OffsetLayout.java

/*
 * Copyright (C) 2015 Hippo Seven
 *
 * 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 com.hippo.widget;

import android.annotation.SuppressLint;
import android.content.Context;
import android.util.AttributeSet;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;

public class OffsetLayout extends FrameLayout {

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

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

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

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        layoutChildrenEx(left, top, right, bottom, false /* no force left gravity */);
    }

    // TODO foreground not work fine
    @SuppressLint("RtlHardcoded")
    void layoutChildrenEx(int left, int top, int right, int bottom,
            boolean forceLeftGravity) {
        final int count = getChildCount();

        final int parentLeft = getPaddingLeft();
        final int parentRight = right - left - getPaddingRight();

        final int parentTop = getPaddingTop();
        final int parentBottom = bottom - top - getPaddingBottom();

        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            if (child.getVisibility() != GONE) {
                final LayoutParams lp = (LayoutParams) child.getLayoutParams();

                final int width = child.getMeasuredWidth();
                final int height = child.getMeasuredHeight();

                int childLeft;
                int childTop;

                int gravity = lp.gravity;
                if (gravity == -1) {
                    gravity = Gravity.TOP | Gravity.LEFT;
                }

                final int absoluteGravity = gravity;
                final int verticalGravity = gravity & Gravity.VERTICAL_GRAVITY_MASK;

                switch (absoluteGravity & Gravity.HORIZONTAL_GRAVITY_MASK) {
                    case Gravity.CENTER_HORIZONTAL:
                        childLeft = parentLeft + (parentRight - parentLeft - width) / 2 +
                                lp.leftMargin - lp.rightMargin;
                        break;
                    case Gravity.RIGHT:
                        if (!forceLeftGravity) {
                            childLeft = parentRight - width - lp.rightMargin;
                            break;
                        }
                    case Gravity.LEFT:
                    default:
                        childLeft = parentLeft + lp.leftMargin;
                }

                switch (verticalGravity) {
                    case Gravity.TOP:
                        childTop = parentTop + lp.topMargin;
                        break;
                    case Gravity.CENTER_VERTICAL:
                        childTop = parentTop + (parentBottom - parentTop - height) / 2 +
                                lp.topMargin - lp.bottomMargin;
                        break;
                    case Gravity.BOTTOM:
                        childTop = parentBottom - height - lp.bottomMargin;
                        break;
                    default:
                        childTop = parentTop + lp.topMargin;
                }

                child.layout(childLeft + lp.offsetX, childTop + lp.offsetY,
                        childLeft + width + lp.offsetX, childTop + height + lp.offsetY);
            }
        }
    }

    @Override
    public LayoutParams generateLayoutParams(AttributeSet attrs) {
        return new LayoutParams(getContext(), attrs);
    }

    @Override
    protected boolean checkLayoutParams(ViewGroup.LayoutParams p) {
        return p instanceof LayoutParams;
    }

    @Override
    protected ViewGroup.LayoutParams generateLayoutParams(ViewGroup.LayoutParams p) {
        return new LayoutParams(p);
    }

    public static class LayoutParams extends FrameLayout.LayoutParams {

        public int offsetX;
        public int offsetY;

        public LayoutParams(Context c, AttributeSet attrs) {
            super(c, attrs);
        }

        public LayoutParams(ViewGroup.LayoutParams source) {
            super(source);
        }

        public LayoutParams(MarginLayoutParams source) {
            super(source);
        }

        public LayoutParams(FrameLayout.LayoutParams source) {
            super((ViewGroup.MarginLayoutParams) source);
            this.gravity = source.gravity;
        }

        public LayoutParams(int width, int height) {
            super(width, height);
        }
    }
}