ContentProvider 一个应用程序访问另一个应用程序

柔光的暖阳◎ 2022-08-20 11:28 186阅读 0赞

例子说明：  
程序A：建立数据库DB，表student、salary，数据SQLiteOpenHelper来存储，  
程序B：对程序A进行数据的增删改查；

SQLiteOpenHelper:

public class DBHelper extends SQLiteOpenHelper { 
        public DBHelper(Context context) 
        {
            super(context, "DB", null, 1);//创建数据库“DB”；
        }
    
        @Override
        public void onCreate(SQLiteDatabase db) 
        {
            db.execSQL("create table student(id integer primary key autoincrement, name text, number integer)");
            db.execSQL("create table salary(id integer primary key autoincrement, name text, money integer)");
        }
    
        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) 
        {
    
        }
    }

SQLiteDatabase：

public class DBUtil 
    {
        DBHelper helper;
        SQLiteDatabase db;
    
        public DBUtil(Context context) 
        {
            helper = new DBHelper(context); //实例化；
        }
    
        private void open() //打开数据库；
        {
            db = helper.getWritableDatabase(); 
        }
    
        private void close()//关闭数据库；
        {
            if(db!=null)
            {
                db.close();
            }
        }
    
        public long insert(String table, ContentValues values)
        {
            open();
            long code=db.insert(table, null, values); //code为插入数据的行数；
            System.out.println(  table + " "+code);
            close();
            return code;    
        }
    
        //查询表中的所有与数据；
        public void query(String table)         
        {
            open();
            System.out.println("table ---" + table);
            if("student".equals(table))
            {
                String sql = "select * from student";
                Cursor cursor = db.rawQuery(sql, null);
                while(cursor.moveToNext())
                {
                    int id = cursor.getInt(cursor.getColumnIndex("id"));
                    String name = cursor.getString(cursor.getColumnIndex("name"));
                    String number = cursor.getString(cursor.getColumnIndex("number"));
                    System.out.println(table + ", id=" + id + ", name=" + name + ", number=" + number);
                }   
            }
            else if("salary".equals(table))
            {
                String sql = "select * from salary";
                Cursor cursor = db.rawQuery(sql, null);
                while(cursor.moveToNext())
                {
                    int id = cursor.getInt(cursor.getColumnIndex("id"));
                    String name = cursor.getString(cursor.getColumnIndex("name"));
                    String money = cursor.getString(cursor.getColumnIndex("money"));
                    System.out.println(table + ", id=" + id + ", name=" + name + ", money=" + money);
                }   
            }
            close();
        }
    
        //删除由whereClause指定的数据；
        public void delete(String table, String whereClause, String[] whereArgs ) 
        {
            open();
            db.delete(table, whereClause, whereArgs); 
            System.out.println("whereClause---" + whereClause);
            close();
        }
    
        //更新数据库，把符合whereClause条件的数据更改为values；
        public void update(String table, ContentValues values, String whereClause)
        {
            open();
            db.update(table, values, whereClause, null);
            close();
        }
    }

自定义类MyContentProvider 继承ContentProvide类：

public class MyContentProvider extends ContentProvider { 
        DBUtil dbutil;
        static UriMatcher uriMatcher=new UriMatcher(UriMatcher.NO_MATCH); 
        final static String AUTHORITY="com.feicui.contentprovider";  //在清单文件注册时的authorities属性值；
    
        final static int URI_STUDENT=1;
        final static int URI_SALARY=2;
        final static int URI_STUDENT_WHICH=3;
        final static int URI_SALARY_WHICH=4;
    
        static
        {
            //为UriMatcher注册四个Uri；
            uriMatcher.addURI(AUTHORITY, "student", URI_STUDENT);
            uriMatcher.addURI(AUTHORITY, "student/#", URI_STUDENT_WHICH);
            uriMatcher.addURI(AUTHORITY, "salary", URI_SALARY);
            uriMatcher.addURI(AUTHORITY, "salary/#", URI_SALARY_WHICH);
        }
        @Override
        public boolean onCreate() 
        {
            dbutil = new DBUtil(getContext());
            return false;
        }
    
    // 查询数据；
        @Override
        public Cursor query(Uri uri, String[] projection, String selection,
                String[] selectionArgs, String sortOrder) 
        {
            int code = uriMatcher.match(uri);
            switch(code)
            {
            case URI_STUDENT:
                dbutil.query("student"); //查询student表下的所有数据；
                break;
            case URI_SALARY:
                dbutil.query("salary"); //查询salary表下的所有数据；
                break;
            default:
                throw new IllegalArgumentException("未知Uri：" + uri);
            }
            return null;
        }
    
        @Override
        public String getType(Uri uri) 
        {
            return null;
        }
    
    // 插入数据；
        @Override
        public Uri insert(Uri uri, ContentValues values) 
        {
            int code=uriMatcher.match(uri); //获取在上面static代码块中对应的code值；
            long insertID=0;
            switch (code) 
            {
            case URI_STUDENT:
                insertID=dbutil.insert("student", values); //往student表中插入数据；
                break;
            case URI_SALARY:
                insertID=dbutil.insert("salary", values); //往salary表中插入数据；
                break;
            default:
                throw new IllegalArgumentException("未知Uri：" + uri);
            }   
            return ContentUris.withAppendedId(uri, insertID);
        }
    
    // 删除数据；
        @Override
        public int delete(Uri uri, String selection, String[] selectionArgs) 
        {   
            int code=uriMatcher.match(uri);
            switch (code) 
            {
            case URI_STUDENT:       //删除整个表的数据；
                System.out.println("---------selection----" + selection);
                dbutil.delete("student", selection, selectionArgs);
                break;
            case URI_STUDENT_WHICH: //删除表中指定的一个数据；
            {
                long id = ContentUris.parseId(uri);
                String whereClause = "id=" + id;
                if(selection != null && selection.equals("")) //如果原来的selection语句存在，则拼接语句；
                {
                    whereClause = selection + " and " + whereClause;
                }
                dbutil.delete("student", whereClause, selectionArgs);
                break;
            }
            case URI_SALARY:       //删除整个表的数据；
                dbutil.delete("salary", selection, selectionArgs);
                break;
            case URI_SALARY_WHICH://删除表中指定的一个数据；
            {
                long id2 = ContentUris.parseId(uri);
                String whereClause2 = "id=" + id2;
                if(selection != null && selection.equals("")) //如果原来的selection语句存在，则拼接语句；
                {
                    whereClause2 = selection + " and " + whereClause2;
                }
                dbutil.delete("salary", whereClause2, selectionArgs);
                break;
            }
            default:
                throw new IllegalArgumentException("未知Uri：" + uri);
            }   
            return 0;
        }
    
        //更新数据；
        @Override
        public int update(Uri uri, ContentValues values, String selection,
                String[] selectionArgs) 
        {
            int code=uriMatcher.match(uri);
            switch (code) 
            {
            case URI_STUDENT:
                dbutil.update("student", values, selection);
                break;
            case URI_SALARY:
                dbutil.update("salary", values, selection);
                break;
            default:
                throw new IllegalArgumentException("未知Uri：" + uri);
            }   
            return 0;
        }
    }

MainActivity：

public class MainActivity extends Activity implements OnClickListener { 
        Button salary;   //为表salary添加数据；
        Button student;  //为表student添加数据；
        ContentResolver resolver;
        final static String CONTENT_URI="content://com.feicui.contentprovider/";
    
        String[] names = {
       "a","b","c","d","e","f","g","h","i"};//姓名；
        int[] numbers = {
       1, 2, 3, 4, 5, 6, 7, 8, 9}; //座号；
        int[] money = {
       2223,2224,2225,2226,2227,2228,2229,2230,2221};//薪水；
    
        @Override
        protected void onCreate(Bundle savedInstanceState) 
        {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            init();
    
            File file = new File("data/data/com.feicui.contentprovider/databases/DB");
            if(file.exists())  //如果文件已经存在则删除；
            {
                file.delete();
            }       
        }
    
        private void init() 
        {
            student = (Button) findViewById(R.id.button1);
            salary = (Button) findViewById(R.id.button2);
    
            student.setOnClickListener(this);
            salary.setOnClickListener(this);
    
            resolver = getContentResolver();  //获取ContentResolver对象；
        }
    
        @Override
        public void onClick(View v) 
        {       
            switch (v.getId()) 
            {
            case R.id.button1:          
                for(int i=0; i<names.length; i++)
                {
                    ContentValues values=new ContentValues();
                    values.put("name", names[i]);
                    values.put("number", numbers[i]);
                    resolver.insert(Uri.parse(CONTENT_URI+"student"), values);
                }       
                break;
            case R.id.button2:
                for(int i=0; i<names.length; i++)
                {
                    ContentValues values2=new ContentValues();
                    values2.put("name", names[i]);
                    values2.put("money", money[i]);
                    Uri uri=resolver.insert(Uri.parse(CONTENT_URI+"salary"), values2);
                    System.out.println(ContentUris.parseId(uri) + "----");
                }           
                break;
            default:
                break;
            }
        }
    }

给程序A注册：

<uses-permission android:name="android.permission.PROCESS_OUTGOING_CALLS"/>
    
    <provider android:name="com.feicui.contentprovider.MyContentProvider" android:authorities="com.feicui.contentprovider" android:exported="true">
    </provider>

上面的代码块都是程序A中的代码；  
程序B就下面这个代码块：

public class MainActivity extends Activity implements OnClickListener { 
        ContentResolver resolver;
        Button insert, delete, update, query;
    
        @Override
        protected void onCreate(Bundle savedInstanceState) 
        {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            resolver=getContentResolver();      
            init();
        }
    
        private void init() 
        {
            insert = (Button)findViewById(R.id.button1);
            delete = (Button)findViewById(R.id.button2);
            update = (Button)findViewById(R.id.button3);
            query = (Button)findViewById(R.id.button4);
    
            insert.setOnClickListener(this);
            delete.setOnClickListener(this);
            update.setOnClickListener(this);
            query.setOnClickListener(this);
        }
    
        @Override
        public void onClick(View v) 
        {
            switch(v.getId())
            {
            case R.id.button1:
                insertData(); //插入数据；
                break;
            case R.id.button2:
    // deleteData(); //删除整个表里的内容；
    // deleteCodeData("student", " name='a'"); //删除student表中name为a的数据；
                deleteCodeData("student/2", null); //删除student表中id为2的数据；(后面是int型数据时默认的就是指id);
                break;
            case R.id.button3:
                updateData(); //更新数据；
                break;
            case R.id.button4:
                queryData();  //查询数据；
                break;
            }
    
        }
    
        private void updateData()
        {
            ContentValues values = new ContentValues();
            values.put("money", 9999);
            resolver.update(Uri.parse("content://com.feicui.contentprovider/salary"), values, "name='d'", null);
        }
    
        private void deleteData()
        {
            resolver.delete(Uri.parse("content://com.feicui.contentprovider/student"), null, null);
        }
    
        private void deleteCodeData(String table, String where)
        {
            resolver.delete(Uri.parse("content://com.feicui.contentprovider/" + table), where, null);
        }
    
        private void queryData()
        {
            resolver.query(Uri.parse("content://com.feicui.contentprovider/student"), null, null, null, null);
            resolver.query(Uri.parse("content://com.feicui.contentprovider/salary"), null, null, null, null);       
        }
    
        private void insertData()
        {
            ContentValues values1=new ContentValues();
            values1.put("name", "j");
            values1.put("number", 10);
            resolver.insert(Uri.parse("content://com.feicui.contentprovider/student"), values1);
            ContentValues values2=new ContentValues();
            values2.put("name", "k");
            values2.put("number", 11);
            resolver.insert(Uri.parse("content://com.feicui.contentprovider/student"), values2);
    
            ContentValues values3=new ContentValues();
            values3.put("name", "j");
            values3.put("money", 2232);
            resolver.insert(Uri.parse("content://com.feicui.contentprovider/salary"), values3);
            ContentValues values4=new ContentValues();
            values4.put("name", "k");
            values4.put("money", 2233);
            resolver.insert(Uri.parse("content://com.feicui.contentprovider/salary"), values4);     
        }
    
    }