PressableImageButton.java

package com.loclet.android.views;

/*
 * Copyright 2015 Klaas Klasing (klaas@loclet.com)
 *
 * 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.util.AttributeSet;
import android.view.MotionEvent;
import android.widget.ImageButton;

/**
 * A simple extension of Android's ImageButton that automatically provides
 * a "reasonable" appearance of the button in a pressed and disabled state.
 * <p/>
 * Modify {@link #BG_COLOR_ENABLED} and {@link #BG_COLOR_DISABLED} to
 * your liking. These are the colors that "shine through" the foreground
 * image when the button is pressed or disabled.
 * <p/>
 * If you have an image with transparency and don't want the rectangular
 * button outline to show, set {@code android:background="@null"} in the
 * XML layout.
 */
public class PressableImageButton extends ImageButton {

    private static final int BG_COLOR_ENABLED = 0xff000000;
    private static final int BG_COLOR_DISABLED = 0xffffffff;
    private static final int ALPHA_ENABLED = 255;
    private static final int ALPHA_DISABLED = 127;
    private static final int ALPHA_PRESSED = 127;

    private boolean transparentBackground;

    public PressableImageButton(Context context) {
        super(context);
        init();
    }

    public PressableImageButton(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public PressableImageButton(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {
        if (getBackground() == null)
            transparentBackground = true;
        if (!transparentBackground)
            setBackgroundColor(BG_COLOR_ENABLED);
        setPadding(0, 0, 0, 0);
        if (getDrawable() != null)
            getDrawable().setAlpha(ALPHA_ENABLED);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if (isEnabled()) {
            if (event.getAction() == MotionEvent.ACTION_DOWN)
                getDrawable().setAlpha(ALPHA_PRESSED);
            else if (event.getAction() == MotionEvent.ACTION_UP)
                getDrawable().setAlpha(ALPHA_ENABLED);
        }
        return super.onTouchEvent(event);
    }

    @Override
    public void setEnabled(boolean enabled) {
        if (enabled) {
            if (!transparentBackground)
                setBackgroundColor(BG_COLOR_ENABLED);
            if (getDrawable() != null)
                getDrawable().setAlpha(ALPHA_ENABLED);
        } else {
            if (!transparentBackground)
                setBackgroundColor(BG_COLOR_DISABLED);
            if (getDrawable() != null)
                getDrawable().setAlpha(ALPHA_DISABLED);
        }
        super.setEnabled(enabled);
    }
}