Add ButtonCompat: a Material-styled button on all versions of Android.

chrome/android/java/src/org/chromium/chrome/browser/widget/ButtonCompat.java

Index: chrome/android/java/src/org/chromium/chrome/browser/widget/ButtonCompat.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/widget/ButtonCompat.java b/chrome/android/java/src/org/chromium/chrome/browser/widget/ButtonCompat.java
new file mode 100644
index 0000000000000000000000000000000000000000..43c17c34709061e60fba0792d2d436b1a8f26fa4
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+++ b/chrome/android/java/src/org/chromium/chrome/browser/widget/ButtonCompat.java
@@ -0,0 +1,130 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.widget;
+
+import android.animation.AnimatorInflater;
+import android.content.Context;
+import android.content.res.TypedArray;
+import android.graphics.Color;
+import android.graphics.PorterDuff;
+import android.graphics.drawable.GradientDrawable;
+import android.os.Build;
+import android.util.AttributeSet;
+import android.view.ContextThemeWrapper;
+import android.widget.Button;
+
+import org.chromium.chrome.R;
+
+/**
+ * A Material-styled button with a customizable background color.
+ *
+ * Create a button in Java:
+ *
+ *   new ButtonCompat(context, Color.RED);
+ *
+ * Create a button in XML:
+ *
+ *   <ButtonCompat
+ *       android:layout_width="wrap_content"
+ *       android:layout_height="wrap_content"
+ *       android:text="Click me"
+ *       chrome:buttonColor="#f00" />
+ *
+ * On L devices, this is a true Material button. On earlier devices, the button is similar but lacks
+ * ripples and lacks a shadow when pressed.
+ */
+public class ButtonCompat extends Button {
+
+    /** The amount by which to dim the button background when pressed. */
+    private static final float PRE_L_DIM_AMOUNT = 0.85f;
+
+    private int mColor;
+
+    /**
+     * Constructs a button with the given buttonColor as its background.
+     */
+    public ButtonCompat(Context context, int buttonColor) {
+        this(context, buttonColor, null);
+    }
+
+    /**
+     * Constructor for inflating from XML.
+     */
+    public ButtonCompat(Context context, AttributeSet attrs) {
+        this(context, getColorFromAttributeSet(context, attrs), attrs);
+    }
+
+    private ButtonCompat(Context context, int buttonColor, AttributeSet attrs) {
+        // To apply the ButtonCompat style to this view, use a ContextThemeWrapper to inject the
+        // ButtonCompat style into the current theme, and pass 0 as the defStyleAttr to the super
+        // constructor to prevent the default Button style from being applied.
+        super(new ContextThemeWrapper(context, R.style.ButtonCompat), attrs, 0);
+
+        getBackground().mutate();
+        setButtonColor(buttonColor);
+
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
+            // Use the StateListAnimator from the Widget.Material.Button style to animate the
+            // elevation when the button is pressed.
+            TypedArray a = getContext().obtainStyledAttributes(null,
+                    new int[]{android.R.attr.stateListAnimator}, 0,
+                    android.R.style.Widget_Material_Button);
+            setStateListAnimator(AnimatorInflater.loadStateListAnimator(getContext(),
+                    a.getResourceId(0, 0)));
+            a.recycle();
+        }
+    }
+
+    /**
+     * Sets the background color of the button.
+     */
+    public void setButtonColor(int color) {
+        mColor = color;
+
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
+            getBackground().setColorFilter(mColor, PorterDuff.Mode.SRC_IN);
+        } else {
+            updateButtonBackgroundPreL();
+        }
+    }
+
+    @Override
+    protected void drawableStateChanged() {
+        super.drawableStateChanged();
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
+            updateButtonBackgroundPreL();
+        }
+    }
+
+    private void updateButtonBackgroundPreL() {
+        int color = mColor;
+        for (int state : getDrawableState()) {
+            if (state == android.R.attr.state_pressed
+                    || state == android.R.attr.state_focused
+                    || state == android.R.attr.state_selected) {
+                color = getActiveColorPreL();
+                break;
+            }
+        }
+
+        GradientDrawable background = (GradientDrawable) getBackground();
+        background.setColor(color);
+    }
+
+    private int getActiveColorPreL() {
+        return Color.rgb(
+                Math.round(Color.red(mColor) * PRE_L_DIM_AMOUNT),
+                Math.round(Color.green(mColor) * PRE_L_DIM_AMOUNT),
+                Math.round(Color.blue(mColor) * PRE_L_DIM_AMOUNT)
+        );
+    }
+
+    private static int getColorFromAttributeSet(Context context, AttributeSet attrs) {
+        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.ButtonCompat, 0, 0);
+        int color = a.getColor(R.styleable.ButtonCompat_buttonColor, Color.WHITE);
+        a.recycle();
+        return color;
+    }
+}