Android Studio - 预期的表达

Question

我正在创建一个天气应用程序，我收到一条消息，提示需要一个表达式。

这是我的主要 Activity :

package com.haziqhussain.hazweather;

import android.support.v7.app.AppCompatActivity;
import android.text.InputType;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.EditText;

public class WeatherActivity extends AppCompatActivity {

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

    if (savedInstanceState == null) {
        getSupportFragmentManager().beginTransaction()
                .add(R.id.container, new WeatherFragment())
                .commit();
    }



}

@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();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);*/
    if(item.getItemId() == R.id.change_city){
        showInputDialog();
    }
    return false;

}


private void showInputDialog(){
    AlertDialog.Builder builder = new AlertDialog.Builder(this);
    builder.setTitle("Change city");
    final EditText input = new EditText(this);
    input.setInputType(InputType.TYPE_CLASS_TEXT);
    builder.setView(input);
    builder.setPositiveButton("Go", new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
            changeCity(input.getText().toString());
        }
    });
    builder.show();
}

public void changeCity(String city){
    WeatherFragment wf = (----->WeatherFragment<------).getSupportFragmentManager()
            .findFragmentById(R.id.container);
    wf.changeCity(city);
    new CityPreference(this).setCity(city);
}

}

错误出现在调用天气 fragment 的 Public Void ChangeCity 中。这是一个不断发生的错误，我不确定发生了什么。

Answer 1

使用这个:

public void changeCity(String city){
WeatherFragment wf = (WeatherFragment) getSupportFragmentManager()
        .findFragmentById(R.id.container); // removed '.' 
wf.changeCity(city);
(new CityPreference(this)).setCity(city);