attrs.xml

<!-- 
    Copyright (C) 2014 Chris Banes

    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at
  
         http://www.apache.org/licenses/LICENSE-2.0
  
    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
-->

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <declare-styleable name="FloatLabelLayout">
        <attr name="floatLabelTextAppearance" format="reference" />
        <attr name="floatLabelPaddingLeft" format="reference|dimension" />
        <attr name="floatLabelPaddingRight" format="reference|dimension" />
        <attr name="floatLabelPaddingTop" format="reference|dimension" />
        <attr name="floatLabelPaddingBottom" format="reference|dimension" />
        <!-- The hint to display in the floating label -->
        <attr name="floatLabelHint" format="reference|string" />
    </declare-styleable>

</resources>

example_colors-float_label.xml

<?xml version="1.0" encoding="utf-8"?>

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

    <!-- The color when activated/focused (usually your app's accent color) -->
    <item android:color="..." android:state_activated="true" />

    <!-- The color when not activated/focused (usually android:textColorSecondary) -->
    <item android:color="..." />

</selector>

example_layout.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              xmlns:app="http://schemas.android.com/apk/res-auto"
              android:orientation="vertical"
              android:layout_width="match_parent"
              android:layout_height="match_parent">

    <your.package.FloatLabelLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:floatLabelTextAppearance="@style/TextAppearance.YourApp.FloatLabel">

        <EditText
            android:id="@+id/edit_username"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="@string/account_username_hint"
            android:singleLine="true"
            android:inputType="textNoSuggestions"
            android:imeOptions="actionNext"
            android:nextFocusDown="@+id/edit_password" />

    </your.package.FloatLabelLayout>

    <your.package.FloatLabelLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:floatLabelTextAppearance="@style/TextAppearance.YourApp.FloatLabel">

        <EditText
            android:id="@+id/edit_password"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="@string/account_password_hint"
            android:singleLine="true"
            android:inputType="textNoSuggestions"
            android:imeOptions="actionDone" />

    </your.package.FloatLabelLayout>

</LinearLayout>

example_styles.xml

<?xml version="1.0" encoding="utf-8"?>

<resources>

    <style name="TextAppearance.YourApp.FloatLabel" parent="android:TextAppearance.Small">
        <item name="android:textColor">@color/float_label</item>
        <item name="android:textSize">12sp</item>
    </style>

</resources>

FloatLabelLayout.java

/*
 * Copyright 2015 Chris Banes, Alex Facciorusso
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Color;
import android.graphics.PorterDuff;
import android.graphics.drawable.Drawable;
import android.support.annotation.NonNull;
import android.support.annotation.StringRes;
import android.support.v4.view.ViewCompat;
import android.support.v4.view.ViewPropertyAnimatorListenerAdapter;
import android.support.v4.view.animation.FastOutSlowInInterpolator;
import android.text.Editable;
import android.text.TextUtils;
import android.text.TextWatcher;
import android.util.AttributeSet;
import android.util.TypedValue;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.Interpolator;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.TextView;


/**
 * Layout which an {@link android.widget.EditText} to show a floating label when the hint is hidden
 * due to the user inputting text.
 *
 * @see <a href="https://dribbble.com/shots/1254439--GIF-Mobile-Form-Interaction">Matt D. Smith on
 * Dribble</a>
 * @see <a href="http://bradfrostweb.com/blog/post/float-label-pattern/">Brad Frost's blog post</a>
 */
public class FloatLabelLayout extends LinearLayout implements ViewGroup.OnHierarchyChangeListener {

    private static final long ANIMATION_DURATION = 150;

    private static final float DEFAULT_LABEL_PADDING_LEFT = 3f;
    private static final float DEFAULT_LABEL_PADDING_TOP = 4f;
    private static final float DEFAULT_LABEL_PADDING_RIGHT = 3f;
    private static final float DEFAULT_LABEL_PADDING_BOTTOM = 4f;

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

    private EditText mEditText;
    private TextView mLabel;

    private CharSequence mHint;
    private Interpolator mInterpolator;

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

    public FloatLabelLayout(Context context) {
        this(context, null);
    }

    public FloatLabelLayout(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public FloatLabelLayout(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

        setOrientation(VERTICAL);

        final TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.FloatLabelLayout);

        int leftPadding = a.getDimensionPixelSize(
                R.styleable.FloatLabelLayout_floatLabelPaddingLeft,
                dipsToPix(DEFAULT_LABEL_PADDING_LEFT));
        int topPadding = a.getDimensionPixelSize(
                R.styleable.FloatLabelLayout_floatLabelPaddingTop,
                dipsToPix(DEFAULT_LABEL_PADDING_TOP));
        int rightPadding = a.getDimensionPixelSize(
                R.styleable.FloatLabelLayout_floatLabelPaddingRight,
                dipsToPix(DEFAULT_LABEL_PADDING_RIGHT));
        int bottomPadding = a.getDimensionPixelSize(
                R.styleable.FloatLabelLayout_floatLabelPaddingBottom,
                dipsToPix(DEFAULT_LABEL_PADDING_BOTTOM));
        mHint = a.getText(R.styleable.FloatLabelLayout_floatLabelHint);

        mLabel = new TextView(context);
        mLabel.setPadding(leftPadding, topPadding, rightPadding, bottomPadding);
        mLabel.setVisibility(INVISIBLE);
        mLabel.setText(mHint);
        ViewCompat.setPivotX(mLabel, 0f);
        ViewCompat.setPivotY(mLabel, 0f);

        mLabel.setTextAppearance(context,
                a.getResourceId(R.styleable.FloatLabelLayout_floatLabelTextAppearance,
                        android.R.style.TextAppearance_Small));
        a.recycle();

        mInterpolator = new FastOutSlowInInterpolator();

        // Error label configuration
        setOnHierarchyChangeListener(this);
        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);
        mErrorLabel.setVisibility(GONE);
    }

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

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

    public void setError(@StringRes int textResId) {
        if (textResId < 0) {
            mErrorLabel.setVisibility(GONE);
            return;
        }

        mErrorLabel.setVisibility(VISIBLE);
        mErrorLabel.setText(textResId);
        tintErrorDrawable();
    }

    private void tintErrorDrawable() {
        mDrawable.setColorFilter(mErrorColor, PorterDuff.Mode.SRC_ATOP);
        mErrorLabel.requestFocus();
    }

    public void setError(String text) {
        if (TextUtils.isEmpty(text)) {
            mErrorLabel.setVisibility(GONE);
            return;
        }

        mErrorLabel.setVisibility(VISIBLE);
        mErrorLabel.setText(text);
        tintErrorDrawable();
    }

    @Override
    public final void addView(@NonNull View child, int index, ViewGroup.LayoutParams params) {
        if (child instanceof EditText) {
            setEditText((EditText) child);
        }

        // Carry on adding the View...
        super.addView(child, index, params);
    }

    private void setEditText(EditText editText) {
        // If we already have an EditText, throw an exception
        if (mEditText != null) {
            throw new IllegalArgumentException("We already have an EditText, can only have one");
        }
        mEditText = editText;

        // Update the label visibility with no animation
        updateLabelVisibility(false);

        // dismiss error on touch
        mEditText.setOnTouchListener(new OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                switch (event.getAction()) {
                    case MotionEvent.ACTION_UP:
                        clearError();
                        break;
                }
                return false;
            }
        });
        // Add a TextWatcher so that we know when the text input has changed
        mEditText.addTextChangedListener(new TextWatcher() {
            @Override
            public void afterTextChanged(Editable s) {
                updateLabelVisibility(true);
            }

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

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {
            }
        });

        // Add focus listener to the EditText so that we can notify the label that it is activated.
        // Allows the use of a ColorStateList for the text color on the label
        mEditText.setOnFocusChangeListener(new OnFocusChangeListener() {
            @Override
            public void onFocusChange(View view, boolean focused) {
                updateLabelVisibility(true);
            }
        });

        // If we do not have a valid hint, try and retrieve it from the EditText
        if (TextUtils.isEmpty(mHint)) {
            setHint(mEditText.getHint());
        }
    }

    private void updateLabelVisibility(boolean animate) {
        boolean hasText = !TextUtils.isEmpty(mEditText.getText());
        boolean isFocused = mEditText.isFocused();

        mLabel.setActivated(isFocused);

        if (hasText || isFocused) {
            // We should be showing the label so do so if it isn't already
            if (mLabel.getVisibility() != VISIBLE) {
                showLabel(animate);
            }
        } else {
            // We should not be showing the label so hide it
            if (mLabel.getVisibility() == VISIBLE) {
                hideLabel(animate);
            }
        }
    }

    /**
     * @return the {@link android.widget.EditText} text input
     */
    public EditText getEditText() {
        return mEditText;
    }

    /**
     * @return the {@link android.widget.TextView} label
     */
    public TextView getLabel() {
        return mLabel;
    }

    /**
     * Set the hint to be displayed in the floating label
     */
    public void setHint(CharSequence hint) {
        mHint = hint;
        mLabel.setText(hint);
    }

    /**
     * Show the label
     */
    private void showLabel(boolean animate) {
        if (animate) {
            mLabel.setVisibility(View.VISIBLE);
            ViewCompat.setTranslationY(mLabel, mLabel.getHeight());

            float scale = mEditText.getTextSize() / mLabel.getTextSize();
            ViewCompat.setScaleX(mLabel, scale);
            ViewCompat.setScaleY(mLabel, scale);

            ViewCompat.animate(mLabel)
                    .translationY(0f)
                    .scaleY(1f)
                    .scaleX(1f)
                    .setDuration(ANIMATION_DURATION)
                    .setListener(null)
                    .setInterpolator(mInterpolator).start();
        } else {
            mLabel.setVisibility(VISIBLE);
        }

        mEditText.setHint(null);
    }

    /**
     * Hide the label
     */
    private void hideLabel(boolean animate) {
        if (animate) {
            float scale = mEditText.getTextSize() / mLabel.getTextSize();
            ViewCompat.setScaleX(mLabel, 1f);
            ViewCompat.setScaleY(mLabel, 1f);
            ViewCompat.setTranslationY(mLabel, 0f);

            ViewCompat.animate(mLabel)
                    .translationY(mLabel.getHeight())
                    .setDuration(ANIMATION_DURATION)
                    .scaleX(scale)
                    .scaleY(scale)
                    .setListener(new ViewPropertyAnimatorListenerAdapter() {
                        @Override
                        public void onAnimationEnd(View view) {
                            mLabel.setVisibility(INVISIBLE);
                            mEditText.setHint(mHint);
                        }
                    })
                    .setInterpolator(mInterpolator).start();
        } else {
            mLabel.setVisibility(INVISIBLE);
            mEditText.setHint(mHint);
        }
    }

    /**
     * Helper method to convert dips to pixels.
     */
    private int dipsToPix(float dps) {
        return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dps,
                getResources().getDisplayMetrics());
    }

    @Override
    public void onChildViewAdded(View parent, View child) {
        int childCount = getChildCount();

        if (childCount == 1) {
            mDrawable = getChildAt(0).getBackground();
            final LayoutParams params = generateDefaultLayoutParams();
            params.width = LayoutParams.WRAP_CONTENT;
            params.height = LayoutParams.WRAP_CONTENT;
            addView(mLabel, 0, params);
            addView(mErrorLabel);
        }
    }

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

    }

    @Override
    protected void onVisibilityChanged(View changedView, int visibility) {
        super.onVisibilityChanged(changedView, visibility);
        if (mEditText != null) {
            mEditText.invalidate();
        }
    }
}