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今天就跟大家聊聊有關如何在Android中自定義ContentProvider與ContentObserver，可能很多人都不太了解，為了讓大家更加了解，小編給大家總結了以下內容，希望大家根據(jù)這篇文章可以有所收獲。
Android 中自定義ContentProvider與ContentObserver的使用簡單實例
示例說明:
該示例中一共包含兩個工程。其中一個工程完成了自定義ContentProvider，另外一個工程用于測試該自定義ContentProvider且在該工程中使用了ContentObserver監(jiān)聽自定義ContentProvider的數(shù)據(jù)變化
以下代碼為工程TestContentProvider
ContentProviderTest如下:
package cn.testcontentprovider;
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;
/**
* Demo描述:
* 自定義ContentProvider的實現(xiàn)
* ContentProvider主要用于在不同的應用程序之間共享數(shù)據(jù),這也是官方推薦的方式.
*
* 注意事項:
* 1 在AndroidManifest.xml中注冊ContentProvider時的屬性
* android:exported="true"表示允許其他應用訪問.
* 2 注意*和#這兩個符號在Uri中的作用
* 其中*表示匹配任意長度的字符
* 其中#表示匹配任意長度的數(shù)據(jù)
* 所以：
* 一個能匹配所有表的Uri可以寫成:
* content://cn.bs.testcontentprovider/*
* 一個能匹配person表中任意一行的Uri可以寫成:
* content://cn.bs.testcontentprovider/person/#
*
*/
public class ContentProviderTest extends ContentProvider {
private SQLiteDatabaseOpenHelper mSQLiteDatabaseOpenHelper;
private final static String AUTHORITY="cn.bs.testcontentprovider";
private static UriMatcher mUriMatcher;
private static final int PERSON_DIR = 0;
private static final int PERSON = 1;
/**
* 利用靜態(tài)代碼塊初始化UriMatcher
* 在UriMatcher中包含了多個Uri,每個Uri代表一種操作
* 當調用UriMatcher.match(Uri uri)方法時就會返回該uri對應的code;
* 比如此處的PERSONS和PERSON
*/
static {
mUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
// 該URI表示返回所有的person,其中PERSONS為該特定Uri的標識碼
mUriMatcher.addURI(AUTHORITY, "person", PERSON_DIR);
// 該URI表示返回某一個person,其中PERSON為該特定Uri的標識碼
mUriMatcher.addURI(AUTHORITY, "person/#", PERSON);
}
/**
* 在自定義ContentProvider中必須覆寫getType(Uri uri)方法.
* 該方法用于獲取Uri對象所對應的MIME類型.
*
* 一個Uri對應的MIME字符串遵守以下三點:
* 1 必須以vnd開頭
* 2 如果該Uri對應的數(shù)據(jù)可能包含多條記錄,那么返回字符串應該以"vnd.android.cursor.dir/"開頭
* 3 如果該Uri對應的數(shù)據(jù)只包含一條記錄,那么返回字符串應該以"vnd.android.cursor.item/"開頭
*/
@Override
public String getType(Uri uri) {
switch (mUriMatcher.match(uri)) {
case PERSON_DIR:
return "vnd.android.cursor.dir/"+AUTHORITY+".persons";
case PERSON:
return "vnd.android.cursor.item/"+AUTHORITY+".person";
default:
throw new IllegalArgumentException("unknown uri"+uri.toString());
}
}
@Override
public boolean onCreate() {
mSQLiteDatabaseOpenHelper=new SQLiteDatabaseOpenHelper(getContext());
return true;
}
/**
* 插入操作:
* 插入操作只有一種可能:向一張表中插入
* 返回結果為新增記錄對應的Uri
* 方法db.insert()返回結果為新增記錄對應的主鍵值
*/
@Override
public Uri insert(Uri uri, ContentValues values) {
SQLiteDatabase db = mSQLiteDatabaseOpenHelper.getWritableDatabase();
switch (mUriMatcher.match(uri)) {
case PERSON_DIR:
long newId = db.insert("person", "name,phone,salary", values);
//向外界通知該ContentProvider里的數(shù)據(jù)發(fā)生了變化 ,以便ContentObserver作出相應
getContext().getContentResolver().notifyChange(uri, null);
return ContentUris.withAppendedId(uri, newId);
default:
throw new IllegalArgumentException("unknown uri" + uri.toString());
}
}
/**
* 更新操作:
* 更新操作有兩種可能:更新一張表或者更新某條數(shù)據(jù)
* 在更新某條數(shù)據(jù)時原理類似于查詢某條數(shù)據(jù),見下.
*/
@Override
public int update(Uri uri, ContentValues values, String selection,String[] selectionArgs) {
SQLiteDatabase db = mSQLiteDatabaseOpenHelper.getWritableDatabase();
int updatedNum = 0;
switch (mUriMatcher.match(uri)) {
// 更新表
case PERSON_DIR:
updatedNum = db.update("person", values, selection, selectionArgs);
break;
// 按照id更新某條數(shù)據(jù)
case PERSON:
long id = ContentUris.parseId(uri);
String where = "personid=" + id;
if (selection != null && !"".equals(selection.trim())) {
where = selection + " and " + where;
}
updatedNum = db.update("person", values, where, selectionArgs);
break;
default:
throw new IllegalArgumentException("unknown uri" + uri.toString());
}
//向外界通知該ContentProvider里的數(shù)據(jù)發(fā)生了變化 ,以便ContentObserver作出相應
getContext().getContentResolver().notifyChange(uri, null);
return updatedNum;
}
/**
* 刪除操作:
* 刪除操作有兩種可能:刪除一張表或者刪除某條數(shù)據(jù)
* 在刪除某條數(shù)據(jù)時原理類似于查詢某條數(shù)據(jù),見下.
*/
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
SQLiteDatabase db = mSQLiteDatabaseOpenHelper.getWritableDatabase();
int deletedNum = 0;
switch (mUriMatcher.match(uri)) {
// 刪除表
case PERSON_DIR:
deletedNum = db.delete("person", selection, selectionArgs);
break;
// 按照id刪除某條數(shù)據(jù)
case PERSON:
long id = ContentUris.parseId(uri);
String where = "personid=" + id;
if (selection != null && !"".equals(selection.trim())) {
where = selection + " and " + where;
}
deletedNum = db.delete("person", where, selectionArgs);
break;
default:
throw new IllegalArgumentException("unknown uri" + uri.toString());
}
//向外界通知該ContentProvider里的數(shù)據(jù)發(fā)生了變化 ,以便ContentObserver作出相應
getContext().getContentResolver().notifyChange(uri, null);
return deletedNum;
}
/**
* 查詢操作:
* 查詢操作有兩種可能:查詢一張表或者查詢某條數(shù)據(jù)
*
* 注意事項:
* 在查詢某條數(shù)據(jù)時要注意--因為此處是按照personid來查詢
* 某條數(shù)據(jù),但是同時可能還有其他限制.例如:
* 要求personid為2且name為xiaoming1
* 所以在查詢時分為兩步:
* 第一步:
* 解析出personid放入where查詢條件
* 第二步:
* 判斷是否有其他限制(如name),若有則將其組拼到where查詢條件.
*
* 詳細代碼見下.
*/
@Override
public Cursor query(Uri uri, String[] projection, String selection,String[] selectionArgs, String sortOrder) {
SQLiteDatabase db = mSQLiteDatabaseOpenHelper.getWritableDatabase();
Cursor cursor =null;
switch (mUriMatcher.match(uri)) {
// 查詢表
case PERSON_DIR:
cursor = db.query("person", projection, selection, selectionArgs,null, null, sortOrder);
break;
// 按照id查詢某條數(shù)據(jù)
case PERSON:
// 第一步:
long id = ContentUris.parseId(uri);
String where = "personid=" + id;
// 第二步:
if (selection != null && !"".equals(selection.trim())) {
where = selection + " and " + where;
}
cursor = db.query("person", projection, where, selectionArgs, null, null, sortOrder);
break;
default:
throw new IllegalArgumentException("unknown uri" + uri.toString());
}
return cursor;
}
}SQLiteDatabaseOpenHelper如下:
package cn.testcontentprovider;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class SQLiteDatabaseOpenHelper extends SQLiteOpenHelper {
public SQLiteDatabaseOpenHelper(Context context) {
super(context, "contentprovidertest.db", null, 1);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table person(personid integer primary key autoincrement,name varchar(20),phone varchar(12),salary Integer(12))");
}
//當數(shù)據(jù)庫版本號發(fā)生變化時調用該方法
@Override
public void onUpgrade(SQLiteDatabase db, int arg1, int arg2) {
//db.execSQL("ALTER TABLE person ADD phone varchar(12) NULL");
//db.execSQL("ALTER TABLE person ADD salary Integer NULL");
}
}
MainActivity如下:
[java] view plain copy
package cn.testcontentprovider;
import android.app.Activity;
import android.os.Bundle;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
}AndroidManifest.xml如下:
<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="cn.testcontentprovider" android:versionCode="1" android:versionName="1.0" > <uses-sdk android:minSdkVersion="8" android:targetSdkVersion="8" /> <uses-permission android:name="android.permission.INTERNET" /> <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" /> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" /> <application android:allowBackup="true" android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme" > <activity android:name="cn.testcontentprovider.MainActivity" android:label="@string/app_name" > <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> <provider android:name="cn.testcontentprovider.ContentProviderTest" android:authorities="cn.bs.testcontentprovider" android:exported="true" /> </application> </manifest>
main.xml如下:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" > <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="該應用包含一個自定義的ContentProvider" android:textSize="15sp" android:layout_centerInParent="true" /> </RelativeLayout>
以下代碼為工程TestBaidu
MainActivity如下:
package cn.testbaidu;
import android.net.Uri;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.app.Activity;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.database.ContentObserver;
import android.database.Cursor;
/**
* Demo描述:
* 應用A(TestBaidu)調用另外一個應用(TestContentProvider)中的自定義ContentProvider,即:
* 1 自定義ContentProvider的使用
* 2 其它應用調用該ContentProvider
* 3 ContentObserver的使用
*
* 備注說明:
* 1 該例子在以前版本的基礎上整理了代碼
* 2 該例子在以前版本的基礎上融合了ContentObserver的使用
* 利用ContentObserver隨時監(jiān)聽ContentProvider的數(shù)據(jù)變化.
* 為實現(xiàn)該功能需要在自定義的ContentProvider的insert(),update(),delete()
* 方法中調用getContext().getContentResolver().notifyChange(uri, null);
* 向外界通知該ContentProvider里的數(shù)據(jù)發(fā)生了變化 ,以便ContentObserver作出相應
*
* 測試方法:
* 1 依次測試ContentProvider的增查刪改(注意該順序)!!
* 2 其它應用查詢該ContentProvider的數(shù)據(jù)
*
*/
public class MainActivity extends Activity {
private Button mAddButton;
private Button mDeleteButton;
private Button mUpdateButton;
private Button mQueryButton;
private Button mTypeButton;
private long lastTime=0;
private ContentResolver mContentResolver;
private ContentObserverSubClass mContentObserverSubClass;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
init();
initContentObserver();
}
private void init() {
mContentResolver=this.getContentResolver();
mAddButton=(Button) findViewById(R.id.addButton);
mAddButton.setOnClickListener(new ClickListenerImpl());
mDeleteButton=(Button) findViewById(R.id.deleteButton);
mDeleteButton.setOnClickListener(new ClickListenerImpl());
mUpdateButton=(Button) findViewById(R.id.updateButton);
mUpdateButton.setOnClickListener(new ClickListenerImpl());
mQueryButton=(Button) findViewById(R.id.queryButton);
mQueryButton.setOnClickListener(new ClickListenerImpl());
mTypeButton=(Button) findViewById(R.id.typeButton);
mTypeButton.setOnClickListener(new ClickListenerImpl());
}
// 注冊一個針對ContentProvider的ContentObserver用來觀察內容提供者的數(shù)據(jù)變化
private void initContentObserver() {
Uri uri = Uri.parse("content://cn.bs.testcontentprovider/person");
mContentObserverSubClass=new ContentObserverSubClass(new Handler());
this.getContentResolver().registerContentObserver(uri, true,mContentObserverSubClass);
}
@Override
protected void onDestroy() {
super.onDestroy();
if (mContentObserverSubClass!=null) {
this.getContentResolver().unregisterContentObserver(mContentObserverSubClass);
}
}
// 自定義一個內容觀察者ContentObserver
private class ContentObserverSubClass extends ContentObserver {
public ContentObserverSubClass(Handler handler) {
super(handler);
}
//采用時間戳避免多次調用onChange( )
@Override
public void onChange(boolean selfChange) {
super.onChange(selfChange);
System.out.println("ContentObserver onChange() selfChange="+ selfChange);
if (System.currentTimeMillis()-lastTime>2000) {
ContentResolver resolver = getContentResolver();
Uri uri = Uri.parse("content://cn.bs.testcontentprovider/person");
// 獲取最新的一條數(shù)據(jù)
Cursor cursor = resolver.query(uri, null, null, null,"personid desc limit 1");
while (cursor.moveToNext()) {
int personid = cursor.getInt(cursor.getColumnIndex("personid"));
System.out.println("內容提供者中的數(shù)據(jù)發(fā)生變化,現(xiàn)數(shù)據(jù)中第一條數(shù)據(jù)的personid="+ personid);
}
cursor.close();
lastTime=System.currentTimeMillis();
}else{
System.out.println("時間間隔過短,忽略此次更新");
}
}
@Override
public boolean deliverSelfNotifications() {
return true;
}
}
private class ClickListenerImpl implements OnClickListener {
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.addButton:
Person person = null;
for (int i = 0; i < 5; i++) {
person = new Person("xiaoming" + i, "9527" + i, (8888 + i));
testInsert(person);
}
break;
case R.id.deleteButton:
testDelete(1);
break;
case R.id.updateButton:
testUpdate(3);
break;
case R.id.queryButton:
// 查詢表
// queryFromContentProvider(-1);
// 查詢personid=2的數(shù)據(jù)
testQuery(2);
break;
case R.id.typeButton:
testType();
break;
default:
break;
}
}
}
private void testInsert(Person person) {
ContentValues contentValues=new ContentValues();
contentValues.put("name", person.getName());
contentValues.put("phone", person.getPhone());
contentValues.put("salary",person.getSalary());
Uri insertUri=Uri.parse("content://cn.bs.testcontentprovider/person");
Uri returnUri=mContentResolver.insert(insertUri, contentValues);
System.out.println("新增數(shù)據(jù):returnUri="+returnUri);
}
private void testDelete(int index){
Uri uri=Uri.parse("content://cn.bs.testcontentprovider/person/"+String.valueOf(index));
mContentResolver.delete(uri, null, null);
}
private void testUpdate(int index){
Uri uri=Uri.parse("content://cn.bs.testcontentprovider/person/"+String.valueOf(index));
ContentValues values=new ContentValues();
values.put("name", "hanmeimei");
values.put("phone", "1234");
values.put("salary", 333);
mContentResolver.update(uri, values, null, null);
}
private void testQuery(int index) {
Uri uri=null;
if (index<=0) {
//查詢表
uri=Uri.parse("content://cn.bs.testcontentprovider/person");
} else {
//按照id查詢某條數(shù)據(jù)
uri=Uri.parse("content://cn.bs.testcontentprovider/person/"+String.valueOf(index));
}
//對應上面的:查詢表
//Cursor cursor= mContentResolver.query(uri, null, null, null, null);
//對應上面的:查詢personid=2的數(shù)據(jù)
//注意:因為name是varchar字段的,所以應該寫作"name='xiaoming1'"
// 若寫成"name=xiaoming1"查詢時會報錯
Cursor cursor= mContentResolver.query(uri, null, "name='xiaoming1'", null, null);
while(cursor.moveToNext()){
int personid=cursor.getInt(cursor.getColumnIndex("personid"));
String name=cursor.getString(cursor.getColumnIndex("name"));
String phone=cursor.getString(cursor.getColumnIndex("phone"));
int salary=cursor.getInt(cursor.getColumnIndex("salary"));
System.out.println("查詢得到:personid=" + personid+",name="+name+",phone="+phone+",salary="+salary);
}
cursor.close();
}
private void testType(){
Uri dirUri=Uri.parse("content://cn.bs.testcontentprovider/person");
String dirType=mContentResolver.getType(dirUri);
System.out.println("dirType:"+dirType);
Uri itemUri=Uri.parse("content://cn.bs.testcontentprovider/person/3");
String itemType=mContentResolver.getType(itemUri);
System.out.println("itemType:"+itemType);
}
}Person如下:
package cn.testbaidu;
public class Person {
private Integer id;
private String name;
private String phone;
private Integer salary;
public Person(String name, String phone,Integer salary) {
this.name = name;
this.phone = phone;
this.salary=salary;
}
public Person(Integer id, String name, String phone,Integer salary) {
this.id = id;
this.name = name;
this.phone = phone;
this.salary=salary;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this.phone = phone;
}
public Integer getSalary() {
return salary;
}
public void setSalary(Integer salary) {
this.salary = salary;
}
@Override
public String toString() {
return "Person [id=" + id + ", name=" + name + ", phone=" + phone+ ", salary=" + salary + "]";
}
}main.xml如下:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" > <Button android:id="@+id/addButton" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_centerHorizontal="true" android:layout_marginTop="30dip" android:text="增加" android:textSize="20sp" /> <Button android:id="@+id/queryButton" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_centerHorizontal="true" android:layout_marginTop="30dip" android:layout_below="@id/addButton" android:text="查詢" android:textSize="20sp" /> <Button android:id="@+id/deleteButton" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_centerHorizontal="true" android:layout_marginTop="30dip" android:layout_below="@id/queryButton" android:text="刪除" android:textSize="20sp" /> <Button android:id="@+id/updateButton" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_centerHorizontal="true" android:layout_marginTop="30dip" android:layout_below="@id/deleteButton" android:text="修改" android:textSize="20sp" /> <Button android:id="@+id/typeButton" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_centerHorizontal="true" android:layout_marginTop="30dip" android:layout_below="@id/updateButton" android:text="類型" android:textSize="20sp" /> </RelativeLayout>
看完上述內容，你們對如何在Android中自定義ContentProvider與ContentObserver有進一步的了解嗎？如果還想了解更多知識或者相關內容，請關注億速云行業(yè)資訊頻道，感謝大家的支持。
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