Android-ContentProvider 实例详解 (1)

实例代码：

ContentResolver resolver = ?getContentResolver();

Uri uri = Uri.parse("content://cn.scu.myprovider/user");

//添加一条记录

ContentValues values = new ContentValues();

values.put("name", "fanrunqi");

values.put("age", 24);

resolver.insert(uri, values); ?

//获取 user 表中所有记录

Cursor cursor = resolver.query(uri, null, null, null, "userid desc");

while(cursor.moveToNext()){

//操作

}

//把 id 为 1 的记录的 name 字段值更改新为 finch

ContentValues updateValues = new ContentValues();

updateValues.put("name", "finch");

Uri updateIdUri = ContentUris.withAppendedId(uri, 1);

resolver.update(updateIdUri, updateValues, null, null);

//删除 id 为 2 的记录

Uri deleteIdUri = ContentUris.withAppendedId(uri, 2);

resolver.delete(deleteIdUri, null, null);

5?ContentObserver

ContentObserver(内容观察者)，目的是观察特定 Uri 引起的数据库的变化，继而做一些相应的处理，它类似于数据库技术中的触发器(Trigger)，当 ContentObserver 所观察的 Uri 发生变化时，便会触发它.

下面是使用内容观察者监听短信的例子：

public class MainActivity extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);//注册观察者 Observser ? ?this.getContentResolver().registerContentObserver(Uri.parse("content://sms"),true,new SMSObserver(new Handler()));}private final class SMSObserver extends ContentObserver {public SMSObserver(Handler handler) {super(handler);}@Overridepublic void onChange(boolean selfChange) {Cursor cursor = MainActivity.this.getContentResolver().query(Uri.parse("content://sms/inbox"), null, null, null, null);while (cursor.moveToNext()) {StringBuilder sb = new StringBuilder();sb.append("address=").append(cursor.getString(cursor.getColumnIndex("address")));sb.append(";subject=").append(cursor.getString(cursor.getColumnIndex("subject")));sb.append(";body=").append(cursor.getString(cursor.getColumnIndex("body")));sb.append(";time=").append(cursor.getLong(cursor.getColumnIndex("date")));System.out.println("--------has Receivered SMS::" + sb.toString());}}}}

同时可以在 ContentProvider 发生数据变化时调用?getContentResolver().notifyChange(uri, null)来通知

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注册在此 URI 上的访问者。

public class UserContentProvider extends ContentProvider {

public Uri insert(Uri uri, ContentValues values) {

db.insert("user", "userid", values);

getContext().getContentResolver().notifyChange(uri, null);

}

}

##6 ?实例说明

数据源是 SQLite, 用 ContentResolver 操作 ContentProvider。

Constant.Java（储存一些常量）

public class Constant { ?

public static final String TABLE_NAME = "user"; ?

public static final String COLUMN_ID = "_id"; ?

public static final String COLUMN_NAME = "name"; ?

public static final String AUTOHORITY = "cn.scu.myprovider"; ?

public static final int ITEM = 1; ?

public static final int ITEM_ID = 2; ?

public static final String CONTENT_TYPE = "vnd.android.cursor.dir/user"; ?

public static final String CONTENT_ITEM_TYPE = "vnd.android.cursor.item/user"; ?

public static final Uri CONTENT_URI = Uri.parse("content://" + AUTOHORITY + "/user"); ?

} ?

DBHelper.java(操作数据库)

public class DBHelper extends SQLiteOpenHelper { ?

private static final String DATABASE_NAME = "finch.db"; ? ?

private static final int DATABASE_VERSION = 1; ? ?

public DBHelper(Context context) { ?

super(context, DATABASE_NAME, null, DATABASE_VERSION); ?} ?

@Override ?

public void onCreate(SQLiteDatabase db) ?throws SQLException { ?

//创建表格 ?

db.execSQL("CREATE TABLE IF NOT EXISTS "+ Constant.TABLE_NAME + "("+ Constant.COLUMN_ID +" INTEGER PRIMARY KEY AUTOINCREMENT," + Constant.COLUMN_NAME +" VARCHAR NOT NULL);"); ?

} ?

@Override ?

public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) ?throws SQLException { ?

//删除并创建表格 ?

db.execSQL("DROP TABLE IF EXISTS "+ Constant.TABLE_NAME+";"); ?

onCreate(db); ?

} ?

} ?

MyProvider.java(自定义的 ContentProvider)

public class MyProvider extends ContentProvider { ? ?

DBHelper mDbHelper = null; ? ?

SQLiteDatabase db = null; ? ?

private static final UriMatcher mMatcher; ? ?

static{ ? ?

mMatcher = new UriMatcher(UriMatcher.NO_MATCH); ? ?mMatcher.addURI(Constant.AUTOHORITY,Constant.TABLE_NAME, Constant.ITEM); ? ?

mMatcher.addURI(Constant.AUTOHORITY, Constant.TABLE_NAME+"/#", Constant.ITEM_ID); ? ?

} ? ?

@Override ? ?

public String getType(Uri uri) { ? ?

switch (mMatcher.match(uri)) { ? ?

case Constant.ITEM: ? ?

return Constant.CONTENT_TYPE; ? ?

case Constant.ITEM_ID: ? ?

return Constant.CONTENT_ITEM_TYPE; ? ?

default: ? ?

throw new IllegalArgumentException("Unknown URI"+uri); ? ?

} ? ?

} ? ?

@Override ? ?

public Uri insert(Uri uri, ContentValues values) { ? ?

// TODO Auto-generated method stub ? ?

long rowId; ? ?

if(mMatcher.match(uri)!=Constant.ITEM){ ? ?

throw new IllegalArgumentException("Unknown URI"+uri); ? ?

} ? ?

rowId = db.insert(Constant.TABLE_NAME,null,values); ? ?

if(rowId>0){ ? ?

Uri noteUri=ContentUris.withAppendedId(Constant.CONTENT_URI, rowId); ? ?

getContext().getContentResolver().notifyChange(noteUri, null); ? ?

return noteUri; ? ?

} ? ?

throw new SQLException("Failed to insert row into " + uri); ? ?

} ? ?

@Override ? ?

public boolean onCreate() { ? ?

// TODO Auto-generated method stub ? ?

mDbHelper = new DBHelper(getContext()); ? ?

db = mDbHelper.getReadableDatabase(); ? ?

return true; ? ?

} ? ?

@Override ? ?

public Cursor query(Uri uri, String[] projection, String selection, ? ?

String[] selectionArgs, String sortOrder) { ? ?

// TODO Auto-generated method stub ? ?

Cursor c = null; ? ?

switch (mMatcher.match(uri)) { ? ?

case Constant.ITEM: ? ?

c = ?db.query(Constant.TABLE_NAME, projection, selection, selectionArgs, null, null, sortOrder); ? ?

break; ? ?

case Constant.ITEM_ID: ? ?

c = db.query(Constant.TABLE_NAME, projection,Constant.COLUMN_ID + "="+uri.getLastPathSegment(), selectionArgs, null, null, sortOrder); ? ?

break; ? ?

default: ? ?

throw new IllegalArgumentException("Unknown URI"+uri); ? ?

} ? ?

c.setNotificationUri(getContext().getContentResolver(), uri); ? ?

return c; ? ?

} ? ?

@Override ? ?

public int update(Uri uri, ContentValues values, String selection, ? ?

String[] selectionArgs) { ? ?

// TODO Auto-generated method stub ? ?

return 0; ? ?

}

@Override

public int delete(Uri uri, String selection, String[] selectionArgs) {

// TODO Auto-generated method stub

return 0;

} ? ?

} ? ?

MainActivity.java(ContentResolver 操作)

public class MainActivity extends Activity {

private ContentResolver mContentResolver = null;?

private Cursor cursor = null; ?

@Override

protected void onCreate(Bundle savedInstanceState) {

// TODO Auto-generated method stub

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

TextView tv = (TextView) findViewById(R.id.tv);

mContentResolver = getContentResolver(); ?

tv.setText("添加初始数据 ");

for (int i = 0; i < 10; i++) { ?

ContentValues values = new ContentValues(); ?

values.put(Constant.COLUMN_NAME, "fanrunqi"+i); ?

mContentResolver.insert(Constant.CONTENT_URI, values); ?

}?

tv.setText("查询数据 ");

cursor = mContentResolver.query(Constant.CONTENT_URI, new String[]{Constant.COLUMN_ID,Constant.COLUMN_NAME}, null, null, null); ?

if (cursor.moveToFirst()) {

String s = cursor.getString(cursor.getColumnIndex(Constant.COLUMN_NAME));

tv.setText("第一个数据： "+s);

}

}

} ?

最后在 manifest 申明

<provider android:name="MyProvider" android:authorities="cn.scu.myprovider" />

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