Question

我正在参与开发Android应用程序udacity课程，并被困在Project Sunshine部分的第2课。

似乎我的代码与此处的代码完全匹配（他们的代码在这里https://github.com/udacity/Sunshine-Version-2/compare/2.01_add_network_code...2.02_refactor_forecast_fragment）但是当我运行我的代码时，我在MainActivity.java标签中遇到一个错误，它说找不到符号类ForecastFragment。

对此为何的任何想法？

我的MainActivity.java代码如下（错误在onCreate方法中）：包com.example.android.sunshine.app;

import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;


public class MainActivity extends ActionBarActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    if (savedInstanceState == null) {
        getSupportFragmentManager().beginTransaction()
                .add(R.id.container, new ForecastFragment())
                .commit();
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@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();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}
}

我的ForecastFragment.java代码如下：

import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import com.example.android.sunshine.app.R;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;


/**
 * A placeholder fragment containing a simple view.
 */
public class ForecastFragment extends Fragment {

private ArrayAdapter<String> mForecastAdapter;

public ForecastFragment() {
}

/**
 * within this placeholder fragment is where you create the arraylist
 */

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

    String[] forecastArray = {
            "Today - Sunny - 88/63",
            "Tomorrow - Foggy - 70/40",
            "Weds - Cloudy - 72/63",
            "Thurs - Asteroids - 75/65",
            "Fri - Heavy Rain - 65/56",
            "Sat - HELP TRAPPED IN WEATHERSTATION - 60/51",
            "SUN - Sunny - 80/68"
    };
    List<String> weekForecast = new ArrayList<String>(Arrays.asList(forecastArray));

    // Now that we have some dummy forecast data, create an ArrayAdapter.
    // The ArrayAdapter will take data from a source (like our dummy forecast) and
    // use it to populate the ListView it's attached to.
    ArrayAdapter<String> forecastAdapter =
            new ArrayAdapter<String>(
                    getActivity(), // The current context (this activity)
                    R.layout.list_item_forecast, // The name of the layout ID.
                    R.id.list_item_forecast_textview, // The ID of the textview to populate.
                    weekForecast);

    View rootView = inflater.inflate(R.layout.fragment_main, container, false);

    // Get a reference to the ListView, and attach this adapter to it.
    ListView listView = (ListView) rootView.findViewById(R.id.listview_forecast);
    listView.setAdapter(forecastAdapter);
    return rootView;
}

    public class FetchWeatherTask extends AsyncTask<Void, Void, Void> {

        private final String LOG_TAG = FetchWeatherTask.class.getSimpleName();

        @Override
        protected Void doInBackground(Void... params) {

            // These two need to be declared outside the try/catch
            // so that they can be closed in the finally block.
            HttpURLConnection urlConnection = null;
            BufferedReader reader = null;

            // Will contain the raw JSON response as a string.
            String forecastJsonStr = null;

            try {
                // Construct the URL for the OpenWeatherMap query
                // Possible parameters are available at OWM's forecast API page, at
                // http://openweathermap.org/API#forecast
                URL url = new URL("http://api.openweathermap.org/data/2.5/forecast/daily?q=94043&mode=json&units=metric&cnt=7");

                // Create the request to OpenWeatherMap, and open the connection
                urlConnection = (HttpURLConnection) url.openConnection();
                urlConnection.setRequestMethod("GET");
                urlConnection.connect();

                // Read the input stream into a String
                InputStream inputStream = urlConnection.getInputStream();
                StringBuffer buffer = new StringBuffer();
                if (inputStream == null) {
                    // Nothing to do.
                    return null;
                }
                reader = new BufferedReader(new InputStreamReader(inputStream));

                String line;
                while ((line = reader.readLine()) != null) {
                    // Since it's JSON, adding a newline isn't necessary (it won't affect parsing)
                    // But it does make debugging a *lot* easier if you print out the completed
                    // buffer for debugging.
                    buffer.append(line + "\n");
                }

                if (buffer.length() == 0) {
                    // Stream was empty.  No point in parsing.
                    return  null;
                }
                forecastJsonStr = buffer.toString();
            } catch (IOException e) {
                Log.e(LOG_TAG, "Error ", e);
                // If the code didn't successfully get the weather data, there's no point in attempting
                // to parse it.
                return null;
            } finally {
                if (urlConnection != null) {
                    urlConnection.disconnect();
                }
                if (reader != null) {
                    try {
                        reader.close();
                    } catch (final IOException e) {
                        Log.e(LOG_TAG, "Error closing stream", e);
                    }
                }
            }
        return null;}
    }
}

终于（抱歉代码重载）我有了fragment_main.xml选项卡：

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context=".MainActivity$ForecastFragment">


<ListView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="Today, June 24 - 21"
    android:id="@+id/listview_forecast"
    />

Answer 1

尝试在片段_main.xml中编写完整路径，如下所示：

tools:context="com.example.android.sunshine.app.MainActivity.ForecastFragment"

Answer 2

只是正式回答所以我可以关闭它 - 我最终解决了这个问题。似乎我忘了删除/关闭我的道歉的问题。如果我没记错的话，问题与缺少导入有关。如果有人遇到与本课程相同的问题，我可能会挖掘工作代码。

Answer 3

我有同样的问题，在同一点（只是将“ForecastFragment”重构为自己的文件，并从“PlaceholderFragment”重命名）。

问题仍然存在，即使文件与课程中使用的文件完全相同。

我使用buiild-clean项目修复了它。在这之后，它建立得很好。

Udacity Project Sunshine - 第2课 - 找不到符号类错误

3 个答案: