src/com/android/launcher2/PagedViewCellLayout.java

/*
 * Copyright (C) 2010 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 com.android.launcher2;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewDebug;
import android.view.ViewGroup;

/**
 * An abstraction of the original CellLayout which supports laying out items
 * which span multiple cells into a grid-like layout.  Also supports dimming
 * to give a preview of its contents.
 */
public class PagedViewCellLayout extends ViewGroup {
    public interface DimmedBitmapSetupListener {
        public void onPreUpdateDimmedBitmap(PagedViewCellLayout layout);
        public void onPostUpdateDimmedBitmap(PagedViewCellLayout layout);
    }

    static final String TAG = "PagedViewCellLayout";

    // we make the dimmed bitmap smaller than the screen itself for memory + perf reasons
    static final float DIMMED_BITMAP_SCALE = 0.75f;

    // a dimmed version of the layout for rendering when in the periphery
    private Bitmap mDimmedBitmap;
    private Canvas mDimmedBitmapCanvas;
    private float mDimmedBitmapAlpha;
    private boolean mDimmedBitmapDirty;
    private final Paint mDimmedBitmapPaint = new Paint();
    private final Rect mLayoutRect = new Rect();
    private final Rect mDimmedBitmapRect = new Rect();

    private boolean mCenterContent;

    private int mCellCountX;
    private int mCellCountY;
    private int mCellWidth;
    private int mCellHeight;
    private static int sDefaultCellDimensions = 96;

    private DimmedBitmapSetupListener mDimmedBitmapSetupListener;

    public PagedViewCellLayout(Context context) {
        this(context, null);
    }

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

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

        // enable drawing if we have to display a dimmed version of this layout
        setWillNotDraw(false);
        setAlwaysDrawnWithCacheEnabled(false);

        // setup default cell parameters
        mCellWidth = mCellHeight = sDefaultCellDimensions;
        mCellCountX = LauncherModel.getCellCountX();
        mCellCountY = LauncherModel.getCellCountY();

        mDimmedBitmapPaint.setFilterBitmap(true);
    }

    public void setDimmedBitmapSetupListener(DimmedBitmapSetupListener listener) {
        mDimmedBitmapSetupListener = listener;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        if (mDimmedBitmap != null && mDimmedBitmapAlpha > 0.0f) {
            if (mDimmedBitmapDirty) {
                updateDimmedBitmap();
                mDimmedBitmapDirty = false;
            }
            mDimmedBitmapPaint.setAlpha((int) (mDimmedBitmapAlpha * 255));

            canvas.drawBitmap(mDimmedBitmap, mDimmedBitmapRect, mLayoutRect, mDimmedBitmapPaint);
        }
    }

    @Override
    public void cancelLongPress() {
        super.cancelLongPress();

        // Cancel long press for all children
        final int count = getChildCount();
        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            child.cancelLongPress();
        }
    }

    public boolean addViewToCellLayout(View child, int index, int childId,
            PagedViewCellLayout.LayoutParams params) {
        final PagedViewCellLayout.LayoutParams lp = params;

        // Generate an id for each view, this assumes we have at most 256x256 cells
        // per workspace screen
        if (lp.cellX >= 0 && lp.cellX <= (mCellCountX - 1) &&
                lp.cellY >= 0 && (lp.cellY <= mCellCountY - 1)) {
            // If the horizontal or vertical span is set to -1, it is taken to
            // mean that it spans the extent of the CellLayout
            if (lp.cellHSpan < 0) lp.cellHSpan = mCellCountX;
            if (lp.cellVSpan < 0) lp.cellVSpan = mCellCountY;

            child.setId(childId);

            // We might be in the middle or end of shrinking/fading to a dimmed view
            // Make sure this view's alpha is set the same as all the rest of the views
            child.setAlpha(1.0f - mDimmedBitmapAlpha);

            addView(child, index, lp);

            // next time we draw the dimmed bitmap we need to update it
            mDimmedBitmapDirty = true;
            invalidate();
            return true;
        }
        return false;
    }

    @Override
    public void removeView(View view) {
        super.removeView(view);

        // next time we draw the dimmed bitmap we need to update it
        mDimmedBitmapDirty = true;
        invalidate();
    }

    @Override
    public void requestChildFocus(View child, View focused) {
        super.requestChildFocus(child, focused);
        if (child != null) {
            Rect r = new Rect();
            child.getDrawingRect(r);
            requestRectangleOnScreen(r);
        }
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        // TODO: currently ignoring padding

        int widthSpecMode = MeasureSpec.getMode(widthMeasureSpec);
        int widthSpecSize = MeasureSpec.getSize(widthMeasureSpec);

        int heightSpecMode = MeasureSpec.getMode(heightMeasureSpec);
        int heightSpecSize =  MeasureSpec.getSize(heightMeasureSpec);

        if (widthSpecMode == MeasureSpec.UNSPECIFIED || heightSpecMode == MeasureSpec.UNSPECIFIED) {
            throw new RuntimeException("CellLayout cannot have UNSPECIFIED dimensions");
        }

        final int cellWidth = mCellWidth;
        final int cellHeight = mCellHeight;

        int numWidthGaps = mCellCountX - 1;
        int numHeightGaps = mCellCountY - 1;

        int vSpaceLeft = heightSpecSize - mPaddingTop
                - mPaddingBottom - (cellHeight * mCellCountY);
        int heightGap = vSpaceLeft / numHeightGaps;

        int hSpaceLeft = widthSpecSize - mPaddingLeft
                - mPaddingRight - (cellWidth * mCellCountX);
        int widthGap = hSpaceLeft / numWidthGaps;

        // center it around the min gaps
        int minGap = Math.min(widthGap, heightGap);
        int paddingLeft = mPaddingLeft;
        int paddingTop = mPaddingTop;
        /*
        if (minGap < heightGap) {
            // vertical space has shrunken, so change padding accordingly
            paddingTop += ((heightGap - minGap) * (mCellCountY - 1)) / 2;
        } else if (minGap < widthGap) {
            // horizontal space has shrunken, so change padding accordingly
            paddingLeft += ((widthGap - minGap) * (mCellCountX - 1)) / 2;
        }
        */
        widthGap = heightGap = minGap;

        int newWidth = mPaddingLeft + mPaddingRight + (mCellCountX * cellWidth) +
            ((mCellCountX - 1) * minGap);
        int newHeight = mPaddingTop + mPaddingBottom + (mCellCountY * cellHeight) +
            ((mCellCountY - 1) * minGap);

        final int count = getChildCount();
        for (int i = 0; i < count; i++) {
            View child = getChildAt(i);
            PagedViewCellLayout.LayoutParams lp =
                (PagedViewCellLayout.LayoutParams) child.getLayoutParams();
            lp.setup(cellWidth, cellHeight, widthGap, heightGap,
                    paddingLeft, paddingTop);

            int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(lp.width,
                    MeasureSpec.EXACTLY);
            int childheightMeasureSpec = MeasureSpec.makeMeasureSpec(lp.height,
                    MeasureSpec.EXACTLY);

            child.measure(childWidthMeasureSpec, childheightMeasureSpec);
        }

        setMeasuredDimension(newWidth, newHeight);
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        int count = getChildCount();

        int offsetX = 0;
        if (mCenterContent) {
            // determine the max width of all the rows and center accordingly
            int maxRowWidth = 0;
            for (int i = 0; i < count; i++) {
                View child = getChildAt(i);
                if (child.getVisibility() != GONE) {
                    PagedViewCellLayout.LayoutParams lp =
                        (PagedViewCellLayout.LayoutParams) child.getLayoutParams();
                    maxRowWidth = Math.max(maxRowWidth, lp.x + lp.width);
                }
            }
            offsetX = (getMeasuredWidth() / 2) - (maxRowWidth / 2);
        }

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

                int childLeft = offsetX + lp.x;
                int childTop = lp.y;
                child.layout(childLeft, childTop, childLeft + lp.width, childTop + lp.height);
            }
        }
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        mLayoutRect.set(0, 0, w, h);
        mDimmedBitmapRect.set(0, 0, (int) (DIMMED_BITMAP_SCALE * w), (int) (DIMMED_BITMAP_SCALE * h));
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        return super.onTouchEvent(event) || true;
    }

    public void enableCenteredContent(boolean enabled) {
        mCenterContent = enabled;
    }

    @Override
    protected void setChildrenDrawingCacheEnabled(boolean enabled) {
        final int count = getChildCount();
        for (int i = 0; i < count; i++) {
            final View view = getChildAt(i);
            view.setDrawingCacheEnabled(enabled);
            // Update the drawing caches
            view.buildDrawingCache(true);
        }
    }

    public void setCellCount(int xCount, int yCount) {
        mCellCountX = xCount;
        mCellCountY = yCount;
        requestLayout();
    }

    public float getDimmedBitmapAlpha() {
        return mDimmedBitmapAlpha;
    }

    public void setDimmedBitmapAlpha(float alpha) {
        // If we're dimming the screen after it was not dimmed, refresh
        // to allow for updated widgets. We don't continually refresh it
        // after this point, however, as an optimization
        if (mDimmedBitmapAlpha == 0.0f && alpha > 0.0f) {
            updateDimmedBitmap();
        }
        mDimmedBitmapAlpha = alpha;
        setChildrenAlpha(1.0f - mDimmedBitmapAlpha);
    }

    public void updateDimmedBitmap() {
        if (mDimmedBitmapSetupListener != null) {
            mDimmedBitmapSetupListener.onPreUpdateDimmedBitmap(this);
        }

        if (mDimmedBitmap == null) {
            mDimmedBitmap = Bitmap.createBitmap((int) (getWidth() * DIMMED_BITMAP_SCALE),
                    (int) (getHeight() * DIMMED_BITMAP_SCALE), Bitmap.Config.ARGB_8888);
            mDimmedBitmapCanvas = new Canvas(mDimmedBitmap);
            mDimmedBitmapCanvas.scale(DIMMED_BITMAP_SCALE, DIMMED_BITMAP_SCALE);
        }
        // clear the canvas
        mDimmedBitmapCanvas.drawColor(0x00000000, PorterDuff.Mode.CLEAR);

        // draw the screen into the bitmap
        // just for drawing to the bitmap, make all the items on the screen opaque
        setChildrenAlpha(1.0f);
        dispatchDraw(mDimmedBitmapCanvas);
        setChildrenAlpha(1.0f - mDimmedBitmapAlpha);

        // make the bitmap 'dimmed' ie colored regions are dark grey,
        // the rest is light grey
        // We draw grey to the whole bitmap, but filter where we draw based on
        // what regions are transparent or not (SRC_OUT), causing the intended effect

        // First, draw light grey everywhere in the background (currently transparent) regions
        // This will leave the regions with the widgets as mostly transparent
        mDimmedBitmapCanvas.drawColor(Color.argb(80, 0, 0, 0), PorterDuff.Mode.SRC_IN);

        if (mDimmedBitmapSetupListener != null) {
            mDimmedBitmapSetupListener.onPostUpdateDimmedBitmap(this);
        }
    }

    public void clearDimmedBitmap() {
        setDimmedBitmapAlpha(0.0f);
        if (mDimmedBitmap != null) {
            mDimmedBitmap.recycle();
            mDimmedBitmap = null;
        }
    }

    private void setChildrenAlpha(float alpha) {
        for (int i = 0; i < getChildCount(); i++) {
            getChildAt(i).setAlpha(alpha);
        }
    }

    public int[] getCellCountForDimensions(int width, int height) {
        // Always assume we're working with the smallest span to make sure we
        // reserve enough space in both orientations
        int smallerSize = Math.min(mCellWidth, mCellHeight);

        // Always round up to next largest cell
        int spanX = (width + smallerSize) / smallerSize;
        int spanY = (height + smallerSize) / smallerSize;

        return new int[] { spanX, spanY };
    }

    /**
     * Start dragging the specified child
     *
     * @param child The child that is being dragged
     */
    void onDragChild(View child) {
        PagedViewCellLayout.LayoutParams lp = (PagedViewCellLayout.LayoutParams) child.getLayoutParams();
        lp.isDragging = true;
    }

    public int estimateCellHSpan(int width) {
        return (width + mCellWidth) / mCellWidth;
    }
    public int estimateCellVSpan(int height) {
        return (height + mCellHeight) / mCellHeight;
    }
    public int[] estimateCellDimensions(int approxWidth, int approxHeight, 
            int cellHSpan, int cellVSpan) {
        // NOTE: we are disabling this until we find a good way to approximate this without fully
        // measuring
        /*
        // we may want to use this before any measuring/layout happens, so we pass in an approximate
        // size for the layout
        int numWidthGaps = mCellCountX - 1;
        int numHeightGaps = mCellCountY - 1;
        int hSpaceLeft = approxWidth - mPaddingLeft
            - mPaddingRight - (mCellWidth * mCellCountX);
        int vSpaceLeft = approxHeight - mPaddingTop
            - mPaddingBottom - (mCellHeight * mCellCountY);
        int widthGap = hSpaceLeft / numWidthGaps;
        int heightGap = vSpaceLeft / numHeightGaps;
        int minGap = Math.min(widthGap, heightGap);
        return new int[] {
            (cellHSpan * mCellWidth) + ((cellHSpan - 1) * minGap),
            (cellVSpan * mCellHeight) + ((cellVSpan - 1) * minGap)
        };
        */
        return new int[] {
            (cellHSpan * mCellWidth),
            (cellVSpan * mCellHeight)
        };
    }

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

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

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

    public static class LayoutParams extends ViewGroup.MarginLayoutParams {
        /**
         * Horizontal location of the item in the grid.
         */
        @ViewDebug.ExportedProperty
        public int cellX;

        /**
         * Vertical location of the item in the grid.
         */
        @ViewDebug.ExportedProperty
        public int cellY;

        /**
         * Number of cells spanned horizontally by the item.
         */
        @ViewDebug.ExportedProperty
        public int cellHSpan;

        /**
         * Number of cells spanned vertically by the item.
         */
        @ViewDebug.ExportedProperty
        public int cellVSpan;

        /**
         * Is this item currently being dragged
         */
        public boolean isDragging;

        // a data object that you can bind to this layout params
        private Object mTag;

        // X coordinate of the view in the layout.
        @ViewDebug.ExportedProperty
        int x;
        // Y coordinate of the view in the layout.
        @ViewDebug.ExportedProperty
        int y;

        public LayoutParams() {
            super(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
            cellHSpan = 1;
            cellVSpan = 1;
        }

        public LayoutParams(Context c, AttributeSet attrs) {
            super(c, attrs);
            cellHSpan = 1;
            cellVSpan = 1;
        }

        public LayoutParams(ViewGroup.LayoutParams source) {
            super(source);
            cellHSpan = 1;
            cellVSpan = 1;
        }

        public LayoutParams(LayoutParams source) {
            super(source);
            this.cellX = source.cellX;
            this.cellY = source.cellY;
            this.cellHSpan = source.cellHSpan;
            this.cellVSpan = source.cellVSpan;
        }

        public LayoutParams(int cellX, int cellY, int cellHSpan, int cellVSpan) {
            super(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
            this.cellX = cellX;
            this.cellY = cellY;
            this.cellHSpan = cellHSpan;
            this.cellVSpan = cellVSpan;
        }

        public void setup(int cellWidth, int cellHeight, int widthGap, int heightGap,
                int hStartPadding, int vStartPadding) {

            final int myCellHSpan = cellHSpan;
            final int myCellVSpan = cellVSpan;
            final int myCellX = cellX;
            final int myCellY = cellY;

            width = myCellHSpan * cellWidth + ((myCellHSpan - 1) * widthGap) -
                    leftMargin - rightMargin;
            height = myCellVSpan * cellHeight + ((myCellVSpan - 1) * heightGap) -
                    topMargin - bottomMargin;

            x = hStartPadding + myCellX * (cellWidth + widthGap) + leftMargin;
            y = vStartPadding + myCellY * (cellHeight + heightGap) + topMargin;
        }

        public Object getTag() {
            return mTag;
        }

        public void setTag(Object tag) {
            mTag = tag;
        }

        public String toString() {
            return "(" + this.cellX + ", " + this.cellY + ", " +
                this.cellHSpan + ", " + this.cellVSpan + ")";
        }
    }
}