android PendingIntent 介紹

1、PendingIntent作用

根據字面意思就知道是延遲的intent，主要用來在某個事件完成後執行特定的Action。PendingIntent包含了Intent及Context，所以就算Intent所屬程序結束，PendingIntent依然有效，可以在其他程序中使用。
常用在通知欄及短信發送系統中。

PendingIntent一般作爲參數傳給某個實例，在該實例完成某個操作後自動執行PendingIntent上的Action，也可以通過PendingIntent的send函數手動執行，並可以在send函數中設置OnFinished表示send成功後執行的動作。

2、PendingIntent舉例

a. 系統通知欄

NotificationManager nm = (NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);
int icon = android.R.drawable.stat_notify_chat;
long when = System.currentTimeMillis() + 2000;
Notification n = new Notification(icon, "通知欄demo提醒", when);
n.defaults = Notification.DEFAULT_SOUND;
n.flags |= Notification.FLAG_AUTO_CANCEL;

Intent openintent = new Intent(this, DemoList.class);
PendingIntent pi = PendingIntent.getActivity(this, 0, openintent, PendingIntent.FLAG_CANCEL_CURRENT);
n.setLatestEventInfo(this, "通知欄demo提醒title", "通知欄demo提醒text", pi);
nm.notify(0, n);

setLatestEventInfo表示設置點擊該通知的事件

b. 短信系統舉例

private final static String SEND_ACTION      = "send";
private final static String DELIVERED_ACTION = "delivered";

private void sendSms(String receiver, String text) {
    SmsManager s = SmsManager.getDefault();
    PendingIntent sentPI = PendingIntent.getBroadcast(this, 0, new Intent(SEND_ACTION),
                                                      PendingIntent.FLAG_CANCEL_CURRENT);
    PendingIntent deliveredPI = PendingIntent.getBroadcast(this, 0, new Intent(DELIVERED_ACTION),
                                                           PendingIntent.FLAG_CANCEL_CURRENT);
    // 發送完成
    registerReceiver(new BroadcastReceiver() {

        @Override
        public void onReceive(Context context, Intent intent) {
            switch (getResultCode()) {
                case Activity.RESULT_OK:
                    Toast.makeText(getBaseContext(), "Send Success!", Toast.LENGTH_SHORT).show();
                    break;
                case SmsManager.RESULT_ERROR_GENERIC_FAILURE:
                    Toast.makeText(getBaseContext(), "Send Failed because generic failure cause.",
                                   Toast.LENGTH_SHORT).show();
                    break;
                case SmsManager.RESULT_ERROR_NO_SERVICE:
                    Toast.makeText(getBaseContext(), "Send Failed because service is currently unavailable.",
                                   Toast.LENGTH_SHORT).show();
                    break;
                case SmsManager.RESULT_ERROR_NULL_PDU:
                    Toast.makeText(getBaseContext(), "Send Failed because no pdu provided.", Toast.LENGTH_SHORT).show();
                    break;
                case SmsManager.RESULT_ERROR_RADIO_OFF:
                    Toast.makeText(getBaseContext(), "Send Failed because radio was explicitly turned off.",
                                   Toast.LENGTH_SHORT).show();
                    break;
                default:
                    Toast.makeText(getBaseContext(), "Send Failed.", Toast.LENGTH_SHORT).show();
                    break;
            }
        }
    }, new IntentFilter(SEND_ACTION));

    // 對方接受完成
    registerReceiver(new BroadcastReceiver() {

        @Override
        public void onReceive(Context context, Intent intent) {
            switch (getResultCode()) {
                case Activity.RESULT_OK:
                    Toast.makeText(getBaseContext(), "Delivered Success!", Toast.LENGTH_SHORT).show();
                    break;
                default:
                    Toast.makeText(getBaseContext(), "Delivered Failed!", Toast.LENGTH_SHORT).show();
                    break;
            }
        }
    }, new IntentFilter(DELIVERED_ACTION));

    // 發送短信，sentPI和deliveredPI將分別在短信發送成功和對方接受成功時被廣播
    s.sendTextMessage(receiver, null, text, sentPI, deliveredPI);
}

以上的兩個PendingIntent sentPI和deliveredPI將分別在短信發送成功和對方接受成功時被廣播

3、Intent和PendingIntent的區別

a. Intent是立即使用的，而PendingIntent可以等到事件發生後觸發，PendingIntent可以cancel
b. Intent在程序結束後即終止，而PendingIntent在程序結束後依然有效
c. PendingIntent自帶Context，而Intent需要在某個Context內運行
d. Intent在原task中運行，PendingIntent在新的task中運行