While looking at the technical book, create an application that acquires weather information using the API.
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<!--View city list-->
<ListView
android:id="@+id/lvCityList"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="0.5" />
<!--Layout of the lower half of the screen displaying weather information-->
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_marginTop="10dp"
android:layout_weight="0.5"
android:orientation="vertical">
<!--Display "Weather details"-->
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="10dp"
android:gravity="center"
android:text="@string/tv_winfo_title"
android:textSize="25dp"
/>
<!--Layout to arrange city names and weather side by side-->
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="10dp"
android:orientation="horizontal">
<!--Display of city name-->
<TextView
android:id="@+id/tvCityName"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="20sp"/>
<!--Show the weather-->
<TextView
android:id="@+id/tvWeatherTelop"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:textSize="20sp"/>
</LinearLayout>
<!--Screen parts that allow the detailed weather information to be scrolled-->
<ScrollView
android:layout_width="match_parent"
android:layout_height="match_parent">
<!--View detailed weather information-->
<TextView
android:id="@+id/tvWeatherDesc"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:textSize="15dp"/>
</ScrollView>
</LinearLayout>
</LinearLayout>
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.asyncsample">
<uses-permission
android:name="android.permission.INTERNET"/>
<uses-permission
android:name="android.permission.ACCESS_NETWORK_STATE"/>
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
strings.xml
<resources>
<string name="app_name">Weather information</string>
<string name="tv_winfo_title">Weather details</string>
</resources>
MainActivity.java
package com.example.asyncsample;
import androidx.appcompat.app.AppCompatActivity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Get screen part ListView
ListView lvCityList = findViewById(R.id.lvCityList);
//Prepare List object to be used in SimpleAdapter
List<Map<String, String>> cityList = new ArrayList<>();
//Preparation of Map object to store city data and data registration to cityList
Map<String, String> city = new HashMap<>();
city.put("name", "Osaka");
city.put("id", "270000");
cityList.add(city);
city = new HashMap<>();
city.put("name", "Kobe");
city.put("id", "280010");
cityList.add(city);
//Used with SimpleAdapter from-Preparation of variables for to
String[] from = {"name"};
int[] to = {android.R.id.text1};
//Set SimpleAdapter
SimpleAdapter adapter = new SimpleAdapter(MainActivity.this, cityList, android.R.layout.simple_expandable_list_item_1, from, to);
//Set SimpleAdapter in ListView
lvCityList.setAdapter(adapter);
//Set listener on ListView
lvCityList.setOnItemClickListener(new ListItemClickListener());
}
//A member class that describes the processing when a list is selected
private class ListItemClickListener implements AdapterView.OnItemClickListener{
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id){
//Get the city name and city ID of the row tapped in ListView
Map<String, String> item = (Map<String, String>) parent.getItemAtPosition(position);
String cityName = item.get("name");
String cityId = item.get("id");
//Set the acquired city name to tvCityName
TextView tvCityName = findViewById(R.id.tvCityName);
tvCityName.setText(cityName + "Weather:");
//Get TextView to display weather information
TextView tvWeatherTelop = findViewById(R.id.tvWeatherTelop);
//Get TextView to display detailed weather information
TextView tvWeatherDesc = findViewById(R.id.tvWeatherDesc);
//WeatherInfoReceiver new. Pass the TextView obtained above as an argument.
WeatherInfoReceiver receiver = new WeatherInfoReceiver(tvWeatherTelop, tvWeatherDesc);
//Run WeatherInfoReceiver
receiver.execute(cityId);
}
}
private class WeatherInfoReceiver extends AsyncTask<String, String, String> {
//Screen part field to display the current weather
private TextView _tvWeatherTelop;
//Screen part field to display weather details
private TextView _tvWeatherDesc;
//constructor
//The screen parts that display the weather information are acquired in advance and stored in the field.
public WeatherInfoReceiver(TextView tvWeatherTelop, TextView tvWeatherDesc){
_tvWeatherTelop = tvWeatherTelop;
_tvWeatherDesc = tvWeatherDesc;
}
@Override
public String doInBackground(String... params){
//Get the first variable length argument (index 0). This is the city ID.
String id = params[0];
//Create a connection URL string using the city ID
String urlStr = "http://weather.livedoor.com/forecast/webservice/json/v1?city=" + id;
//JSON string obtained from the weather information service. Weather information is stored.
String result = "";
//Describe the process to connect to the above URL and get the JSON string here
//Returns a JSON string
HttpURLConnection con = null;
InputStream is = null;
try{
URL url = new URL(urlStr);
con = (HttpURLConnection) url.openConnection();
con.setRequestMethod("GET");
con.connect();
is = con.getInputStream();
result = is2String(is);
}
catch(MalformedURLException ex){
}
catch(IOException ex){
}
finally{
if(con != null){
con.disconnect();
}
if(is != null){
try{
is.close();
}
catch(IOException ex){
}
}
}
return result;
}
@Override
public void onPostExecute(String result){
//Prepare a character string variable for weather information
String telop = "";
String desc = "";
try{
JSONObject rootJSON = new JSONObject(result);
JSONObject descriptionJSON = rootJSON.getJSONObject("description");
desc = descriptionJSON.getString("text");
JSONArray forecasts = rootJSON.getJSONArray("forecasts");
JSONObject forecastNow = ((JSONArray) forecasts).getJSONObject(0);
telop = forecastNow.getString("telop");
}
catch(JSONException ex){
}
//Describe the process to analyze the weather information JSON character string here.
//Set the weather information string in TextView
_tvWeatherTelop.setText(telop);
_tvWeatherDesc.setText(desc);
}
}
private String is2String(InputStream is) throws IOException{
BufferedReader reader = new BufferedReader(new InputStreamReader(is, "UTF-8"));
StringBuffer sb = new StringBuffer();
char[] b = new char[1024];
int line;
while(0 <= (line = reader.read(b))){
sb.append(b, 0, line);
}
return sb.toString();
}
}
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