后台更新(四)
实现原理:
创建一个Service类,在创建一个BroadcastReceiver类,用这个类的onReceive()方法
AutoUpdateService.java
import android.app.AlarmManager; import android.app.PendingIntent; import android.app.Service; import android.content.Intent; import android.content.SharedPreferences; import android.os.IBinder; import android.os.SystemClock; import android.preference.PreferenceManager; public class AutoUpdateService extends Service { @Override public IBinder onBind(Intent intent) { return null; } @Override public int onStartCommand(Intent intent, int flags, int startId) { new Thread(new Runnable() { @Override public void run() { updateWeather(); } }).start(); AlarmManager manager = (AlarmManager) getSystemService(ALARM_SERVICE); int anHour = 8 * 60 * 60 * 1000; // 这是8小时的毫秒数 long triggerAtTime = SystemClock.elapsedRealtime() + anHour; Intent i = new Intent(this, AutoUpdateReceiver.class); PendingIntent pi = PendingIntent.getBroadcast(this, 0, i, 0); manager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP, triggerAtTime, pi); return super.onStartCommand(intent, flags, startId); } /** * 更新天气信息。 */ private void updateWeather() { SharedPreferences prefs = PreferenceManager .getDefaultSharedPreferences(this); String weatherCode = prefs.getString("weather_code", ""); String address = "http://www.weather.com.cn/data/cityinfo/" + weatherCode + ".html"; HttpUtil.sendHttpRequest(address, new HttpCallbackListener() { @Override public void onFinish(String response) { Utility.handleWeatherResponse(AutoUpdateService.this, response); } @Override public void onError(Exception e) { e.printStackTrace(); } }); } }
AutoUpdateReceiver.java
import android.content.BroadcastReceiver; import android.content.Context; import android.content.Intent; public class AutoUpdateReceiver extends BroadcastReceiver { @Override public void onReceive(Context context, Intent intent) { Intent i = new Intent(context, AutoUpdateService.class); context.startService(i); } }
WeatherActivity.java
import android.app.Activity; import android.content.Intent; import android.content.SharedPreferences; import android.os.Bundle; import android.preference.PreferenceManager; import android.text.TextUtils; import android.view.View; import android.view.View.OnClickListener; import android.view.Window; import android.widget.Button; import android.widget.LinearLayout; import android.widget.TextView; public class WeatherActivity extends Activity implements OnClickListener { private LinearLayout weatherInfoLayout; /** * 用于显示城市名 第 14 章 进入实战，开发酷欧天气 533 */ private TextView cityNameText; /** * 用于显示发布时间 */ private TextView publishText; /** * 用于显示天气描述信息 */ private TextView weatherDespText; /** * 用于显示气温1 */ private TextView temp1Text; /** * 用于显示气温2 */ private TextView temp2Text; /** * 用于显示当前日期 */ private TextView currentDateText; /** * 切换城市按钮 */ private Button switchCity; /** * 更新天气按钮 */ private Button refreshWeather; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); requestWindowFeature(Window.FEATURE_NO_TITLE); setContentView(R.layout.weather_layout); // 初始化各控件 weatherInfoLayout = (LinearLayout) findViewById(R.id.weather_info_layout); cityNameText = (TextView) findViewById(R.id.city_name); publishText = (TextView) findViewById(R.id.publish_text); weatherDespText = (TextView) findViewById(R.id.weather_desp); temp1Text = (TextView) findViewById(R.id.temp1); temp2Text = (TextView) findViewById(R.id.temp2); currentDateText = (TextView) findViewById(R.id.current_date); switchCity = (Button) findViewById(R.id.switch_city); refreshWeather = (Button) findViewById(R.id.refresh_weather); String countyCode = getIntent().getStringExtra("county_code"); if (!TextUtils.isEmpty(countyCode)) { // 有县级代号时就去查询天气 publishText.setText("同步中..."); weatherInfoLayout.setVisibility(View.INVISIBLE); cityNameText.setVisibility(View.INVISIBLE); queryWeatherCode(countyCode); } else { // 没有县级代号时就直接显示本地天气 showWeather(); } switchCity.setOnClickListener(this); refreshWeather.setOnClickListener(this); } @Override public void onClick(View v) { switch (v.getId()) { case R.id.switch_city: Intent intent = new Intent(this, ChooseAreaActivity.class); intent.putExtra("from_weather_activity", true); startActivity(intent); finish(); break; case R.id.refresh_weather: publishText.setText(" 同步中..."); SharedPreferences prefs = PreferenceManager .getDefaultSharedPreferences(this); String weatherCode = prefs.getString("weather_code", ""); if (!TextUtils.isEmpty(weatherCode)) { queryWeatherInfo(weatherCode); } break; default: break; } } /** * 查询县级代号所对应的天气代号。 */ private void queryWeatherCode(String countyCode) { String address = "http://www.weather.com.cn/data/list3/city" + countyCode + ".xml"; queryFromServer(address, "countyCode"); } /** * 查询天气代号所对应的天气。 */ private void queryWeatherInfo(String weatherCode) { String address = "http://www.weather.com.cn/data/cityinfo/" + weatherCode + ".html"; queryFromServer(address, "weatherCode"); } /** * 根据传入的地址和类型去向服务器查询天气代号或者天气信息。 */ private void queryFromServer(final String address, final String type) { HttpUtil.sendHttpRequest(address, new HttpCallbackListener() { @Override public void onFinish(final String response) { if ("countyCode".equals(type)) { if (!TextUtils.isEmpty(response)) { // 从服务器返回的数据中解析出天气代号 String[] array = response.split("\\|"); if (array != null && array.length == 2) { String weatherCode = array[1]; queryWeatherInfo(weatherCode); } } } else if ("weatherCode".equals(type)) { // 处理服务器返回的天气信息 Utility.handleWeatherResponse(WeatherActivity.this, response); runOnUiThread(new Runnable() { @Override public void run() { showWeather(); } }); } } @Override public void onError(Exception e) { runOnUiThread(new Runnable() { @Override public void run() { publishText.setText("同步失败"); } }); } }); } /** * 从SharedPreferences文件中读取存储的天气信息，并显示到界面上。 */ private void showWeather() { SharedPreferences prefs = PreferenceManager .getDefaultSharedPreferences(this); cityNameText.setText(prefs.getString("city_name", "")); temp1Text.setText(prefs.getString("temp1", "")); temp2Text.setText(prefs.getString("temp2", "")); weatherDespText.setText(prefs.getString("weather_desp", "")); publishText.setText("今天" + prefs.getString("publish_time", "") + "发布"); currentDateText.setText(prefs.getString("current_date", "")); weatherInfoLayout.setVisibility(View.VISIBLE); cityNameText.setVisibility(View.VISIBLE); Intent intent = new Intent(this, AutoUpdateService.class); startService(intent); } }
