ContentProvider

ContentProivde 内容提供者，内部封装了对数据库的代码操作过程，对外暴露几个方法，可以提供给其他应用程序对本程序的数据库进行操作的的方法。

public class Constant {
    public static final String AUTHORITIES="com.example.emma.demo0504.provider.peoplecontentprovider";
    public static final String TABLENAME="t_person";
    public static final String TABLE_PERSON_ID="_id";
    public static final String TABLE_PERSON_NAME="name";
    public static final String TABLE_PERSON_AGE="age";
    public static final String TABLE_PERSON_ADDR="addr";
}

public class PeopleContentProvider extends ContentProvider {
    private Bean bean;
    private static UriMatcher uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
    private static final int MULTITUDE = 2;
    private static final int SINGLE = 1;

    static {
        uriMatcher.addURI(Constant.AUTHORITIES, "/people", MULTITUDE);
        uriMatcher.addURI(Constant.AUTHORITIES, "/people/#", SINGLE);
    }

    @Override
    public boolean onCreate() {
        bean = Bean.getInstance(getContext());
        return true;
    }

    @Nullable
    @Override
    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {

        int matchCode = uriMatcher.match(uri);

        switch (matchCode) {
            case MULTITUDE:
                return bean.select(projection, selection, selectionArgs, sortOrder);

            case SINGLE:
                long id = ContentUris.parseId(uri);

                if (selection == null) {
                    return bean.select(projection, "_id=" + id, selectionArgs, sortOrder);
                } else {
                    return bean.select(projection, selection + " AND _id=" + id, selectionArgs, sortOrder);
                }

            default:
                throw new RuntimeException("非法Uri");
        }

    }

    @Nullable
    @Override
    public String getType(Uri uri) {
        int matchCode = uriMatcher.match(uri);
        switch (matchCode) {
            case MULTITUDE:
                return "vnd.android.cursor/dir";
            case SINGLE:
                return "vnd.android.cursor/item";
            default:
                throw new RuntimeException("非法Uri");
        }
    }

    @Nullable
    @Override
    public Uri insert(Uri uri, ContentValues values) {
        int matchCode = uriMatcher.match(uri);
        switch (matchCode) {
            case MULTITUDE:
                long id = bean.insert(values);
                return Uri.withAppendedPath(uri, String.valueOf(id));
            default:
                throw new RuntimeException("非法Uri");
        }
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        int matchCode = uriMatcher.match(uri);
        switch (matchCode) {
            case MULTITUDE:
                return bean.delete(selection, selectionArgs);
            case SINGLE:
                long id = ContentUris.parseId(uri);
                if (selection == null) {
                    return bean.delete("_id=" + id, selectionArgs);
                } else {
                    return bean.delete(selection + " AND _id=" + id, selectionArgs);
                }
            default:
                throw new RuntimeException("非法Uri");
        }

    }

    @Override
    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
        int matchCode = uriMatcher.match(uri);
        switch (matchCode) {
            case SINGLE:
                return bean.update(values, selection, selectionArgs);
            default:
                throw new RuntimeException("非法Uri");
        }

    }
}

注册Provider
最后一句表示授予其他程序访问的权限

 <provider
            android:name=".provider.PeopleContentProvider"
            android:authorities="com.example.emma.demo0504.provider.peoplecontentprovider"
            android:exported="true"></provider>

操作数据库的类

public class Bean extends SQLiteOpenHelper {
    private static Bean bean;
    private static String DBNAME = "person.db";
    private static int VERSION = 1;

    private Bean(Context context) {
        super(context, DBNAME, null, VERSION, null);
    }

    public static Bean getInstance(Context context) {
        if (bean == null) {
            bean = new Bean(context);
        }
        return bean;
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        StringBuffer creat = new StringBuffer();
        creat.append("CREATE TABLE IF NOT EXISTS ")
                .append(Constant.TABLENAME)
                .append("(")
                .append(Constant.TABLE_PERSON_ID)
                .append(" INTEGER PRIMARY KEY AUTOINCREMENT,")
                .append(Constant.TABLE_PERSON_NAME)
                .append(" VARCHAR(200),")
                .append(Constant.TABLE_PERSON_AGE)
                .append(" INTEGER DEFAULT 1 CHECK (age BETWEEN 1 AND 150),")
                .append(Constant.TABLE_PERSON_ADDR)
                .append(" VARCHAR(200)")
                .append(")");
        db.execSQL(creat.toString());

        StringBuffer insert = new StringBuffer();
        insert.append("INSERT INTO ")
                .append(Constant.TABLENAME)
                .append("(")
                .append(Constant.TABLE_PERSON_ID + ",")
                .append(Constant.TABLE_PERSON_NAME + ",")
                .append(Constant.TABLE_PERSON_AGE + ",")
                .append(Constant.TABLE_PERSON_ADDR)
                .append(")")
                .append(" VALUES ")
                .append("(null,?,?,?)");
        db.execSQL(insert.toString(), new String[]{"赵", String.valueOf(21), "上海"});
        db.execSQL(insert.toString(), new String[]{"钱", String.valueOf(22), "温州"});
        db.execSQL(insert.toString(), new String[]{"孙", String.valueOf(23), "北京"});
        db.execSQL(insert.toString(), new String[]{"李", String.valueOf(24), "杭州"});
        db.execSQL(insert.toString(), new String[]{"周", String.valueOf(25), "丽水"});
        db.execSQL(insert.toString(), new String[]{"吴", String.valueOf(26), "天津"});
        db.execSQL(insert.toString(), new String[]{"郑", String.valueOf(27), "福州"});
        db.execSQL(insert.toString(), new String[]{"王", String.valueOf(28), "莆田"});
        db.execSQL(insert.toString(), new String[]{"冯", String.valueOf(29), "福鼎"});
        db.execSQL(insert.toString(), new String[]{"陈", String.valueOf(30), "金华"});
        db.execSQL(insert.toString(), new String[]{"楚", String.valueOf(31), "嘉兴"});
        db.execSQL(insert.toString(), new String[]{"魏", String.valueOf(32), "广州"});
        db.execSQL(insert.toString(), new String[]{"蒋", String.valueOf(33), "深圳"});
        db.execSQL(insert.toString(), new String[]{"沈", String.valueOf(34), "香港"});
        db.execSQL(insert.toString(), new String[]{"韩", String.valueOf(35), "澳门"});
        db.execSQL(insert.toString(), new String[]{"杨", String.valueOf(36), "南京"});
    }

    public Cursor select(String[] projection, String selection, String[] selectionArgs, String sortOrder) {
        SQLiteDatabase db = null;
        db = bean.getWritableDatabase();
        return db.query(Constant.TABLENAME, projection, selection, selectionArgs, null, null, sortOrder);
    }

    public long insert(ContentValues values) {
        SQLiteDatabase db = null;
        try {
            db = bean.getWritableDatabase();
            return db.insert(Constant.TABLENAME, "hello", values);
        } catch (Exception e) {
            e.printStackTrace();
            return 0;
        } finally {
            if(db!=null&&db.isOpen()){
                db.close();
                db=null;
            }
        }
    }

    public int delete(String selection, String[] selectionArgs) {
        SQLiteDatabase db = null;
        try {
            db = bean.getWritableDatabase();
            return db.delete(Constant.TABLENAME, selection, selectionArgs);
        } catch (Exception e) {
            e.printStackTrace();
            return 0;
        } finally {
            if(db!=null&&db.isOpen()){
                db.close();
                db=null;
            }
        }

    }

    public int update(ContentValues values, String selection, String[] selectionArgs) {
        SQLiteDatabase db = null;
        try {
            db = bean.getWritableDatabase();
            return db.update(Constant.TABLENAME,values,selection,selectionArgs);
        } catch (Exception e) {
            e.printStackTrace();
            return 0;
        } finally {
            if(db!=null&&db.isOpen()){
                db.close();
                db=null;
            }
        }
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }
}