Question

我在android中创建我的第一个应用程序，我使用抽屉布局和服务获取当前位置并将数据发送到Broadacast接收器，这个应该在Dashboard Fragment中更新纬度和经度textview，但是当updateDashLocation调用我收到此错误：引起：java.lang.NullPointerException：尝试调用虚方法＆＃39; void android.widget.TextView.setText（java.lang.CharSequence）＆＃39;在DashLatitude.setText（纬度）的空对象引用上;和DashLongitude.setText（经度）;

片段代码

public class DashboardFragment extends Fragment {


public DashboardFragment() {
    // Required empty public constructor
}

View dashboardInflatedView;
TextView DashLatitude,DashLongitude;
String TAG = "GPSTracker";

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    Toolbar toolbar = ((MainActivity)getActivity()).toolbar;
    toolbar.setTitle("Dashboard");

    dashboardInflatedView = inflater.inflate(R.layout.fragment_dashboard, container, false);
    DashLatitude = (TextView)dashboardInflatedView.findViewById(R.id.DashLatitude);
    DashLongitude = (TextView)dashboardInflatedView.findViewById(R.id.DashLongitude);

    return dashboardInflatedView;
}

public void updateDashLocation(String latitude, String longitude){

    //Log.d(TAG, "Update Dashboard Location");
    DashLatitude.setText(latitude);
    DashLongitude.setText(longitude);
}

}

如何在调用updateDashLocation时访问Dashboard片段的元素？

Answer 1

在调用updateDashLocation方法时尝试声明TextViews？

    public class DashboardFragment extends Fragment {

        public DashboardFragment() {
            // Required empty public constructor
        }

        View dashboardInflatedView;
        TextView DashLatitude,DashLongitude;
        String TAG = "GPSTracker";

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {

            Toolbar toolbar = ((MainActivity)getActivity()).toolbar;
            toolbar.setTitle("Dashboard");

            dashboardInflatedView = inflater.inflate(R.layout.fragment_dashboard, container, false);
            return dashboardInflatedView;
        }

        public void updateDashLocation(String latitude, String longitude){

            DashLatitude = (TextView)dashboardInflatedView.findViewById(R.id.DashLatitude);
            DashLongitude = (TextView)dashboardInflatedView.findViewById(R.id.DashLongitude);

            //Log.d(TAG, "Update Dashboard Location");
            DashLatitude.setText(latitude);
            DashLongitude.setText(longitude);
        }

Answer 2

我找到了解决方案，问题出在主要活动中，现在在广播接收器中，当坐标已经通过时，代码是：

// Define the callback for what to do when data is received
private BroadcastReceiver locationReceiver = new BroadcastReceiver() {

    @Override
    public void onReceive(Context context, Intent intent) {

        Log.d(TAG, "Broadcastreceiver Coordinates");

        int resultCode = intent.getIntExtra("resultCode", RESULT_CANCELED);
        if (resultCode == RESULT_OK) {
            Double latitude= intent.getDoubleExtra("latitude",0);
            Double longitude= intent.getDoubleExtra("longitude",0);

            DashboardFragment dashboardFrag  = (DashboardFragment)
                    manager.findFragmentByTag("Dashboard");
            dashboardFrag .updateLocation(latitude.toString(),longitude.toString());
            Log.d(TAG, latitude.toString()+" --- "+longitude.toString());
        }
    }
};

我通过Tag获取片段并访问方法

更改片段中的Textview文本

2 个答案: