ForegroundLinearLayout

attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright (C) 2006 The Android Open Source Project
     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.
-->
<resources>
    <declare-styleable name="ForegroundLinearLayout">
        <!-- Defines the drawable to draw over the content. This can be used as an overlay.
             The foreground drawable participates in the padding of the content if the gravity
             is set to fill. -->
        <attr name="android:foreground" format="reference|color" />
        <!-- Defines the gravity to apply to the foreground drawable. The gravity defaults
             to fill. -->
        <attr name="android:foregroundGravity" format="flag">
            <!-- Push object to the top of its container, not changing its size. -->
            <flag name="top" value="0x30" />
            <!-- Push object to the bottom of its container, not changing its size. -->
            <flag name="bottom" value="0x50" />
            <!-- Push object to the left of its container, not changing its size. -->
            <flag name="left" value="0x03" />
            <!-- Push object to the right of its container, not changing its size. -->
            <flag name="right" value="0x05" />
            <!-- Place object in the vertical center of its container, not changing its size. -->
            <flag name="center_vertical" value="0x10" />
            <!-- Grow the vertical size of the object if needed so it completely fills its container. -->
            <flag name="fill_vertical" value="0x70" />
            <!-- Place object in the horizontal center of its container, not changing its size. -->
            <flag name="center_horizontal" value="0x01" />
            <!-- Grow the horizontal size of the object if needed so it completely fills its container. -->
            <flag name="fill_horizontal" value="0x07" />
            <!-- Place the object in the center of its container in both the vertical and horizontal axis, not changing its size. -->
            <flag name="center" value="0x11" />
            <!-- Grow the horizontal and vertical size of the object if needed so it completely fills its container. -->
            <flag name="fill" value="0x77" />
            <!-- Additional option that can be set to have the top and/or bottom edges of
                 the child clipped to its container's bounds.
                 The clip will be based on the vertical gravity: a top gravity will clip the bottom
                 edge, a bottom gravity will clip the top edge, and neither will clip both edges. -->
            <flag name="clip_vertical" value="0x80" />
            <!-- Additional option that can be set to have the left and/or right edges of
                 the child clipped to its container's bounds.
                 The clip will be based on the horizontal gravity: a left gravity will clip the right
                 edge, a right gravity will clip the left edge, and neither will clip both edges. -->
            <flag name="clip_horizontal" value="0x08" />
            <!-- Push object to the beginning of its container, not changing its size. -->
            <flag name="start" value="0x00800003" />
            <!-- Push object to the end of its container, not changing its size. -->
            <flag name="end" value="0x00800005" />
        </attr>
        <!-- Defines whether the foreground drawable should be drawn inside the padding.
             This property is turned on by default. -->
        <attr name="android:foregroundInsidePadding" format="boolean" />
    </declare-styleable>
</resources>

ForegroundLinearLayout.java

/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * 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.
 */

package your.package;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.support.annotation.NonNull;
import android.support.v4.graphics.drawable.DrawableCompat;
import android.util.AttributeSet;
import android.view.Gravity;
import android.widget.LinearLayout;

import your.package.R;

public class ForegroundLinearLayout extends LinearLayout {
    private Drawable mForeground;

    private final Rect mSelfBounds = new Rect();
    private final Rect mOverlayBounds = new Rect();

    private int mForegroundGravity = Gravity.FILL;

    protected boolean mForegroundInPadding = true;

    boolean mForegroundBoundsChanged = false;

    public ForegroundLinearLayout(Context context) {
        super(context);
    }

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

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

        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.ForegroundLinearLayout,
                defStyle, 0);

        mForegroundGravity = a.getInt(
                R.styleable.ForegroundLinearLayout_android_foregroundGravity, mForegroundGravity);

        final Drawable d = a.getDrawable(R.styleable.ForegroundLinearLayout_android_foreground);
        if (d != null) {
            setForeground(d);
        }

        mForegroundInPadding = a.getBoolean(
                R.styleable.ForegroundLinearLayout_android_foregroundInsidePadding, true);

        a.recycle();
    }

    /**
     * Describes how the foreground is positioned.
     *
     * @return foreground gravity.
     * @see #setForegroundGravity(int)
     */
    public int getForegroundGravity() {
        return mForegroundGravity;
    }

    /**
     * Describes how the foreground is positioned. Defaults to START and TOP.
     *
     * @param foregroundGravity See {@link android.view.Gravity}
     * @see #getForegroundGravity()
     */
    public void setForegroundGravity(int foregroundGravity) {
        if (mForegroundGravity != foregroundGravity) {
            if ((foregroundGravity & Gravity.RELATIVE_HORIZONTAL_GRAVITY_MASK) == 0) {
                foregroundGravity |= Gravity.START;
            }

            if ((foregroundGravity & Gravity.VERTICAL_GRAVITY_MASK) == 0) {
                foregroundGravity |= Gravity.TOP;
            }

            mForegroundGravity = foregroundGravity;


            if (mForegroundGravity == Gravity.FILL && mForeground != null) {
                Rect padding = new Rect();
                mForeground.getPadding(padding);
            }

            requestLayout();
        }
    }

    @Override
    protected boolean verifyDrawable(Drawable who) {
        return super.verifyDrawable(who) || (who == mForeground);
    }

    @Override
    public void jumpDrawablesToCurrentState() {
        super.jumpDrawablesToCurrentState();
        if (mForeground != null) {
            DrawableCompat.jumpToCurrentState(mForeground);
        }
    }

    @Override
    protected void drawableStateChanged() {
        super.drawableStateChanged();
        if (mForeground != null && mForeground.isStateful()) {
            mForeground.setState(getDrawableState());
        }
    }

    /**
     * Supply a Drawable that is to be rendered on top of all of the child
     * views in the frame layout.  Any padding in the Drawable will be taken
     * into account by ensuring that the children are inset to be placed
     * inside of the padding area.
     *
     * @param drawable The Drawable to be drawn on top of the children.
     */
    public void setForeground(Drawable drawable) {
        if (mForeground != drawable) {
            if (mForeground != null) {
                mForeground.setCallback(null);
                unscheduleDrawable(mForeground);
            }

            mForeground = drawable;

            if (drawable != null) {
                setWillNotDraw(false);
                drawable.setCallback(this);
                if (drawable.isStateful()) {
                    drawable.setState(getDrawableState());
                }
                if (mForegroundGravity == Gravity.FILL) {
                    Rect padding = new Rect();
                    drawable.getPadding(padding);
                }
            } else {
                setWillNotDraw(true);
            }
            requestLayout();
            invalidate();
        }
    }

    /**
     * Returns the drawable used as the foreground of this FrameLayout. The
     * foreground drawable, if non-null, is always drawn on top of the children.
     *
     * @return A Drawable or null if no foreground was set.
     */
    public Drawable getForeground() {
        return mForeground;
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
        if (changed) {
            mForegroundBoundsChanged = true;
        }
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        mForegroundBoundsChanged = true;
    }

    @Override
    public void draw(@NonNull Canvas canvas) {
        super.draw(canvas);

        if (mForeground != null) {
            final Drawable foreground = mForeground;

            if (mForegroundBoundsChanged) {
                mForegroundBoundsChanged = false;
                final Rect selfBounds = mSelfBounds;
                final Rect overlayBounds = mOverlayBounds;

                final int w = getRight() - getLeft();
                final int h = getBottom() - getTop();

                if (mForegroundInPadding) {
                    selfBounds.set(0, 0, w, h);
                } else {
                    selfBounds.set(getPaddingLeft(), getPaddingTop(),
                            w - getPaddingRight(), h - getPaddingBottom());
                }

                Gravity.apply(mForegroundGravity, foreground.getIntrinsicWidth(),
                        foreground.getIntrinsicHeight(), selfBounds, overlayBounds);
                foreground.setBounds(overlayBounds);
            }

            foreground.draw(canvas);
        }
    }

    @Override
    public void drawableHotspotChanged(float x, float y) {
        super.drawableHotspotChanged(x, y);
        if (mForeground != null) {
            DrawableCompat.setHotspot(mForeground, x, y);
        }
    }
}