Android之ListView分頁獲取網路數據客戶端實現（開啓異步任務，獲取網絡數據）（三）

①新建工程android_ListView_Paging

②新建包com.example.android_listview_paging.http中創建工具類HttpUtils.java

package com.example.android_listview_paging.http;

import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;

public class HttpUtils {

	/**
	 * 
	 * @param path
	 * @param encoding
	 * @return
	 */
	public static String sendPostMethod(String path, String encoding) {
		String result = "";
		HttpClient httpClient = new DefaultHttpClient();
		try {
			HttpPost post = new HttpPost(path);
			HttpResponse response = httpClient.execute(post);
			if (response.getStatusLine().getStatusCode() == 200) {
				result = EntityUtils.toString(response.getEntity(), encoding);
			}
		} catch (Exception e) {
			// TODO: handle exception
			e.printStackTrace();
		} finally {
			httpClient.getConnectionManager().shutdown();
		}
		return result;
	}
}

③新建包com.example.android_listview_paging.json中創建工具類JsonTools.java

package com.example.android_listview_paging.json;

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

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

public class JsonTools {

	/**
	 * 
	 * @param jsonString
	 * @return
	 */
	public static List<String> parseJsonList(String jsonString) {
		List<String> list = new ArrayList<String>();
		try {
			JSONObject jsonObject = new JSONObject(jsonString);
			JSONArray jsonArray = jsonObject.getJSONArray("citys");
			for (int i = 0; i < jsonArray.length(); i++) {
				list.add(jsonArray.getString(i));
			}
		} catch (Exception e) {
			// TODO: handle exception
			e.printStackTrace();
		}

		return list;
	}
}

④在包com.example.android_listview_paging中MainActivity.java

package com.example.android_listview_paging;

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

import com.example.android_listview_paging.http.HttpUtils;
import com.example.android_listview_paging.json.JsonTools;

import android.support.v7.app.ActionBarActivity;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends ActionBarActivity {

	private ListView listView;
	private MyAdapter adapter;
	private boolean isPaging;//是否進行分頁操作
	
	private String CITY_PATH="http://192.168.1.101:8080/Web_ListView_Paging/CityAction?pageNo=";
	List<String> total=new ArrayList<String>();//放置記錄的總條數
	
	private ProgressDialog dialog;
	private static int pageNo=1;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		listView=(ListView) this.findViewById(R.id.listView1);
		dialog=new ProgressDialog(MainActivity.this);
		dialog.setTitle("提示");
		dialog.setMessage("loading...");
		new MyTask().execute(CITY_PATH+pageNo);
		adapter=new MyAdapter();
		listView.setOnScrollListener(new OnScrollListener() {
			
			@Override
			public void onScrollStateChanged(AbsListView view, int scrollState) {
				// TODO Auto-generated method stub
				if(isPaging&&scrollState==OnScrollListener.SCROLL_STATE_IDLE){
					
					new MyTask().execute(CITY_PATH+pageNo);
				}
			}
			
			@Override
			public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
				// TODO Auto-generated method stub
				isPaging=(firstVisibleItem+visibleItemCount==totalItemCount);
			}
		});
	}
	
	class MyTask extends AsyncTask<String, Void, List<String>>{

		@Override
		protected void onPreExecute() {
			// TODO Auto-generated method stub
			super.onPreExecute();
			dialog.show();
		}
		@Override
		protected List<String> doInBackground(String... params) {
			// TODO Auto-generated method stub
			String jsonString=HttpUtils.sendPostMethod(params[0], "utf-8");//用一個http協議取出數據
			 List<String> list=JsonTools.parseJsonList(jsonString);
			return list;
		}
		
		@Override
		protected void onPostExecute(List<String> result) {
			// TODO Auto-generated method stub
			super.onPostExecute(result);
			//adapter=new MyAdapter();
			total.addAll(result);
			adapter.binData(total);//解決下拉不能返回
			if(pageNo==1){
				listView.setAdapter(adapter);
			}//解決每次刷新之後都返回到第一項
			//listView.setAdapter(adapter);
			adapter.notifyDataSetChanged();
			pageNo++;//更新UI的時候頁碼加1
			dialog.dismiss();
		}
		
	}
	
	//自定義適配器
	class MyAdapter extends BaseAdapter{

		List<String> list;//本地化list
		public MyAdapter() {
			// TODO Auto-generated constructor stub
		}
		
		//綁定數據
		public void binData(List<String> list){
			this.list=list;
		}
		
		@Override
		public int getCount() {
			// TODO Auto-generated method stub
			return list.size();
		}

		@Override
		public Object getItem(int position) {
			// TODO Auto-generated method stub
			return list.get(position);
		}

		@Override
		public long getItemId(int position) {
			// TODO Auto-generated method stub
			return position;
		}

		@Override
		public View getView(int position, View convertView, ViewGroup parent) {
			// TODO Auto-generated method stub
			TextView textView=null;
			if(convertView==null){
				textView=new TextView(MainActivity.this);
			}else{
				textView=(TextView) convertView;
			}
			textView.setTextSize(20);
			textView.setText(list.get(position));
			return textView;
		}
		
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

	@Override
	public boolean onOptionsItemSelected(MenuItem item) {
		// Handle action bar item clicks here. The action bar will
		// automatically handle clicks on the Home/Up button, so long
		// as you specify a parent activity in AndroidManifest.xml.
		int id = item.getItemId();
		if (id == R.id.action_settings) {
			return true;
		}
		return super.onOptionsItemSelected(item);
	}
}

運行效果圖