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内容观察者
需要提供读取短信权限
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package com.example.contentobserver;
import android.app.Activity;
import android.content.ContentResolver;
import android.database.ContentObserver;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.os.Handler;
import android.widget.Toast;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Uri uri=Uri.parse("content://sms");
ContentResolver resolver= getContentResolver();
resolver.registerContentObserver(uri, true, new Mycontentobeserver(new Handler()));
}
// 当内容观察者观察到数据库的内容发生变化了调用该方法。
// 实际上是观察到消息邮箱（一个公共内存区域）里有一条数据库内容变化的通知
private class Mycontentobeserver extends ContentObserver{
public Mycontentobeserver(Handler handler) {
super(handler);
// TODO Auto-generated constructor stub
}
public void onChange(boolean selfChange){
super.onChange(selfChange);
Toast.makeText(MainActivity.this, "数据库内容变化了", 1).show();
Uri uri=Uri.parse("content://sms");
ContentResolver resolver= getContentResolver();
Cursor cursor=resolver.query(uri, new String[]{"address","date","type","body"}, null, null, null);
// 得到最后一条短信
cursor.moveToFirst();
String address=cursor.getString(0);
String body=cursor.getString(3);
System.out.println("address:"+address+"::"+"body:"+body);
cursor.close();
}
}
}
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内容观察者观察自定义的数据库时：
数据库变化时要主动发送通知到公共内存区域
package com.example.simpledatabase.dao;
import java.util.ArrayList;
import java.util.List;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
import com.example.simpledatabase.PersonSQLiteOpenHelper;
import com.example.simpledatabase.domain.Person;
public class PersonDao {
// 在构造方法里完成helper初始化
public PersonSQLiteOpenHelper helper;
private Context context;
public static Uri message = Uri.parse("content://person");
public PersonDao(Context context) {
helper = new PersonSQLiteOpenHelper(context);
}
/**
* 添加记录
*
* @param name
* @param number
*/
public void add(String name, String number) {
SQLiteDatabase db = helper.getWritableDatabase();
db.execSQL("insert into person (name,number) values (?,?)",
new Object[] { name, number });
db.close();
context.getContentResolver().notifyChange(message, null);
}
/**
* 查询
*
* @param name
* @return
*/
public boolean find(String name) {
SQLiteDatabase db = helper.getReadableDatabase();
Cursor cursor = db.rawQuery("select * from person where name=?",
new String[] { name });
boolean result = cursor.moveToNext();
cursor.close();
db.close();
return result;
}
/**
* 修改
*
* @param name
* @param newnumber
*/
public void update(String name, String newnumber) {
SQLiteDatabase db = helper.getWritableDatabase();
db.execSQL("update person set number=? where name=?", new Object[] {
newnumber, name });
db.close();
context.getContentResolver().notifyChange(message, null);
}
/**
* 删除
*
* @param name
*/
public void delete(String name) {
SQLiteDatabase db = helper.getWritableDatabase();
db.execSQL("delete from person where name=?", new Object[] { name });
db.close();
context.getContentResolver().notifyChange(message, null);
}
// 查询数据库全部信息
public List<Person> findAll() {
SQLiteDatabase db = helper.getReadableDatabase();
List<Person> persons = new ArrayList<Person>();
Cursor cursor = db.rawQuery("select * from person", null);
while (cursor.moveToNext()) {
int id = cursor.getInt(cursor.getColumnIndex("id"));
String name = cursor.getString(cursor.getColumnIndex("name"));
String number = cursor.getString(cursor.getColumnIndex("number"));
Person p = new Person(id, name, number);
persons.add(p);
}
db.close();
return persons;
}
}
package com.example.simpledatabase;
import com.example.simpledatabase.dao.PersonDao;
import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
public class PersonDBProvider extends ContentProvider {
// 用于规定addURI的返回值
private static final int INSERT = 1;
private static final int DELETE = 2;
private static final int UPDATE = 3;
private static final int QUERY = 4;
private static final int QUERYONE = 5;
private PersonSQLiteOpenHelper helper;
private String tag = "PersonDBProvider";
// 定义一个URI匹配器用于匹配uri，如果路径不满足条件则
private static UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH);
// 指定匹配器的规则
static {
// 添加一组匹配规则
matcher.addURI("com.example.simpledatabase.personprovider", "insert",
INSERT);
matcher.addURI("com.example.simpledatabase.personprovider", "delete",
DELETE);
matcher.addURI("com.example.simpledatabase.personprovider", "update",
UPDATE);
matcher.addURI("com.example.simpledatabase.personprovider", "query",
QUERY);
matcher.addURI("com.example.simpledatabase.personprovider", "query/#",
QUERYONE);
}
// 在安卓中内容提供者路径名格式为
// content://com.example.simpledatabase.personprovider/insert 添加操作
// content://com.example.simpledatabase.personprovider/update
// content://com.example.simpledatabase.personprovider/query
// content://com.example.simpledatabase.personprovider/delete
@Override
public boolean onCreate() {
// TODO Auto-generated method stub
helper = new PersonSQLiteOpenHelper(getContext());
return false;
}
@Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
if (matcher.match(uri) == QUERY) {
// Log.i(tag, "看效果");
SQLiteDatabase db = helper.getReadableDatabase();
Cursor cursor = db.query("person", projection, selection,
selectionArgs, null, null, sortOrder);
return cursor;// 不能关闭数据库否则无法获取结果集，返回的是多条结果集
}
else if (matcher.match(uri) == QUERYONE) {
long id = ContentUris.parseId(uri);
SQLiteDatabase db = helper.getReadableDatabase();
Cursor cursor = db.query("person", projection, "id=?",
new String[] { id + "" }, null, null, sortOrder);
return cursor;// 返回的是一条记录
}
else {
throw new IllegalArgumentException("查询失败，路径名不合法");
}
}
@Override
public String getType(Uri uri) {
if (matcher.match(uri) == QUERY) {
return "vnd.android.cursor.dir/person";// 返回的是多条记录
}
else if (matcher.match(uri) == QUERYONE) {
return "vnd.android.cursor.item/person";// 返回的是具体记录
}
return null;
}
@Override
public Uri insert(Uri uri, ContentValues values) {
if (matcher.match(uri) == INSERT) {
// Log.i(tag, "看效果");
SQLiteDatabase db = helper.getWritableDatabase();
db.insert("person", null, values);
getContext().getContentResolver().notifyChange(PersonDao.message, null);
} else {
throw new IllegalArgumentException("查询失败，路径名不合法");
}
return null;
}
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
if (matcher.match(uri) == DELETE) {
SQLiteDatabase db = helper.getWritableDatabase();
db.delete("person", selection, selectionArgs);
getContext().getContentResolver().notifyChange(PersonDao.message, null);
} else {
throw new IllegalArgumentException("查询失败，路径名不合法");
}
return 0;
}
@Override
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs) {
if (matcher.match(uri) == UPDATE) {
SQLiteDatabase db = helper.getWritableDatabase();
db.update("person", values, selection, selectionArgs);
getContext().getContentResolver().notifyChange(PersonDao.message, null);
} else {
throw new IllegalArgumentException("查询失败，路径名不合法");
}
return 0;
}
}
第三个应用观察数据库变化情况：
package com.example.persondbobserver;
import android.app.Activity;
import android.database.ContentObserver;
import android.net.Uri;
import android.os.Bundle;
import android.os.Handler;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Uri uri=Uri.parse("content://person");
getContentResolver().registerContentObserver(uri, true, new Myobserver(new Handler()));
}
private class Myobserver extends ContentObserver{
public Myobserver(Handler handler) {
super(handler);
// TODO Auto-generated constructor stub
}
@Override
public void onChange(boolean selfChange) {
// TODO Auto-generated method stub
super.onChange(selfChange);
System.out.println("第三方应用，数据库变化了");
}
}
}
当测试程序执行添加 删除 修改时，第三方观察者应用可观察到数据库变化
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