GridSpanLayout.java

/*
 * 
    <declare-styleable name="GridSpanLayout">
        <attr name="rows" format="integer" />
        <attr name="columns" format="integer" />

        <attr name="column" format="integer" />
        <attr name="row" format="integer" />
        <attr name="columnSpan" format="integer" />
        <attr name="rowSpan" format="integer" />
    </declare-styleable>
 *
 */

public class GridSpanLayout extends ViewGroup {
    private final static String TAG = "GridSpanLayout";

    private int mColumns;
    private int mRows;
    private int mIndex;

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

    public GridSpanLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
        TypedArray a = getContext().obtainStyledAttributes(attrs, R.styleable.GridSpanLayout);
        mColumns = a.getInt(R.styleable.GridSpanLayout_columns, 0);
        mRows = a.getInt(R.styleable.GridSpanLayout_rows, 0);
        a.recycle();
    }
    
    @Override
    public LayoutParams generateLayoutParams(AttributeSet attrs) {
        TypedArray a = getContext().obtainStyledAttributes(attrs, R.styleable.GridSpanLayout);
        try {
            int c = a.getInt(R.styleable.GridSpanLayout_column, -1);
            int r = a.getInt(R.styleable.GridSpanLayout_row, -1);
            if (c != -1 && r != -1) {
                mIndex = c + r * mColumns;
            } else {
                if (c != -1) {
                    throw new RuntimeException(attrs.getPositionDescription() + ": alone column definition");
                }
                if (r != -1) {
                    throw new RuntimeException(attrs.getPositionDescription() + ": alone row definition");
                }
                c = mIndex % mColumns;
                r = mIndex / mColumns;
            }
            mIndex++;
            int cs = a.getInt(R.styleable.GridSpanLayout_columnSpan, 1);
            int rs = a.getInt(R.styleable.GridSpanLayout_rowSpan, 1);
            return new LayoutParams(c, r, cs, rs);
        } finally {
            a.recycle();
        }
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        float xs = ((float) getWidth()) / mColumns;
        float ys = ((float) getHeight()) / mRows;
        int cnt = getChildCount();
        for (int i = 0; i < cnt; i++) {
            View child = getChildAt(i);
            LayoutParams params = (LayoutParams) child.getLayoutParams();
//            Log.d(TAG, "onLayout " + params);
            child.layout(Math.round(params.rect.left * xs), Math.round(params.rect.top * ys),
                    Math.round(params.rect.right * xs), Math.round(params.rect.bottom * ys));
        }
    }
    
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        float xs = ((float) getWidth()) / mColumns;
        float ys = ((float) getHeight()) / mRows;
        int cnt = getChildCount();
        for (int i = 0; i < cnt; i++) {
            View child = getChildAt(i);
            LayoutParams params = (LayoutParams) child.getLayoutParams();
            widthMeasureSpec = MeasureSpec.makeMeasureSpec(Math.round(params.rect.width() * xs), MeasureSpec.EXACTLY);
            heightMeasureSpec = MeasureSpec.makeMeasureSpec(Math.round(params.rect.height() * ys), MeasureSpec.EXACTLY);
            child.measure(widthMeasureSpec, heightMeasureSpec);
        }
    }
    
    class LayoutParams extends ViewGroup.LayoutParams {
        private Rect rect;

        public LayoutParams(int c, int r, int cs, int rs) {
            super(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
            rect = new Rect(c, r, c + cs, r + rs);
        }

        @Override
        public String toString() {
            if (rect.width() == 1 && rect.height() == 1) {
                return rect.left + ":" + rect.top;
            }
            return rect.left + ":" + rect.top + ", " + rect.width() + "x" + rect.height();
        }
    }
}