标题是阿里电话面试的问题,一直以为自己很清楚MVC模式,结果被问到时,居然没法将MVC和Android中各个组件对应起来,所以,面试肯定挂了,不过面试也是学习的一种方式,可以知道大公司看中什么,以及自己还有哪些知识漏洞,例如这次面试就学到了很多东西。

  大家可以在看下面的内容之前,也想想能否把MVC及与Android各个组件的对应关系讲清楚,看是否还有和我一样对MVC一知半解的。

    如果写的有问题的地方,欢迎讨论。转载请注明出处:http://www.cnblogs.com/John-Chen/p/4458823.html

 

  学习中读了很多别人总结的文章,有几篇不错,推荐给大家:  

  前端之Android入门(3):MVC模式:
  http://isux.tencent.com/learn-android-from-zero-session3.html
  http://isux.tencent.com/learn-android-from-zero-session4.html
  http://isux.tencent.com/learn-android-from-zero-session5-html.html

  The Activity Revisited:
  http://www.therealjoshua.com/2012/07/android-architecture-part-10-the-activity-revisited/

  谈谈UI架构设计的演化:
  http://www.cnblogs.com/winter-cn/p/4285171.html

  MVC,MVP 和 MVVM 的图示:
  http://www.ruanyifeng.com/blog/2015/02/mvcmvp_mvvm.html

  关于另一种框架模式MVP的实践:

  http://www.imooc.com/wenda/detail/216700

 

  重新学习思考之后,再看自己项目中的某些实现,其实很多地方已经是遵循MVC的思想在实现,只是在设计和实现时,没提升到框架模式,只是根据以前的经验,以及一些基本的设计思想在做,所以被问到MVC模式时,也没想到项目中有用到的地方。我觉得不管了不了解什么框架模式以及设计模式,最主要的是得想办法做到解耦以及提升应用的稳定性。

 

  首先说下我现在认识的MVC与Android的各个组件的对应关系:

  View:自定义View或ViewGroup,负责将用户的请求通知Controller,并根据model更新界面;

  Controller:Activity或者Fragment,接收用户请求并更新model;

  Model:数据模型,负责数据处理相关的逻辑,封装应用程序状态,响应状态查询,通知View改变,对应Android中的datebase、SharePreference等。

 

  下面以我做的项目中的一个模块来详细介绍Android中的MVC框架模式:

  项目中有一个记录轨迹的功能,记录有几种状态:记录、暂停、停止:

  

  接下来我把轨迹控制部分的逻辑提取出来,做了一个简单地demo,

  demo源码地址:https://github.com/John-Chen/BlogSamples/tree/master/MVCDemo  

  

  View实现:

public class TrackCtrlView implements View.OnClickListener{
    private ImageView btnStartTrack, btnStopTrack, btnPauseTrack;
    private TrackCtrlViewListener listener;
    private TrackRecordInfo trackRecordInfo;

public TrackCtrlView(Activity activity, TrackCtrlViewListener listener){ this.listener = listener; btnStartTrack = (ImageView) activity.findViewById(R.id.btnStartTrack); btnStopTrack = (ImageView) activity.findViewById(R.id.btnStopTrack); btnPauseTrack = (ImageView) activity.findViewById(R.id.btnPauseTrack); btnStartTrack.setOnClickListener(this); btnStopTrack.setOnClickListener(this); btnPauseTrack.setOnClickListener(this); btnPauseTrack.setOnClickListener(this); } /** * 将用户请求通知Controller */ @Override public void onClick(View v) { switch(v.getId()){ case R.id.btnStartTrack: if(listener != null){ listener.trackStatusRequest(TrackRecordStatus.Recording); } break; case R.id.btnStopTrack: if(listener != null){ listener.trackStatusRequest(TrackRecordStatus.Stoped); } break; case R.id.btnPauseTrack: if(listener != null){ if(trackRecordInfo.status == TrackRecordStatus.Paused){ listener.trackStatusRequest(TrackRecordStatus.Recording); }else{ listener.trackStatusRequest(TrackRecordStatus.Paused); } } break; default: break; } } private void refreshView(){ TrackRecordStatus trackStatus = trackRecordInfo == null ? TrackRecordStatus.Stoped : trackRecordInfo.status; if (trackStatus == TrackRecordStatus.Recording) { btnStartTrack.setVisibility(View.GONE); btnPauseTrack.setVisibility(View.VISIBLE); btnStopTrack.setVisibility(View.VISIBLE); btnPauseTrack.setImageResource(R.drawable.btn_track_ctrl_pause); } else if (trackStatus == TrackRecordStatus.Paused) { btnStartTrack.setVisibility(View.GONE); btnPauseTrack.setVisibility(View.VISIBLE); btnStopTrack.setVisibility(View.VISIBLE); btnPauseTrack.setImageResource(R.drawable.btn_track_ctrl_resume); } else { // TrackRecordStatus.Stoped btnStartTrack.setVisibility(View.VISIBLE); btnPauseTrack.setVisibility(View.GONE); btnStopTrack.setVisibility(View.GONE); } }
   public void setTrackRecordInfo(@Nullable TrackRecordInfo trackRecordInfo) { this.trackRecordInfo = trackRecordInfo; refreshView(); } public interface TrackCtrlViewListener{ /** * 用户点击按钮 */ public void trackStatusRequest(@Nullable TrackRecordStatus newStatus); } }

 

  Model实现:

public class TrackRecordInfo {
    private static final Gson gson = new Gson();

    /**
     * 应该是保存轨迹数据库id,此demo中数据库操作不实现,暂时trackId一直为0
     */
    public int trackId;

    public TrackRecordStatus status;

    public TrackRecordInfo(int trackId, TrackRecordStatus status) {
        this.trackId = trackId;
        this.status = status;
    }

    @NonNull
    public static TrackRecordInfo loadTrackRecordInfo(@NonNull Context context){
        String pref = SpUtil.getString(context, SpUtil.KEY_TRACK_RECORD_INFO, "");
        if(!TextUtils.isEmpty(pref)){
            return gson.fromJson(pref, TrackRecordInfo.class);
        }
        return null;
    }

    public static void changeTrackRecordInfo(@NonNull Context context, @Nullable TrackRecordInfo info){
        SpUtil.saveString(context,
                SpUtil.KEY_TRACK_RECORD_INFO,
                info == null ? "" : gson.toJson(info));

        //model通过消息总线,通知View刷新
        EventBus.getDefault().post(new EventTrackRecordInfoChanged(info));
    }
}

 

  Controller实现:

public class MainActivity extends ActionBarActivity implements TrackCtrlView.TrackCtrlViewListener{
    private TrackCtrlView trackCtrlView;
    private TrackRecordInfo trackRecordInfo;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        trackCtrlView = new TrackCtrlView(this, this);

        EventBus.getDefault().register(this);

        trackRecordInfo = TrackRecordInfo.loadTrackRecordInfo(this);
        trackCtrlView.setTrackRecordInfo(trackRecordInfo);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();

        EventBus.getDefault().unregister(this);
    }


    @Override
    public void trackStatusRequest(@Nullable TrackRecordStatus newStatus) {
        if(newStatus == TrackRecordStatus.Recording){
            int trackId = 0;  //在数据库创建一条轨迹,并获取到数据库id
            trackRecordInfo = new TrackRecordInfo(trackId, TrackRecordStatus.Recording);

        }else if (newStatus == TrackRecordStatus.Paused) {
            if(trackRecordInfo != null){
                trackRecordInfo.status = newStatus;
            }

        } else {
            trackRecordInfo = null;
        }
        TrackRecordInfo.changeTrackRecordInfo(this, trackRecordInfo);
    }

    public void onEventMainThread(EventTrackRecordInfoChanged event){
        trackRecordInfo = event.info;
        trackCtrlView.setTrackRecordInfo(trackRecordInfo);
    }

}

 

  最后总结下3者之间的关系:

  

    Android中,model通知view改变,可以通过消息总线实现。