Android ContentProvider之自定义内容提供者以及UriMatcher使用

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内容提供者

应用的数据库是不允许其他应用访问的
内容提供者的作用就是让别的应用访问到你的私有数据
自定义内容提供者，继承ContentProvider类，重写增删改查方法，在方法中写增删改查数据库的代码，举例增方法
```
@Overridepublic Uri insert(Uri uri, ContentValues values) {    db.insert("person", null, values);    return uri;}
```
在清单文件中定义内容提供者的标签，注意必须要有authorities属性，这是内容提供者的主机名，功能类似地址
```
<provider android:name="com.cy.contentprovider.PersonProvider"    android:authorities="com.cy.person"    android:exported="true" ></provider>
```

创建一个其他应用，访问自定义的内容提供者，实现对数据库的插入操作

public void click(View v){    //得到内容分解器对象    ContentResolver cr = getContentResolver();    ContentValues cv = new ContentValues();    cv.put("name", "小方");    cv.put("phone", 138856);    cv.put("money", 3000);    //url:内容提供者的主机名    cr.insert(Uri.parse("content://com.cy.person"), cv);}

UriMatcher

用于判断一条uri跟指定的多条uri中的哪条匹配

添加匹配规则

//指定多条urium.addURI("com.cy.person", "person", PERSON_CODE);um.addURI("com.cy.person", "company", COMPANY_CODE);//#号可以代表任意数字um.addURI("com.cy.person", "person/#", QUERY_ONE_PERSON_CODE);

通过Uri匹配器可以实现操作不同的表

@Overridepublic Uri insert(Uri uri, ContentValues values) {    if(um.match(uri) == PERSON_CODE){        db.insert("person", null, values);    }    else if(um.match(uri) == COMPANY_CODE){        db.insert("company", null, values);    }    else{        throw new IllegalArgumentException();    }    return uri;}

如果路径中带有数字，把数字提取出来的api
```
int id = (int) ContentUris.parseId(uri);
```

内容提供者
* Android四大组件
* ContentProvider
* 把私有数据共享给其他应用访问
* 使用内容提供者可以自己定义访问规则，选择私有数据中哪些共享出去，哪些不共享

   <provider            android:name="com.cy.mycontentprovider.PersonProvider"            android:authorities="com.cy.people"            android:exported="true" >        </provider>

public class PersonProvider extends ContentProvider {    private SQLiteDatabase db;    //创建uri匹配器    UriMatcher um = new UriMatcher(UriMatcher.NO_MATCH);    {        //添加匹配规则        //arg0:主机名        //arg1:路径        //arg2:匹配码        um.addURI("com.cy.people", "person", 1);//content://com.cy.people/person        um.addURI("com.cy.people", "handsome", 2);//content://com.cy.people/handsome        um.addURI("com.cy.people", "person/#", 3);//content://com.cy.people/person/10    }    //内容提供者创建时调用    @Override    public boolean onCreate() {        MyOpenHelper oh = new MyOpenHelper(getContext());        db = oh.getWritableDatabase();        return false;    }    //values:其他应用要插的数据    @Override    public Uri insert(Uri uri, ContentValues values) {        if(um.match(uri) == 1){            db.insert("person", null, values);            //数据库改变了,内容提供者发出通知            //arg0:通知发到哪个uri上，注册在这个uri上的内容观察者都可以收到通知            getContext().getContentResolver().notifyChange(uri, null);        }        else if(um.match(uri) == 2){            db.insert("handsome", null, values);            getContext().getContentResolver().notifyChange(uri, null);        }        else{            throw new IllegalArgumentException("uri传错啦傻逼");        }        return uri;    }    @Override    public int delete(Uri uri, String selection, String[] selectionArgs) {        int i = 0;        if(um.match(uri) == 1){            i = db.delete("person", selection, selectionArgs);        }        else if(um.match(uri) == 2){            i = db.delete("handsome", selection, selectionArgs);        }        else{            throw new IllegalArgumentException("uri又传错啦傻逼");        }        return i;    }    @Override    public int update(Uri uri, ContentValues values, String selection,            String[] selectionArgs) {        int i = db.update("person", values, selection, selectionArgs);        return i;    }    @Override    public Cursor query(Uri uri, String[] projection, String selection,            String[] selectionArgs, String sortOrder) {        Cursor cursor = null;        if(um.match(uri) == 1){            cursor = db.query("person", projection, selection, selectionArgs, null, null, sortOrder, null);        }        else if(um.match(uri) == 2){            cursor = db.query("handsome", projection, selection, selectionArgs, null, null, sortOrder, null);        }        else if(um.match(uri) == 3){            //取出uri末尾携带的数字            long id = ContentUris.parseId(uri);            cursor = db.query("person", projection, "_id = ?", new String[]{"" + id}, null, null, sortOrder, null);        }        return cursor;    }    //返回通过指定uri获取的数据的mimetype    @Override    public String getType(Uri uri) {        if(um.match(uri) == 1){            return "vnd.android.cursor.dir/person";        }        else if(um.match(uri) == 2){            return "vnd.android.cursor.dir/handsome";        }        else if(um.match(uri) == 3){            return "vnd.android.cursor.item/person";        }        return null;    }}

public class MyOpenHelper extends SQLiteOpenHelper {    public MyOpenHelper(Context context) {        super(context, "people.db", null, 2);    }    @Override    public void onCreate(SQLiteDatabase db) {        db.execSQL("create table person(_id integer primary key autoincrement, name char(10), phone char(20), money integer(10))");    }    @Override    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {        db.execSQL("create table handsome(_id integer primary key autoincrement, name char(10), phone char(20))");    }}

public class MainActivity extends Activity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);    }    public void insert(View v){        //通过内容提供者把数据插入01数据库        //1.获取contentResolver        ContentResolver resolver = getContentResolver();        //2.访问内容提供者，插入数据        ContentValues values = new ContentValues();        values.put("name", "傻逼");        values.put("phone", 138992);        values.put("money", 14000);        //arg0:指定内容提供者的主机名        resolver.insert(Uri.parse("content://com.cy.people/person"), values);        values.clear();        values.put("name", "彩比");        values.put("phone", 15999);        //arg0:指定内容提供者的主机名        resolver.insert(Uri.parse("content://com.cy.people/handsome"), values);    }    public void delete(View v){        ContentResolver resolver = getContentResolver();        int i = resolver.delete(Uri.parse("content://com.cy.people"), "name = ?", new String[]{"凤姐"});        System.out.println(i);    }    public void update(View v){        ContentResolver resolver = getContentResolver();        ContentValues values = new ContentValues();        values.put("money", 16001);        int i = resolver.update(Uri.parse("content://com.cy.people"), values, "name = ?", new String[]{"抠逼"});        System.out.println(i);    }    public void query(View v){        ContentResolver resolver = getContentResolver();        Cursor cursor = resolver.query(Uri.parse("content://com.cy.people/person"), null, null, null, null);        while(cursor.moveToNext()){            String name = cursor.getString(1);            String phone = cursor.getString(2);            String money = cursor.getString(3);            System.out.println(name + ";" + phone + ";" + money);        }    }    public void queryOne(View v){        ContentResolver resolver = getContentResolver();        Cursor cursor = resolver.query(Uri.parse("content://com.cy.people/person/4"), null, null, null, null);        if(cursor.moveToNext()){            String name = cursor.getString(1);            String phone = cursor.getString(2);            String money = cursor.getString(3);            System.out.println(name + ";" + phone + ";" + money);        }    }}

参考：Android ContentProvider

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