Android应用开发—通用的GridView网格分割线

注：本文基于 Android RecyclerView 使用完全解析 体验艺术般的控件 中关于GridView网格分割线部分代码扩展而来。

原接口代码：

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.v7.widget.GridLayoutManager;import android.support.v7.widget.RecyclerView;import android.support.v7.widget.RecyclerView.LayoutManager;import android.support.v7.widget.RecyclerView.State;import android.support.v7.widget.StaggeredGridLayoutManager;import android.view.View;public class DividerGridItemDecoration extends RecyclerView.ItemDecoration {    private static final int[] ATTRS = new int[]{android.R.attr.listDivider};    private Drawable mDivider;    public DividerGridItemDecoration(Context context) {        final TypedArray a = context.obtainStyledAttributes(ATTRS);        mDivider = a.getDrawable(0);        a.recycle();    }    @Override    public void onDraw(Canvas c, RecyclerView parent, State state) {        drawHorizontal(c, parent);        drawVertical(c, parent);    }    private int getSpanCount(RecyclerView parent) {        // 列数        int spanCount = -1;        LayoutManager layoutManager = parent.getLayoutManager();        if (layoutManager instanceof GridLayoutManager) {            spanCount = ((GridLayoutManager) layoutManager).getSpanCount();        } else if (layoutManager instanceof StaggeredGridLayoutManager) {            spanCount = ((StaggeredGridLayoutManager) layoutManager).getSpanCount();        }        return spanCount;    }    public void drawHorizontal(Canvas c, RecyclerView parent) {        int childCount = parent.getChildCount();        for (int i = 0; i < childCount; i++) {            final View child = parent.getChildAt(i);            final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();            final int left = child.getLeft() - params.leftMargin;            final int right = child.getRight() + params.rightMargin + mDivider.getIntrinsicWidth();            final int top = child.getBottom() + params.bottomMargin;            final int bottom = top + mDivider.getIntrinsicHeight();            mDivider.setBounds(left, top, right, bottom);            mDivider.draw(c);        }    }    public void drawVertical(Canvas c, RecyclerView parent) {        final int childCount = parent.getChildCount();        for (int i = 0; i < childCount; i++) {            final View child = parent.getChildAt(i);            final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();            final int top = child.getTop() - params.topMargin;            final int bottom = child.getBottom() + params.bottomMargin;            final int left = child.getRight() + params.rightMargin;            final int right = left + mDivider.getIntrinsicWidth();            mDivider.setBounds(left, top, right, bottom);            mDivider.draw(c);        }    }    private boolean isLastColum(RecyclerView parent, int pos, int spanCount, int childCount) {        LayoutManager layoutManager = parent.getLayoutManager();        if (layoutManager instanceof GridLayoutManager) {            // 如果是最后一列，则不需要绘制右边            if ((pos + 1) % spanCount == 0) {                return true;            }        } else if (layoutManager instanceof StaggeredGridLayoutManager) {            int orientation = ((StaggeredGridLayoutManager) layoutManager).getOrientation();            if (orientation == StaggeredGridLayoutManager.VERTICAL) {                // 如果是最后一列，则不需要绘制右边                if ((pos + 1) % spanCount == 0) {                    return true;                }            } else {                childCount = childCount - childCount % spanCount;                if (pos >= childCount)// 如果是最后一列，则不需要绘制右边                    return true;            }        }        return false;    }    private boolean isLastRaw(RecyclerView parent, int pos, int spanCount, int childCount) {        LayoutManager layoutManager = parent.getLayoutManager();        if (layoutManager instanceof GridLayoutManager) {            childCount = childCount - childCount % spanCount;            if (pos >= childCount)// 如果是最后一行，则不需要绘制底部                return true;        } else if (layoutManager instanceof StaggeredGridLayoutManager) {            int orientation = ((StaggeredGridLayoutManager) layoutManager).getOrientation();            // StaggeredGridLayoutManager 且纵向滚动            if (orientation == StaggeredGridLayoutManager.VERTICAL) {                childCount = childCount - childCount % spanCount;                // 如果是最后一行，则不需要绘制底部                if (pos >= childCount)                    return true;            } else {                // 如果是最后一行，则不需要绘制底部                if ((pos + 1) % spanCount == 0) {                    return true;                }            }        }        return false;    }    @Override    public void getItemOffsets(Rect outRect, int itemPosition, RecyclerView parent) {        int spanCount = getSpanCount(parent);        int childCount = parent.getAdapter().getItemCount();        // 如果是最后一行，则不需要绘制底部        if (isLastRaw(parent, itemPosition, spanCount, childCount)) {            outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);        } else if (isLastColum(parent, itemPosition, spanCount, childCount)) {            // 如果是最后一列，则不需要绘制右边            outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());        } else {            outRect.set(0, 0, mDivider.getIntrinsicWidth(),                    mDivider.getIntrinsicHeight());        }    }}

扩展后的代码：

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.v7.widget.GridLayoutManager;import android.support.v7.widget.RecyclerView;import android.support.v7.widget.RecyclerView.LayoutManager;import android.support.v7.widget.RecyclerView.State;import android.support.v7.widget.StaggeredGridLayoutManager;import android.view.View;public class DividerGridItemDecoration extends RecyclerView.ItemDecoration {    private static final int[] ATTRS = new int[]{android.R.attr.listDivider};    private Drawable mDivider;    private Paint mColorPaint;    private int mDividerHeight = 1;    public DividerGridItemDecoration(Context context) {        final TypedArray a = context.obtainStyledAttributes(ATTRS);        mDivider = a.getDrawable(0);        a.recycle();    }    public DividerGridItemDecoration(Context context, int color, int height) {        this(context);        mColorPaint = new Paint();        mColorPaint.setColor(color);        mDividerHeight = height;    }    @Override    public void onDraw(Canvas c, RecyclerView parent, State state) {        drawHorizontal(c, parent);        drawVertical(c, parent);    }    private int getSpanCount(RecyclerView parent) {        // 列数        int spanCount = -1;        LayoutManager layoutManager = parent.getLayoutManager();        if (layoutManager instanceof GridLayoutManager) {            spanCount = ((GridLayoutManager) layoutManager).getSpanCount();        } else if (layoutManager instanceof StaggeredGridLayoutManager) {            spanCount = ((StaggeredGridLayoutManager) layoutManager).getSpanCount();        }        return spanCount;    }    public void drawHorizontal(Canvas c, RecyclerView parent) {        int childCount = parent.getChildCount();        int spanCount = getSpanCount(parent);        int count = 0;        if (childCount % spanCount != 0) {            count = childCount;        } else {            count = childCount - spanCount;        }        for (int i = 0; i < count; i++) {            final View child = parent.getChildAt(i);            final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();            final int left = child.getLeft() - params.leftMargin;            final int right = child.getRight() + params.rightMargin + mDivider.getIntrinsicWidth();            final int top = child.getBottom() + params.bottomMargin;            final int bottom = top + mDivider.getIntrinsicHeight();            if (mColorPaint != null) {                c.drawRect(left, top, right, top + mDividerHeight, mColorPaint);            } else {                mDivider.setBounds(left, top, right, bottom);                mDivider.draw(c);            }        }    }    public void drawVertical(Canvas c, RecyclerView parent) {        final int childCount = parent.getChildCount();        for (int i = 0; i < childCount; i++) {            final View child = parent.getChildAt(i);            final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();            final int top = child.getTop() - params.topMargin;            final int bottom = child.getBottom() + params.bottomMargin;            final int left = child.getRight() + params.rightMargin;            final int right = left + mDivider.getIntrinsicWidth();            if (mColorPaint != null) {                c.drawRect(left, top, left + mDividerHeight, bottom, mColorPaint);            } else {                mDivider.setBounds(left, top, right, bottom);                mDivider.draw(c);            }        }    }    private boolean isLastColum(RecyclerView parent, int pos, int spanCount, int childCount) {        LayoutManager layoutManager = parent.getLayoutManager();        if (layoutManager instanceof GridLayoutManager) {            // 如果是最后一列，则不需要绘制右边            if ((pos + 1) % spanCount == 0) {                return true;            }        } else if (layoutManager instanceof StaggeredGridLayoutManager) {            int orientation = ((StaggeredGridLayoutManager) layoutManager).getOrientation();            if (orientation == StaggeredGridLayoutManager.VERTICAL) {                // 如果是最后一列，则不需要绘制右边                if ((pos + 1) % spanCount == 0) {                    return true;                }            } else {                childCount = childCount - childCount % spanCount;                if (pos >= childCount)// 如果是最后一列，则不需要绘制右边                    return true;            }        }        return false;    }    private boolean isLastRaw(RecyclerView parent, int pos, int spanCount, int childCount) {        LayoutManager layoutManager = parent.getLayoutManager();        if (layoutManager instanceof GridLayoutManager) {            childCount = childCount - childCount % spanCount;            if (pos >= childCount)// 如果是最后一行，则不需要绘制底部                return true;        } else if (layoutManager instanceof StaggeredGridLayoutManager) {            int orientation = ((StaggeredGridLayoutManager) layoutManager).getOrientation();            // StaggeredGridLayoutManager 且纵向滚动            if (orientation == StaggeredGridLayoutManager.VERTICAL) {                childCount = childCount - childCount % spanCount;                // 如果是最后一行，则不需要绘制底部                if (pos >= childCount)                    return true;            } else {                // 如果是最后一行，则不需要绘制底部                if ((pos + 1) % spanCount == 0) {                    return true;                }            }        }        return false;    }    @Override    public void getItemOffsets(Rect outRect, int itemPosition, RecyclerView parent) {        int spanCount = getSpanCount(parent);        int childCount = parent.getAdapter().getItemCount();        // 如果是最后一行，则不需要绘制底部        if (isLastRaw(parent, itemPosition, spanCount, childCount)) {            outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);        } else if (isLastColum(parent, itemPosition, spanCount, childCount)) {            // 如果是最后一列，则不需要绘制右边            outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());        } else {            outRect.set(0, 0, mDivider.getIntrinsicWidth(), mDivider.getIntrinsicHeight());        }    }}

扩展的内容：

• 最后一行不画分割线。通常我们的需求是边框都不进行分割的绘制，而原来的代码没有做这部分的处理。（原接口只处理了最后一列的情况）
• 支持分割线的颜色和宽度绘制的定制化。（原接口只支持系统属性分割线的绘制）。绘制方式：DividerGridItemDecoration(Context context, int color, int height) 通过传递color和height进行绘制定制化。