java - 不幸的是 Sunshine 应用程序无法正常工作

Question

我刚刚经历了 udacity sunshine 应用程序，我无法解决这个问题，即在添加 openweather api 之后，该应用程序无法运行它只是显示“不幸的是 Sunshine 应用程序无法运行”

MainActivity.java文件如下:

package com.example.android.sunshine.app;

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;

public class MainActivity extends AppCompatActivity
{

@Override
protected void onCreate(Bundle savedInstanceState)
    {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();

        }
    });
    }

@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);
    }
}

MainActivityFragment.java文件如下:

package com.example.android.sunshine.app;

import android.support.v4.app.Fragment;
import android.os.Bundle;
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 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 MainActivityFragment extends Fragment {

public MainActivityFragment() {
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View rootView=inflater.inflate(R.layout.fragment_main, container, false);

   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-60/51",
            "Sun-Sunny-80/68"
    };

    List<String> weekForecast=new ArrayList<String>(Arrays.asList(forecastArray));

    ArrayAdapter<String> mForecastAdapter = new ArrayAdapter<String>(getActivity(),R.layout.list_item_forecast,R.id.list_item_forecast_textview,weekForecast);
    ListView lv=(ListView) rootView.findViewById(R.id.list_view_forecast);
    lv.setAdapter(mForecastAdapter);


    // 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 avaiable 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=London&mode=json&units=metric&cnt=7&appid=d0657975451a7efca018097b88c4d975");


        // 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("PlaceholderFragment", "Error ", e);
        // If the code didn't successfully get the weather data, there's no point in attemping
        // to parse it.
        return null;
    } finally{
        if (urlConnection != null) {
            urlConnection.disconnect();
        }
        if (reader != null) {
            try {
                reader.close();
            } catch (final IOException e) {
                Log.e("PlaceholderFragment", "Error closing stream", e);
            }
        }
    }

    return rootView;

}
}

Answer 1

在 android 中，您不能在 UI 线程上进行网络调用。

URL url = new URL("http://api.openweathermap.org/data/2.5/forecast/daily?q=London&mode=json&units=metric&cnt=7&appid=d0657975451a7efca018097b88c4d975");
urlConnection = (HttpURLConnection) url.openConnection(); //This causes an exception

您必须在后台线程中运行这些以及任何用于网络操作的代码，使用 AsyncTask 甚至是传递给 Thread 的 Runnable 或执行者。