android - 如何在 Java (Android Studio) 中的类之间传递变量值？

Question

这是我的变量:

public class List extends Activity {

double lat;
double lon;

public class MyLocationListener implements LocationListener{
  @Override
  public void onLocationChanged(Location loc){
    lat = loc.getLatitude();
    lon = loc.getLongitude();
  }
.......
}

我想在这里获取纬度和经度值:

public class AmbilData extends AsyncTask<String, String, String> {
    .....

    protected String doInBackground(String... arg0) {
    // TODO Auto-generated method stub

    String url;

    url = "http://anjayanjay.esy.es?lat="+lat+"&lon="+lon; //here i need the variable value
 .......................
 }

我刚开始使用 android studio，当我运行这段代码时，lat = 0 和 lon = 0。谁能告诉我如何解决这个问题？

Answer 1

您可以通过构造函数传递它:

public class List extends Activity {

double lat;
double lon;

public class MyLocationListener implements LocationListener{
  @Override
  public void onLocationChanged(Location loc){
    lat = loc.getLatitude();
    lon = loc.getLongitude();
    new AmbilData(loc).execute();
  }
.......
}

public class AmbilData extends AsyncTask<String, String, String> {
    private Location mLoc;
    .....

    public AmbilData(Location loc) {
        mLoc = loc;
    }

    protected String doInBackground(String... arg0) {
    // TODO Auto-generated method stub

    String url;

    url = "http://anjayanjay.esy.es?lat="+mLoc.getLatitude()+"&lon="+mLoc.getLongitude(); //here i need the variable value
 .......................
 }

或者通过AsyncTask的Param，这需要改变你的AsyncTask的第一个泛型:

public class List extends Activity {

double lat;
double lon;

public class MyLocationListener implements LocationListener{
  @Override
  public void onLocationChanged(Location loc){
    lat = loc.getLatitude();
    lon = loc.getLongitude();
    new AmbilData().execute(loc);
  }
.......
}

public class AmbilData extends AsyncTask<Location, String, String> {
    .....

    protected String doInBackground(Location... arg0) {
    // TODO Auto-generated method stub

    String url;

    url = "http://anjayanjay.esy.es?lat="+arg0[0].getLatitude()+"&lon="+arg0[0].getLongitude(); //here i need the variable value
 .......................
 }