内容提供器

作者: C_G__ | 来源:发表于2019-04-26 15:35 被阅读0次

Content Provider

主要用于在不同App间共享数据。

权限申请

App中某些功能的执行需要申请Android系统权限，如打电话等。
AndroidManifest.xml中可以申请权限。

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.bl.blandroidpro">
    <uses-permission android:name="android.permission.CALL_PHONE" />
</manifest>

Android权限机制

Android 6.0之前安装app时，提示app需要获取某些权限，其中包括一些个人隐私相关，如地理位置等，但是这些app日常粘度很高，还不能不安，所以用户只能被迫同意安装。
Android开发团队也意识到了这个问题，于是Android 6.0开始引入了运行时权限。但是安卓的权限很多，有上百个，如果让用户一个个授权也很繁琐，所以Android团队将权限分成两部分：普通权限 和 危险权限。只有危险权限才需要用户授权。

危险权限

Android的危险权限一共9组 24个。每个权限属于一个权限组，同意其中一个权限就同意了同组中的所有权限。

CALENDAR
READ_CALENDAR
WRITE_CALENDAR
CAMERA
CONTACTS
READ_CONTACTS
WRITE_CONTACTS
GET_ACCOUNTS
LOCATION
ACCESS_FINE_LOCATION
ACCESS_COARSE_LOCATION
MICROPHONE
RECORD_AUTIO
PHONE
READ_PHONE_STATE
CALL_PHONE
READ_CALL_LOG
WRITE_CALL_LOG
ADD_VOICEMAIL
USE_SIP
PROCESS_OUTGOING_CALLS
SENSORS
BODY_SENSORS
SMS
SEND_SMS
RECEIVE_SMS
READ_SMS
RECEIVE_WAP_PUSH
RECEIVE_MMS
STORAGE
READ_EXTERNAL_STORAGE
WRITE_EXTERNAL_STORAGE

运行时权限

运行时权限就是app在安装时不需要授权，在运行时具体用到某些功能时，再由用户决定是否授权，程序不可以擅自做主。

// 校验是否获取某权限
if (ContextCompat.checkSelfPermission(this,
    Manifest.permission.READ_CONTACTS) != PackageManager.PERMISSION_GRANTED) {
    // 没有获取则请求权限
    ActivityCompat.requestPermissions(this,
        new String[]{Manifest.permission.READ_CONTACTS}, 1);
} else {
    // 已经获取权限则做相应业务
    readContacts();
}

@Override
public void onRequestPermissionsResult(int requestCode,
                   @NonNull String[] permissions, @NonNull int[] grantResults) {
    switch (requestCode) {
        case 1:
            // 同意授权
            if (grantResults.length > 0
                    && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                readContacts();

            // 不同意授权
            } else {
                Toast.makeText(this,
                            "You denied the permission", Toast.LENGTH_LONG).show();
            }
            break;
        default:
            break;
    }
}

访问其他app的数据

ContentResolver 通过该类访问其它app的数据。该类提供了CRUD操作的相关方法。以Uri作为参数。

insert() 插入数据
update() 修改数据
delete() 删除数据
query() 查询数据

Uri参数格式及组成结构
以path结尾表示访问该表所有数据
以id结尾表示仅访问此条数据
'*'：匹配任意长度字符
'#'：匹配任意长度数字

scheme 协议
authority 区分应用程序，以包名命名。
path 对同一应用不同表做区分。
id 对同一表下的记录做区分

// path结尾
Uri uri = Uri.parse("content://com.example.app.provider/table1");
// id结尾
Uri uri = Uri.parse("content://com.example.app.provider/table2/1");
// path *
"content://com.example.app.provider/*";
// id #
"content://com.example.app.provider/table2/#";

// 查询是通过query方法返回的游标，逐行按字段获取想要的信息
// 获取联系人列表
private void readContacts() {
        Cursor cursor = null;
        try {
            // 查询
            cursor = getContentResolver().query(
                    ContactsContract.CommonDataKinds.Phone.CONTENT_URI,
                    null, null, null, null);
            if (cursor != null) {
                // 移动到下一条
                while (cursor.moveToNext()) {
                    // 获取联系人名
                    String disName = cursor.getString(cursor.getColumnIndex(
                            ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME
                    ));
                    // 获取联系人号码
                    String number = cursor.getString(cursor.getColumnIndex(
                            ContactsContract.CommonDataKinds.Phone.NUMBER
                    ));
                    contactList.add(disName + "\n" + number);
                }
                // 刷新列表
                adapter.notifyDataSetChanged();
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (cursor != null) {
                // 关闭游标
                cursor.close();
            }
        }
}

自定义内容提供器

需要继承ContentProvider类，重写其中6个方法

onCreate()
query()
insert()
update()
delete()
getType() 获取MIME类型
MIME类型由3部分组成
必须以vnd开头
以path结尾，后接 android.cursor.dir/, 以id结尾android.cursor.item/
最后接上vnd.'authority'.'path'

// path结尾
vnd.android.cursor.dir/vnd.com.exxample.app.provider.table1
// id结尾
vnd.android.cursor.item/vnd.com.exxample.app.provider.table2

示例代码

MyContentProvider.java

public class MyContentProvider extends ContentProvider {

    public static final int BOOK_DIR = 0;
    public static final int BOOK_ITEM = 1;
    public static final int CATEGORY_DIR = 2;
    public static final int CATEGORY_ITEM = 3;

    public static String URI_BOOK;
    public static String URI_CATEGORY;

    private static final String AUTHORITY = "com.bl.blandroidpro.provider";
    private static final String DB_NAME = "BookStore.db";
    private static final String PREFIX_CONTENT = "content://";
    private static final String SURFIX_BOOK = "book";
    private static final String SURFIX_BOOK_ID = "book/#";
    private static final String SURFIX_BOOK_TABLE = "Book";
    private static final String SURFIX_CATEGORY = "category";
    private static final String SURFIX_CATEGORY_ID = "category/#";
    private static final String SURFIX_CATEGORY_TABLE = "Category";

    private static final String VND_BOOK_DIR =
            "vnd.android.cursor.dir/vnd.com.bl.blandroidpro.provider.book";
    private static final String VND_BOOK_ITEM =
            "vnd.android.cursor.item/vnd.com.bl.blandroidpro.provider.book";
    private static final String VND_CATEGORY_DIR =
            "vnd.android.cursor.dir/vnd.com.bl.blandroidpro.provider.category";
    private static final String VND_CATEGORY_ITEM =
            "vnd.android.cursor.item/vnd.com.bl.blandroidpro.provider.category";

    private static UriMatcher sUriMatcher;
    private MyDatabaseHelper dbHelper;

    static {
        sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        sUriMatcher.addURI(AUTHORITY, SURFIX_BOOK, BOOK_DIR);
        sUriMatcher.addURI(AUTHORITY, SURFIX_BOOK_ID, BOOK_ITEM);
        sUriMatcher.addURI(AUTHORITY, SURFIX_CATEGORY, CATEGORY_DIR);
        sUriMatcher.addURI(AUTHORITY, SURFIX_CATEGORY_ID, CATEGORY_ITEM);

        URI_BOOK = PREFIX_CONTENT + AUTHORITY + "/" + SURFIX_BOOK;
        URI_CATEGORY = PREFIX_CONTENT + AUTHORITY + "/" + SURFIX_CATEGORY;
    }

    public MyContentProvider () {
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        int deleteRows = 0;
        switch (sUriMatcher.match(uri)) {
            case BOOK_DIR:
                deleteRows = db.delete(SURFIX_BOOK_TABLE, selection, selectionArgs);
                break;
            case BOOK_ITEM:
                String bookId = uri.getPathSegments().get(1);
                deleteRows = db.delete(SURFIX_BOOK_TABLE,
                        "id = ?", new String[]{bookId});
                break;
            case CATEGORY_DIR:
                deleteRows = db.delete(SURFIX_CATEGORY_TABLE, selection, selectionArgs);
                break;
            case CATEGORY_ITEM:
                String categoryId = uri.getPathSegments().get(1);
                deleteRows = db.delete(SURFIX_CATEGORY_TABLE,
                        "id = ?", new String[]{categoryId});
                break;
            default:
                break;

        }
        return deleteRows;
    }

    @Override
    public String getType(Uri uri) {
        switch (sUriMatcher.match(uri)) {
            case BOOK_DIR:
                return VND_BOOK_DIR;
            case BOOK_ITEM:
                return VND_BOOK_ITEM;
            case CATEGORY_DIR:
                return VND_CATEGORY_DIR;
            case CATEGORY_ITEM:
                return VND_CATEGORY_ITEM;
        }
        return null;
    }

    @Override
    public Uri insert(Uri uri, ContentValues values) {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        Uri uriReturn = null;
        switch (sUriMatcher.match(uri)) {
            case BOOK_DIR:
            case BOOK_ITEM:
                long newBookId = db.insert(SURFIX_BOOK_TABLE, null, values);
                uriReturn = Uri.parse(URI_BOOK + "/" + newBookId);
                break;
            case CATEGORY_DIR:
            case CATEGORY_ITEM:
                long newCategoryId = db.insert(SURFIX_CATEGORY_TABLE, null, values);
                uriReturn = Uri.parse(URI_CATEGORY + "/" + newCategoryId);
                break;
            default:
                break;

        }
        return uriReturn;
    }

    @Override
    public boolean onCreate() {
        dbHelper = new MyDatabaseHelper(getContext(), DB_NAME, null, 2);
        return true;
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection,
                        String[] selectionArgs, String sortOrder) {
        SQLiteDatabase db = dbHelper.getReadableDatabase();
        Cursor cursor = null;
        switch (sUriMatcher.match(uri)) {
            case BOOK_DIR:
                cursor = db.query(SURFIX_BOOK_TABLE, projection, selection,
                        selectionArgs, null, null, sortOrder);
                break;
            case BOOK_ITEM:
                String bookId = uri.getPathSegments().get(1);
                cursor = db.query(SURFIX_BOOK_TABLE, projection, "id = ?",
                        new String[]{bookId}, null, null, sortOrder);
                break;
            case CATEGORY_DIR:
                cursor = db.query(SURFIX_CATEGORY_TABLE, projection, selection,
                        selectionArgs, null, null, sortOrder);
                break;
            case CATEGORY_ITEM:
                String categoryId = uri.getPathSegments().get(1);
                cursor = db.query(SURFIX_CATEGORY_TABLE, projection, "id = ?",
                        new String[]{categoryId}, null, null, sortOrder);
                break;
            default:
                break;
        }
        return cursor;
    }

    @Override
    public int update(Uri uri, ContentValues values, String selection,
                      String[] selectionArgs) {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        int updateRows = 0;
        switch (sUriMatcher.match(uri)) {
            case BOOK_DIR:
                updateRows = db.update(SURFIX_BOOK_TABLE, values, selection, selectionArgs);
                break;
            case BOOK_ITEM:
                String bookId = uri.getPathSegments().get(1);
                updateRows = db.update(SURFIX_BOOK_TABLE, values,
                        "id = ?", new String[]{bookId});
                break;
            case CATEGORY_DIR:
                updateRows = db.update(SURFIX_CATEGORY_TABLE, values, selection, selectionArgs);
                break;
            case CATEGORY_ITEM:
                String categoryId = uri.getPathSegments().get(1);
                updateRows = db.update(SURFIX_CATEGORY_TABLE, values,
                        "id = ?", new String[]{categoryId});
                break;
            default:
                break;

        }
        return updateRows;
    }
}

activity_content_provider.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".chapter07.ContentProviderCustomActivity"
    android:orientation="vertical">

    <ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scrollbars="vertical">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical">

            <Button
                android:id="@+id/btn_cpc_addbook"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="添加一本书" />
            <Button
                android:id="@+id/btn_cpc_querybook"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="查询书籍" />
            <Button
                android:id="@+id/btn_cpc_updatebook"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="修改一本书" />
            <Button
                android:id="@+id/btn_cpc_deletebook"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="删除一本书" />
            <TextView
                android:id="@+id/tv_cpc_info"
                android:layout_width="match_parent"
                android:layout_height="match_parent" />
        </LinearLayout>
    </ScrollView>

</LinearLayout>

ContentProviderActivity.java

public class ContentProviderActivity extends AppCompatActivity {

    public String newId;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_content_provider);

        final TextView tv_cpc_info = findViewById(R.id.tv_cpc_info);

        // 添加书籍
        Button btn_cpc_addbook = findViewById(R.id.btn_cpc_addbook);
        btn_cpc_addbook.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                ContentValues values = new ContentValues();
                values.put("name", "Book");
                values.put("author", "BL");
                values.put("pages", 308);
                values.put("price", 38);
                Uri uri = Uri.parse(MyContentProvider.URI_BOOK);
                Uri newUri = getContentResolver().insert(uri, values);

                newId = newUri.getPathSegments().get(1);
                tv_cpc_info.setText(queryBooks());
            }
        });
        // 查询书籍
        Button btn_cpc_querybook = findViewById(R.id.btn_cpc_querybook);
        btn_cpc_querybook.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                tv_cpc_info.setText(queryBooks());
            }
        });
        // 修改书籍
        Button btn_cpc_updatebook = findViewById(R.id.btn_cpc_updatebook);
        btn_cpc_updatebook.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Uri uri = Uri.parse(MyContentProvider.URI_BOOK + "/" + newId);
                ContentValues values = new ContentValues();
                values.put("name", "Good Book");
                values.put("author", "Andy");
                values.put("pages", 400);
                values.put("price", 40);
                getContentResolver().update(uri, values, null, null);
                tv_cpc_info.setText(queryBooks());
            }
        });

        // 删除书籍
        Button btn_cpc_deletebook = findViewById(R.id.btn_cpc_deletebook);
        btn_cpc_deletebook.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Uri uri = Uri.parse(MyContentProvider.URI_BOOK + "/" + newId);
                getContentResolver().delete(uri, null, null);
                tv_cpc_info.setText(queryBooks());
            }
        });
    }

    public String queryBooks() {
        StringBuilder sb = new StringBuilder();
        sb.append("书名    作者    页数    价格\n");

        Uri uri = Uri.parse(MyContentProvider.URI_BOOK);
        Cursor cursor = getContentResolver().query(uri,
                null, null, null, null);
        if (cursor != null) {
            while (cursor.moveToNext()) {
                String name = cursor.getString(
                        cursor.getColumnIndex("name"));
                String author = cursor.getString(
                        cursor.getColumnIndex("author"));
                int pages = cursor.getInt(
                        cursor.getColumnIndex("pages"));
                double price = cursor.getDouble(
                        cursor.getColumnIndex("price"));
                sb.append(name + "    " + author + "    " + pages + "    " + price + "\n");
            }
            cursor.close();
        }
        return sb.toString();
    }
}

内容提供器

Content Provider

权限申请

Android权限机制

危险权限

运行时权限

访问其他app的数据

自定义内容提供器

示例代码

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