Android 新闻客户端开发

主界面的最终实现效果如下;



下面是MainActivity.java的代码

[java]

package com.xiaowu.news;

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

import org.json.JSONArray;
import org.json.JSONObject;

import android.app.Activity;
import android.content.Intent;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;

import android.os.AsyncTask;
import android.os.Bundle;
import android.view.Gravity;
import android.view.KeyEvent;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;

import android.widget.Button;
import android.widget.GridView;
import android.widget.HorizontalScrollView;

import android.widget.LinearLayout;
import android.widget.LinearLayout.LayoutParams;

import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;

import com.xiaowu.news.custom.ConstomSimpleAdapter;

import com.xiaowu.news.model.Category;

import com.xiaowu.news.service.SyncHttp;
import com.xiaowu.news.update.UpdateManager;

import com.xiaowu.news.util.DensityUtil;
import com.xiaowu.news.util.StringUtil;

/**
*
* @author wwj
*
*/
public class MainActivity
extends Activity {

private final
int COLUMNWIDTH_PX = 56;
// GridView每个单元格的宽度(像素)
private final
int FLINGVELOCITY_PX = 800;
// ViewFilper滑动的距离(像素)
private final
int NEWSCOUNT = 5; // 显示新闻的条数

private final
int SUCCESS = 0;
// 加载新闻成功
private final
int NONEWS = 1; // 没有新闻

private final
int NOMORENEWS = 2;
// 没有更多新闻
private final
int LOADERROR = 3; // 加载失败

private long exitTime;
//按返回键退出的时间
private int mColumnWidth_dip;

private int mFlingVelocity_dip;

private int mCid;
// 新闻编号
private String mCategoryTitle;
// 新闻分类标题
private ListView mNewslist;
// 新闻列表
private SimpleAdapter mNewslistAdapter;
// 为新闻内容提供需要显示的列表
private ArrayList<HashMap<String, Object>> mNewsData;
// 存储新闻信息的数据集合
private LayoutInflater mInflater;
// 用来动态载入没有loadmore_layout界面

private Button category_Button =
null; // 新闻分类标题栏的向右查看的按钮

private HorizontalScrollView categoryScrollView =
null;// 水平滚动图

private Button mTitleBarRefresh;
// 标题栏的刷新按钮
private ProgressBar mTitleBarProgress;
// 进度条
private Button mLoadmoreButton;
// 加载更多按钮

private LoadNewsAsyncTack mLoadNewsAsyncTack;
// 声明LoadNewsAsyncTack引用

@Override
public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);
setContentView(R.layout.news_home_layout);

//通过id来获取按钮的引用
mTitleBarRefresh = (Button) findViewById(R.id.titlebar_refresh);
mTitleBarProgress = (ProgressBar) findViewById(R.id.titlebar_progress);

mTitleBarRefresh.setOnClickListener(loadmoreListener);
// 将px转换为dip
mColumnWidth_dip = DensityUtil.px2dip(this, COLUMNWIDTH_PX);

mFlingVelocity_dip = DensityUtil.px2dip(this, FLINGVELOCITY_PX);

//初始化新闻分类的编号
mCid = 1;
mCategoryTitle = "焦点";
mInflater = getLayoutInflater();
//存储新闻信息的数据集合
mNewsData = new ArrayList<HashMap<String, Object>>();

// 获取数组资源
String[] categoryArray = getResources().getStringArray(
R.array.categories);

// 定义一个List数组，用来存放HashMap对象
final List<HashMap<String, Category>> categories =
new ArrayList<HashMap<String, Category>>();
// 分割新闻字符串
for (int i =
0; i < categoryArray.length; i++) {
String temp[] = categoryArray[i].split("[|]");
if (temp.length ==
2) {
int cid = StringUtil.string2Int(temp[0]);

String title = temp[1];
Category type = new Category(cid, title);
// 定义一个HashMap对象，用来存放键值对
HashMap<String, Category> hashMap = new HashMap<String, Category>();

hashMap.put("category_title", type);
categories.add(hashMap);
}
}
ConstomSimpleAdapter categoryAdapter = new ConstomSimpleAdapter(this,

categories, R.layout.category_item_layout,
new String[] {
"category_title" },
new int[] { R.id.category_title });

// 创建一个网格视图, 用于实现新闻标题的布局
GridView category = new GridView(this);

// 设置单元格的背景色为透明，这样选择分类时就不会显示黄色背景了
category.setSelector(new ColorDrawable(Color.TRANSPARENT));

// 设置每一个新闻标题的宽度
category.setColumnWidth(mColumnWidth_dip);
// 设置网格视图的列数
category.setNumColumns(GridView.AUTO_FIT);
// 设置对齐方式
category.setGravity(Gravity.CENTER);
// 根据单元格的宽度和数目计算网格视图的宽度
int width = mColumnWidth_dip * categories.size();

// 获取布局参数
LayoutParams params = new LayoutParams(width, LayoutParams.MATCH_PARENT);

// 设置参数
category.setLayoutParams(params);
// 设置Adapter
category.setAdapter(categoryAdapter);
// 通过ID获取LinearLayout布局对象
LinearLayout categoryLayout = (LinearLayout) findViewById(R.id.category_layout);

// 将网格视图组件添加到LinearLayout布局当中
categoryLayout.addView(category);

// 添加单元格点击事件
category.setOnItemClickListener(new OnItemClickListener() {

TextView categoryTitle;

@Override
public void onItemClick(AdapterView<?> parent, View view,

int position, long id) {

// TODO Auto-generated method stub
for (int i =
0; i < parent.getCount(); i++) {
categoryTitle = (TextView) parent.getChildAt(i);
categoryTitle.setTextColor(0XFFADB2AD);
categoryTitle.setBackgroundDrawable(null);

}
categoryTitle = (TextView) view;
categoryTitle.setTextColor(0xFFFFFFFF);

categoryTitle
.setBackgroundResource(R.drawable.image_categorybar_item_selected_background);

Toast.makeText(MainActivity.this, categoryTitle.getText(),

Toast.LENGTH_SHORT).show();
//获取新闻分类编号
mCid = categories.get(position).get("category_title").getCid();

mCategoryTitle = categories.get(position).get("category_title").getTitle();

mLoadNewsAsyncTack = new LoadNewsAsyncTack();

mLoadNewsAsyncTack.execute(0,
true);
}

});

//第一次获取新闻列表
getSpecCatNews(mCid, mNewsData, 0,
true);
// 箭头
categoryScrollView = (HorizontalScrollView) findViewById(R.id.categorybar_scrollView);

category_Button = (Button) findViewById(R.id.category_arrow_right);

category_Button.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {

// TODO Auto-generated method stub
categoryScrollView.fling(mFlingVelocity_dip);
}
});

mNewslistAdapter = new SimpleAdapter(this, mNewsData,

R.layout.newslist_item_layout, new String[] {
"newslist_item_title",
"newslist_item_digest",
"newslist_item_source", "newslist_item_ptime" },

new int[] { R.id.newslist_item_title,

R.id.newslist_item_digest, R.id.newslist_item_source,
R.id.newslist_item_ptime });
mNewslist = (ListView) findViewById(R.id.news_list);

View footerView = mInflater.inflate(R.layout.loadmore_layout,
null);
//在LiseView下面添加“加载更多”
mNewslist.addFooterView(footerView);
//显示列表
mNewslist.setAdapter(mNewslistAdapter);

mNewslist.setOnItemClickListener(new OnItemClickListener() {

@Override
public void onItemClick(AdapterView<?> parent, View view,

int position, long id) {

// TODO Auto-generated method stub
Intent intent = new Intent(MainActivity.this,

NewsDetailActivity.class);
intent.putExtra("categoryTitle", mCategoryTitle);

intent.putExtra("newsData", mNewsData);

intent.putExtra("position", position);
startActivity(intent);
}

});

mLoadmoreButton = (Button) findViewById(R.id.loadmore_btn);
mLoadmoreButton.setOnClickListener(loadmoreListener);

}

/**
* 获取指定类型的新闻列表
*
* @param cid
* @return
*/
private int getSpecCatNews(int cid, List<HashMap<String, Object>> newsList,

int startnid, boolean firstTime) {

// 如果是第一次加载的话
if (firstTime) {
newsList.clear();
}
//本机:http://10.0.2.2:8080/web/getSpecifyCategoryNews

//wifi局域网：192.168.220.1
String url = "http://10.0.2.2:8080/web/getSpecifyCategoryNews";

String params = "startnid=" + startnid +
"&count=" + NEWSCOUNT
+ "&cid=" + cid;
SyncHttp syncHttp = new SyncHttp();

try {
// 通过Http协议发送Get请求，返回字符串
String retStr = syncHttp.httpGet(url, params);
JSONObject jsonObject = new JSONObject(retStr);
int retCode = jsonObject.getInt("ret");

if (retCode == 0) {
JSONObject dataObj = jsonObject.getJSONObject("data");

// 获取返回数目
int totalNum = dataObj.getInt("totalnum");

if (totalNum > 0) {
// 获取返回新闻集合
JSONArray newslistArray = dataObj.getJSONArray("newslist");

// 将用JSON格式解析的数据添加到数据集合当中
for (int i =
0; i < newslistArray.length(); i++) {
JSONObject newsObject = (JSONObject) newslistArray
.opt(i);
HashMap<String, Object> hashMap = new HashMap<String, Object>();

hashMap.put("nid", newsObject.getInt("nid"));

hashMap.put("newslist_item_title",
newsObject.getString("title"));
hashMap.put("newslist_item_digest",
newsObject.getString("digest"));
hashMap.put("newslist_item_source",
newsObject.getString("source"));
hashMap.put("newslist_item_ptime",
newsObject.getString("ptime"));
hashMap.put("newslist_item_comments",

newsObject.getInt("commentcount"));
newsList.add(hashMap);
}
return SUCCESS;
} else {
//第一次加载新闻列表
if (firstTime) {
return NONEWS;
//没有新闻
} else {
return NOMORENEWS;
//没有更多新闻
}
}
} else {
return LOADERROR;
//加载新闻失败
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
return LOADERROR; //加载新闻失败

}
}

/**
* 为“加载更多”按钮定义匿名内部类
*/
private OnClickListener loadmoreListener =
new OnClickListener() {

@Override
public void onClick(View v) {

mLoadNewsAsyncTack = new LoadNewsAsyncTack();

switch (v.getId()) {
//点击加载更多
case R.id.loadmore_btn:
mLoadNewsAsyncTack.execute(mNewsData.size(),
false); //不是第一次加载新闻里列表
break;
//点击刷新按钮
case R.id.titlebar_refresh:
mLoadNewsAsyncTack.execute(0,
true);
break;
}
}
};

/**
* 异步更新UI
* @author wwj
*
*/
private class LoadNewsAsyncTack
extends AsyncTask<Object, Integer, Integer> {

//准备运行
@Override
protected void onPreExecute() {

mTitleBarRefresh.setVisibility(View.GONE);
mTitleBarProgress.setVisibility(View.VISIBLE);
mLoadmoreButton.setText(R.string.loadmore_text);
}
//在后台运行
@Override
protected Integer doInBackground(Object... params) {

return getSpecCatNews(mCid, mNewsData, (Integer) params[0],

(Boolean) params[1]);
}
//完成后台任务
@Override
protected void onPostExecute(Integer result) {

switch (result) {
//该栏目没有新闻
case NONEWS:
Toast.makeText(MainActivity.this, R.string.nonews, Toast.LENGTH_SHORT)

.show();
break;
//该栏目没有更多新闻
case NOMORENEWS:
Toast.makeText(MainActivity.this, R.string.nomorenews,

Toast.LENGTH_SHORT).show();
break;
//加载失败
case LOADERROR:
Toast.makeText(MainActivity.this, R.string.loadnewserror, Toast.LENGTH_SHORT)

.show();
break;
}
mTitleBarRefresh.setVisibility(View.VISIBLE);
//刷新按钮设置为可见
mTitleBarProgress.setVisibility(View.GONE); //进度条设置为不可见

mLoadmoreButton.setText(R.string.loadmore_btn);
//按钮信息替换为“加载更多”
mNewslistAdapter.notifyDataSetChanged(); //通知ListView更新数据

}
}

/**
* 添加菜单
*/
@Override
public boolean onCreateOptionsMenu(Menu menu) {

// TODO Auto-generated method stub
menu.add(1, 1,
1, "更新");
menu.add(1, 2,
2, "退出");
return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {

switch(item.getItemId()) {
case 1:
UpdateManager updateManager = new UpdateManager(MainActivity.this);

//检测更新
updateManager.checkUpdate();
break;
case 2:
finish();
break;
}
return true;

}

/**
* 按键触发的事件
*/
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {

if(keyCode == KeyEvent.KEYCODE_BACK
&& event.getAction() == KeyEvent.ACTION_DOWN){
if((System.currentTimeMillis() - exitTime >
2000)){
Toast.makeText(getApplicationContext(), R.string.backcancel
, Toast.LENGTH_LONG).show();
exitTime = System.currentTimeMillis();
}
else{
finish();
System.exit(0);
}
return true;
}
return super.onKeyDown(keyCode, event);

}
}

主界面的业务逻辑实现，要一步就实现是非常困难的，因为项目总是从简单到复杂，所以小巫只把关键点说一下就行了：

这里主要有三个关键点：

1.分类栏的实现？

首先创建一个GridView视图，通过GridView来填充数据，把每一类新闻分类显示到GridView视图中去，最后通过获取到界面布局中的LinearLayout对象，把GridView添加到LinearLayout布局当中去，最终实现效果。

2.获取新闻分类列表（对JSON格式数据的解析）？

JSON数据的解析并不算太难，主要把JSON数据的数据结构搞清楚，解析起来还是挺方便的。

进行解析虽然方便，但前提是要把数据得到，因为数据是要在服务器端得到，需要利用Android的Http通信来实现。

这里需要利用到httpGet还有httpPost方法，这个代码很需要贴一贴滴。自定义的SyncHttp类

[java]

package com.xiaowu.news.service;

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

import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;

import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;

import org.apache.http.impl.client.DefaultHttpClient;

import org.apache.http.message.BasicNameValuePair;

import org.apache.http.params.BasicHttpParams;
import org.apache.http.params.HttpConnectionParams;

import org.apache.http.params.HttpParams;
import org.apache.http.protocol.HTTP;

import org.apache.http.util.EntityUtils;

import com.xiaowu.news.model.Parameter;

public class SyncHttp {

/**
* 通过Get方式发送请求
* @param url
* @param params
* @return
* @throws Exception
*/
public String httpGet(String url, String params)
throws Exception {
String response = null;
//返回信息
//拼接请求URl
if(null != params && !params.equals("")) {

url += "?" + params;
}

int timeOutConnection =
3000;
int timeOutSocket = 5000;

HttpParams httpParams = new BasicHttpParams();

HttpConnectionParams.setConnectionTimeout(httpParams, timeOutConnection);
HttpConnectionParams.setSoTimeout(httpParams, timeOutSocket);

//构造HttpClient实例
HttpClient httpClient = new DefaultHttpClient();

//创建GET方法实例
HttpGet httpGet = new HttpGet(url);
try {
HttpResponse httpResponse = httpClient.execute(httpGet);
int statusCode = httpResponse.getStatusLine().getStatusCode();

if(statusCode == HttpStatus.SC_OK) {
//获得返回结果
response = EntityUtils.toString(httpResponse.getEntity());
}
else{
response = "返回码:" + statusCode;
}
} catch (Exception e) {
// TODO: handle exception
throw new Exception(e);

}
return response;
}

/**
* 通过post方式发送请求
* @param url
* @param params
* @return
* @throws Exception
*/
public String httpPost(String url, List<Parameter> params)
throws Exception {
String response = null;
int timeOutConnection =
3000;
int timeOutSocket = 5000;

HttpParams httpParams = new BasicHttpParams();

HttpConnectionParams.setConnectionTimeout(httpParams, timeOutConnection);
HttpConnectionParams.setSoTimeout(httpParams, timeOutSocket);

//构造HttpClient实例
HttpClient httpClient = new DefaultHttpClient();

HttpPost httpPost = new HttpPost(url);
if(params.size() >
0) {
//设置post请求参数
httpPost.setEntity(new UrlEncodedFormEntity(buildNameValuePair(params), HTTP.UTF_8));

}

//使用execute方法发送Http Post 请求，并返回HttpResponse对象
HttpResponse httpResponse = httpClient.execute(httpPost);

int statusCode = httpResponse.getStatusLine().getStatusCode();

if(statusCode == HttpStatus.SC_OK) {
//获得返回结果
response = EntityUtils.toString(httpResponse.getEntity());
}
else {
response = "返回码:" + statusCode;
}
return response;
}

/**
* 把Paramster类型集合转换为NameValuePair类型集合

* @param params
* @return
*/
private List<BasicNameValuePair> buildNameValuePair (List<Parameter> params) {

List<BasicNameValuePair> result = new ArrayList<BasicNameValuePair>();

for(Parameter param : params) {
BasicNameValuePair pair = new BasicNameValuePair(param.getName(), param.getValue());

result.add(pair);
}
return result;
}
}

定义好了SyncHttp类之后，就可以通过调用httpGet方法来获取数据，在Activity的getSpecCatNews方法有详细实现，看一下就可以知道了。

3.异步更新UI的实现？

关于异步更新UI也算是一个比较难理解的东西，在Activity里定义了一个继承AsyncTask类的内部类，并实现三个方法，比较灵活。