這裡通過監聽內容提供者數據變化和監聽發送短信進行講解監聽器。如果用戶提供者數據發生瞭變化,監聽器立刻就能收到對數據庫操作的記錄,而監聽器是采用通知的機制,如果不采用通知的機制也可以做,那就是不斷的查詢數據庫,這樣的話效率就會很低。而采用通知機制的話,當用戶向數據庫發送一條記錄,ContentObserver立刻就能獲取到,我們就可以進行處理數據。
監聽內容提供者數據的變化
1.在內容提供者中可以通知其他程序數據發生變化時進行監聽
通過Context的getContentResolver()方法獲取ContentResolver
調用其notifyChange()方法發送數據修改通知
2.在其他程序中可以通過ContentObserver監聽數據變化
通過Context的getContentResolver()方法獲取ContentResolver
調用其registerContentObserver()方法指定對某個Uri註冊ContentObserver
自定義ContentObserver,重寫onChange()方法獲取數據
比如在用戶插入數據的時候進行監聽通知:
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public Uri insert(Uri uri, ContentValues values) {
SQLiteDatabase db = helper.getWritableDatabase();
switch (matcher.match(uri)) {
case PERSON_ALL:
long id = db.insert("person", "id", values);
// 監聽通知
getContext().getContentResolver().notifyChange(uri, null);
return ContentUris.withAppendedId(uri, id);
default:
throw new IllegalArgumentException("Unmatch Uri: " + uri);
}
}
在另外一個工程中進行監聽,一旦用戶進行插入操作,我立刻就可以自動獲取到用戶插入的記錄:
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public class MainActivity extends Activity {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
getContentResolver().registerContentObserver(Uri.parse("content://cn.itcast.provider.itcast/person"), true, new MyObserver(new Handler()));
}
class MyObserver extends ContentObserver {
public MyObserver(Handler handler) {
super(handler);
}
//當監聽到數據發生瞭變化就調用這個方法,並將新添加的數據查詢出來
public void onChange(boolean selfChange) {
ContentResolver resolver = getContentResolver();
Uri uri = Uri.parse("content://cn.itcast.provider.itcast/person");
Cursor cursor = resolver.query(uri, new String[] { "id", "name", "phone", "balance" }, null, null, "id DESC LIMIT 1");
while (cursor.moveToNext()) {
System.out.print(cursor.getString(0) + " ");
System.out.print(cursor.getString(1) + " ");
System.out.print(cursor.getString(2) + " ");
System.out.println(cursor.getString(3));
}
}
}
}
監聽發送短信
1.Android系統提供瞭Provider對短信進行查詢,當發出短信時也會發送更改通知
2.定義一個Observer監聽"content://sms"
3.在onChange()方法中查詢用戶發送的短信"content://sms/outbox"
4.短信發送信息存放在數據庫 date/date/com.android.providers.telephony
5.需要權限<uses-permission android:name="android.permission.READ_SMS" />
示例:
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public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
getContentResolver().registerContentObserver(Uri.parse("content://sms"), true, new SmsObserver(new Handler()));
}
//監聽發送的短信
private final class SmsObserver extends ContentObserver {
public SmsObserver(Handler handler) {
super(handler);
}
public void onChange(boolean selfChange) {
ContentResolver resolver = getContentResolver();
//查到發出的短信
Uri uri = Uri.parse("content://sms/outbox");
Cursor cursor = resolver.query(uri, new String[] { "date", "address", "body" }, null, null, "_id desc limit 1");
if (cursor.moveToNext()) {
long ms = cursor.getLong(0);
String date = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date(ms));
String address = cursor.getString(1);
String body = cursor.getString(2);
System.out.println(date + " " + address + " " + body);
}
}
}
作者“傅榮康專欄”