android（20）（从网络抓取html显示在本地，把流转换成String，请求网络，简单的消息处理机制，编码问题）

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);

}
//得到html代码
public void getHtml(View v) {
final String url = etUrl.getText().toString();

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
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();
String html = getStringFromInputStream(is);//把流转换成字符串
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
* 也就是把流转换成字符串
* @param is
* @return
* @throws IOException
*/
private String getStringFromInputStream(InputStream is) throws IOException {
ByteArrayOutputStream baos = new ByteArrayOutputStream();//字节数组输出流
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（打回原形再设置编码）
baos.close();
return html;
}