场景:

近期做的TODO APP需要在主页添加一个功能,就是可以左滑删除,右滑完成。看了一下当前其他人做的例如仿探探式的效果,核心功能基本一样,但是和我预想的还是有少量区别,于是干脆自己重头学一遍如何自定义layout并且实现我所期望的功能。顺便写个傻瓜式教程,总结一下前人的经验。

需要:

Android Studio, RecyclerView

方法:

1. ItemTouchHelper

首先来看一下这个类的官方定义:

This is a utility class to add swipe to dismiss and drag & drop support to RecyclerView.

It works with a RecyclerView and a Callback class, which configures what type of interactions are enabled and also receives events when user performs these actions.

Depending on which functionality you support, you should override onMove(RecyclerView, ViewHolder, ViewHolder) and / or onSwiped(ViewHolder, int).

This class is designed to work with any LayoutManager but for certain situations, it can be optimized for your custom LayoutManager by extending methods in the ItemTouchHelper.Callback class or implementing ItemTouchHelper.ViewDropHandler interface in your LayoutManager.

By default, ItemTouchHelper moves the items' translateX/Y properties to reposition them. You can customize these behaviors by overriding onChildDraw(Canvas, RecyclerView, ViewHolder, float, float, int, boolean) or onChildDrawOver(Canvas, RecyclerView, ViewHolder, float, float, int, boolean).

Most of the time you only need to override onChildDraw.

可以看出,这是一个可以支持RecyclerView实现用于滑动删除,拖拽效果的类。

他和recyclerview配合工作以确定什么样的交互方式可以使用,并且创建回调来对这些事件来进行接收

我们可以复写onMove和onSwiped来定义它的功能

这个类通常需要配合LayoutManager来使用

ItemHelper会将item重新移动,可以通过复写onChildDraw和onChildDrawOver来重新定义其行为

ok,我们直接用一下试试看

RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerview);
recyclerView.setLayoutManager(new LinearLayoutManager(this, RecyclerView.VERTICAL, false));
MyAdapter adapter = new MyAdapter(list);
recyclerView.setAdapter(adapter);
ItemTouchHelper helper = new ItemTouchHelper(new ItemTouchHelper.Callback() {
@Override
public int getMovementFlags(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder) {
return 0;
} @Override
public boolean onMove(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, @NonNull RecyclerView.ViewHolder target) {
return false;
} @Override
public void onSwiped(@NonNull RecyclerView.ViewHolder viewHolder, int direction) { }
});
helper.attachToRecyclerView(recyclerView);

运行之后,并没有任何效果,显然,这里我们需要定义之前说的回调来定义事件的接收,直接来看一下这个ItemTouchHelper.Callback的定义:

This class is the contract between ItemTouchHelper and your application. It lets you control which touch behaviors are enabled per each ViewHolder and also receive callbacks when user performs these actions.

To control which actions user can take on each view, you should override getMovementFlags(RecyclerView, ViewHolder) and return appropriate set of direction flags. (LEFTRIGHTSTARTENDUPDOWN). You can usemakeMovementFlags(int, int) to easily construct it. Alternatively, you can use ItemTouchHelper.SimpleCallback.

If user drags an item, ItemTouchHelper will call onMove(recyclerView, dragged, target). Upon receiving this callback, you should move the item from the old position (dragged.getAdapterPosition()) to new position (target.getAdapterPosition()) in your adapter and also call notifyItemMoved(int, int). To control where a View can be dropped, you can override canDropOver(RecyclerView, ViewHolder, ViewHolder). When a dragging View overlaps multiple other views, Callback chooses the closest View with which dragged View might have changed positions. Although this approach works for many use cases, if you have a custom LayoutManager, you can overridechooseDropTarget(ViewHolder, java.util.List, int, int) to select a custom drop target.

When a View is swiped, ItemTouchHelper animates it until it goes out of bounds, then calls onSwiped(ViewHolder, int). At this point, you should update your adapter (e.g. remove the item) and call related Adapter#notify event.

这个包含三个主要函数:

getMovementFlags(): 用来定义哪些方向可以用,例如上下左右,用来处理拖拽,START和END用来处理侧滑

onMove() 在这里需要定义item是怎么移动的,从哪移动到哪,并且可以修改被移动所遮挡的其他view的行为,这里主要实现的是拖拽

onSwipe() 同理,这里实现滑动

ok,我们来具体实现上面各个方法:

getMovementFlags()

int makeMovementFlags (int dragFlags,
int swipeFlags)
 

Convenience method to create movement flags.

For instance, if you want to let your items be drag & dropped vertically and swiped left to be dismissed, you can call this method with: makeMovementFlags(UP | DOWN, LEFT);

这里我们使用它推荐的makeMovementFlags(int dragFlag,int swipeFlag)来构建返回结果,这里两个参数是由二进制表示的,转化成二进制后各位01表示是否有这个方向, 因此我们对这些方向做 或 ( | ) 操作来构成参数。

onMove()

boolean onMove (RecyclerView recyclerView,
RecyclerView.ViewHolder viewHolder,
RecyclerView.ViewHolder target)
 

Called when ItemTouchHelper wants to move the dragged item from its old position to the new position.

If this method returns true, ItemTouchHelper assumes viewHolder has been moved to the adapter position of targetViewHolder (ViewHolder#getAdapterPosition()).

If you don't support drag & drop, this method will never be called.

viewHolder就是你正在拖拽的view,target就是你移动时被覆盖的view,想要实现拖拽效果,我们必须要更新从拖拽view到覆盖view之间所有item的位置,具体逻辑请看示例

onSwipe()

void onSwiped (RecyclerView.ViewHolder viewHolder,
int direction)
 

Called when a ViewHolder is swiped by the user.

If you are returning relative directions (START , END) from the getMovementFlags(RecyclerView, ViewHolder)method, this method will also use relative directions. Otherwise, it will use absolute directions.

If you don't support swiping, this method will never be called.

ItemTouchHelper will keep a reference to the View until it is detached from RecyclerView. As soon as it is detached, ItemTouchHelper will call clearView(RecyclerView, ViewHolder).

这里我们直接找到当前的item,然后删掉它,接着notify一下就行了,当然我们可以定义方向来判断到底是左滑还是右滑

完整代码如下:

这里由于需要传入adapter的信息,因此我们重新创建个类extend ItemTouchHelper.Callback

package com.wjk32.myapplication;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.ItemTouchHelper;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView; import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.ViewGroup;
import android.widget.TextView; import java.util.ArrayList;
import java.util.Collections;
import java.util.List; public class MainActivity extends AppCompatActivity { public static final String TAG="123";
public static final String TAG2="MainActivity"; String s="MainAc";
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.i(TAG, TAG2+" onCreate");
setContentView(R.layout.activity_main);
List<String> list = new ArrayList<>();
for(int i=0;i<100;i++) {
list.add(""+i);
}
RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerview);
recyclerView.setLayoutManager(new LinearLayoutManager(this, RecyclerView.VERTICAL, false));
final MyAdapter adapter = new MyAdapter(list);
recyclerView.setAdapter(adapter);
ItemTouchHelper helper = new ItemTouchHelper(new MyItemTouchCallback(adapter));
helper.attachToRecyclerView(recyclerView);
} public class MyItemTouchCallback extends ItemTouchHelper.Callback { private final MyAdapter adapter; public MyItemTouchCallback(MyAdapter adapter) {
this.adapter = adapter;
} @Override
public int getMovementFlags(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder) {
return makeMovementFlags(ItemTouchHelper.DOWN|ItemTouchHelper.RIGHT|ItemTouchHelper.UP|ItemTouchHelper.LEFT,
ItemTouchHelper.START|ItemTouchHelper.END);
} @Override
public boolean onMove(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, @NonNull RecyclerView.ViewHolder target) {
int startPosition = viewHolder.getAdapterPosition();
int endPosition = target.getAdapterPosition();
//the item to swap
int index=startPosition; //drag direction
int dir=startPosition-endPosition>0?-1:1; while(index<endPosition){
Collections.swap(adapter.getmItemLists(), index,index+dir );
index+=dir;
} recyclerView.getAdapter().notifyItemMoved(startPosition, endPosition);
return true;
} @Override
public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
int position = viewHolder.getAdapterPosition();
if (direction == ItemTouchHelper.END||direction == ItemTouchHelper.START) {
adapter.getmItemLists().remove(position);
adapter.notifyItemRemoved(position);
}
} } public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {
private List<String> mItemLists; public class MyViewHolder extends RecyclerView.ViewHolder {
public TextView textView;
public MyViewHolder(TextView v) {
super(v);
textView = v;
}
} public List<String> getmItemLists() {
return mItemLists;
}
public MyAdapter(List<String> myDataset) {
mItemLists = myDataset;
} @Override
public MyAdapter.MyViewHolder onCreateViewHolder(ViewGroup parent,
int viewType) {
TextView v = (TextView) LayoutInflater.from(parent.getContext())
.inflate(R.layout.item, parent, false);
MyViewHolder vh = new MyViewHolder(v);
return vh;
} @Override
public void onBindViewHolder(MyViewHolder holder, int position) {
holder.textView.setText(mItemLists.get(position)); }
@Override
public int getItemCount() {
return mItemLists.size();
}
}
}

好了,到现在我们已经实现了基本的一些功能。

接下来我们将进行一些深入的探索。

参考

1. https://yuqirong.me/2017/02/03/RecyclerView%E5%AE%9E%E7%8E%B0%E6%8B%96%E6%8B%BD%E6%8E%92%E5%BA%8F%E5%92%8C%E4%BE%A7%E6%BB%91%E5%88%A0%E9%99%A4/

Android滑动列表(拖拽,左滑删除,右滑完成)功能实现(1)的更多相关文章

  1. Android滑动列表(拖拽,左滑删除,右滑完成)功能实现(2)

    ItemTouchHelper类 之前我们实现了滑动列表的一些基本功能,为了实现更多的效果,我们来仔细看一下ItemTouchHelper中的类: ItemTouchHelper.SimpleCall ...

  2. RecyclerView进阶:使用ItemTouchHelper实现拖拽和侧滑删除

    现在RecyclerView的应用越来越广泛了,不同的应用场景需要其作出不同的改变.有时候我们可能需要实现侧滑删除的功能,比如知乎首页的侧滑删除,又或者长按Item进行拖动与其他Item进行位置的交换 ...

  3. ListView列表拖拽排序

    ListView列表拖拽排序能够參考Android源代码下的Music播放列表,他是能够拖拽的,源代码在[packages/apps/Music下的TouchInterceptor.java下]. 首 ...

  4. h5页面ios,双击向上滑动,拖拽到底部还能继续拖拽(露出黑色背景)

    h5页面ios,双击向上滑动,拖拽到底部还能继续拖拽 标签: 手机 2016-02-02 18:09 696人阅读 评论(0) 收藏 举报   在ios下,双击屏幕某些地方,滚动条会自动向上走一段. ...

  5. Appium(九):Appium API(三) 滑动和拖拽、高级手势、手机操作

    1. 滑动和拖拽 我们在做自动化测试的时候,有些按钮是需要滑动几次屏幕后才会出现,此时,我们需要使用代码来模拟手指的滑动,也就是接下来要学的滑动和拖拽了. 1.1 swipe滑动事件 从一个坐标位置滑 ...

  6. Taro UI开发小程序实现左滑喜欢右滑不喜欢效果

    前言:年后入职了一家新公司,与前同事交接完之后,发现公司有一个四端的项目(iOS,Android,H5,小程序),iOS和安卓都实现了左滑右滑的效果,而h5和小程序端没实现,询问得知前同事因网上没找到 ...

  7. js判断手指的上滑,下滑,左滑,右滑,事件监听

    原理:1:当开始一个touchstart事件的时候,获取此刻手指的横坐标startX和staerY: 2:当触发touchmove事件的时候,再获取此时手指的横坐标moveEndX和纵坐标moveEn ...

  8. Android中GridView拖拽的效果【android进化三十六】

      最 近看到联想,摩托罗拉等,手机launcher中有个效果,进入mainmenu后,里面的应用程序的图标可以拖来拖去,所以我也参照网上给的代码,写了 一个例子.还是很有趣的,实现的流畅度没有人家的 ...

  9. Android中GridView拖拽的效果

    最 近看到联想,摩托罗拉等,手机launcher中有个效果,进入mainmenu后,里面的应用程序的图标可以拖来拖去,所以我也参照网上给的代码,写了 一个例子.还是很有趣的,实现的流畅度没有人家的那么 ...

随机推荐

  1. 好的java资源地址

    前人栽树,后人乘凉.想当初自己初学Java时为了解决一个很基础的问题,好多的朋友热心的回复我,帮我分析错误.现在为了方便那些Java新手,特给出自己感觉比较好的学习网站和论坛,希望对朋友们能有点帮助. ...

  2. Standford NLP study

    Homepage https://stanfordnlp.github.io/CoreNLP/index.html Source Code: https://github.com/stanfordnl ...

  3. 深度学习与NLP简单应用

    在深度学习中,文本分类的主要原型:Text  label,坐边是输入端“X”,右边是输出端“Y”.行业baseline:用BoW(bag of words)表示sentences(如何将文本表达成一 ...

  4. CentOS命令登录MySQL时,报错ERROR 1045 (28000): Access denied for user root@localhost (using password: NO)错误解决方法

    1.停用mysql服务:# /etc/rc.d/init.d/mysqld stop 2.输入命令:# mysqld_safe --user=mysql --skip-grant-tables --s ...

  5. 风火轮SMC532使用

    2018年3月份申请了一个院创,要做一个基于NFC技术的考勤设备,想法是用手机的NFC将学号信息传导考勤机,由考勤机统计缺勤信息,因为自己的拖延症,一直拖到现在.现在一边写毕业论文一边准备院创答辩,又 ...

  6. 清北学堂学习总结day2

    今天是钟皓曦大佬讲课,先来膜一波   %%%%% •数论 数论是这次培训的一个重点,那么什么是数论呢? 数论是研究整数性质的东西,所以理论上day2不会涉及小数QwQ (切入正题) •整除性: 设a, ...

  7. Python自动化中的键盘事件

    1) from selenium import webdriver 加载模块 2) b = webdriver.Friefox() 打开浏览器 3) b.get(‘http://xxxxxxx’) 打 ...

  8. Java 多线程 - Synchronized关键字

    目录 1-Synchronized 关键字概述 2- Synchronized关键字作用域 3- Synchronized 原理(反编译指令解释) 正文 1-Synchronized 关键字概述 由于 ...

  9. 不能忽视 php warning

    2018-12-5 10:50:22 星期三 遇到一个问题: 前一行是取数组中的某一个值, 后一行是用heredoc输出一串javascript脚本; 因为取数组中值的时候键不存在, 导致后续输出的j ...

  10. 那什么时候会触发BFC呢?块级格式化上下文

    <html>根元素: float的值不为none: overflow的值为auto.scroll或hidden: display的值为table-cell.table-caption和in ...