android 中GPS的使有有关问题

public class GpsActivity extends Activity {
    LocationManager lm;
    TextView tv;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        this.setContentView(R.layout.gps);
        tv =(TextView) this.findViewById(R.id.tv1);
        lm= (LocationManager)  getSystemService(Context.LOCATION_SERVICE);
        List<String> proviers = lm.getAllProviders();
        for (String string : proviers) {
            System.out.println(string);
        }
        Location  location = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);
        updateLocation(location);
    
        
         
    }
    private void updateLocation(Location location){
        if(location!=null){
            StringBuffer sb = new StringBuffer();
            sb.append("当前位置信息\n");
            sb.append("经度:").append(location.getLongitude())
            .append("\n纬度：").append(location.getLatitude())
            .append("\n高度:").append(location.getAltitude())
            .append("\n方向:").append(location.getBearing());
            tv.setText(sb.toString());
            System.out.println(sb.toString());
        }else{
            tv.setText("没有获取到信息 ");
        }
    }
}