1.简单示例：通过ContentProvider暴露数据库，然后读取数据。
2.先加上一个工具类，用来使用copy assets下面的db文件代码如下：
public class MyDBOpenHelper extends SQLiteOpenHelper{
private static final String TAG = "MyDBOpenHelper";
/*** 这里是是data/data/包名 /databases/ **/
private static String DB_PATH = "/data/data/com.example.mycontentproviderleader/databases/";
private static String DB_NAME = "song.db";
private SQLiteDatabase myDataBase;
private final Context myContext;
public void SetFilePath(String path){
DB_PATH = path;
}
public MyDBOpenHelper(Context context) {
super(context, DB_NAME, null, 1);
this.myContext = context;
// TODO Auto-generated constructor stub
}
public void createDataBase() throws IOException{
boolean dbExist = checkDataBase();
if(dbExist){
}else{
this.getReadableDatabase();
try {
copyDataBase();
} catch (IOException e) {
throw new Error("Error copying database");
}
}
}
private boolean checkDataBase(){
SQLiteDatabase checkDB = null;
try{
String myPath = DB_PATH + DB_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}catch(SQLiteException e){
//database does't exist yet.
}
if(checkDB != null){
checkDB.close();
return true;
}
return false;
//return checkDB != null ? true : false;
}
private void copyDataBase() throws IOException{
//Open your local db as the input stream
InputStream myInput = myContext.getAssets().open(DB_NAME);
// Path to the just created empty db
String outFileName = DB_PATH + DB_NAME;
//Open the empty db as the output stream
OutputStream myOutput = new FileOutputStream(outFileName);
//transfer bytes from the inputfile to the outputfile
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer))>0){
myOutput.write(buffer, 0, length);
}
//Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
}
public void openDataBase() throws SQLException{
//Open the database
String myPath = DB_PATH + DB_NAME;
myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}
@Override
public synchronized void close() {
if(myDataBase != null)
myDataBase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
Log.d(TAG, "onCreate: ***********");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
}
}
3.uri匹配器
UriMatcher uri匹配器
初始匹配器：UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH);
添加uri：
matcher.addURI(authority, "TableSong", 1);
matcher.addURI(authority, "TableSongSinger", 2);
matcher.addURI(authority,"TableSong/#",3);
后面的1,2,3为标识ID，TbaleSong可以指查询表全部数据，TableSong/#可以指查询特定的数据
switch (math) {
case 1:
cursor = db.rawQuery("select * from TableSong where Words=?",new Sreing[]{""+4} );
break;
case 2
cursor = db.rawQuery("select * from TableSong where Words=?",new Sreing[]{""+2} );
break;
case 3:
long id= ContentUris.parseId(uri);
cursor = db.rawQuery("select * from TableSong where SongIndex =?",new String[]{""+id} );
}
4.编写ContentProvider类
/****这里只实现了个查询功能，简单的示例 ，插入，删除等没实现********/
public class MyProvider extends ContentProvider {
private SQLiteDatabase db = null;
/*** 写入你的包名*/
private static final String authority = "com.example.mycontentproviderleader";
private static UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH);
static {
/****TabelSong,TabslSongSinger 是2张不同的数据表***/
matcher.addURI(authority, "TableSong", 1);
matcher.addURI(authority, "TableSongSinger", 2);
matcher.addURI(authority,"TableSong/#",3);
}
/*** 创建app数据库 ,我这里是从assets 下copy的*/
@Override
public boolean onCreate() {
MyDBOpenHelper myDBOpenHelper=new MyDBOpenHelper(getContext());
try {
myDBOpenHelper.createDataBase();
} catch (IOException e) {
e.printStackTrace();
}
db = myDBOpenHelper.getReadableDatabase();
return true;
}
@Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
int math = matcher.match(uri);
Cursor cursor = null;
switch (math) {
case 1:
cursor = db.rawQuery("select * from TableSong where Words=?" ,new String[]{"3"});
//cursor = db.query("TableSong", projection, selection, selectionArgs, null, null, sortOrder);
break;
case 2:
cursor = db.rawQuery("select * from TableSong where Words=?",new String[]{"6"} );
break;
case 3:
long id= ContentUris.parseId(uri);
cursor = db.rawQuery("select * from TableSong where SongIndex =?",new String[]{""+id} );
default:
break;
}
return cursor;
}
@Override
public String getType(Uri uri) {
// TODO Auto-generated method stub
return null;
}
@Override
public Uri insert(Uri uri, ContentValues values) {
int code = matcher.match(uri);
switch (code) {
case 1:
db.insert("info", null, values);
break;
default:
break;
}
return null;
}
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
// TODO Auto-generated method stub
return 0;
}
@Override
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs) {
// TODO Auto-generated method stub
return 0;
}
}
5. 编写contentProvider类后要在xml里面配置：
/***这里是通过一个demo实现了暴露，获取数据，如果在另一个程序获取数据需要加上 权限 android:permission="com.example.mycontentproviderleader.permission"*******/
<!-- android:exported 是否对外开放 -->
<provider android:name="com.example.mycontentproviderleader.MyProvider"
android:authorities="com.example.mycontentproviderleader"
android:exported="true"
android:multiprocess="true"
android:permission="com.example.mycontentproviderleader.permission"/>
6.然后在Main里面通过contentResolver ，uri 获取Cursor就行了。
ContentResolver contentResolver;
Uri uri;
contentResolver = getContentResolver();
uri = Uri.parse("content://com.example.mycontentproviderleader/TableSong");
Cursor cursor = contentResolver.query(uri, null, null, null, null);
while (cursor.moveToNext()){
String SongName=cursor.getString(cursor.getColumnIndex("SongName"));
Log.d(TAG, "select:歌曲名称:"+SongName);
}
7: code
链接: https://pan.baidu.com/s/1c2aViBQ 密码: 8qtw