ContentProvider-----一个完整的样例（一）

来源：互联网发布：王保保知乎编辑：程序博客网时间：2024/06/03 21:32

ContentProvider

ContentProvider 是Android的四大组件之一，对于许多比较复杂的数据的处理，许多APP都是采用ContentProvider，来创建一个DB数据库，从而可以统一对DB数据进行处理。

下面的这个样例，是创建一个员工管理的DB数据库，员工信息包括姓名，年龄，性别。我们可以对这个DB数据库进行基本的增，删，查，改操作。

用户界面如下图：

关键的代码：

1.Employees.java

[java] view plain copy
public class Employees {  
  
    public static final String AUTHORITY = "com.konka.provider.Employees";  
      
    private Employees() {}  
      
    // 内部类  
    public static final class Employee implements BaseColumns {  
          
        // 构造方法  
        private Employee() {}  
          
        // 访问Uri  
        public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/employee");  
          
        // 内容类型  
        public static final String CONTENT_TYPE = "vnd.android.cursor.dir/vnd.amaker.employees";  
        public static final String CONTENT_ITEM_TYPE = "vnd.android.cursor.item/vnd.amaker.employees";  
          
        // 默认排序常量  
        public static final String DEFAULT_SORT_ORDER = "name DESC";// 按姓名排序  
          
        // 表字段常量  
        public static final String NAME = "name";                    // 姓名  
        public static final String GENDER= "gender";                // 性别  
        public static final String AGE = "age";                     // 年龄  
    }         
}  

2.DBHelper.java

[java] view plain copy
/** 
 *  
 * 数据库工具类 
 */  
public class DBHelper extends SQLiteOpenHelper{  
      
    // 数据库名称常量  
    private static final String DATABASE_NAME = "Employees.db";  
      
    // 数据库版本常量  
    private static final int DATABASE_VERSION = 1;  
      
    // 表名称常量  
    public static final String EMPLOYEES_TABLE_NAME = "employee";  
      
      
    // 构造方法  
    public DBHelper(Context context) {  
        // 创建数据库  
        super(context, DATABASE_NAME,null, DATABASE_VERSION);  
    }  
  
      
    // 创建时调用  
    public void onCreate(SQLiteDatabase db) {  
        db.execSQL("CREATE TABLE " + EMPLOYEES_TABLE_NAME + " ("  
                + Employee._ID + " INTEGER PRIMARY KEY,"  
                + Employee.NAME + " TEXT,"  
                + Employee.GENDER + " TEXT,"  
                + Employee.AGE + " INTEGER"  
                + ");");  
    }  
  
      
    // 版本更新时调用  
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {  
        // 删除表  
        db.execSQL("DROP TABLE IF EXISTS employee");  
        onCreate(db);  
    }  
}  

3.EmployeeProvider.java

[java] view plain copy
public class EmployeeProvider extends ContentProvider{  
  
    // 数据库帮助类  
    private DBHelper dbHelper = null;  
      
    // Uri工具类  
    private static final UriMatcher sUriMatcher;  
      
    // 查询、更新条件  
    private static final int EMPLOYEE = 1;  
    private static final int EMPLOYEE_ID = 2;  
      
    // 查询列集合  
    private static HashMap<String, String> empProjectionMap;  
      
    static {  
        // Uri匹配工具类  
        sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);  
        sUriMatcher.addURI(Employees.AUTHORITY, "employee", EMPLOYEE);  
        sUriMatcher.addURI(Employees.AUTHORITY, "employee/#", EMPLOYEE_ID);  
        // 实例化查询列集合  
        empProjectionMap = new HashMap<String, String>();  
        // 添加查询列  
        empProjectionMap.put(Employee._ID, Employee._ID);  
        empProjectionMap.put(Employee.NAME, Employee.NAME);  
        empProjectionMap.put(Employee.GENDER, Employee.GENDER);  
        empProjectionMap.put(Employee.AGE, Employee.AGE);  
    }  
  
      
    // 创建是调用  
    public boolean onCreate() {  
        // 实例化数据库帮助类  
        dbHelper = new DBHelper(getContext());  
        return true;  
    }  
      
      
    // 添加方法  
    public Uri insert(Uri uri, ContentValues values) {  
        // 获得数据库实例  
        SQLiteDatabase db = dbHelper.getWritableDatabase();  
        // 插入数据，返回行ID  
        long rowId = db.insert(DBHelper.EMPLOYEES_TABLE_NAME, Employee.NAME, values);  
        // 如果插入成功返回uri  
        if (rowId > 0) {  
            Uri empUri = ContentUris.withAppendedId(Employee.CONTENT_URI, rowId);  
            getContext().getContentResolver().notifyChange(empUri, null);  
            return empUri;  
        }  
        return null;  
    }  
      
    // 删除方法  
    public int delete(Uri uri, String selection, String[] selectionArgs) {  
        // 获得数据库实例  
        SQLiteDatabase db = dbHelper.getWritableDatabase();  
         // 获得数据库实例  
        int count;  
        switch (sUriMatcher.match(uri)) {  
        // 根据指定条件删除  
        case EMPLOYEE:  
            count = db.delete(DBHelper.EMPLOYEES_TABLE_NAME, selection, selectionArgs);  
            break;  
        // 根据指定条件和ID删除  
        case EMPLOYEE_ID:  
            String noteId = uri.getPathSegments().get(1);  
            count = db.delete(DBHelper.EMPLOYEES_TABLE_NAME, Employee._ID + "=" + noteId  
                    + (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : ""), selectionArgs);  
            break;  
  
        default:  
            throw new IllegalArgumentException("错误的 URI " + uri);  
        }  
        getContext().getContentResolver().notifyChange(uri, null);  
        return count;  
    }  
  
      
    // 获得类型  
    public String getType(Uri uri) {  
        return null;  
    }  
  
      
    // 查询方法  
    public Cursor query(Uri uri, String[] projection, String selection,String[] selectionArgs, String sortOrder) {  
         SQLiteQueryBuilder qb = new SQLiteQueryBuilder();  
            switch (sUriMatcher.match(uri)) {  
            // 查询所有  
            case EMPLOYEE:  
                qb.setTables(DBHelper.EMPLOYEES_TABLE_NAME);  
                qb.setProjectionMap(empProjectionMap);  
                break;  
            // 根据ID查询  
            case EMPLOYEE_ID:  
                qb.setTables(DBHelper.EMPLOYEES_TABLE_NAME);  
                qb.setProjectionMap(empProjectionMap);  
                qb.appendWhere(Employee._ID + "=" + uri.getPathSegments().get(1));  
                break;  
            default:  
                throw new IllegalArgumentException("Uri错误！ " + uri);  
            }  
  
            // 使用默认排序  
            String orderBy;  
            if (TextUtils.isEmpty(sortOrder)) {  
                orderBy = Employee.DEFAULT_SORT_ORDER;  
            } else {  
                orderBy = sortOrder;  
            }  
  
            // 获得数据库实例  
            SQLiteDatabase db = dbHelper.getReadableDatabase();  
            // 返回游标集合  
            Cursor c = qb.query(db, projection, selection, selectionArgs, null, null, orderBy);  
            c.setNotificationUri(getContext().getContentResolver(), uri);  
            return c;  
    }  
  
      
    // 更新方法  
    public int update(Uri uri, ContentValues values, String selection,String[] selectionArgs) {  
        // 获得数据库实例  
        SQLiteDatabase db = dbHelper.getWritableDatabase();  
        int count;  
        switch (sUriMatcher.match(uri)) {  
        // 根据指定条件更新  
        case EMPLOYEE:  
            count = db.update(DBHelper.EMPLOYEES_TABLE_NAME, values, selection, selectionArgs);  
            break;  
        // 根据指定条件和ID更新  
        case EMPLOYEE_ID:  
            String noteId = uri.getPathSegments().get(1);  
            count = db.update(DBHelper.EMPLOYEES_TABLE_NAME, values, Employee._ID + "=" + noteId  
                    + (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : ""), selectionArgs);  
            break;  
        default:  
            throw new IllegalArgumentException("错误的 URI " + uri);  
        }  
        getContext().getContentResolver().notifyChange(uri, null);  
        return count;  
    }     
}  

4.ContentProviderFullDemoActivity.java

[java] view plain copy
public class ContentProviderFullDemoActivity extends Activity implements OnClickListener {  
      
    public static String TAG = "ContentProviderFullDemoActivity";  
      
    public Uri uri = Employee.CONTENT_URI;  
      
    private Button insertData = null;  
    private Button queryData = null;  
    private Button deleteData = null;  
    private Button updateData = null;  
      
          
    @Override  
    public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.main);          
          
        insertData = (Button) findViewById(R.id.insertData);  
        insertData.setOnClickListener(ContentProviderFullDemoActivity.this);  
          
        queryData = (Button) findViewById(R.id.queryData);  
        queryData.setOnClickListener(ContentProviderFullDemoActivity.this);  
          
        deleteData = (Button) findViewById(R.id.deleteData);  
        deleteData.setOnClickListener(ContentProviderFullDemoActivity.this);  
          
        updateData = (Button) findViewById(R.id.updateData);  
        updateData.setOnClickListener(ContentProviderFullDemoActivity.this);                        
    }  
       
    @Override  
    public void onClick(View view) {  
        // TODO Auto-generated method stub        
        if(view == insertData){  
                          
            ContentValues values = new ContentValues();  
            values.put(Employee.NAME, "amaker");  
            values.put(Employee.GENDER, "male");  
            values.put(Employee.AGE,30);  
              
            // 插入  
            insert(uri,values);  
            Log.i(TAG, "insert");  
              
        }else if(view == queryData){  
              
            // 查询  
            query();  
            Log.i(TAG, "query");  
              
        }else if(view == deleteData){  
              
            //这是删除名字为：amaker的数据的方法：  
            String[] deleteValue = {"amaker"};  
            String where = "name";  
                                      
            // 删除  
            del(uri,where,deleteValue);  
            Log.i(TAG, "del");  
              
        }else if(view == updateData){  
              
            ContentValues values = new ContentValues();  
            values.put(Employee.NAME, "testUpdate");  
            values.put(Employee.GENDER, "female");  
            values.put(Employee.AGE,39);  
                          
            String where = "name";  
            String[] selectValue = {"amaker"};  
              
            // 更新  
            update(uri,values,where,selectValue);  
            Log.i(TAG, "update");  
        }     
    }  
      
      
      // 插入  
    private void insert(Uri uri, ContentValues values){  
        getContentResolver().insert(uri, values);  
    }  
      
      
    // 查询  
    private void query(){  
        // 查询列数组  
           String[] PROJECTION = new String[] {   
                   Employee._ID,         // 0  
                   Employee.NAME,         // 1  
                   Employee.GENDER,     // 2  
                   Employee.AGE         // 3  
        };  
        // 查询所有备忘录信息  
        Cursor cursor = getContentResolver().query(Employee.CONTENT_URI,PROJECTION, null, null,Employee.DEFAULT_SORT_ORDER);  
        //Cursor c = managedQuery(Employee.CONTENT_URI, PROJECTION, null,null, Employee.DEFAULT_SORT_ORDER);  
        if (cursor.moveToFirst()) {  
            // 遍历游标  
            for (int i = 0; i < cursor.getCount(); i++) {  
                cursor.moveToPosition(i);  
  
                String name = cursor.getString(1);  
                String gender = cursor.getString(2);  
                int age = cursor.getInt(3);  
  
                Log.i(TAG, "db第"+i+"个数据："+"--name:"+name+"--gender:"+gender+"--age:"+age);  
            }  
        }  
        cursor.close();  
    }  
      
      
    // 删除方法  
    private void del(Uri uri,String where, String[] deleteValue){  
              
        /****  删除ID为1的记录的方法： 
          
        // 删除ID为1的记录 
        Uri uri = ContentUris.withAppendedId(Employee.CONTENT_URI, 1); 
        // 获得ContentResolver，并删除 
        getContentResolver().delete(uri, null, null); 
         
        ****/  
          
        getContentResolver().delete(uri, where+"=?", deleteValue);  
    }  
      
    // 更新  
    private void update(Uri uri, ContentValues values, String where, String[] selectValue){  
          
        /************************************************************** 
        // 更新ID为1的记录 
        Uri uri = ContentUris.withAppendedId(Employee.CONTENT_URI, 1); 
         
        ContentValues values = new ContentValues(); 
        // 添加员工信息 
        values.put(Employee.NAME, "hz.guo"); 
        values.put(Employee.GENDER, "male"); 
        values.put(Employee.AGE,31); 
         
        // 获得ContentResolver，并更新 
        getContentResolver().update(uri, values, null, null); 
        *************************************************************/  
  
        //getContentResolver().update(uri, values, "name"+"=?", selectValue);  
        getContentResolver().update(uri, values, where+"=?", selectValue);  
    }  
}  

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