Android开发探秘之四：利用Intent实现数据传递

在Android开发过程中，很多人都熟悉Intent，这是个用于在多个View之间共享数据的类。本节主要是继承上节，通过点选ListView中的文本，把文本中的URL加载到一个新的页面上，并且打印出来。为了方便，我先把上一节的代码重新贴一下，因为在上一节后，代码做了少许修改：

Codetry {

			doc = Jsoup.parse(new URL("http://www.51yam.com"), 5000);

		} catch (MalformedURLException e1) {

			e1.printStackTrace();

		} catch (IOException e1) {

			e1.printStackTrace();

		}

		

		final List<Map<String, String>> list = new ArrayList<Map<String, String>>();

		Elements es = doc.getElementsByClass("subnav");

		

		for (int i=0;i<es.size();i++) {

			Element e = es.get(i);

						

			int count = e.getElementsByTag("a").size();

			for(int j=0;j<count;j++)

			{

				Map<String, String> map = new HashMap<String, String>();

				Element ex = e.getElementsByTag("a").get(j);

				map.put("title", ex.text());

				map.put("href", "http://www.51yam.com/"+ex.attr("href"));

				list.add(map);

			}

			

		}

		

		ListView listView = (ListView) findViewById(R.id.listView1);

		listView.setAdapter(new SimpleAdapter(this, list, android.R.layout.simple_list_item_2,

				new String[] { "title","href" }, new int[] {

				android.R.id.text1,android.R.id.text2

		}));

 

实现的效果如下：

然后我们需要做的就是当点击ListView中的项目的时候，程序会将每个话题下面的URL链接发送到新的页面显示：

下面是当点击ListView项目的时候，利用Intent传递数据的方法：

CodelistView.setOnItemClickListener(new OnItemClickListener(){



			@Override

			public void onItemClick(AdapterView<?> parent, View v, int position,long id) {

				//Toast.makeText(getApplicationContext(), (TextView), duration)

				

				System.out.println("position:"+position);

				System.out.println("id:"+id);

				

				//Toast.makeText(_GetWebResoureActivity.this, list.get(position).get("href"), Toast.LENGTH_SHORT).show();

				Intent intent = new Intent(v.getContext(),topicdetails.class);

				intent.putExtra("src", list.get(position).get("href"));

				startActivityForResult(intent,0);

			}

			

		});

在子页面“topicdetails.java”中，我们可以通过如下的方式来接收传递过来的值：

Codepackage com.android.web;



import android.app.Activity;

import android.content.Intent;

import android.os.Bundle;

import android.widget.EditText;

import java.lang.Object;



public class topicdetails extends Activity {



	private EditText editText;

	

	@Override

	protected void onCreate(Bundle savedInstanceState)

	{

		super.onCreate(savedInstanceState);

		setContentView(R.layout.topiccontent);

		editText = (EditText)this.findViewById(R.id.editText);

		

		

		String srcUrl = getIntent().getStringExtra("src");

		editText.setText(srcUrl);

		

	}

}

当然，一定不要忘记了在AndroidManifest.xml文件中添加Activity映射（黄色背景部分）：

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

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

    package="com.android.web"

    android:versionCode="1"

    android:versionName="1.0" >



    <uses-sdk android:minSdkVersion="7" />



    <!-- 加入访问网络的权限 -->

    <uses-permission android:name="android.permission.INTERNET" />



    <application

        android:icon="@drawable/ic_launcher"

        android:label="@string/app_name" >

        <activity

            android:label="@string/app_name"

            android:name="._GetWebResoureActivity" >

            <intent-filter >

                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

        </activity>

        <activity android:name=".topicdetails"></activity>

    </application>



</manifest>

这样当一切工作准备完毕后，运行程序，点击ListView 的Item，我们成功地跳转到了子页面：

以下是所有的源码：

主页面源码package com.android.web;



import java.io.BufferedInputStream;

import java.io.IOException;

import java.io.InputStream;

import java.net.MalformedURLException;

import java.net.URL;

import java.net.URLConnection;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import java.lang.Object;



import org.apache.http.util.ByteArrayBuffer;

import org.apache.http.util.EncodingUtils;

import org.jsoup.Jsoup;

import org.jsoup.nodes.Document;

import org.jsoup.nodes.Element;

import org.jsoup.select.Elements;



import android.app.Activity;

import android.content.Intent;

import android.os.Bundle;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.AdapterView;

import android.widget.AdapterView.OnItemClickListener;

import android.widget.ListView;

import android.widget.SimpleAdapter;

import android.widget.Toast;





public class _GetWebResoureActivity extends Activity {



	Document doc;



	@Override

	public void onCreate(Bundle savedInstanceState) {

		super.onCreate(savedInstanceState);

		setContentView(R.layout.main);



		findViewById(R.id.button1).setOnClickListener(new OnClickListener() {

			@Override

			public void onClick(View v) {

				load();

			}

		});

	}



	protected void load() {

		

		try {

			doc = Jsoup.parse(new URL("http://www.51yam.com"), 5000);

		} catch (MalformedURLException e1) {

			e1.printStackTrace();

		} catch (IOException e1) {

			e1.printStackTrace();

		}

		

		final List<Map<String, String>> list = new ArrayList<Map<String, String>>();

		Elements es = doc.getElementsByClass("subnav");

		

		for (int i=0;i<es.size();i++) {

			Element e = es.get(i);

						

			int count = e.getElementsByTag("a").size();

			for(int j=0;j<count;j++)

			{

				Map<String, String> map = new HashMap<String, String>();

				Element ex = e.getElementsByTag("a").get(j);

				map.put("title", ex.text());

				map.put("href", "http://www.51yam.com/"+ex.attr("href"));

				list.add(map);

			}

			

		}

		

		ListView listView = (ListView) findViewById(R.id.listView1);

		listView.setAdapter(new SimpleAdapter(this, list, android.R.layout.simple_list_item_2,

				new String[] { "title","href" }, new int[] {

				android.R.id.text1,android.R.id.text2

		}));

		listView.setOnItemClickListener(new OnItemClickListener(){



			@Override

			public void onItemClick(AdapterView<?> parent, View v, int position,long id) {

				//Toast.makeText(getApplicationContext(), (TextView), duration)

				

				System.out.println("position:"+position);

				System.out.println("id:"+id);

				

				//Toast.makeText(_GetWebResoureActivity.this, list.get(position).get("href"), Toast.LENGTH_SHORT).show();

				Intent intent = new Intent(v.getContext(),topicdetails.class);

				intent.putExtra("src", list.get(position).get("href"));

				startActivityForResult(intent,0);

			}

			

		});

		

	}



	/**

	 * @param urlString

	 * @return

	 */

	public String getHtmlString(String urlString) {

		try {

			URL url = null;

			url = new URL(urlString);



			URLConnection ucon = null;

			ucon = url.openConnection();



			InputStream instr = null;

			instr = ucon.getInputStream();



			BufferedInputStream bis = new BufferedInputStream(instr);



			ByteArrayBuffer baf = new ByteArrayBuffer(500);

			int current = 0;

			while ((current = bis.read()) != -1) {

				baf.append((byte) current);

			}

			return EncodingUtils.getString(baf.toByteArray(), "gbk");

		} catch (Exception e) {

			return "";

		}

	}

}

 

子页面源码package com.android.web;



import android.app.Activity;

import android.content.Intent;

import android.os.Bundle;

import android.widget.EditText;

import java.lang.Object;



public class topicdetails extends Activity {



	private EditText editText;

	

	@Override

	protected void onCreate(Bundle savedInstanceState)

	{

		super.onCreate(savedInstanceState);

		setContentView(R.layout.topiccontent);

		editText = (EditText)this.findViewById(R.id.editText);

		

		

		String srcUrl = getIntent().getStringExtra("src");

		editText.setText(srcUrl);

		

	}

}