通用的GridDividerItemDecoration特點
1.支持設置左右間距
2.支持設置first item/last item ，top和bottom margin
3.剩餘空間每個item平均分配
package com.starlight.mobile.android.smsone.common;
import android.content.Context;
import android.graphics.Color;
import android.support.v7.widget.StaggeredGridLayoutManager;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.support.annotation.ColorInt;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;
/**
* Created by Haozi on 2018/10/10 0023.
*/
public class GridDividerItemDecoration extends RecyclerView.ItemDecoration {
private Paint mPaint;
private int mDividerWidth; //您所需指定的間隔寬度，主要爲第一列和最後一列與父控件的間隔；行間距，列間距將動態分配
private int mFirstRowTopMargin = 0; //第一行頂部是否需要間隔
private boolean isNeedSpace = false;//第一列和最後一列是否需要指定間隔(默認不指定)
private boolean isLastRowNeedSpace = false;//最後一行是否需要間隔(默認不需要)
int spanCount = 0;
private Context mContext;
/**
*
* @param dividerWidth 間隔寬度
* @param isNeedSpace 第一列和最後一列是否需要間隔
*/
public GridDividerItemDecoration(Context context, int dividerWidth, boolean isNeedSpace) {
this(context,dividerWidth,0,isNeedSpace,false);
}
/**
*
* @param dividerWidth 間隔寬度
* @param isNeedSpace 第一列和最後一列是否需要間隔
* @param firstRowTopMargin 第一行頂部是否需要間隔(根據間隔大小判斷)
*/
public GridDividerItemDecoration(Context context, int dividerWidth, int firstRowTopMargin, boolean isNeedSpace) {
this(context,dividerWidth,firstRowTopMargin,isNeedSpace,false);
}
/**
* @param dividerWidth 間隔寬度
* @param firstRowTopMargin 第一行頂部是否需要間隔
* @param isNeedSpace 第一列和最後一列是否需要間隔
* @param isLastRowNeedSpace 最後一行是否需要間隔
*/
public GridDividerItemDecoration(Context context, int dividerWidth, int firstRowTopMargin, boolean isNeedSpace, boolean isLastRowNeedSpace) {
this(context,dividerWidth,firstRowTopMargin,isNeedSpace,isLastRowNeedSpace, Color.WHITE);
}
/**
* @param dividerWidth 間隔寬度
* @param firstRowTopMargin 第一行頂部是否需要間隔
* @param isNeedSpace 第一列和最後一列是否需要間隔
* @param isLastRowNeedSpace 最後一行是否需要間隔
*/
public GridDividerItemDecoration(Context context, int dividerWidth, int firstRowTopMargin, boolean isNeedSpace, boolean isLastRowNeedSpace, @ColorInt int color) {
mDividerWidth = dividerWidth;
this.isNeedSpace = isNeedSpace;
this.mContext = context;
this.isLastRowNeedSpace = isLastRowNeedSpace;
this.mFirstRowTopMargin = firstRowTopMargin;
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mPaint.setColor(color);
mPaint.setStyle(Paint.Style.FILL);
}
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
super.getItemOffsets(outRect, view, parent, state);
int top = 0;
int left = 0;
int right = 0;
int bottom = 0;
int itemPosition = ((RecyclerView.LayoutParams) view.getLayoutParams()).getViewLayoutPosition();
spanCount = getSpanCount(parent);
int childCount = parent.getAdapter().getItemCount();
int maxAllDividerWidth = getMaxDividerWidth(view); //
int spaceWidth = 0;//首尾兩列與父佈局之間的間隔
if(isNeedSpace)
spaceWidth = mDividerWidth;
int eachItemWidth = maxAllDividerWidth/spanCount;//每個Item left+right
int dividerItemWidth = (maxAllDividerWidth-2*spaceWidth)/(spanCount-1);//item與item之間的距離
left = itemPosition % spanCount * (dividerItemWidth - eachItemWidth) + spaceWidth;
right = eachItemWidth - left;
bottom = mDividerWidth;
if(mFirstRowTopMargin > 0 && isFirstRow(parent, itemPosition, spanCount, childCount))//第一行頂部是否需要間隔
top = mFirstRowTopMargin;
if (!isLastRowNeedSpace && isLastRow(parent, itemPosition, spanCount, childCount)){//最後一行是否需要間隔
bottom = 0;
}
outRect.set(left, top, right, bottom);
}
/**
* 獲取Item View的大小，若無則自動分配空間
* 並根據 屏幕寬度-View的寬度*spanCount 得到屏幕剩餘空間
* @param view
* @return
*/
private int getMaxDividerWidth(View view) {
int itemWidth = view.getLayoutParams().width;
int itemHeight = view.getLayoutParams().height;
int screenWidth = mContext.getResources().getDisplayMetrics().widthPixels > mContext.getResources().getDisplayMetrics().heightPixels
? mContext.getResources().getDisplayMetrics().heightPixels : mContext.getResources().getDisplayMetrics().widthPixels;
int maxDividerWidth = screenWidth-itemWidth * spanCount;
if(itemHeight < 0 || itemWidth < 0 || (isNeedSpace && maxDividerWidth <= (spanCount-1) * mDividerWidth)){
view.getLayoutParams().width = getAttachCloumnWidth();
view.getLayoutParams().height = getAttachCloumnWidth();
maxDividerWidth = screenWidth-view.getLayoutParams().width * spanCount;
}
return maxDividerWidth;
}
/**
* 根據屏幕寬度和item數量分配 item View的width和height
* @return
*/
private int getAttachCloumnWidth() {
int itemWidth = 0;
int spaceWidth = 0;
try {
int width = mContext.getResources().getDisplayMetrics().widthPixels > mContext.getResources().getDisplayMetrics().heightPixels
? mContext.getResources().getDisplayMetrics().heightPixels : mContext.getResources().getDisplayMetrics().widthPixels;
if(isNeedSpace)
spaceWidth = 2 * mDividerWidth;
itemWidth = (width-spaceWidth) / spanCount - 40;//why - 40???
} catch (Exception e) {
e.printStackTrace();
}
return itemWidth;
}
@Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
super.onDraw(c, parent, state);
draw(c, parent);
}
//繪製item分割線
private void draw(Canvas canvas, RecyclerView parent) {
int childCount = parent.getChildCount();
for (int i = 0; i < childCount; i++) {
View child = parent.getChildAt(i);
RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) child.getLayoutParams();
//畫水平分隔線
int left = child.getLeft();
int right = child.getRight();
int top = child.getBottom() + layoutParams.bottomMargin;
int bottom = top + mDividerWidth;
if (mPaint != null) {
canvas.drawRect(left, top, right, bottom, mPaint);
}
//畫垂直分割線
top = child.getTop();
bottom = child.getBottom() + mDividerWidth;
left = child.getRight() + layoutParams.rightMargin;
right = left + mDividerWidth;
if (mPaint != null) {
canvas.drawRect(left, top, right, bottom, mPaint);
}
}
}
/**
* 判讀是否是第一列
* @param parent
* @param pos
* @param spanCount
* @param childCount
* @return
*/
private boolean isFirstColumn(RecyclerView parent, int pos, int spanCount, int childCount) {
RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
if (layoutManager instanceof GridLayoutManager) {
if (pos % spanCount == 0) {
return true;
}
} else if (layoutManager instanceof StaggeredGridLayoutManager) {
int orientation = ((StaggeredGridLayoutManager) layoutManager)
.getOrientation();
if (orientation == StaggeredGridLayoutManager.VERTICAL) {
if (pos % spanCount == 0) {// 第一列
return true;
}
} else {
}
}
return false;
}
/**
* 判斷是否是最後一列
* @param parent
* @param pos
* @param spanCount
* @param childCount
* @return
*/
private boolean isLastColumn(RecyclerView parent, int pos, int spanCount, int childCount) {
RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
if (layoutManager instanceof GridLayoutManager) {
if ((pos + 1) % spanCount == 0) {// 如果是最後一列，則不需要繪製右邊
return true;
}
} else if (layoutManager instanceof StaggeredGridLayoutManager) {
int orientation = ((StaggeredGridLayoutManager) layoutManager)
.getOrientation();
if (orientation == StaggeredGridLayoutManager.VERTICAL) {
if ((pos + 1) % spanCount == 0) {// 最後一列
return true;
}
} else {
}
}
return false;
}
/**
* 判讀是否是最後一行
* @param parent
* @param pos
* @param spanCount
* @param childCount
* @return
*/
private boolean isLastRow(RecyclerView parent, int pos, int spanCount, int childCount) {
RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
if (layoutManager instanceof GridLayoutManager) {
int lines = childCount % spanCount == 0 ? childCount / spanCount : childCount / spanCount + 1;
return lines == pos / spanCount + 1;
} else if (layoutManager instanceof StaggeredGridLayoutManager) {
}
return false;
}
/**
* 判斷是否是第一行
* @param parent
* @param pos
* @param spanCount
* @param childCount
* @return
*/
private boolean isFirstRow(RecyclerView parent, int pos, int spanCount, int childCount) {
RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
if (layoutManager instanceof GridLayoutManager) {
if ((pos / spanCount + 1) == 1) {
return true;
} else {
return false;
}
} else if (layoutManager instanceof StaggeredGridLayoutManager) {
}
return false;
}
/**
* 獲取列數
* @param parent
* @return
*/
private int getSpanCount(RecyclerView parent) {
int spanCount = -1;
RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
if (layoutManager instanceof GridLayoutManager) {
spanCount = ((GridLayoutManager) layoutManager).getSpanCount();
} else if (layoutManager instanceof StaggeredGridLayoutManager) {
spanCount = ((StaggeredGridLayoutManager) layoutManager).getSpanCount();
}
return spanCount;
}
}