contentProvider作为android四大组件其地位也是不可忽视的。contentProvider实现是在Sqlite数据库基础上实现的。其数据存储使用Sqlite实现，上层使用URI进行数据操作，是数据存储变得更简单些。在简化数据存储的同时，contentProvider也提供数据共享功能，数据可以为其它程序提供读写功能。下面看一下具体使用。
创建数据源DBContent（通常是数据库进行存储）
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
public class DBContent extends SQLiteOpenHelper {
private final static String DB_NAME = "emcElevator";
public final static String TABLE_SHUACARD = "shuaCard";
public final static int DB_VERSION = 1;
public final static String SID = "_id";
public final static String CARD_IDNUM="card_id_number";
public final static String CARD_PICTRUE="card_picture_path";
public DBContent(Context context){
super(context, DB_NAME, null, DB_VERSION);
}
public DBContent(Context context, String name, CursorFactory factory,
int version) {
super(context, name, factory, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
final String sql="CREATE TABLE " + TABLE_SHUACARD + "(" + SID
+ " INTEGER PRIMARY KEY AUTOINCREMENT," +
CARD_IDNUM+" TEXT,"+CARD_PICTRUE+" TEXT"+");";
db.execSQL(sql);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_SHUACARD);
}
}
contentProvider实现类：
import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
import android.text.TextUtils;
public class CardContentProvider extends ContentProvider {
public static final String AUTHORITY = "com.ctsing.provider.shuacarddata";
public static final String ReadContentPermission="com.permission.allow.readcontent";
public static final int ITEM = 1;
public static final int ITEM_ID = 2;
public static final String CONTENT_TYPE = "vnd.android.cursor.dir/" + DBContent.TABLE_SHUACARD;
public static final String CONTENT_ITEM_TYPE = "vnd.android.cursor.item/" + DBContent.TABLE_SHUACARD;
public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/item");
//匹配器
private static final UriMatcher mMatcher;
static{
mMatcher = new UriMatcher(UriMatcher.NO_MATCH);
mMatcher.addURI(AUTHORITY, "item", ITEM);
mMatcher.addURI(AUTHORITY, "item/#", ITEM_ID);
}
private DBContent dbHelper=null;
@Override
public boolean onCreate() {
dbHelper=new DBContent(getContext());
return true;
}
@Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
SQLiteDatabase sdb = dbHelper.getReadableDatabase();
Cursor cur;
switch (mMatcher.match(uri)) {
case ITEM:
cur = sdb.query(DBContent.TABLE_SHUACARD, projection, selection,
selectionArgs, null, null, sortOrder);
break;
case ITEM_ID:
long id = ContentUris.parseId(uri);
cur = sdb.query(DBContent.TABLE_SHUACARD, projection, DBContent.SID
+ "=" + id
+ (!TextUtils.isEmpty(selection) ? " AND (" + selection
+ ")" : ""), selectionArgs, null, null, sortOrder);
break;
default:
// Log.i("sMatcher.match(uri)", String.valueOf(mMatcher.match(uri)));
throw new IllegalArgumentException("Query with unknown URI: " + uri);
}
/* sdb.close();
sdb=null; */
cur.setNotificationUri(getContext().getContentResolver(), uri);
return cur;
}
@Override
public String getType(Uri uri) {
String matchType=null;
switch(mMatcher.match(uri)){
case ITEM:
matchType=CONTENT_TYPE;
break;
case ITEM_ID:
matchType=CONTENT_ITEM_TYPE;
break;
default:
throw new IllegalArgumentException("Unknown URI " + uri);
}
return matchType;
}
@Override
public Uri insert(Uri uri, ContentValues values) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
if (mMatcher.match(uri) != ITEM) {
db.close();
db=null;
throw new IllegalArgumentException("Unknow URI " + uri);
}
long rowId = db.insert(DBContent.TABLE_SHUACARD, DBContent.SID, values);
if (rowId > 0) {
Uri noteUri = ContentUris.withAppendedId(CONTENT_URI, rowId);
this.getContext().getContentResolver().notifyChange(noteUri, null);
return noteUri;
}
db.close();
db=null;
throw new SQLException("Failed to insert row into " + uri);
}
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
SQLiteDatabase sdb = dbHelper.getWritableDatabase();
int count;
switch (mMatcher.match(uri)) {
case ITEM:
count = sdb.delete(DBContent.TABLE_SHUACARD, selection, selectionArgs);
break;
case ITEM_ID:
//String id = uri.getPathSegments().get(1);
long id = ContentUris.parseId(uri);
count = sdb.delete(DBContent.TABLE_SHUACARD, DBContent.SID
+ "=" + id
+ (!TextUtils.isEmpty(selection) ? " AND (" + selection
+ ")" : ""), selectionArgs);
break;
default:
throw new IllegalArgumentException("Unknown URI " + uri);
}
sdb.close();
sdb=null;
this.getContext().getContentResolver().notifyChange(uri, null);
return count;
}
@Override
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
int count;
switch (mMatcher.match(uri)) {
case ITEM:
count = db.update(DBContent.TABLE_SHUACARD, values, selection,
selectionArgs);
break;
case ITEM_ID:
String id = uri.getPathSegments().get(1);
count = db.update(DBContent.TABLE_SHUACARD, values, DBContent.SID
+ "=" + id
+ (!TextUtils.isEmpty(selection) ? " AND (" + selection
+ ")" : ""), selectionArgs);
break;
default:
throw new IllegalArgumentException("Unknown URI " + uri);
}
db.close();
db=null;
this.getContext().getContentResolver().notifyChange(uri, null);
return count;
}
}
配置ContentProvider
<provider
android:name="com.ctsing.content.CardContentProvider"
android:authorities="com.ctsing.provider.shuacarddata"
/>
单元测试进行功能测试：
import android.content.ContentResolver;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.test.AndroidTestCase;
import android.util.Log;
public class TestUse extends AndroidTestCase {
public void testInsert()throws Exception{ //插入数据
Uri uri = Uri.parse("content://" + CardContentProvider.AUTHORITY + "/item");
ContentResolver resolver = this.getContext().getContentResolver();
ContentValues values1 = new ContentValues();
values1.put(DBContent.CARD_IDNUM, "1001");
values1.put(DBContent.CARD_PICTRUE, "pro/elevater/11.jpeg");
resolver.insert(uri, values1);
ContentValues values2 = new ContentValues();
values2.put(DBContent.CARD_IDNUM, "1002");
values2.put(DBContent.CARD_PICTRUE, "pro/elevater/12.jpeg");
resolver.insert(uri, values2);
ContentValues values3 = new ContentValues();
values3.put(DBContent.CARD_IDNUM, "1003");
values3.put(DBContent.CARD_PICTRUE, "pro/elevater/13.jpeg");
resolver.insert(uri, values3);
}
public void testUpdate()throws Exception{ //更新id=2的记录
Uri uri = Uri.parse("content://" + CardContentProvider.AUTHORITY + "/item/2");
ContentResolver resolver = this.getContext().getContentResolver();
ContentValues values = new ContentValues();
values.put(DBContent.CARD_IDNUM, "1012");
values.put(DBContent.CARD_PICTRUE, "pro/elevater/102.jpeg");
resolver.update(uri, values, null, null);
}
public void testDelete()throws Exception{ //删除id=1的记录
Uri uri = Uri.parse("content://" + CardContentProvider.AUTHORITY + "/item/1"); //删除id=1的记录
ContentResolver resolver = this.getContext().getContentResolver();
resolver.delete(uri, null, null);
}
public void testQuery()throws Exception{ //查询数据并显示
Uri uri = Uri.parse("content://" + CardContentProvider.AUTHORITY + "/item"); //查询所有记录
ContentResolver resolver = this.getContext().getContentResolver();
Cursor cursor = resolver.query(uri, null, null, null, null);
while(cursor.moveToNext()){
// StudentData person = new StudentData(cursor.getInt(cursor.getColumnIndex("id")),cursor.getString(cursor.getColumnIndex("name")),cursor.getInt(cursor.getColumnIndex("age")));
Log.v("ContentProvider", " NO.= "+cursor.getInt((cursor.getColumnIndex("_id")))+
" card_id= "+cursor.getString(cursor.getColumnIndex(DBContent.CARD_IDNUM))+
" pic_path= "+cursor.getString(cursor.getColumnIndex(DBContent.CARD_PICTRUE)));
}
}
}
这里简单说一下单元测试实现：
1，在配置文件内声明权限，测试目标工具（在application外部声明）：
<uses-permission android:name="android.permission.RUN_INSTRUMENTATION" />
<instrumentation
android:name="android.test.InstrumentationTestRunner"
android:targetPackage="com.ctsing.emca" >
</instrumentation>
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
注意！在android:targetPackage所指的的包是应用程序包名，而不是测试类所在的包名称。
在application内部添加使用测试工具：
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<uses-library android:name="android.test.runner" />
实现继承AndroidTestCase类，再要测试的方法名称前加test，例如测试Insert方法,则编写测试方法testInsert()，在右侧outline窗口选择要测试功能方法，
想要测试哪个方法，则在哪个测试方法上右键鼠标，选择Run As，然后再选择Android JUnit Test即可，如果有异常或者错误,左边测试台会显示红色，下边是错误提示。测试通过，测试条为绿色。
下面在介绍一下Content权限问题，为了数据安全性我们需要添加适当的读写权限
如果contentProvider要被第三方使用读写则需要添加android:exported="true"属性，设置为false时，只有同一个应用程序的组件或带有相同用户ID的应用程序才能启动或绑定该服务。默认为false。当被第三方访问时我们可以添加权限来控制局部或者全部数据使用。
例如设置读取数据权限
声明权限：
<permission android:name="com.permission.allow.readcontent"
android:label="Allow read contentProvider"
android:protectionLevel="normal" />
添加权限到contentProvider:
<provider
android:name="com.ctsing.content.CardContentProvider"
android:authorities="com.ctsing.provider.shuacarddata"
android:exported="true"
android:readPermission="com.permission.allow.readcontent"
/>
t同样我们还可以设置写入权限，write android:witePermission权限，或者两者兼有permission。数据访问者需要添加权限声明
<uses-permission android:name="com.permission.allow.readcontent" />，才能正常访问数据内容，这在一定程度上起到保护数据功能。
部分权限功能：
实际使用中，provider可以只开放部分URI的权限，例如，我们可以只开放content://com.ctsing.provider.shuacarddata/item路径下权限，不允许访问其他路径，如下声明
<provider android:name="com.ctsing.content.CardContentProvider"
android:name="com.ctsing.content.CardContentProvider"
android:authorities="com.ctsing.provider.shuacarddata"
android:exported="true"
android:readPermission="com.permission.allow.readcontent">
<path-permission android:pathPrefix="/item" android:readPermission="READ_ITEM_CONTENTPROVIDER" />
</provider>
除了android:pathPrefix，还可以有android:path和android:pathPatten，例如android:pathPattern="/hello/.*"（注意，通配符*之前有个‘.’）。
如果要读取content:content://com.ctsing.content.CardContentProvider/item/1则需要声明整个provider的权限com.permission.allow.readcontent或者该路径的权限READ_ITM_CONTENTPROVIDER。
14.11.20更新，下面说一下数据变化监听问题：
当数据发生变化时，我们需要知道当数据变化时，希望能够得到通知，在android中已经设计了这种监听是用ContentObserver接口实现。联系人和短信内容发生变化时我们能够实现监听变化就是ContentObserver实现的。上述例子中我已经加入notifyChange方法进行内容变化通知，我们只有实现ContentObserver进行注册监听即可。
实现数据监听类：
public class ShuaCardContentObserver extends ContentObserver{
private Context mContext;
final String SHUACARD_ACTION="com.shuaCard.action";
final String SHUACARD_DATA="getData";
final String SHUACARD_KEYCARDNUM="card_num";
final String SHUACARD_KEYCARDADDRESS="card_path";
public ShuaCardContentObserver(Handler handler,Context ctx) {
super(handler);
this.mContext=ctx;
}
@Override
public void onChange(boolean selfChange) {
super.onChange(selfChange);
}
@TargetApi(Build.VERSION_CODES.JELLY_BEAN)
@Override
public void onChange(boolean selfChange, Uri uri) {
super.onChange(selfChange, uri);
dealChange();
}
void dealChange(){
Uri uri = Uri.parse("content://" + CardContentProvider.AUTHORITY + "/item");
ContentResolver resolver = mContext.getContentResolver();
Cursor cursor = resolver.query(uri, null, null, null, null);
List<Map<String,String>> cardList=null;
if(cursor.getCount()>0)
cardList=new ArrayList<Map<String,String>>();
while(cursor.moveToNext()){
String cardNum=cursor.getString(cursor.getColumnIndex(DBContent.CARD_IDNUM));
String cardAddress=cursor.getString(cursor.getColumnIndex(DBContent.CARD_PICTRUE_PATH));
Map<String,String> map=new HashMap<String, String>();
map.put(SHUACARD_KEYCARDNUM, cardNum);
map.put(SHUACARD_KEYCARDADDRESS, cardAddress);
cardList.add(map);
}
if(cursor!=null)
cursor.close();
if(cardList!=null){
Intent it=new Intent(SHUACARD_ACTION);
Bundle b=new Bundle();
b.putSerializable(SHUACARD_DATA, (Serializable)cardList);
it.putExtras(b);
mContext.sendBroadcast(it);
}
}
注册监听：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
cardChangeObserver=new ShuaCardContentObserver(new android.os.Handler(), this);
getContentResolver().registerContentObserver(Uri.parse("content://" + CardContentProvider.AUTHORITY + "/item"), true,cardChangeObserver);
}
退出取消监听：
@Override
protected void onDestroy() {
if(null!=cardChangeObserver)
getContentResolver().unregisterContentObserver(cardChangeObserver);
super.onDestroy();
}
虽然我们可以知道数据发生变化，但是我们并不知道具体发生变化数据具体情况（删除哪些数据或是添加哪些），如何实现这一个需求呢？android并没有实现，这就需要我们自己实现了。有待后续研究，更新中。。。