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;
    }