请求网络，Handler信息传递，流转字符串

Handler消息传递

HttpURLConnection请求访问网络

根据流返回一个字符串信息

访问网络的权限：<uses-permission android:name="android.permission.INTERNET"/>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity" >

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >

        <EditText
            android:id="@+id/et_url"
            android:layout_width="0dip"
            android:text="http://192.168.1.254:8080/ServerItheima28/test.jsp"
            android:layout_height="wrap_content"
            android:singleLine="true"
            android:layout_weight="1" />

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:onClick="getHtml"
            android:text="GO" />
    </LinearLayout>

    <ScrollView
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" >

        <TextView
            android:id="@+id/tv_html"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent" />
    </ScrollView>

</LinearLayout>

package com.itheima28.htmldemo;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

	private static final String TAG = "MainActivity";
	private static final int SUCCESS = 0;
	protected static final int ERROR = 1;
	private EditText etUrl;
	private TextView tvHtml;

	private Handler handler = new Handler() {

		@Override
		public void handleMessage(Message msg) {
			super.handleMessage(msg);
			switch (msg.what) {
			case SUCCESS:
				 tvHtml.setText((String) msg.obj);
				break;
			case ERROR:
				Toast.makeText(MainActivity.this, "访问失败", 0).show();
				break;
			default:
				break;
			}
		}

	};

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		etUrl = (EditText) findViewById(R.id.et_url);
		tvHtml = (TextView) findViewById(R.id.tv_html);

	}

	public void getHtml(View v) {
		final String url = etUrl.getText().toString();
		//4.0之后，请求网络访问的代码都要放在一个线程中
		//这样请求出问题了也不会影响到原来的主线程
		new Thread(new Runnable() {

			@Override
			public void run() {
				// 请求网络
				String html = getHtmlFromInternet(url);

				if(!TextUtils.isEmpty(html)) {
					// 更新textview的显示了
					Message msg = new Message();
					msg.what = SUCCESS;
					msg.obj = html;
					handler.sendMessage(msg);
				} else {
					Message msg = new Message();
					msg.what = ERROR;
					handler.sendMessage(msg);
				}
			}
		}).start();
	}

	/**
	 * 根据给定的url访问网络, 抓去html代码
	 * @param url
	 * @return
	 */
	protected String getHtmlFromInternet(String url) {

		try {
			URL mURL = new URL(url);
			HttpURLConnection conn = (HttpURLConnection) mURL.openConnection();

			conn.setRequestMethod("GET");
			conn.setConnectTimeout(10000);
			conn.setReadTimeout(5000);

//			conn.connect();

			int responseCode = conn.getResponseCode();

			if(responseCode == 200) {
				InputStream is = conn.getInputStream();
				//根据流返回一个字符串信息
				String html = getStringFromInputStream(is);
				return html;
			} else {
				Log.i(TAG, "访问失败: " + responseCode);
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
		return null;
	}

	/**
	 * 根据流返回一个字符串信息
	 * @param is
	 * @return
	 * @throws IOException
	 */
	private String getStringFromInputStream(InputStream is) throws IOException {
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		byte[] buffer = new byte[1024];
		int len = -1;

		while((len = is.read(buffer)) != -1) {
			baos.write(buffer, 0, len);
		}
		is.close();

		String html = baos.toString();	// 把流中的数据转换成字符串, 采用的编码是: utf-8

		String charset = "utf-8";
		if(html.contains("gbk") || html.contains("gb2312")
				|| html.contains("GBK") || html.contains("GB2312")) {		// 如果包含gbk, gb2312编码, 就采用gbk编码进行对字符串编码
			charset = "gbk";
		}

		html = new String(baos.toByteArray(), charset);	// 对原有的字节数组进行使用处理后的编码名称进行编码
		baos.close();
		return html;
	}
}