欢迎您访问程序员文章站本站旨在为大家提供分享程序员计算机编程知识!
您现在的位置是: 首页

碎片的最佳实践 《第一行代码Android》

程序员文章站 2022-03-09 19:24:38
...

从14:00到20:00一直在做这个实践,毕竟自己也是刚刚开始学习Android 开发,实践过程中也是一直遇到各种各样的问题。下图是最终该一个结果,因为我用的是真机,因此只用手机测试了一下。

碎片的最佳实践 《第一行代码Android》碎片的最佳实践 《第一行代码Android》

最终的项目结构就是这样。总的说这个的思路并不是很难,但是由于它是一部分一部分教的,因此需要按照步骤一步步进行,不行写错地方,或者少写了一些函数,或者是直接粘贴复制。说说自己遇到的问题吧:
1.一开始写的项目有很多错误,于是我重新创建了一个项目,原本图省事,没想到粘贴复制过来的代码系统不识别,很多关键词直接报错,只好重新写那些关键词并导入对应的包

2.一定要按照书本上的原原本本的进行操作!!!否则你会非常痛苦,除非你思路很清晰。我和书本上xml文件的命名方法有几个不同,导致最后在引用对应的xml中的id的时候,需要思考很长时间....这段代码到底要实现什么功能...然后去找xml文件中的进行对应...累

3.一个很容易遇到的问题是Fragment的问题!!!!就像书上说的那样,可能会有两个不同包下的Fragment供你选择,一个是系统内置的android.app.Fragment,另一个是support-v4库中的android.support.v4.app.Fragment.书本强烈建议使用后者,因为它可以让碎片在所有Android系统版本中保持功能一致性。也就是说对于这个问题的处理方法可以是以下所示的(仅供参考)

import android.app.Fragment; 改为import android.support.v4.app.Fragment;以及将getSupportFragmentManager()改为getFragmentManager()如下图所示

碎片的最佳实践 《第一行代码Android》

如果你在建class的时候没有extends Fragment可会出现这个问题...直接加上就好

4.因为这本书是按照步骤一步步教我们实践的,因此很可能做到后面我们会把代码写错地方,这时候它会提示“...method cannot applied to...”诸如此类,此时一定要有耐心,重新看着书本整理一下代码出现的顺序.

5.超级不喜欢Android studio 中的提示,我总以为它的提示是正确的,but...最后很多书写错误都是因为它“善意的”提示。

不管怎么说,祝大家好运,一定要相信:是你的代码写错了而不是书本有问题!!!!

//MainActivity

package com.example.hui.fragmentbestpractice;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

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



//News
package com.example.hui.fragmentbestpractice;

/**
 * Created by hui on 2018/1/24.
 */

public class News {
    private String title;
    private String content;

    public String getTitle(){
        return title;
    }

    public void setTitle(String title){
        this.title = title;
    }

    public String getContent(){
        return content;
    }

    public void setContent(String content){
        this.content = content;

}}
//NewsContentActivity

package com.example.hui.fragmentbestpractice;

import android.content.Context;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class NewsContentActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_news_content);
        String newsTitle = getIntent().getStringExtra("news_title");
        String newsContent = getIntent().getStringExtra("activity_news_content");
        NewsContentFragment newsContentFragment= (NewsContentFragment)getSupportFragmentManager().findFragmentById(R.id.news_content_fragment);
        newsContentFragment.refresh(newsTitle,newsContent);
    }

        public static void actionStart(Context context, String newsTitle, String newsContent){
            Intent intent = new Intent(context,NewsContentActivity.class);
            intent.putExtra("news_title",newsTitle);
            intent.putExtra("news_content",newsContent);
            context.startActivity(intent);

        }


}
//NewsContentFragment

package com.example.hui.fragmentbestpractice;

import android.support.v4.app.Fragment;
//import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

/**
 * Created by hui on 2018/1/24.
 */

public class NewsContentFragment extends Fragment {
    private View view;

    public View onCreatView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
        view = inflater.inflate(R.layout.news_content_frag,container,false);
        return view;
    }

    public void refresh(String newsTitle,String newsContent){
        View visibilityLayout = view.findViewById(R.id.visibility_layout);
        visibilityLayout.setVisibility(View.VISIBLE);
        TextView newsTitleText = (TextView)view.findViewById(R.id.news_title);
        TextView newsContentText = (TextView)view.findViewById(R.id.news_content);
        newsTitleText.setText(newsTitle);
        newsContentText.setText(newsContent);
    }
}












//NewsTitleFragment


package com.example.hui.fragmentbestpractice;

import android.support.v4.app.Fragment;
import android.content.Context;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.app.Activity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

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

import static android.content.ContentValues.TAG;

/**
 * Created by hui on 2018/1/24.
 */

public class NewsTitleFragment extends Fragment{
    private boolean isTwoPane;


    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
        View view = inflater.inflate(R.layout.news_title_frag,container,false);
        RecyclerView newsTitleRecyclerView = (RecyclerView)view.findViewById(R.id.news_title_recycle_view);
        LinearLayoutManager LayoutManger = new LinearLayoutManager(getActivity());
        newsTitleRecyclerView.setLayoutManager(LayoutManger);
        NewsAdapter adapter = new NewsAdapter(getNews());
        newsTitleRecyclerView.setAdapter(adapter);
        return view;


    }

    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        if ((getActivity().findViewById(R.id.news_content_layout))!= null){
            isTwoPane = true;
        }else {
            isTwoPane = false;

        }
    }



     class NewsAdapter extends RecyclerView.Adapter<NewsAdapter.ViewHolder> {

         private List<News> mNewsList;

         class ViewHolder extends RecyclerView.ViewHolder {
             TextView newsTitleText;

             public ViewHolder(View view) {
                 super(view);
                 newsTitleText = (TextView) view.findViewById(R.id.news_title);
             }
         }

         public NewsAdapter(List<News> newsList) {
             mNewsList = newsList;
         }

         public NewsAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
             View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.news_item, parent, false);
             final ViewHolder holder = new ViewHolder(view);
             view.setOnClickListener(new View.OnClickListener() {
                 @Override
                 public void onClick(View v) {
                     News news = mNewsList.get(holder.getAdapterPosition());
                     if (isTwoPane) {
                         NewsContentFragment newsContentFragment = (NewsContentFragment) getFragmentManager().findFragmentById(R.id.news_content_fragment);
                         //NewsContentFragment newsContentFragment =(NewsContentFragment)getSupportFragmentManager().findFragmentById(R.id.news_content_fragment);
                         newsContentFragment.refresh(news.getTitle(), news.getContent());
                     } else {
                         NewsContentActivity.actionStart(getActivity(), news.getTitle(), news.getContent());
                     }
                 }
             });
             return holder;
         }

         @Override
         public void onBindViewHolder(NewsAdapter.ViewHolder holder, int position) {
             News news = mNewsList.get(position);
             holder.newsTitleText.setText(news.getTitle());
         }

         @Override
         public int getItemCount() {
             return mNewsList.size();
         }
     }

         private List<News> getNews(){
             List<News> newsList = new ArrayList<>();
             for(int i = 1; i<=50;i++){
                 News news = new News();
                 news.setTitle("This is news title"+i);
                 news.setContent(getRandomLengthContent("This is news content"+i+"."));
                 newsList.add(news);
             }
             return newsList;
         }

         private String getRandomLengthContent(String content){
             Random random = new Random();
             int length = random.nextInt(20)+1;
             StringBuilder builder = new StringBuilder();
             for(int i = 0;i<length;i++){
                 builder.append(content);
             }
             return builder.toString();
         }


}







相关标签: Android