加酷知识源

zsh: command not found:xxx

PATH=/bin:/usr/bin:/usr/local/bin:${PATH}

//正确
export PATH="$PATH:[PATH_TO_FLUTTER_GIT_DIRECTORY]/flutter/bin"
//错误
export PATH="PATH:[PATH_TO_FLUTTER_GIT_DIRECTORY]/flutter/bin"
//注意 PATH_TO_FLUTTER_GIT_DIRECTORY 是需要输入全路径的，/User/xxx/xxx,不是~符号！

package com.learning;

/* package whatever; // don't place package name! */

import java.util.HashMap;
class Entry {
	int value;
	int key;
	Entry left;
	Entry right;
}
public class LRUCache {

	HashMap<Integer, Entry> hashmap;
	Entry start, end;
	int LRU_SIZE = 4; // Here i am setting 4 to test the LRU cache
						// implementation, it can make be dynamic
	public LRUCache() {
		hashmap = new HashMap<Integer, Entry>();
	}

	public int getEntry(int key) {
		if (hashmap.containsKey(key)) // Key Already Exist, just update the
		{
			Entry entry = hashmap.get(key);
			removeNode(entry);
			addAtTop(entry);
			return entry.value;
		}
		return -1;
	}

	public void putEntry(int key, int value) {
		if (hashmap.containsKey(key)) // Key Already Exist, just update the value and move it to top
		{
			Entry entry = hashmap.get(key);
			entry.value = value;
			removeNode(entry);
			addAtTop(entry);
		} else {
			Entry newnode = new Entry();
			newnode.left = null;
			newnode.right = null;
			newnode.value = value;
			newnode.key = key;
			if (hashmap.size() > LRU_SIZE) // We have reached maxium size so need to make room for new element.
			{
				hashmap.remove(end.key);
				removeNode(end);				
				addAtTop(newnode);

			} else {
				addAtTop(newnode);
			}

			hashmap.put(key, newnode);
		}
	}
	public void addAtTop(Entry node) {
		node.right = start;
		node.left = null;
		if (start != null)
			start.left = node;
		start = node;
		if (end == null)
			end = start;
	}

	public void removeNode(Entry node) {

		if (node.left != null) {
			node.left.right = node.right;
		} else {
			start = node.right;
		}

		if (node.right != null) {
			node.right.left = node.left;
		} else {
			end = node.left;
		}
	}
	public static void main(String[] args) throws java.lang.Exception {
		// your code goes here
		LRUCache lrucache = new LRUCache();
		lrucache.putEntry(1, 1);
		lrucache.putEntry(10, 15);
		lrucache.putEntry(15, 10);
		lrucache.putEntry(10, 16);
		lrucache.putEntry(12, 15);
		lrucache.putEntry(18, 10);
		lrucache.putEntry(13, 16);

		System.out.println(lrucache.getEntry(1));
		System.out.println(lrucache.getEntry(10));
		System.out.println(lrucache.getEntry(15));

	}
}

body:   CustomScrollView(
        slivers: <Widget>[

          SliverGrid.count(
           //具体的配置
          ),
          
          
          //列表
          SliverFixedExtentList(
            delegate: SliverChildBuilderDelegate(
                  (context, index) => ConversationListItem(
                      delegate: this, conversation: conList[index]
                  ),
              childCount: conList.length,
            ),
            itemExtent: 100,
          ),
        ],
      ),

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';

//定义函数类型
typedef StringValue = void Function(String);

class ImageBtn extends StatelessWidget {
 //作为属性
  StringValue callback;

  ImageBtn({Key key,this.callback}) : super(key: key);

  @override
  Widget build(BuildContext context) {
   
    return new GestureDetector(
      onTap: () {
        print('MyButton was tappedq!');
        //调用
        this.callback("testString");
      },
      child: ...
      ),
    );
  }
}

//顶部按钮点击事件
void _ontap(String name){
  print(name);
}
//实例对象时传进去
ImageBtn(callback:_ontap)

//另外一种写法，不传参数也可以，仅仅是invoke外部函数，
ImageBtn(callback:(){
   //do sth...
})

Column(
          children: <Widget>[
            Expanded(child:
            Image.asset('assets/images/$imageName.png')
            ),
            
            Text(
              this.model.title,
              style: TextStyle(
                fontSize: 15,
                color: Colors.white,
              ),
            ),
          ],
        ),

ModalRoute.of(context).isCurrent

_tabController.addListener(() {
      if(_tabController.index == _tabController.animation.value){
        int index = _tabController.index;
        print("====================当前点击了$index===============");
      }

    });

//延迟1秒加载
Future.delayed(Duration(seconds: 1), (){
      //do sth
    });