FloatLabelLayout.java

/*
 * Copyright (c) 2014. Marshal Chen.
 */

package com.marshalchen.common.ui;


import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.content.Context;
import android.content.res.TypedArray;
import android.text.Editable;
import android.text.TextUtils;
import android.text.TextWatcher;
import android.util.AttributeSet;
import android.util.TypedValue;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.EditText;
import android.widget.FrameLayout;
import android.widget.TextView;
import com.marshalchen.common.R;

/**
 * Created by cym on 14-8-2.
 */
public class FloatLabelLayout extends FrameLayout{
        private static final long ANIMATION_DURATION = 150;

        private static final float DEFAULT_PADDING_LEFT_RIGHT_DP = 12f;

        private EditText mEditText;
        private TextView mLabel;

        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);

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

            final int sidePadding = a.getDimensionPixelSize(
                    R.styleable.FloatLabelLayout_floatLabelSidePadding,
                    dipsToPix(DEFAULT_PADDING_LEFT_RIGHT_DP));
            mLabel = new TextView(context);
            mLabel.setPadding(sidePadding, 0, sidePadding, 0);
            mLabel.setVisibility(INVISIBLE);

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

            addView(mLabel, LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);

            a.recycle();
        }

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

                // Update the layout params so that the EditText is at the bottom, with enough top
                // margin to show the label
                final LayoutParams lp = new LayoutParams(params);
                lp.gravity = Gravity.BOTTOM;
                lp.topMargin = (int) mLabel.getTextSize();
                params = lp;

                setEditText((EditText) child);
            }

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

        private void setEditText(EditText editText) {
            mEditText = editText;

            // Add a TextWatcher so that we know when the text input has changed
            mEditText.addTextChangedListener(new TextWatcher() {

                @Override
                public void afterTextChanged(Editable s) {
                    if (TextUtils.isEmpty(s)) {
                        // The text is empty, so hide the label if it is visible
                        if (mLabel.getVisibility() == View.VISIBLE) {
                            hideLabel();
                        }
                    } else {
                        // The text is not empty, so show the label if it is not visible
                        if (mLabel.getVisibility() != View.VISIBLE) {
                            showLabel();
                        }
                    }
                }

                @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) {
                    mLabel.setActivated(focused);
                }
            });

            mLabel.setText(mEditText.getHint());
        }

        /**
         * @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;
        }

        /**
         * Show the label using an animation
         */
        private void showLabel() {
            mLabel.setVisibility(View.VISIBLE);
            mLabel.setAlpha(0f);
            mLabel.setTranslationY(mLabel.getHeight());
            mLabel.animate()
                    .alpha(1f)
                    .translationY(0f)
                    .setDuration(ANIMATION_DURATION)
                    .setListener(null).start();
        }

        /**
         * Hide the label using an animation
         */
        private void hideLabel() {
            mLabel.setAlpha(1f);
            mLabel.setTranslationY(0f);
            mLabel.animate()
                    .alpha(0f)
                    .translationY(mLabel.getHeight())
                    .setDuration(ANIMATION_DURATION)
                    .setListener(new AnimatorListenerAdapter() {
                        @Override
                        public void onAnimationEnd(Animator animation) {
                            mLabel.setVisibility(View.GONE);
                        }
                    }).start();
        }

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