SystemService

<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/><uses-permission android:name="android.permission.CHANGE_WIFI_STATE"/><uses-permission android:name="android.permission.INTERNET"></uses-permission><uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"></uses-permission><uses-permission android:name="android.permission.GET_TASKS"/>

public class MainActivity extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        LayoutInflater inflater = (LayoutInflater) MainActivity.this.getSystemService(LAYOUT_INFLATER_SERVICE);        View view = View.inflate(MainActivity.this ,R.layout.activity_main, null);        setContentView(view);        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);        setSupportActionBar(toolbar);        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);        fab.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View view) {                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)                        .setAction("Action", null).show();            }        });    }    public void doClick(View v){        switch (v.getId()) {            case R.id.network:                if(isNetWorkConnected(MainActivity.this) == true){                    Toast.makeText(MainActivity.this, "网络已经打开", Toast.LENGTH_SHORT).show();                }else {                    Toast.makeText(MainActivity.this, "网络未连接", Toast.LENGTH_SHORT).show();                }                break;            case R.id.wifi:                WifiManager wifiManager = (WifiManager) MainActivity.this.getSystemService(WIFI_SERVICE);                if(wifiManager.isWifiEnabled()){                    wifiManager.setWifiEnabled(false);                    Toast.makeText(MainActivity.this, "WIFI已经关闭", Toast.LENGTH_SHORT).show();                }else{                    wifiManager.setWifiEnabled(true);                    Toast.makeText(MainActivity.this, "WIFI已经打开", Toast.LENGTH_SHORT).show();                }                break;            case R.id.sound:                AudioManager audioManager = (AudioManager) MainActivity.this.getSystemService(AUDIO_SERVICE);                //得到系统音量                int max = audioManager.getStreamMaxVolume(AudioManager.STREAM_SYSTEM);                int current = audioManager.getStreamVolume(AudioManager.STREAM_RING);                Toast.makeText(MainActivity.this, "系统的最大音量为" + max + "当前音量为" + current,                                Toast.LENGTH_SHORT).show();                break;            case R.id.getPackageName:                ActivityManager activityManager = (ActivityManager) MainActivity.this.getSystemService(ACTIVITY_SERVICE);                String packageName = activityManager.getRunningTasks(1).get(0).topActivity.getPackageName();                Toast.makeText(MainActivity.this, "当前运行的Activity的包名" + packageName, Toast.LENGTH_SHORT).show();                break;        }    }    @Override    public boolean onCreateOptionsMenu(Menu menu) {        // Inflate the menu; this adds items to the action bar if it is present.        getMenuInflater().inflate(R.menu.menu_main, menu);        return true;    }    @Override    public boolean onOptionsItemSelected(MenuItem item) {        // Handle action bar item clicks here. The action bar will        // automatically handle clicks on the Home/Up button, so long        // as you specify a parent activity in AndroidManifest.xml.        int id = item.getItemId();        //noinspection SimplifiableIfStatement        if (id == R.id.action_settings) {            return true;        }        return super.onOptionsItemSelected(item);    }    public boolean isNetWorkConnected(Context context) {        if (context != null) {            ConnectivityManager mConnectivityManager = (ConnectivityManager) context                    .getSystemService(CONNECTIVITY_SERVICE);            NetworkInfo mNetWorkInfo = mConnectivityManager                    .getActiveNetworkInfo();            if (mNetWorkInfo != null) {                return mNetWorkInfo.isAvailable();            }        }        return false;    }}