android 消息机制与仿新闻客户端

效果图如下：

android 消息机制与仿新闻客户端_第1张图片

具体步骤如下：

1 布局文件中控件的设计

2 访问远程服务器的资源xml文件，该文件包含新闻的内容等信息

3 访问到内容后把访问内容显示到页面上

具体代码如下：

1 MainActivity

package com.yuanlp.newsclient;import android.graphics.Color;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.support.v7.app.AppCompatActivity;import android.view.View;import android.view.ViewGroup;import android.widget.BaseAdapter;import android.widget.LinearLayout;import android.widget.ListView;import android.widget.TextView;import android.widget.Toast;import com.yuanlp.newsclient.bean.NewsBean;import com.yuanlp.newsclient.utils.XMLToBean;import com.yuanlp.newsclient.view.SmartImageView;import java.io.InputStream;import java.net.HttpURLConnection;import java.net.URL;import java.util.List;public class MainActivity extends AppCompatActivity {    private static final int LOAD_ERROR =2 ;    private static final int LOAD_SUCCESS =1 ;    private ListView mLv_news;    private LinearLayout mLoading;    //new 一个Handler来做android的消息机制，处理子线程数据    private Handler handler=new Handler(){        @Override        public void handleMessage(Message msg) {            //不管加载成功失败，进度条应该隐藏            mLoading.setVisibility(View.INVISIBLE);            switch (msg.what){                case LOAD_ERROR:                    Toast.makeText(MainActivity.this, "加载失败", Toast.LENGTH_SHORT).show();                    break;                case LOAD_SUCCESS:                    //显示listView的内容                    mLv_news.setAdapter(new MyNewsAdapter());                    break;            }        }    };    private List mList;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        /**         * 初始化获取界面元素         */        initView();        /**         * 加载远程资源到本地文件         */        loadMessage();        //readMessage();    }    /**     * 初始化界面     */    private void initView() {        setContentView(R.layout.activity_main);        mLv_news = (ListView) findViewById(R.id.lv_news);        mLoading = (LinearLayout) findViewById(R.id.ll_loading);        //打开客户端后，设置ll_loading可见        mLoading.setVisibility(View.VISIBLE);    }    /**     * 加载远程资源到本地     */    private void loadMessage() {        NewsBean newsBean=null;        //访问网络不能再主线程中进行，需要一个新线程        new Thread(){            @Override            public void run() {                try {                    Thread.sleep(5000);                    NewsBean newsBean=null;                    URL url = new URL("http://192.168.1.107:8080/WebServer/news.xml");                    HttpURLConnection conn= (HttpURLConnection) url.openConnection();                    conn.setRequestMethod("GET");                    int code = conn.getResponseCode();                    if (code==200){                        //获取到资源                        InputStream is = conn.getInputStream();                        //调用utils方法，将xml文件转为list类型返回                        mList = XMLToBean.readStream(newsBean,is);                        //利用android的循环消息机制，放到UI线程中执行结果                        Message msg = Message.obtain();                        msg.what=LOAD_SUCCESS;                        handler.sendMessage(msg);                    }else{                        Message msg = Message.obtain();                        msg.what=LOAD_ERROR;                        handler.sendMessage(msg);                    }                } catch (Exception e) {                    e.printStackTrace();                    Message msg = Message.obtain();                    msg.what=LOAD_ERROR;                    handler.sendMessage(msg);                }            }        }.start();    }    /**     * 显示listView中的数据     */    private class MyNewsAdapter extends BaseAdapter {        @Override        public int getCount() {            return mList.size();        }        @Override        public View getView(int position, View convertView, ViewGroup parent) {            //布局打气筒，把xml资源文件转变为view     即加载另外的一个布局文件            View view = View.inflate(MainActivity.this, R.layout.news, null);            //获取子布局文件中的各个控件            SmartImageView img = (SmartImageView) view.findViewById(R.id.iv_img);            TextView tv_title= (TextView) view.findViewById(R.id.tv_title);            TextView tv_desc= (TextView) view.findViewById(R.id.tv_desc);            TextView tv_type= (TextView) view.findViewById(R.id.tv_type);            //获取当前位置的对象            NewsBean item = getItem(position);            //设置图片显示            img.showImgByPath(item.getImg());            tv_title.setText(item.getTitle());            tv_desc.setText(item.getDescription());            String type=item.getType();            if ("1".equals(type)){ //当类型为1时，表示有评论，而且显示评论数                tv_type.setText("评论:"+item.getComment());                tv_type.setTextColor(Color.BLACK);                tv_type.setBackgroundColor(Color.TRANSPARENT);            }else if ("2".equals(type)){                tv_type.setText("专题");                tv_type.setBackgroundColor(Color.RED);                tv_type.setTextColor(Color.WHITE);            }else if ("3".equals(type)){                tv_type.setText("直播");                tv_type.setBackgroundColor(Color.RED);                tv_type.setTextColor(Color.WHITE);            }            return view;        }        @Override        public NewsBean getItem(int position) {            return mList.get(position);        }        @Override        public long getItemId(int position) {            return position;        }    }}

2 utils 中的将xml转为list，可以参考前面几天写的博客，android解析xml。

package com.yuanlp.newsclient.utils;import android.util.Xml;import com.yuanlp.newsclient.bean.NewsBean;import org.xmlpull.v1.XmlPullParser;import java.io.InputStream;import java.util.ArrayList;import java.util.List;/** * Created by 原立鹏 on 2017/6/21. */public class XMLToBean {    public static List readStream(NewsBean newsBean, InputStream is){        List list=null;        try {            XmlPullParser xmlPullParser = Xml.newPullParser();            xmlPullParser.setInput(is,"utf-8");            int event=xmlPullParser.getEventType();            while(event!=XmlPullParser.END_DOCUMENT){                switch (event){  //根据eventType来区分，分为START_DOCUMENT,START_TAG,END_TAG,END_DOCUMENT                    case XmlPullParser.START_DOCUMENT:                        list=new ArrayList();                        break;                    case XmlPullParser.START_TAG:                        String tagName=xmlPullParser.getName();  //获取标签名称                        if (tagName.equalsIgnoreCase("item")){                            newsBean=new NewsBean();                        }else if (tagName.equalsIgnoreCase("title")){                            newsBean.setTitle(xmlPullParser.nextText());                        }else if (tagName.equalsIgnoreCase("description")){                            newsBean.setDescription(xmlPullParser.nextText());                        }else if (tagName.equalsIgnoreCase("p_w_picpath")){                            newsBean.setImg(xmlPullParser.nextText());                        }else if (tagName.equalsIgnoreCase("type")){                            newsBean.setType(xmlPullParser.nextText());                        }else if (tagName.equalsIgnoreCase("comment")){                            newsBean.setComment(xmlPullParser.nextText());                        }                        break;                    case XmlPullParser.END_TAG:                        if (xmlPullParser.getName().equalsIgnoreCase("item")&&newsBean!=null){                            list.add(newsBean);                            newsBean=null;                        }                }                event=xmlPullParser.next();            }        } catch (Exception e) {            e.printStackTrace();        }        return list;    }}

3 获取远程新闻的方法

package com.yuanlp.newsclient.view;import android.content.Context;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.os.Handler;import android.os.Message;import android.support.annotation.Nullable;import android.util.AttributeSet;import android.widget.ImageView;import java.io.InputStream;import java.net.HttpURLConnection;import java.net.URL;/** * Created by 原立鹏 on 2017/6/21. *//** * 根据url地址去获取远程图片，并显示到新闻标题的左侧 */public class SmartImageView extends ImageView {    private Handler handler=new Handler(){        @Override        public void handleMessage(Message msg) {            Bitmap bitmap= (Bitmap) msg.obj;            setImageBitmap(bitmap);        }    };    public SmartImageView(Context context) {        super(context);    }    public SmartImageView(Context context, @Nullable AttributeSet attrs) {        super(context, attrs);    }    public SmartImageView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);    }    public  void showImgByPath(final String imgURL){        new Thread(){            @Override            public void run() {                try {                    URL url = new URL(imgURL);                    HttpURLConnection conn = (HttpURLConnection) url.openConnection();                    conn.setRequestMethod("GET");                    int code = conn.getResponseCode();                    if (code==200){                        InputStream is = conn.getInputStream();                        Bitmap bitmap = BitmapFactory.decodeStream(is);                        Message msg = Message.obtain();                        msg.what=1;                        msg.obj=bitmap;                        handler.sendMessage(msg);                    }                } catch (Exception e) {                    e.printStackTrace();                }            }        }.start();    }}

4 activity_main.xml

<?xml version="1.0" encoding="utf-8"?>

5 news.xml

<?xml version="1.0" encoding="utf-8"?>

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