根据IP地址定位城市

java:

public class MainActivity extends AppCompatActivity {
    private TextView mText;
    private String mIPAddress;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mText = (TextView) findViewById(R.id.text);
    }

    public void click(View view) {
        requestIp();
    }

    private void requestIp() {
        String url = "http://2017.ip138.com/ic.asp";
        OkGo.get(url).execute(new AbsCallback<byte[]>() {


            @Override
            public byte[] convertSuccess(Response response) throws Exception {
                return new byte[0];
            }

            @Override
            public void onSuccess(byte[] bytes, Call call, Response response) {

                try {
                    //转化为GBK编码,返回结果为html格式
                    byte[] responseBytes = response.body().bytes();
                    String responseUrl = new String(responseBytes, "GBK");
                    Log.v("simon", responseUrl);
                    mText.setText(responseUrl);
                    //提取html中需要的部分
                    List resultList = getContext(responseUrl);
                    for (Iterator iterator = resultList.iterator(); iterator.hasNext(); ) {
                        String context = (String) iterator.next();
                        mText.setText(context);
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }

            }
        });
    }


    /**
     * 提取"<title>XXXX</title>"中的文字XXXX
     *
     * @param html 要解析的html文档内容
     * @return 解析结果，可以多次匹配，每次匹配的结果按文档中出现的先后顺序添加进结果List
     */
    public static List getContext(String html) {
        List resultList = new ArrayList();
        Pattern p = Pattern.compile("<center>([^</center>]*)");//匹配<title>开头，</title>结尾的文档
        Matcher m = p.matcher(html);//开始编译
        while (m.find()) {
            resultList.add(m.group(1));//获取被匹配的部分
        }
        return resultList;
    }
}

xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.simon.ipcheckdemo.MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="ip地址:"/>

    <TextView
        android:id="@+id/text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"/>

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="click"
        android:text="获取ip地址"/>
</LinearLayout>

权限:

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

返回的数据为:

结果: