添加访问权限（AndroidManifest.xml文件里）

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

Java代码（MainActivity.java文件）

    package com.example.androidtest;                import android.net.ConnectivityManager;        import android.net.NetworkInfo.State;        import android.os.Bundle;        import android.app.Activity;        import android.content.Context;        import android.util.Log;        import android.view.Menu;                public class MainActivity extends Activity {                    @Override            protected void onCreate(Bundle savedInstanceState) {                super.onCreate(savedInstanceState);                setContentView(R.layout.activity_main);                                boolean bFlag = isWifiAvailable(this.getApplicationContext());                if (bFlag) {                    Log.i("Wifi state - ", "connected");                } else {                    Log.i("Wifi state - ", "not connected");                }                            }                        /**            * 判断wifi连接状态            *             * @param ctx            * @return            */            public boolean isWifiAvailable(Context ctx) {                ConnectivityManager conMan = (ConnectivityManager) ctx                        .getSystemService(Context.CONNECTIVITY_SERVICE);                State wifi = conMan.getNetworkInfo(ConnectivityManager.TYPE_WIFI)                        .getState();                if (State.CONNECTED == wifi) {                    return true;                } else {                    return false;                }            }                        @Override            public boolean onCreateOptionsMenu(Menu menu) {                // Inflate the menu; this adds items to the action bar if it is present.                getMenuInflater().inflate(R.menu.activity_main, menu);                return true;            }                }