Question

What is the API call I need to make in Android 2.2 (Froyo) to create a Wifi hotspot (as seen in the Tethering and Portable Hotspot settings item).

Answer 1

There is no official API, but you can use reflection to handle it. I know some say, it’s not recommended, however imho I say, screw it if Google doesn’t want to provide an API for whatever reason.

Below is the code of an activity I used in my application, where the user can enable/disable the Wifi AP.
When you enable Wifi AP, usually the regular Wifi will be turned off, so after the user disables the Wifi AP again, we’ll be activating regular wifi again.

The code sample below is taken from one of my projects, hope you can get the logic there easily. Let me know if you have further questions.

Code is tested on Nexus One 2.2 (and I think also 2.3) as well as on Samsung Galaxy S (2.2).

package com.myapp.android.activity.wifi;

import android.app.ProgressDialog;
import android.content.Context;
import android.net.wifi.WifiConfiguration;
import android.net.wifi.WifiManager;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.view.WindowManager;
import android.widget.Button;

import java.lang.reflect.Method;

public class WifiAP extends BaseActivity {

    // boolean mIsWifiEnabled = false;
    private static final int WIFI_AP_STATE_UNKNOWN = -1;
    private static final int WIFI_AP_STATE_DISABLING = 0;
    private static final int WIFI_AP_STATE_DISABLED = 1;
    private static final int WIFI_AP_STATE_ENABLING = 2;
    private static final int WIFI_AP_STATE_ENABLED = 3;
    private static final int WIFI_AP_STATE_FAILED = 4;

    private final String[] WIFI_STATE_TEXTSTATE = new String[] {
        "DISABLING","DISABLED","ENABLING","ENABLED","FAILED"
    };

    private WifiManager wifi;

    @Override
    protected void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        setContentView(R.layout.wifi);
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD
                |WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
                |WindowManager.LayoutParams.FLAG_DIM_BEHIND
        );

        wifi = (WifiManager) getSystemService(Context.WIFI_SERVICE);
    }

    @Override
    public void onResume() {
        super.onResume();
        updateStatusDisplay();
    }

    public void toggleWifi(View v) {
        boolean wifiApIsOn = getWifiAPState()==WIFI_AP_STATE_ENABLED || getWifiAPState()==WIFI_AP_STATE_ENABLING;
        new SetWifiAPTask(!wifiApIsOn,false).execute();
    }

    public void close(View v) {
        boolean wifiApIsOn = getWifiAPState()==WIFI_AP_STATE_ENABLED || getWifiAPState()==WIFI_AP_STATE_ENABLING;
        if (wifiApIsOn) {
            new SetWifiAPTask(false,true).execute();
        } else {
            finish();
        }
    }


    /**
     * Endable/disable wifi
     * @param enabled
     * @return WifiAP state
     */
    private int setWifiApEnabled(boolean enabled) {
        Log.d("WifiAP", "*** setWifiApEnabled CALLED **** " + enabled);
        if (enabled && wifi.getConnectionInfo() !=null) {
            wifi.setWifiEnabled(false);
            try {Thread.sleep(1500);} catch (Exception e) {}
        }

        //int duration = Toast.LENGTH_LONG;
        //String toastText = "MobileAP status: ";
        int state = WIFI_AP_STATE_UNKNOWN;
        try {
            wifi.setWifiEnabled(false);
            Method method1 = wifi.getClass().getMethod("setWifiApEnabled",
                WifiConfiguration.class, boolean.class);
            method1.invoke(wifi, null, enabled); // true
            Method method2 = wifi.getClass().getMethod("getWifiApState");
            state = (Integer) method2.invoke(wifi);
        } catch (Exception e) {
           Log.e(WIFI_SERVICE, e.getMessage());
           // toastText += "ERROR " + e.getMessage();
        }

        if (!enabled) {
            int loopMax = 10;
            while (loopMax>0 && (getWifiAPState()==WIFI_AP_STATE_DISABLING
                    || getWifiAPState()==WIFI_AP_STATE_ENABLED
                    || getWifiAPState()==WIFI_AP_STATE_FAILED)) {
                try {Thread.sleep(500);loopMax--;} catch (Exception e) {}
            }
            wifi.setWifiEnabled(true);
        } else if (enabled) {
            int loopMax = 10;
            while (loopMax>0 && (getWifiAPState()==WIFI_AP_STATE_ENABLING
                    || getWifiAPState()==WIFI_AP_STATE_DISABLED
                    || getWifiAPState()==WIFI_AP_STATE_FAILED)) {
                try {Thread.sleep(500);loopMax--;} catch (Exception e) {}
            }
        }

        return state;
    }


    private int getWifiAPState() {
        int state = WIFI_AP_STATE_UNKNOWN;
        try {
            Method method2 = wifi.getClass().getMethod("getWifiApState");
            state = (Integer) method2.invoke(wifi);
        } catch (Exception e) {}
        Log.d("WifiAP", "getWifiAPState.state " + (state==-1?"UNKNOWN":WIFI_STATE_TEXTSTATE[state]));
        return state;
    }

    private void updateStatusDisplay() {

        if (getWifiAPState()==WIFI_AP_STATE_ENABLED || getWifiAPState()==WIFI_AP_STATE_ENABLING) {
            ((Button)findViewById(R.id.btnWifiToggle)).setText("Turn off");
            findViewById(R.id.bg).setBackgroundResource(R.drawable.bg_wifi_on);
        } else {
            ((Button)findViewById(R.id.btnWifiToggle)).setText("Turn on");
            findViewById(R.id.bg).setBackgroundResource(R.drawable.bg_wifi_off);
        }

    }


    class SetWifiAPTask extends AsyncTask<Void, Void, Void> {

        boolean mMode;
        boolean mFinish;

        public SetWifiAPTask(boolean mode, boolean finish) {
            mMode = mode;
            mFinish = finish;
        }

        ProgressDialog d = new ProgressDialog(WifiAP.this);

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            d.setTitle("Turning WiFi AP " + (mMode?"on":"off") + "...");
            d.setMessage("...please wait a moment.");
            d.show();
        }

        @Override
        protected void onPostExecute(Void aVoid) {
            super.onPostExecute(aVoid);
            try {d.dismiss();} catch (IllegalArgumentException e) {};
            updateStatusDisplay();
            if (mFinish) finish();
        }

        @Override
        protected Void doInBackground(Void... params) {
            setWifiApEnabled(mMode);
            return null;
        }
    }


}