描述

為了在應(yīng)用程序之間交換數(shù)據(jù)音五，Android提供了ContentProvider羔沙，它是不同應(yīng)用程序之間進(jìn)行數(shù)據(jù)交換的標(biāo)準(zhǔn)API躺涝，當(dāng)一個應(yīng)用程序需要把自己的數(shù)據(jù)暴露給其他程序使用時，該應(yīng)用程序就可通過提供ContentProvider來實現(xiàn)坚嗜；其他應(yīng)用程序就可通過ContentResolver來操作ContentResolver暴露的數(shù)據(jù)诗充。

ContentProvider以指定Uri的形式對外提供數(shù)據(jù)苍蔬，允許其他應(yīng)用訪問或修改數(shù)據(jù)；其他應(yīng)用程序使用ContentResolver根據(jù)Uri去訪問操作指定數(shù)據(jù)蝴蜓。

一旦某個應(yīng)用程序通過 ContentProvider 暴露了自己的數(shù)據(jù)操作接口碟绑，那么不管該應(yīng)用程序是否啟動格仲，其他應(yīng)用程序都可通過該接口來操作該應(yīng)用程序的內(nèi)部數(shù)據(jù)，包括增加數(shù)據(jù)凯肋、刪除數(shù)據(jù)缩歪、修改數(shù)據(jù)穿仪、查詢數(shù)據(jù)等幸海。

從源碼分析ContentProvider的初始化

App進(jìn)程啟動 -> ActivityThread#main() -> ActivityThread#attach() -> ActivityManagerNative#attachApplication() ->
ActivityManagerService#attachApplication() -> ActivityManagerService#generateApplicationProvidersLocked() 舟舒。
generateApplicationProvidersLocked()這個方法通過 PackageManager 去獲取解析后的應(yīng)用的清單文件中 provider 信息癌佩，為每個 provider 新建 ContentProviderRecord 作為 ActivityManagerService 端的 ContentProvider 表現(xiàn)便锨。

即ContentProvider的 onCreate()方法在ActivityThread#main()運行時間接調(diào)用，即ContentProvider是在APP啟動的時候就初始化了姚建。運行在主線程吱殉，不能做耗時的操作友雳。

ContentProvider應(yīng)用內(nèi)數(shù)據(jù)共享

1稿湿、創(chuàng)建數(shù)據(jù)庫類(使用數(shù)據(jù)庫做數(shù)據(jù)共享)

public class DbHelper extends SQLiteOpenHelper {

    // 數(shù)據(jù)庫名
    private static final String DATABASE_NAME = "pkqup.db";
    // 數(shù)據(jù)庫版本號
    private static final int DATABASE_VERSION = 1;

    // 表名
    public static final String USER_TABLE_NAME = "user";
    public static final String ADDRESS_TABLE_NAME = "address";
    public static final String SPECIAL_CHARACTER = "/#";

    //在構(gòu)造方法中指定數(shù)據(jù)庫的 數(shù)據(jù)庫名 和 數(shù)據(jù)庫版本號
    public DbHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        // 創(chuàng)建兩個表格:用戶表 和地址表
        try {
            db.execSQL("CREATE TABLE IF NOT EXISTS " + USER_TABLE_NAME + " (" + User.INDEX   + " INTEGER PRIMARY KEY AUTOINCREMENT," + User.NAME + " TEXT, " + User.USER_ID + " TEXT)");
            db.execSQL("CREATE TABLE IF NOT EXISTS " + ADDRESS_TABLE_NAME + " (" + Address.INDEX   + " INTEGER PRIMARY KEY AUTOINCREMENT,"+ Address.NAME + " TEXT, " + Address.PHONE + " TEXT)");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        try {
            //數(shù)據(jù)庫版本發(fā)生變化押赊，刪除舊表
            db.execSQL("DROP TABLE IF EXISTS " + USER_TABLE_NAME);
            db.execSQL("DROP TABLE IF EXISTS " + ADDRESS_TABLE_NAME);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

2、自定義 ContentProvider 類

public class MyContentProvider extends ContentProvider {

    private DbHelper dbHelper;
    private SQLiteDatabase db;
    private ContentResolver resolver;

    // UriMatcher類使用:在ContentProvider 中注冊URI
    private static final UriMatcher uriMatcher;

    // 用戶定義列名->數(shù)據(jù)庫列名的映射
    private static final HashMap<String, String> userHashMap;
    private static final HashMap<String, String> addressHashMap;


    // 定義ContentProvider的授權(quán)信息涕俗，即唯一標(biāo)識
    public static final String AUTHORITY = "com.pkqup.android.note";

    // 定義Uri匹配返回碼
    public static final int USER_CODE = 1;
    public static final int USER_CODE_SINGLE = 2;
    public static final int ADDRESS_CODE = 3;
    public static final int ADDRESS_CODE_SINGLE = 4;

    // 設(shè)置URI
    // Uri uri = Uri.parse("content://com.carson.provider/User/1")
    // 上述URI指向的資源是：名為 com.carson.provider 的 ContentProvider  中表名 為`User` 中的 `id`為1的數(shù)據(jù)

    // 特別注意：URI模式存在匹配通配符* 和 ＃

    // *：匹配任意長度的任何有效字符的字符串
    // 以下的URI 表示 匹配provider的任何內(nèi)容
    // content://com.example.app.provider/*

    // ＃：匹配任意長度的數(shù)字字符的字符串
    // 以下的URI 表示 匹配provider中的table表的所有行
    // content://com.example.app.provider/table/#



    // 在靜態(tài)代碼塊中初始化 UriMatcher
    static {
        // 初始化 UriMatcher
        // 常量UriMatcher.NO_MATCH 再姑，不匹配任何路徑的返回碼 即初始化時不匹配任何東西
        uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);

        // 在ContentProvider 中注冊URI（即addURI()）
        uriMatcher.addURI(AUTHORITY, DbHelper.USER_TABLE_NAME, USER_CODE);
        uriMatcher.addURI(AUTHORITY, DbHelper.USER_TABLE_NAME + DbHelper.SPECIAL_CHARACTER,
                USER_CODE_SINGLE);

        uriMatcher.addURI(AUTHORITY, DbHelper.ADDRESS_TABLE_NAME, ADDRESS_CODE);
        uriMatcher.addURI(AUTHORITY, DbHelper.ADDRESS_TABLE_NAME + DbHelper.SPECIAL_CHARACTER,
                ADDRESS_CODE_SINGLE);
        // 若URI資源路徑 = content://com.pkqup.android.note/user 询刹，則返回注冊碼USER_CODE,
        // 即 mMatcher.match(User.USER_CONTENT_URI)的返回值
        // 若URI資源路徑 = content://com.pkqup.android.note/address ，則返回注冊碼ADDRESS_CODE凹联，
        // 即 mMatcher.match(Address.ADDRESS_CONTENT_URI)的返回值

        userHashMap = new HashMap<>();
        userHashMap.put(User.INDEX, User.INDEX);
        userHashMap.put(User.NAME, User.NAME);
        userHashMap.put(User.USER_ID, User.USER_ID);

        addressHashMap = new HashMap<>();
        addressHashMap.put(Address.INDEX, Address.INDEX);
        addressHashMap.put(Address.NAME, Address.NAME);
        addressHashMap.put(Address.PHONE, Address.PHONE);
    }


    // onCreate()方法在ActivityThread#main()運行時間接調(diào)用蔽挠，即ContentProvider是在APP啟動的時候就初始化了瓜浸。運行在主線程插佛，不能做耗時的操作。
    @Override
    public boolean onCreate() {
        resolver = getContext().getContentResolver();
        dbHelper = new DbHelper(getContext());
        db = dbHelper.getWritableDatabase();
        return true;
    }

    @Override
    public String getType(Uri uri) {
        return null;
    }


    // 注：以下增刪改成四個方法的說明：
    // 1氢拥、下面4個方法由外部進(jìn)程回調(diào)锨侯，并運行在ContentProvider進(jìn)程的Binder線程池中（不是主線程）
    // 2、存在多線程并發(fā)訪問叁怪，需要實現(xiàn)線程同步
    // 3深滚、若ContentProvider的數(shù)據(jù)存儲方式是使用SQLite &
    // 一個，則不需要血柳，因為SQLite內(nèi)部實現(xiàn)好了線程同步蹬昌，若是多個SQLite則需要皂贩，因為SQL對象之間無法進(jìn)行線程同步
    // 4、若ContentProvider的數(shù)據(jù)存儲方式是內(nèi)存婴栽，則需要自己實現(xiàn)線程同步


    @Override
    public Uri insert(Uri uri, ContentValues values) {
        Uri newUri;
        switch (uriMatcher.match(uri)) {
            case USER_CODE:
                long user_id = db.insert(DbHelper.USER_TABLE_NAME, "", values);
                if (user_id < 0) {
                    throw new SQLiteException("Unable to insert " + values + " for " + uri);
                }
                newUri = ContentUris.withAppendedId(uri, user_id);
                resolver.notifyChange(newUri, null);
                break;
            case ADDRESS_CODE:
                long property_id = db.insert(DbHelper.ADDRESS_TABLE_NAME, "", values);
                if (property_id < 0) {
                    throw new SQLiteException("Unable to insert " + values + " for " + uri);
                }
                newUri = ContentUris.withAppendedId(uri, property_id);
                resolver.notifyChange(newUri, null);
                break;
            default:
                throw new IllegalArgumentException("Error Uri: " + uri);
        }
        return newUri;
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        int count;
        switch (uriMatcher.match(uri)) {
            case USER_CODE:
                count = db.delete(DbHelper.USER_TABLE_NAME, selection, selectionArgs);
                break;
            case USER_CODE_SINGLE:
                String booking_id = uri.getPathSegments().get(1);
                count = db.delete(DbHelper.USER_TABLE_NAME,
                        User.INDEX + "=" + booking_id
                                + (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : ""),
                        selectionArgs);
                break;

            case ADDRESS_CODE:
                count = db.delete(DbHelper.ADDRESS_TABLE_NAME, selection, selectionArgs);
                break;
            case ADDRESS_CODE_SINGLE:
                String property_id = uri.getPathSegments().get(1);
                count = db.delete(DbHelper.ADDRESS_TABLE_NAME,
                        User.INDEX + "=" + property_id
                                + (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : ""),
                        selectionArgs);
                break;
            default:
                throw new IllegalArgumentException("Unnown URI" + uri);
        }
        getContext().getContentResolver().notifyChange(uri, null);
        return count;
    }

    @Override
    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
        int count;
        switch (uriMatcher.match(uri)) {
            case USER_CODE:
                count = db.update(DbHelper.USER_TABLE_NAME, values, selection, selectionArgs);
                break;
            case USER_CODE_SINGLE:
                String booking_id = uri.getPathSegments().get(1);
                count = db.update(DbHelper.USER_TABLE_NAME, values,
                        User.INDEX + "=" + booking_id
                                + (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : ""),
                        selectionArgs);
                break;

            case ADDRESS_CODE:
                count = db.update(DbHelper.ADDRESS_TABLE_NAME, values, selection, selectionArgs);
                break;
            case ADDRESS_CODE_SINGLE:
                String property_id = uri.getPathSegments().get(1);
                count = db.update(DbHelper.ADDRESS_TABLE_NAME, values,
                        Address.INDEX + "=" + property_id
                                + (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : ""),
                        selectionArgs);
                break;
            default:
                throw new IllegalArgumentException("Unnown URI" + uri);
        }
        getContext().getContentResolver().notifyChange(uri, null);
        return count;
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
            String sortOrder) {
        Cursor cursor = null;
        SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
        String orderBy;
        switch (uriMatcher.match(uri)) {
            case USER_CODE:
                qb.setTables(DbHelper.USER_TABLE_NAME);
                // 用戶定義列名->數(shù)據(jù)庫列名的映射
                qb.setProjectionMap(userHashMap);
                if (TextUtils.isEmpty(sortOrder)) {
                    orderBy = User.DEFAULT_SORT_ORDER;
                } else {
                    orderBy = sortOrder;
                }
                cursor = qb.query(db, projection, selection, selectionArgs, null, null, orderBy);
                // 用來為Cursor對象注冊一個觀察數(shù)據(jù)變化的URI
                cursor.setNotificationUri(getContext().getContentResolver(), uri);
                break;
            case ADDRESS_CODE:
                qb.setTables(DbHelper.ADDRESS_TABLE_NAME);
                // 用戶定義列名->數(shù)據(jù)庫列名的映射
                qb.setProjectionMap(addressHashMap);
                if (TextUtils.isEmpty(sortOrder)) {
                    orderBy = Address.DEFAULT_SORT_ORDER;
                } else {
                    orderBy = sortOrder;
                }
                cursor = qb.query(db, projection, selection, selectionArgs, null, null, orderBy);
                // 用來為Cursor對象注冊一個觀察數(shù)據(jù)變化的URI
                cursor.setNotificationUri(getContext().getContentResolver(), uri);
                break;
        }
        return cursor;
    }
}

3、在AndroidManifest文件中注冊創(chuàng)建的 ContentProvider類

   <!-- 聲明訪問ContentProvider的權(quán)限-->
   <permission
       android:name="com.android.pkqup.androidnote.PROVIDER"
       android:protectionLevel="normal" />


   <provider
           android:name=".content_provider_test.MyContentProvider"
           //定義授權(quán)信息
           android:authorities="com.pkqup.android.note"
           //設(shè)置外部應(yīng)用可訪問
           android:exported="true"
          //設(shè)置自定義權(quán)限
android:permission="com.android.pkqup.androidnote.PROVIDER" />

4捅彻、進(jìn)程內(nèi)訪問 ContentProvider的數(shù)據(jù)
4.1定義實體類

public class User {

    public static final String INDEX = "_index";// 主鍵
    public static final String NAME = "name";
    public static final String USER_ID = "userId";


    // 定義 user 表的 uri
    public static final Uri USER_CONTENT_URI =
            Uri.parse("content://" + MyContentProvider.AUTHORITY + "/" + DbHelper.USER_TABLE_NAME);

    // 定義 user 表的 uri
    public static final Uri USER_CONTENT_URI_SINGLE =
            Uri.parse("content://" + MyContentProvider.AUTHORITY + "/" + DbHelper.USER_TABLE_NAME
                    + DbHelper.SPECIAL_CHARACTER);

    // 排序方式步淹，定義為主鍵排序
    public static final String DEFAULT_SORT_ORDER = INDEX;

    private String name;
    private String userId;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getUserId() {
        return userId;
    }

    public void setUserId(String userId) {
        this.userId = userId;
    }
}

4.2诚撵、定義ContentProvider數(shù)據(jù)庫操作類

public class UserUtils {

    private Context context;

    public UserUtils(Context context) {
        this.context = context;
    }

    public void insertUser(String name, String age) {
        ContentValues values = new ContentValues();
        values.put(User.NAME, name);
        values.put(User.USER_ID, age);
        context.getContentResolver().insert(User.USER_CONTENT_URI, values);
    }

    public void deleteUser() {
        context.getContentResolver().delete(User.USER_CONTENT_URI, null, null);
    }

    public void updateUser(String name, String age) {
        ContentValues values = new ContentValues();
        values.put(User.NAME, name);
        values.put(User.USER_ID, age);
        context.getContentResolver().update(User.USER_CONTENT_URI, values, null, null);
    }

    public User queryUser() {
        User user = new User();
        Cursor mCursor = context.getContentResolver().query(User.USER_CONTENT_URI, null, null, null,
                User.DEFAULT_SORT_ORDER);
        if (null != mCursor) {
            while (mCursor.moveToNext()) {
                String name = mCursor.getString(mCursor.getColumnIndexOrThrow(User.NAME));
                String age = mCursor.getString(mCursor.getColumnIndexOrThrow(User.USER_ID));
                user.setName(name);
                user.setUserId(age);
            }
            mCursor.close();
        }
        return user;
    }


    // 數(shù)據(jù)庫查詢方法的參數(shù)說明
    public void query(Uri uri, String[] projection, String selection, String[] selectionArgs,
            String sortOrder) {
        // projection表示要查詢哪些列寿烟，比如查詢媒體庫，可能要關(guān)注音樂的藝術(shù)家缝其，長度畅铭，文件位置等。
        // selection表示查詢條件假残，就是查詢里面的where語句炉擅，
        // selectionArgs是查詢條件的值。
        // sortOrder是排序方式眶俩。
    }

    // 根據(jù)id查詢名稱
    public String getUserNameFrom(String userId) {
        String userName = "";
        Cursor mCursor = context.getContentResolver().query(User.USER_CONTENT_URI,
                new String[] {User.NAME, User.USER_ID}, "userId=?", new String[] {userId},
                User.DEFAULT_SORT_ORDER);
        if (null != mCursor) {
            while (mCursor.moveToNext()) {
                userName = mCursor.getString(mCursor.getColumnIndexOrThrow(User.NAME));
            }
            mCursor.close();
        }
        return userName;
    }
}

進(jìn)程間數(shù)據(jù)共享

1快鱼、創(chuàng)建數(shù)據(jù)庫類
見 DbHelper 類抹竹。同上。

2窃判、自定義 ContentProvider 類
見 MyContentProvider 類袄琳。同上燃乍。

3宛琅、在AndroidManifest文件中注冊創(chuàng)建的 ContentProvider類，注意配置權(quán)限和外部可使用屬性座咆。
同上仓洼。

4堤舒、在外部應(yīng)用中也需要配置相同的權(quán)限

<!--自定義上個應(yīng)用ContentProvider需要的權(quán)限-->
<permission
     android:name="com.android.pkqup.androidnote.PROVIDER"
     android:protectionLevel="normal" />

<!--使用該權(quán)限-->
<uses-permission android:name="com.android.pkqup.androidnote.PROVIDER"/>

5、外部應(yīng)用通過提供的Uri 對ContentProvider進(jìn)行增刪改查箕戳。
見 UserUtils 類国撵。同上。