实现FlowLayout
何为FlowLayout,如果对Java的Swing比较熟悉的话一定不会陌生,就是控件根据ViewGroup的宽,自动的往右添加,如果当前行剩余空间不足,则自动添加到下一行。有点所有的控件都往左飘的感觉,第一行满了,往第二行飘~所以也叫流式布局。Android并没有提供流式布局,但是某些场合中,流式布局还是非常适合使用的,比如关键字标签,搜索热词列表等,比如下图:
简单的分析
1、对于FlowLayout,需要指定的LayoutParams,我们目前只需要能够识别margin即可,即使用MarginLayoutParams.
2、onMeasure中计算所有childView的宽和高,然后根据childView的宽和高,计算自己的宽和高。(当然,如果不是wrap_content,直接使用父ViewGroup传入的计算值即可)
3、onLayout中对所有的childView进行布局。
generateLayoutParams
因为我们只需要支持margin,所以直接使用系统的MarginLayoutParams
@Overrideprotected ViewGroup.LayoutParams generateLayoutParams(ViewGroup.LayoutParams p){return new MarginLayoutParams(p);}@Overridepublic ViewGroup.LayoutParams generateLayoutParams(AttributeSet attrs){return new MarginLayoutParams(getContext(), attrs);}@Overrideprotected ViewGroup.LayoutParams generateDefaultLayoutParams(){return new MarginLayoutParams(LayoutParams.MATCH_PARENT,LayoutParams.MATCH_PARENT);}
onMeasure
/*** 负责设置子控件的测量模式和大小 根据所有子控件设置自己的宽和高*/@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec){super.onMeasure(widthMeasureSpec, heightMeasureSpec);// 获得它的父容器为它设置的测量模式和大小int sizeWidth = MeasureSpec.getSize(widthMeasureSpec);int sizeHeight = MeasureSpec.getSize(heightMeasureSpec);int modeWidth = MeasureSpec.getMode(widthMeasureSpec);int modeHeight = MeasureSpec.getMode(heightMeasureSpec);Log.e(TAG, sizeWidth + "," + sizeHeight);// 如果是warp_content情况下,记录宽和高int width = 0;int height = 0;/*** 记录每一行的宽度,width不断取最大宽度*/int lineWidth = 0;/*** 每一行的高度,累加至height*/int lineHeight = 0;int cCount = getChildCount();// 遍历每个子元素for (int i = 0; i < cCount; i++){View child = getChildAt(i);// 测量每一个child的宽和高measureChild(child, widthMeasureSpec, heightMeasureSpec);// 得到child的lpMarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();// 当前子空间实际占据的宽度int childWidth = child.getMeasuredWidth() + lp.leftMargin+ lp.rightMargin;// 当前子空间实际占据的高度int childHeight = child.getMeasuredHeight() + lp.topMargin+ lp.bottomMargin;/*** 如果加入当前child,则超出最大宽度,则的到目前最大宽度给width,类加height 然后开启新行*/if (lineWidth + childWidth > sizeWidth){width = Math.max(lineWidth, childWidth);// 取最大的lineWidth = childWidth; // 重新开启新行,开始记录// 叠加当前高度,height += lineHeight;// 开启记录下一行的高度lineHeight = childHeight;} else// 否则累加值lineWidth,lineHeight取最大高度{lineWidth += childWidth;lineHeight = Math.max(lineHeight, childHeight);}// 如果是最后一个,则将当前记录的最大宽度和当前lineWidth做比较if (i == cCount - 1){width = Math.max(width, lineWidth);height += lineHeight;}}setMeasuredDimension((modeWidth == MeasureSpec.EXACTLY) ? sizeWidth: width, (modeHeight == MeasureSpec.EXACTLY) ? sizeHeight: height);}
首先得到其父容器传入的测量模式和宽高的计算值,然后遍历所有的childView,使用measureChild方法对所有的childView进行测量。然后根据所有childView的测量得出的宽和高得到该ViewGroup如果设置为wrap_content时的宽和高。最后根据模式,如果是MeasureSpec.EXACTLY则直接使用父ViewGroup传入的宽和高,否则设置为自己计算的宽和高。
onLayout
/*** 存储所有的View,按行记录*/private List<List<View>> mAllViews = new ArrayList<List<View>>();/*** 记录每一行的最大高度*/private List<Integer> mLineHeight = new ArrayList<Integer>();@Overrideprotected void onLayout(boolean changed, int l, int t, int r, int b){mAllViews.clear();mLineHeight.clear();int width = getWidth();int lineWidth = 0;int lineHeight = 0;// 存储每一行所有的childViewList<View> lineViews = new ArrayList<View>();int cCount = getChildCount();// 遍历所有的孩子for (int i = 0; i < cCount; i++){View child = getChildAt(i);MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();int childWidth = child.getMeasuredWidth();int childHeight = child.getMeasuredHeight();// 如果已经需要换行if (childWidth + lp.leftMargin + lp.rightMargin + lineWidth > width){// 记录这一行所有的View以及最大高度mLineHeight.add(lineHeight);// 将当前行的childView保存,然后开启新的ArrayList保存下一行的childViewmAllViews.add(lineViews);lineWidth = 0;// 重置行宽lineViews = new ArrayList<View>();}/*** 如果不需要换行,则累加*/lineWidth += childWidth + lp.leftMargin + lp.rightMargin;lineHeight = Math.max(lineHeight, childHeight + lp.topMargin+ lp.bottomMargin);lineViews.add(child);}// 记录最后一行mLineHeight.add(lineHeight);mAllViews.add(lineViews);int left = 0;int top = 0;// 得到总行数int lineNums = mAllViews.size();for (int i = 0; i < lineNums; i++){// 每一行的所有的viewslineViews = mAllViews.get(i);// 当前行的最大高度lineHeight = mLineHeight.get(i);Log.e(TAG, "第" + i + "行 :" + lineViews.size() + " , " + lineViews);Log.e(TAG, "第" + i + "行, :" + lineHeight);// 遍历当前行所有的Viewfor (int j = 0; j < lineViews.size(); j++){View child = lineViews.get(j);if (child.getVisibility() == View.GONE){continue;}MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();//计算childView的left,top,right,bottomint lc = left + lp.leftMargin;int tc = top + lp.topMargin;int rc =lc + child.getMeasuredWidth();int bc = tc + child.getMeasuredHeight();Log.e(TAG, child + " , l = " + lc + " , t = " + t + " , r ="+ rc + " , b = " + bc);child.layout(lc, tc, rc, bc);left += child.getMeasuredWidth() + lp.rightMargin+ lp.leftMargin;}left = 0;top += lineHeight;}
allViews的每个Item为每行所有View的List集合。
mLineHeight记录的为每行的最大高度。
23-48行,遍历所有的childView,用于设置allViews的值,以及mLineHeight的值。
57行,根据allViews的长度,遍历所有的行数
67-91行,遍历每一行的中所有的childView,对childView的left , top , right , bottom 进行计算,和定位。
92-93行,重置left和top,准备计算下一行的childView的位置。
好了,到此完成了所有的childView的绘制区域的确定,到此,我们的FlowLayout的代码也结束了~~静下心来看一看是不是也不难~
布局文件
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools"android:layout_width="fill_parent"android:layout_height="fill_parent"android:background="#E1E6F6"android:orientation="vertical" ><com.zhy.zhy_flowlayout02.FlowLayout
android:layout_width="fill_parent"android:layout_height="wrap_content" ><TextView
style="@style/text_flag_01"android:text="Welcome" /><TextView
style="@style/text_flag_01"android:text="IT工程师" /><TextView
style="@style/text_flag_01"android:text="学习ing" /><TextView
style="@style/text_flag_01"android:text="恋爱ing" /><TextView
style="@style/text_flag_01"android:text="挣钱ing" /><TextView
style="@style/text_flag_01"android:text="努力ing" /><TextView
style="@style/text_flag_01"android:text="I thick i can" /></com.zhy.zhy_flowlayout02.FlowLayout><com.zhy.zhy_flowlayout02.FlowLayout
android:layout_width="fill_parent"android:layout_height="wrap_content"android:layout_marginTop="20dp" ><TextView
style="@style/text_flag_01"android:background="@drawable/flag_02"android:text="Welcome"android:textColor="#888888" /><TextView
style="@style/text_flag_01"android:background="@drawable/flag_02"android:text="IT工程师"android:textColor="#888888" /><TextView
style="@style/text_flag_01"android:background="@drawable/flag_02"android:text="学习ing"android:textColor="#888888" /><TextView
style="@style/text_flag_01"android:background="@drawable/flag_02"android:text="恋爱ing"android:textColor="#888888" /><TextView
style="@style/text_flag_01"android:background="@drawable/flag_02"android:text="挣钱ing"android:textColor="#888888" /><TextView
style="@style/text_flag_01"android:background="@drawable/flag_02"android:text="努力ing"android:textColor="#888888" /><TextView
style="@style/text_flag_01"android:background="@drawable/flag_02"android:text="I thick i can"android:textColor="#888888" /></com.zhy.zhy_flowlayout02.FlowLayout><com.zhy.zhy_flowlayout02.FlowLayout
android:layout_width="fill_parent"android:layout_height="wrap_content"android:layout_marginTop="20dp" ><TextView
style="@style/text_flag_01"android:background="@drawable/flag_03"android:text="Welcome"android:textColor="#43BBE7" /><TextView
style="@style/text_flag_01"android:background="@drawable/flag_03"android:text="IT工程师"android:textColor="#43BBE7" /><TextView
style="@style/text_flag_01"android:background="@drawable/flag_03"android:text="学习ing"android:textColor="#43BBE7" /><TextView
style="@style/text_flag_01"android:background="@drawable/flag_03"android:text="恋爱ing"android:textColor="#43BBE7" /><TextView
style="@style/text_flag_01"android:background="@drawable/flag_03"android:text="挣钱ing"android:textColor="#43BBE7" /><TextView
style="@style/text_flag_01"android:background="@drawable/flag_03"android:text="努力ing"android:textColor="#43BBE7" /><TextView
style="@style/text_flag_01"android:background="@drawable/flag_03"android:text="I thick i can"android:textColor="#43BBE7" /></com.zhy.zhy_flowlayout02.FlowLayout></LinearLayout>
参考链接
Android 自定义ViewGroup 实战篇 -> 实现FlowLayout - Hongyang - 博客频道 - CSDN.NET
源代码
源代码