clear error"/>

    </LinearLayout>

</LinearLayout>

ErrorLabelLayout.java

public class ErrorLabelLayout extends LinearLayout implements ViewGroup.OnHierarchyChangeListener {

    private static final int ERROR_LABEL_TEXT_SIZE = 12;
    private static final int ERROR_LABEL_PADDING = 4;

    private TextView mErrorLabel;
    private Drawable mDrawable;
    private int mErrorColor;

    public ErrorLabelLayout(Context context) {
        super(context);
        initView();
    }

    public ErrorLabelLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
        initView();
    }

    public ErrorLabelLayout(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        initView();
    }

    private void initView() {
        setOnHierarchyChangeListener(this);
        setOrientation(VERTICAL);
        mErrorColor = Color.parseColor("#D32F2F");
        initErrorLabel();
    }

    private void initErrorLabel() {
        mErrorLabel = new TextView(getContext());
        mErrorLabel.setFocusable(true);
        mErrorLabel.setFocusableInTouchMode(true);
        mErrorLabel.setTextSize(ERROR_LABEL_TEXT_SIZE);
        mErrorLabel.setTextColor(mErrorColor);
        mErrorLabel.setPadding(dipsToPix(ERROR_LABEL_PADDING), 0, dipsToPix(ERROR_LABEL_PADDING), 0);
    }

    public void setErrorColor(int color) {
        mErrorColor = color;
        mErrorLabel.setTextColor(mErrorColor);
    }

    public void clearError() {
        mErrorLabel.setVisibility(INVISIBLE);
        mDrawable.clearColorFilter();
    }

    public void setError(String text) {
        mErrorLabel.setVisibility(VISIBLE);
        mErrorLabel.setText(text);
        // tint drawable
        mDrawable.setColorFilter(mErrorColor, PorterDuff.Mode.SRC_ATOP);
        // changing focus from EditText to error label, necessary for Android L only
        // EditText background Drawable is not tinted, until EditText remains focus
        mErrorLabel.requestFocus();
    }

    @Override
    public void onChildViewAdded(View parent, View child) {
        int childCount = getChildCount();
        if (childCount == 1) {
            mDrawable = getChildAt(0).getBackground();
            addView(mErrorLabel);
        }
    }

    @Override
    public void onChildViewRemoved(View parent, View child) {
    }

    private int dipsToPix(float dps) {
        return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dps, getResources().getDisplayMetrics());
    }
}

MainActivity.java

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        final ErrorLabelLayout errorLabelLayout = (ErrorLabelLayout) findViewById(R.id.nameErrorLayout);

        Button btnError = (Button) findViewById(R.id.btnError);
        btnError.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                errorLabelLayout.setError("First name is required");
            }
        });

        Button btnClear = (Button) findViewById(R.id.btnClear);
        btnClear.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                errorLabelLayout.clearError();
            }
        });

        // whenever user click on edit text - remove error
        EditText editFirsName = (EditText) findViewById(R.id.editFirsName);
        editFirsName.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                switch (event.getAction()) {
                    case MotionEvent.ACTION_UP:
                        errorLabelLayout.clearError();
                        break;
                }
                return false;
            }
        });
    }
}

Very nice tutorial and gist! I'm only wondering if you care about state saving? I'm not sure if your instance variables are restored automatically on configuration change.