Question

我对android编程有疑问。我有一个MainActivity类和实现LocationListner的类。我想从第二个类中更改onLocationChanged方法中的一些UI元素，但我不知道应该如何完成这样的事情。

这是我的mainActivity：

public class MainActivity extends AppCompatActivity {

private LocationGPS gps;
private TextView text;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    enableGPS();
    initGuiElements();
}

private void enableGPS()
{
    gps = new LocationGPS(this);
}

private void initGuiElements()
{
    text = (TextView) findViewById(R.id.textTop);
    text.setText("nothing yet");
}

}

这是我的位置课程。

public class LocationGPS implements LocationListener {

private Activity mainActivity;
private LocationManager locationManager;

public LocationGPS(Activity activity)
{
    this.mainActivity = activity;
    locationManager = (LocationManager) activity.getSystemService(Context.LOCATION_SERVICE);
    locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);
}

@Override
public void onLocationChanged(Location location) {
    //here I want to set text for TextView element
}

@Override
public void onStatusChanged(String provider, int status, Bundle extras) {

}

@Override
public void onProviderEnabled(String provider) {

}

@Override
public void onProviderDisabled(String provider) {

}

}

Answer 1

你有很多方法可以做到这一点，我将给出2个：

更改您的活动以实现LocationListener，当您调用locationManager.requestLocationUpdates时，将活动作为侦听器传递，这样您将获得在Activity中调用的回调，而不是在LocationGPS类中，MainActivity将会看到像：

public class MainActivity extends AppCompatActivity
    implements LocationListener {

private LocationGPS gps;

private TextView text;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    enableGPS();
    initGuiElements();
}

private void enableGPS() {
    gps = new LocationGPS(this);
}

private void initGuiElements() {
    text = (TextView) findViewById(R.id.textTop);
    text.setText("nothing yet");
}

@Override
public void onLocationChanged(Location location) {

}

@Override
public void onStatusChanged(String provider, int status,          
Bundle extras) {

}

@Override
public void onProviderEnabled(String provider) {

}

@Override
public void onProviderDisabled(String provider) {

}
}

和LocationGPS类：

public class LocationGPS {

private Activity mainActivity;

private LocationManager locationManager;

public LocationGPS(Activity activity) {
    this.mainActivity = activity;
    locationManager = (LocationManager) activity.getSystemService(Context.LOCATION_SERVICE);
    locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, mainActivity);
}
}

您可以在MainActivty中创建需要传递给LocationGPS类的通信接口的第二种方法，一旦您想要更新活动中的UI，您可以通过下一种方式调用此接口方法：

public class MainActivity extends AppCompatActivity implements
    MainActivity.MainActivityInteractionInterface{

private LocationGPS gps;

private TextView text;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    enableGPS();
    initGuiElements();
}

private void enableGPS() {
    gps = new LocationGPS(this, getApplicationContext());
}

private void initGuiElements() {
    text = (TextView) findViewById(R.id.textTop);
    text.setText("nothing yet");
}

@Override
public void updateUI() {
   text.setText("Some new text");
}

public interface MainActivityInteractionInterface {
    void updateUI();
}
}

而LocationGPS现在看起来像：

    public class LocationGPS implements LocationListener{

    private MainActivity.MainActivityInteractionInterface interactionInterface;

    private LocationManager locationManager;

    private Context applicationContext;

    public LocationGPS(MainActivity.MainActivityInteractionInterface interactionInterface, Context applicationContext) {
        this.interactionInterface = interactionInterface;
        this.applicationContext = applicationContext;
        locationManager = (LocationManager) applicationContext.getSystemService(Context.LOCATION_SERVICE);
        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);
    }

    @Override
    public void onLocationChanged(Location location) {
        interactionInterface.updateUI(); // Or call this method whenever you need 
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {

    }

    @Override
    public void onProviderEnabled(String provider) {

    }

    @Override
    public void onProviderDisabled(String provider) {

    }
    }

Answer 2

我发现Artyom Okun的第二个代码建议最有帮助，但是确实需要进行一些调试。我必须将接口移到它自己的文件中。这是由于“循环继承”导致您尝试继承要在活动中创建的对象。

See this stackoverflow page explaining the issue

MainActivity.java

public class MainActivity extends AppCompatActivity implements
    MainActivityInteractionInterface{

private LocationGPS gps;

private TextView text;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    enableGPS();
    initGuiElements();
}

private void enableGPS() {
    gps = new LocationGPS(this, getApplicationContext());
}

private void initGuiElements() {
    text = (TextView) findViewById(R.id.textTop);
    text.setText("nothing yet");
}

@Override
public void updateUI() {
   text.setText("Some new text");
}


}

LocationGPS.java

public class LocationGPS implements LocationListener{

    private MainActivityInteractionInterface interactionInterface;

    private LocationManager locationManager;

    private Context applicationContext;

    public LocationGPS(MainActivityInteractionInterface interactionInterface, Context applicationContext) {
        this.interactionInterface = interactionInterface;
        this.applicationContext = applicationContext;
        locationManager = (LocationManager) applicationContext.getSystemService(Context.LOCATION_SERVICE);
        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);
    }

    @Override
    public void onLocationChanged(Location location) {
        interactionInterface.updateUI(); // Or call this method whenever you need 
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {

    }

    @Override
    public void onProviderEnabled(String provider) {

    }

    @Override
    public void onProviderDisabled(String provider) {

    }
    }

然后新建文件MainActivityInteractionInterface.java

public interface MainActivityInteractionInterface {
    void updateUI();
}

要更新UI，我要在LocationGPS类的onLocationChanged（）方法中更新全局变量。然后在updateUI（）中，我使用全局变量写入文本视图。

注意在MainActivity中向全局写入如下内容：

MainActivity.bestLat =纬度；

Answer 3

在MainActivity中创建方法

public void updateText(String updatedText){
 text.setText(updatedText);
}

在LocationGPS类中，您已经拥有MainActivity的上下文，因此在onLocationChanged中，调用此方法

mainActivity.updateText(updatedText);

还有另一种推荐方式。创建一个接口并在onLocationChanged方法中调用它。在MainActivity和实现的界面中实现更新文本。我更喜欢这种方法，因为您不需要共享Activity的上下文或rootview，以防止可能的内存泄漏。

Answer 4

只需将LocationGps类放在MainActivity类中。完成。抱歉无法发表评论，以便发帖回答。

Answer 5

这可以帮助你

public class LocationGPS implements LocationListener {

private Activity mainActivity;
private LocationManager locationManager;

public interface OnChangeListener{
 public void onChangeListener();

}

OnChangeListener mOnChangeListener;

public LocationGPS(Activity activity,OnChangeListener onChangeListener)
{
    this.mainActivity = activity;
  mOnChangeListener = onChangeListener;
  locationManager = (LocationManager) activity.getSystemService(Context.LOCATION_SERVICE);
    locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);
}

@Override
public void onLocationChanged(Location location) {

//here I want to set text for TextView element
 mOnChangeListener.onChangeListener();   

}

@Override
public void onStatusChanged(String provider, int status, Bundle extras) {

}

@Override
public void onProviderEnabled(String provider) {

}

@Override
public void onProviderDisabled(String provider) {

}

Activity必须实现接口OnChangeListener

public class MainActivity extends AppCompatActivity implements OnChangeListener {

private LocationGPS gps;
private TextView text;

@Override
 public void onChangeListener(){
//For example you may edit TextView
text.setText("data recieved:onLocationChanged")
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    enableGPS();
    initGuiElements();
}

private void enableGPS()
{

//You transfer interface
  gps = new LocationGPS(this,this);
}

private void initGuiElements()
{
    text = (TextView) findViewById(R.id.textTop);
    text.setText("nothing yet");
}

Android更新来自其他类的ui元素

5 个答案: