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：

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
		}));

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：

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);
			}
			
		});

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：

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);
		
	}
}

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）：

<?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：

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 "";
		}
	}
}

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);
		
	}
}