java的布局中最为简单的便是FlowLayout流式布局，组件按照设置对齐方式从左向右排列，一行排满到下一行继续排列。
让我们直接看一下代码：
package com.per.flowlayout;
import android.content.Context;
import android.content.res.TypedArray;
import android.database.DataSetObserver;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import com.meetime.etherflyer.R;
/**
* @author: dongwenlong
* @description: 流式布局-标签流容器
* @projectName: FlowLayout
* @date: 2018-12-06
* @time: 10:21
*/
public class FlowLayoutextends ViewGroup {
/**
* 每个item纵向间距
*/
private int mVerticalSpacing;
/**
* 每个item横向间距
*/
private int mHorizontalSpacing;
private BaseAdaptermAdapter;
private TagItemClickListenermListener;
private DataChangeObservermObserver;
public FlowLayout(Context context) {
this(context, null);
}
public FlowLayout(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public FlowLayout(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
/**
* 获得我们所定义的自定义样式属性
*/
TypedArray a = context.getTheme().obtainStyledAttributes(attrs, R.styleable.FlowLayout, defStyle, 0);
for (int i =0; i < a.getIndexCount(); i++) {
int attr = a.getIndex(i);
switch (attr) {
case 0:
mHorizontalSpacing = a.getDimensionPixelSize(0, 10);//10
break;
case 1:
mVerticalSpacing = a.getDimensionPixelSize(1, 5);//5
break;
}
}
a.recycle();
}
/**
* 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
*/
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
/**
* 默认宽为父容器为它设置的测量宽度
*/
int width = View.MeasureSpec.getSize(widthMeasureSpec);
/**
* 高
*/
int height =0;
/**
* 每一行的高度，累加至height
*/
int lineHeight =0;
/**
* 在warp_content情况下，记录当前childView的左边的一个位置
*/
int childLeft = getPaddingLeft();
/**
* 在warp_content情况下，记录当前childView的上边的一个位置
*/
int childTop = getPaddingTop();
// getChildCount得到子view的数目,遍历循环出每个子View
for (int i =0; i < getChildCount(); i++) {
//拿到index上的子view
View childView = getChildAt(i);
// 测量每一个child的宽和高
measureChild(childView, widthMeasureSpec, heightMeasureSpec);
//当前子空间实际占据的高度
int childHeight = childView.getMeasuredHeight();
//当前子空间实际占据的宽度
int childWidth = childView.getMeasuredWidth();
lineHeight = Math.max(childHeight, lineHeight);// 取最大值
//如果加入当前childView，超出最大宽度，则将目前最大宽度给width，类加height 然后开启新行
if (childWidth + childLeft + getPaddingRight() > width) {
childLeft = getPaddingLeft();// 重新开启新行，开始记录childLeft
childTop +=mVerticalSpacing + childHeight + lineHeight/2+30;// 叠加当前的高度
lineHeight = childHeight;// 开启记录下一行的高度
}else{
//否则累加当前childView的宽度
childLeft += childWidth +mHorizontalSpacing;
}
}
height += childTop + lineHeight + getPaddingBottom();
setMeasuredDimension(width, height);
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
int width = r - l;
int childLeft = getPaddingLeft();
int childTop = getPaddingTop();
int lineHeight =0;
//遍历所有childView根据其宽和高，计算子控件应该出现的位置
for (int i =0; i < getChildCount(); i++) {
final View childView = getChildAt(i);
if (childView.getVisibility() == View.GONE) {
continue;
}
int childWidth = childView.getMeasuredWidth();
int childHeight = childView.getMeasuredHeight();
lineHeight = Math.max(childHeight, lineHeight);
// 如果已经需要换行
if (childLeft + childWidth > width) {
childLeft = getPaddingLeft();
childTop +=mVerticalSpacing + lineHeight;
lineHeight =mVerticalSpacing + lineHeight;
}
childView.layout(childLeft, childTop, childLeft + childWidth, childTop + childHeight);
childLeft += childWidth +mVerticalSpacing;
}
}
@Override
public ViewGroup.LayoutParamsgenerateLayoutParams(AttributeSet attrs) {
return new ViewGroup.LayoutParams(this.getContext(), attrs);
}
private void drawLayout() {
if (mAdapter ==null ||mAdapter.getCount() ==0) {
return;
}
removeAllViews();
for (int i =0; i
View view =mAdapter.getView(i, null, null);
final int position = i;
view.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (mListener !=null) {
mListener.itemClick(position);
}
}
});
addView(view);
}
}
public void setAdapter(BaseAdapter adapter) {
if (mAdapter ==null) {
mAdapter = adapter;
if (mObserver ==null) {
mObserver =new DataChangeObserver();
mAdapter.registerDataSetObserver(mObserver);
}
drawLayout();
}
}
public void setItemClickListener(TagItemClickListener mListener) {
this.mListener = mListener;
}
public interface TagItemClickListener {
void itemClick(int position);
}
class DataChangeObserverextends DataSetObserver {
@Override
public void onChanged() {
drawLayout();
}
@Override
public void onInvalidated() {
super.onInvalidated();
}
}
}
欢迎线下交流：WX:dwl-1591293009
