android消息机制与仿新闻客户端
具体步骤如下:
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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 ListmList; @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 ListreadStream(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
5 news.xml
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