今天就跟大家聊聊有关如何在Android中自定义ContentProvider与ContentObserver，可能很多人都不太了解，为了让大家更加了解，小编给大家总结了以下内容，希望大家根据这篇文章可以有所收获。
Android 中自定义ContentProvider与ContentObserver的使用简单实例
示例说明:
该示例中一共包含两个工程。其中一个工程完成了自定义ContentProvider，另外一个工程用于测试该自定义ContentProvider且在该工程中使用了ContentObserver监听自定义ContentProvider的数据变化
以下代码为工程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; 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; static { mUriMatcher = new UriMatcher(UriMatcher.NO_MATCH); // 该URI表示返回所有的person,其中PERSONS为该特定Uri的标识码 mUriMatcher.addURI(AUTHORITY, "person", PERSON_DIR); // 该URI表示返回某一个person,其中PERSON为该特定Uri的标识码 mUriMatcher.addURI(AUTHORITY, "person/#", PERSON); } @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; } @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); //向外界通知该ContentProvider里的数据发生了变化 ,以便ContentObserver作出相应 getContext().getContentResolver().notifyChange(uri, null); return ContentUris.withAppendedId(uri, newId); default: throw new IllegalArgumentException("unknown uri" + uri.toString()); } } @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更新某条数据 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()); } //向外界通知该ContentProvider里的数据发生了变化 ,以便ContentObserver作出相应 getContext().getContentResolver().notifyChange(uri, null); return updatedNum; } @Override public int delete(Uri uri, String selection, String[] selectionArgs) { SQLiteDatabase db = mSQLiteDatabaseOpenHelper.getWritableDatabase(); int deletedNum = 0; switch (mUriMatcher.match(uri)) { // 删除表 case PERSON_DIR: deletedNum = db.delete("person", selection, selectionArgs); break; // 按照id删除某条数据 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()); } //向外界通知该ContentProvider里的数据发生了变化 ,以便ContentObserver作出相应 getContext().getContentResolver().notifyChange(uri, null); return deletedNum; } @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)) { // 查询表 case PERSON_DIR: cursor = db.query("person", projection, selection, selectionArgs,null, null, sortOrder); break; // 按照id查询某条数据 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))"); } //当数据库版本号发生变化时调用该方法 @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 copypackage 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="该应用包含一个自定义的ContentProvider" android:textSize="15sp" android:layout_centerInParent="true" /> </RelativeLayout>以下代码为工程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; 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()); } // 注册一个针对ContentProvider的ContentObserver用来观察内容提供者的数据变化 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); } } // 自定义一个内容观察者ContentObserver private class ContentObserverSubClass extends ContentObserver { public ContentObserverSubClass(Handler handler) { super(handler); } //采用时间戳避免多次调用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"); // 获取最新的一条数据 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("内容提供者中的数据发生变化,现数据中第一条数据的personid="+ personid); } cursor.close(); lastTime=System.currentTimeMillis(); }else{ System.out.println("时间间隔过短,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: // 查询表 // queryFromContentProvider(-1); // 查询personid=2的数据 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("新增数据: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) { //查询表 uri=Uri.parse("content://cn.bs.testcontentprovider/person"); } else { //按照id查询某条数据 uri=Uri.parse("content://cn.bs.testcontentprovider/person/"+String.valueOf(index)); } //对应上面的:查询表 //Cursor cursor= mContentResolver.query(uri, null, null, null, null); //对应上面的:查询personid=2的数据 //注意:因为name是varchar字段的,所以应该写作"name='xiaoming1'" // 若写成"name=xiaoming1"查询时会报错 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("查询得到: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="查询" 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="删除" 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="类型" android:textSize="20sp" /> </RelativeLayout>看完上述内容，你们对如何在Android中自定义ContentProvider与ContentObserver有进一步的了解吗？如果还想了解更多知识或者相关内容，请关注编程网行业资讯频道，感谢大家的支持。
