Android 大杂烩工程之ListView的开发2以及数据仓库开发模式

Posted 2020-07-04 WindAndHorse

今天是放完假后工作的第一天，为了证明我不是一段幽灵代码，我给各位看客老爷们说句：祝大家节日过得愉快（过得不愉快那也是人之常情）。

我们继续来讲一讲ListView的开发，上次讲到了ListView的适配器和布局模式，今天要讲的就是简单却也适用的点击事件处理了。之前我们的界面一进去就是跟机器人对话，面向的对象始终只有机器人一个，这次我们来仿照QQ的消息界面那样有一个对象列表，点击其中一个就能进入相应的聊天界面。话不多说，先上代码：

新增一个布局文件activity_chatlist.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal">

    <ImageView
        android:id="@+id/iv_chatList_icon"
        android:layout_width="40dp"
        android:layout_height="40dp"
        android:layout_marginLeft="@dimen/activity_vertical_margin"/>

    <TextView
        android:id="@+id/tv_chatList_account"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_marginLeft="@dimen/activity_vertical_margin"
        android:gravity="center"
        android:textSize="@dimen/mid_text_size"/>
</LinearLayout>

新增两个java文件ChatActivity.java

package com.teachmodel.fragment;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;

import com.teachmodel.R;
import com.teachmodel.adapter.ChatAdapter;
import com.teachmodel.bean.Chat;

import java.util.ArrayList;
import java.util.Hashtable;
import java.util.List;

/**
 * Created by windbreaker on 16/4/5.
 */
public class ChatActivity extends Activity {

    private ListView mListView;
    private List<Chat> mList;
    private ChatAdapter mChatAdapter;
    private Hashtable<String, String> ansChats;
    private EditText et_chat;
    private Button btn_chat;
    private String chatName;
    private int chatIcon;


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.fragment_first);
        init();
    }

    private void init() {
        Intent intent = getIntent();
        chatName = intent.getStringExtra("account");
        chatIcon = intent.getIntExtra("icon", 0);
        et_chat = (EditText) findViewById(R.id.et);
        btn_chat = (Button) findViewById(R.id.btn);
        mListView = (ListView) findViewById(R.id.lv_chat_list);
        mList = new ArrayList<>();
        ansChats = new Hashtable<>();
        ansChats.put("Hi", "Hello");
        ansChats.put("What is your name?", "My name is DuBe.");
        ansChats.put("What?DouBi?", "Yeah....");
        ansChats.put("Ha...,How interesting", "Thank you.");
        mChatAdapter = new ChatAdapter(mList, this);
        mListView.setAdapter(mChatAdapter);
        btn_chat.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Chat mChat = new Chat();
                mChat.setName("白马秋风");
                mChat.setIcon(R.mipmap.my);
                mChat.setMessage(et_chat.getText().toString());
                mChatAdapter.addItem(mChat);
                getAns(et_chat.getText().toString());
                et_chat.setText("");
            }
        });
    }

    private void getAns(String question) {
        Chat mChat = new Chat();
        mChat.setName(chatName);
        mChat.setIcon(chatIcon);
        if (ansChats.get(question) != null) {
            mChat.setMessage(ansChats.get(question));
        } else {
            mChat.setMessage("I dont know what you ask?");
        }
        mChatAdapter.addItem(mChat);
        mListView.setSelection(mListView.getBottom());
    }

}

ChatListAdapter.java

package com.teachmodel.adapter;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import com.teachmodel.R;
import com.teachmodel.bean.Chat;

import java.util.List;

/**
 * Created by windbreaker on 16/4/5.
 */
public class ChatListAdapter extends BaseAdapter {
    private List<Chat> chatList;
    private LayoutInflater mLayoutInflater;

    public ChatListAdapter(List<Chat> chatList, Context context) {
        this.chatList = chatList;
        this.mLayoutInflater = LayoutInflater.from(context);
    }

    @Override
    public int getCount() {
        return chatList.size();
    }

    @Override
    public Object getItem(int position) {
        return chatList.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder mViewHolder;
        if (convertView == null) {
            convertView = mLayoutInflater.inflate(R.layout.item_chatlist, null);
            mViewHolder = new ViewHolder();
            mViewHolder.iv = (ImageView) convertView.findViewById(R.id.iv_chatList_icon);
            mViewHolder.tv = (TextView) convertView.findViewById(R.id.tv_chatList_account);
            convertView.setTag(mViewHolder);
        } else {
            mViewHolder = (ViewHolder) convertView.getTag();
        }
        mViewHolder.tv.setText(chatList.get(position).getName());
        mViewHolder.iv.setImageResource(chatList.get(position).getIcon());
        return convertView;
    }

    class ViewHolder {
        ImageView iv;
        TextView tv;
    }
}

再改一下FirstFragment.java

package com.teachmodel.fragment;

import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ListView;

import com.teachmodel.R;
import com.teachmodel.adapter.ChatListAdapter;
import com.teachmodel.bean.Chat;

import java.util.ArrayList;
import java.util.List;

/**
 * Created by windbreaker on 16/3/23.
 */
public class FirstFragment extends Fragment {
    private View v;

    private ListView lv;
    private List<Chat> mList;
    private int[] iconLab = {R.mipmap.ic_launcher, R.mipmap.usericon, R.mipmap.my};
    private String[] nameLab = {"机器人", "管理员", "夜的风衣"};


    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle
            savedInstanceState) {
        v = inflater.inflate(R.layout.activity_chatlist, null);
        init();
        initData();
        return v;
    }

    private void init() {
        lv = (ListView) v.findViewById(R.id.lv_chatList);
        lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Intent intent = new Intent(getActivity(), ChatActivity.class);
                intent.putExtra("account", mList.get(position).getName());
                intent.putExtra("icon", mList.get(position).getIcon());
                startActivity(intent);
            }
        });
    }

    private void initData() {
        mList = new ArrayList<>();
        for (int i = 0; i < 3; i++) {
            Chat mChat = new Chat();
            mChat.setName(nameLab[i]);
            mChat.setIcon(iconLab[i]);
            mList.add(mChat);
        }
        ChatListAdapter mChatListAdapter = new ChatListAdapter(mList, getActivity());
        lv.setAdapter(mChatListAdapter);
    }

}

记得在AndroidManifest.xml注册新的activity组件：<activity android:name=".fragment.ChatActivity"/>

至此咋们运行一下，看看效果如何，请看大屏幕：

嗯哼，这略略一看，效果还不错。咋们来分析分析一下代码吧，首先是补充说一下上次没有说的适配器里的getView（）这个方法。

public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder mViewHolder;
        if (convertView == null) {
            convertView = mLayoutInflater.inflate(R.layout.item_chatlist, null);
            mViewHolder = new ViewHolder();
            mViewHolder.iv = (ImageView) convertView.findViewById(R.id.iv_chatList_icon);
            mViewHolder.tv = (TextView) convertView.findViewById(R.id.tv_chatList_account);
            convertView.setTag(mViewHolder);
        } else {
            mViewHolder = (ViewHolder) convertView.getTag();
        }
        mViewHolder.tv.setText(chatList.get(position).getName());
        mViewHolder.iv.setImageResource(chatList.get(position).getIcon());
        return convertView;
    }

第一行代码我们就看到了这个ViewHolder内部类，这个类是用来干什么的呢？这个其实是对布局文件item_chatlist里的控件的一个抽象，这个类里有有一个ImageView和TextView 刚好对应于布局文件里的两个控件。接下来的代码则是检查是否已经存在View对象了，如果没有则重新实例化，有的话就直接使用了。这样说起来可能比较抽象。咋们打个比方：把程序比较教官，把要实例化的对象看成是一排要报名的队员。现在教官知道一共有多少人，但是不知道有多少人已经发了身份卡（ViewHolder）。所以他开始点名，也就是这个过程：

if (convertView == null) {
            convertView = mLayoutInflater.inflate(R.layout.item_chatlist, null);
            mViewHolder = new ViewHolder();
            mViewHolder.iv = (ImageView) convertView.findViewById(R.id.iv_chatList_icon);
            mViewHolder.tv = (TextView) convertView.findViewById(R.id.tv_chatList_account);
            convertView.setTag(mViewHolder);
        } else {
            mViewHolder = (ViewHolder) convertView.getTag();
        }

先判断你有没有身份卡，没有的话我发给你一张

mViewHolder = new ViewHolder();
mViewHolder.iv = (ImageView) convertView.findViewById(R.id.iv_chatList_icon);
mViewHolder.tv = (TextView) convertView.findViewById(R.id.tv_chatList_account);

这个身份卡就是我以后找你你的标志了convertView.setTag(mViewHolder);

你拿了之后，把姓名和头像给写上

mViewHolder.tv.setText(chatList.get(position).getName());
mViewHolder.iv.setImageResource(chatList.get(position).getIcon());

如果你有的话，教官根据标签要求你拿出你相应的身份卡我看看

mViewHolder = (ViewHolder) convertView.getTag();

然后再给你核对一下你的身份卡信息

mViewHolder.tv.setText(chatList.get(position).getName());
mViewHolder.iv.setImageResource(chatList.get(position).getIcon());

直到把所有的队友的检查完一遍没问题就OK了。

讲完适配器的工作原理，咋们再来讲讲ListView如何响应点击事件。

listView的点击事件是很简单的，只需要在实例化后（lv = (ListView) v.findViewById(R.id.lv_chatList);）使用这个方法

lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
//你的执行代码                

Intent intent = new Intent(getActivity(), ChatActivity.class);
                intent.putExtra("account", mList.get(position).getName());
                intent.putExtra("icon", mList.get(position).getIcon());
                startActivity(intent);
            }
        });
就可以处理点击事件了。这里的position就是你点击的列表的第几项。

就这样，ListView的讲解就先到这里。我们接下来讲讲数据仓库的设计模式。

再讲这个概念之前，我们先来讲讲我们的程序，如你所见的，我们程序里的所有数据都是在activity里生成的，也就是说activity不仅仅要定义变量，管理变量，获取控件，处理控件的监听事件还要生成并且处理数据，管理跳转逻辑，管理自身的生命周期等等。如果让一个人来处理这些事情，我想那个人即使不会跳楼，也会不胜其烦。同样，这样对于activity来说也是不好的，因为他管理的东西太多太杂了。那咋办呢？难道也要上天吗？与太阳肩并肩？对于这个问题，我们只要做一下职能分离就好，就是把数据生成和数据处理的功能单独出来，activity只负责获取数据集合就OK了，这就是所谓的数据仓库设计了。不瞎逼逼，咋们来看看具体实现。

新增一个java文件：ChatLab.java

package com.teachmodel.bean;

import com.teachmodel.R;

import java.util.ArrayList;
import java.util.Hashtable;
import java.util.List;

/**
 * Created by windbreaker on 16/4/5.
 */
public class ChatLab {

    private static ChatLab mChatLab;
    private static List<Chat> mList;
    private Hashtable<String, String> ansChats;
    private int[] iconLab = {R.mipmap.ic_launcher, R.mipmap.usericon, R.mipmap.my};
    private String[] nameLab = {"机器人", "管理员", "夜的风衣"};

    private ChatLab() {

        mList = new ArrayList<>();
        for (int i = 0; i < 3; i++) {
            Chat mChat = new Chat();
            mChat.setName(nameLab[i]);
            mChat.setIcon(iconLab[i]);
            mList.add(mChat);
        }

        ansChats = new Hashtable<>();
        ansChats.put("Hi", "Hello");
        ansChats.put("What is your name?", "My name is DuBe.");
        ansChats.put("What?DouBi?", "Yeah....");
        ansChats.put("Ha...,How interesting", "Thank you.");
    }

    public static ChatLab getInstance() {
        if (mChatLab == null) {
            mChatLab = new ChatLab();
        }
        return mChatLab;
    }

    public List<Chat> getList() {
        return mList;
    }

    public Hashtable<String, String> getAns() {
        return ansChats;
    }
}

然后修改一下FirstFragment.java和ChatActivity.java

package com.teachmodel.fragment;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;

import com.teachmodel.R;
import com.teachmodel.adapter.ChatAdapter;
import com.teachmodel.bean.Chat;
import com.teachmodel.bean.ChatLab;

import java.util.ArrayList;
import java.util.Hashtable;
import java.util.List;

/**
 * Created by windbreaker on 16/4/5.
 */
public class ChatActivity extends Activity {

    private ListView mListView;
    private List<Chat> mList;
    private ChatAdapter mChatAdapter;
    private EditText et_chat;
    private Button btn_chat;
    private String chatName;
    private int chatIcon;
    private Hashtable<String, String> ansChats;


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.fragment_first);
        init();
        initData();
    }

    private void init() {
        et_chat = (EditText) findViewById(R.id.et);
        btn_chat = (Button) findViewById(R.id.btn);
        mListView = (ListView) findViewById(R.id.lv_chat_list);
    }

    private void initData() {
        Intent intent = getIntent();
        chatName = intent.getStringExtra("account");
        chatIcon = intent.getIntExtra("icon", 0);
        ansChats = ChatLab.getInstance().getAns();
        mList = new ArrayList<>();

        mChatAdapter = new ChatAdapter(mList, this);
        mListView.setAdapter(mChatAdapter);
        btn_chat.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Chat mChat = new Chat();
                mChat.setName("白马秋风");
                mChat.setIcon(R.mipmap.my);
                mChat.setMessage(et_chat.getText().toString());
                mChatAdapter.addItem(mChat);
                getAns(et_chat.getText().toString());
                et_chat.setText("");
            }
        });
    }

    private void getAns(String question) {
        Chat mChat = new Chat();
        mChat.setName(chatName);
        mChat.setIcon(chatIcon);
        if (ansChats.get(question) != null) {
            mChat.setMessage(ansChats.get(question));
        } else {
            mChat.setMessage("I dont know what you ask?");
        }
        mChatAdapter.addItem(mChat);
        mListView.setSelection(mListView.getBottom());
    }

}

package com.teachmodel.fragment;

import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ListView;

import com.teachmodel.R;
import com.teachmodel.adapter.ChatListAdapter;
import com.teachmodel.bean.Chat;
import com.teachmodel.bean.ChatLab;

import java.util.List;

/**
 * Created by windbreaker on 16/3/23.
 */
public class FirstFragment extends Fragment {
    private View v;

    private ListView lv;
    private List<Chat> mList;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle
            savedInstanceState) {
        v = inflater.inflate(R.layout.activity_chatlist, null);
        init();
        initData();
        return v;
    }

    private void init() {
        lv = (ListView) v.findViewById(R.id.lv_chatList);
        lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Intent intent = new Intent(getActivity(), ChatActivity.class);
                intent.putExtra("account", mList.get(position).getName());
                intent.putExtra("icon", mList.get(position).getIcon());
                startActivity(intent);
            }
        });
    }

    private void initData() {
        mList = ChatLab.getInstance().getList();
        ChatListAdapter mChatListAdapter = new ChatListAdapter(mList, getActivity());
        lv.setAdapter(mChatListAdapter);
    }

}

运行一下即可得出上图的结果。然后有的人也许会问这种设计模式有什么用？难道能提高程序的运行效率？这个也许没有提高程序的运行效率，反而还有可能略略影响了你的程序运行效率。说到这里，你也许会说我是个坑比。对此，我只能说，为什么会有这种设计模式呢？其实程序的所有设计模式都是以方便管理和编程为目的的，对于运行效率的提高主要是与你编程的算法有关。对于之前的无模式编程，如果你只有几行代码，其实有没有设计模式都无所谓了。但是你有几千甚至上万行代码的话，设计模式的就显得尤其重要。以数据仓库为例，如果你的程序有很多地方都要用到相同的数据，每个地方都要生成并且初始化数据，那不如把数据和调用数据的方法集中在一起，要用的数据的地方直接调用数据仓库里的数据就行了，自己也不用去管理数据了。这样是十分有利于整理思路和修改代码的。

今天就说到这里了，感谢各位看客老爷们的围观。

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