Question

我似乎无法掌握内容提供商的概念。我个人认为它使代码膨胀，它使它过于复杂，而且显然非常糟糕。

BTW这将是您在网上找到的多表ContentProvider的第一个示例代码。绝对没有其他，除了可能是ContactsProvider（＆＃34; veeeerrrrry有用＆＃34; - 通过超级填充和不可识别）。我相信像我这样的许多新手都会欣赏这一点。

请帮我从内容提供商处制作一个简单的光标。我有正常的代码（使用简单的SQLiteOpenHelper），我需要将其翻译成内容提供者代码：

    Button btnp = (Button) findViewById(R.id.btnproc);
    btnp.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
        Context mycontext = getApplicationContext();
        SQLiteDatabase db = new myDbHelper(mycontext).getWritableDatabase();
        String sql = "select _id,data,titlu,cont from notificari where date(data)<=date(datetime())";
        Cursor cursor = db.rawQuery(sql, null);
        Log.w("...MainActivity...", "Record count:"+Integer.toString(curu.getCount()));
            while(curu.moveToNext()){
                String lista = curu.getString(0)+",'"+curu.getString(1)+"',"+curu.getString(2)+",'"+
                        curu.getString(3)+"'";
                Log.e("...MainActivity...", lista);
            }

        }
    });

所以我需要从内容提供者那里获得光标。我已经开始开发这个＆＃34;令人兴奋的＆＃34;内容提供者，但我不知道我在做什么是好的，因为它太复杂了。在这里它（我的内容提供者需要引用多个表）：

public class MyFirstProvider extends ContentProvider {
static final String PROVIDER_NAME = "com.mystuff.myapp.MyFirstProvider";
    static final String URL = "content://" + PROVIDER_NAME + "/cte";
    static final String URL2 = "content://" + PROVIDER_NAME + "/clienti";
    static final String URL3 = "content://" + PROVIDER_NAME + "/uzeri";
    static final String URL4 = "content://" + PROVIDER_NAME + "/notificari";
    static final Uri CONTENT_URI = Uri.parse(URL);
    static final Uri CONTENT_URI2 = Uri.parse(URL2);
    static final Uri CONTENT_URI3 = Uri.parse(URL3);
    static final Uri CONTENT_URI4 = Uri.parse(URL4);


    static final int uriCode = 1;
    static final int uriCode1 = 2;
    static final int uriCode2 = 3;
    static final int uriCode3 = 4;
    static final int uriCode4 = 5;
    static final int uriCode5 = 6;
    static final int uriCode6 = 7;
    static final int uriCode7 = 8;


    static final UriMatcher uriMatcher;
    private static HashMap<String, String> values;
    static {
        uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        uriMatcher.addURI(PROVIDER_NAME, "cte", uriCode);
        uriMatcher.addURI(PROVIDER_NAME, "cte/*", uriCode1);
        uriMatcher.addURI(PROVIDER_NAME, "clienti", uriCode2);
        uriMatcher.addURI(PROVIDER_NAME, "clienti/*", uriCode3);
        uriMatcher.addURI(PROVIDER_NAME, "uzeri", uriCode4);
        uriMatcher.addURI(PROVIDER_NAME, "uzeri/*", uriCode5);
        uriMatcher.addURI(PROVIDER_NAME, "notificari", uriCode6);
        uriMatcher.addURI(PROVIDER_NAME, "notificari/*", uriCode7);
    }

    @Override
    public boolean onCreate() {
        Context context = getContext();
        DatabaseHelper dbHelper = new DatabaseHelper(context);
        db = dbHelper.getWritableDatabase();
        if (db != null) {
            return true;
        }
        return false;
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection,String[] selectionArgs, String sortOrder) {
        SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
        switch (uriMatcher.match(uri)) {
            case uriCode:
                qb.setTables(TABLE_NAME);
                qb.setProjectionMap(values);
                break;
            case uriCode2:
                qb.setTables(TABLE_CLIENTI);
                qb.setProjectionMap(values);
                if (sortOrder == null || sortOrder == "") {
                    sortOrder = TCL_NUME_CLIENT;
                }
                break;
            case uriCode6:
                qb.setTables(TABLE_NOTIF);
                qb.setProjectionMap(values);
                break;

            default:
                throw new IllegalArgumentException("Unsupported URI: " + uri);
        }
        Cursor c = qb.query(db, projection, selection, selectionArgs, null,null, sortOrder);
        c.setNotificationUri(getContext().getContentResolver(), uri);
        return c;
    }


    // ... there is other code here regarding the insert,update and delete (not relevant now)

    private SQLiteDatabase db;
    static final String DATABASE_NAME = "mydb";
    static final String TABLE_NAME = "names";
    public static final String TABLE_UZERI = "uzeri";
    public static final String TABLE_NOTIF = "notificari";


    static final int DATABASE_VERSION = 3;
    static final String CREATE_DB_TABLE = " CREATE TABLE " + TABLE_NAME
            + " (_id INTEGER PRIMARY KEY AUTOINCREMENT, "
            + " name TEXT NOT NULL);";

    static final String CREATE_DB_TABLE_NOTIFICARI = "CREATE TABLE IF NOT EXISTS " + TABLE_NOTIF + " (_id INTEGER PRIMARY KEY AUTOINCREMENT, " +
            TNOT_ID_NOT + " INTEGER NOT NULL DEFAULT 0, " +
            TNOT_DATA + " DATE NOT NULL, " +
            TNOT_SURSA + " INTEGER NOT NULL DEFAULT 0, "+
            TNOT_DEST + " INTEGER NOT NULL DEFAULT 0, "+
            TNOT_TIP + " TEXT, "+
            TNOT_TITLU + " TEXT, "+
            TNOT_TITLUCONT + " TEXT, "+
            TNOT_CONT + " TEXT, "+
            TNOT_STERS + " INTEGER DEFAULT 0, "+
            TNOT_NOU + " INTEGER NOT NULL DEFAULT 0)";

   private static class DatabaseHelper extends SQLiteOpenHelper {
        DatabaseHelper(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
        }

        @Override
        public void onCreate(SQLiteDatabase db) {
            db.execSQL(CREATE_DB_TABLE);
            db.execSQL(CREATE_DB_TABLE_UZERI);
            db.execSQL(CREATE_DB_TABLE_NOTIFICARI);
        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
            db.execSQL("DROP TABLE IF EXISTS " + TABLE_UZERI);
            db.execSQL("DROP TABLE IF EXISTS " + TABLE_NOTIFICARI);
            onCreate(db);
        }
    }

我试图＆＃34;翻译＆＃34;记录光标内容的活动代码，但它只是没有。这非常令人沮丧。这是我的翻译＆＃34;：

Button btnp = (Button) findViewById(R.id.btnproc);
btnp.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        String[] coloane = {MyFirstProvider.TNOT_ID_ID, MyFirstProvider.TNOT_DATA,MyFirstProvider.TNOT_TITLU, MyFirstProvider.TNOT_CONT};
        Cursor curu = MainActivity.this.getContentResolver().query(MyFirstProvider.CONTENT_URI_NOTIF,coloane,null,null,MyFirstProvider.TNOT_DATA);

        Log.w("...MainActivity...", "Recorduri:"+Integer.toString(curu.getCount()));
        while(curu.moveToNext()){
            String lista = curu.getString(0)+",'"+curu.getString(1)+"',"+curu.getString(2)+",'"+
                    curu.getString(3)+"'";
            Log.e("...MainActivity...", lista);
        }

    }
});

我必须向你保证，表中有4条记录（我在创建表后手动插入它们）此外，如果我将此代码放在ContentProvider中，则日志会根据需要显示表的内容：

Cursor c = qb.query(db, projection, selection, selectionArgs, null,null, sortOrder);
        while(c.moveToNext()){
            Log.w("...Provider...",c.getString(0)+"-"+c.getString(1)+"-"+c.getString(2));
        }

但我不想在内容提供商中这样做，我想在活动代码中这样做。我做错了什么？

请帮忙。

谢谢

Answer 1

如果您不必，则不必使用ContentProvider。确定您的要求。如果数据对您的应用程序是私有的，并且必须以表格格式存储，那么您可以直接在Android中访问SQLite引擎，而无需通过ContentProvider。但是，如果您希望其他应用或系统访问您应用的数据，那么是 - 这是ContentProvider的合法用例。

尽管如此，我建议您阅读此article - 告诉您如何使用SQLite访问ContentProvider引擎{/ 1}}。

希望这有帮助。

无论如何，对于你手头的问题，试试这个 -

Cursor c = qb.query(db, projection, selection, selectionArgs, null,null, sortOrder);
if (c == null) {
  // error - log some message
}
else if (c.getCount() < 1) {
  // nothing to show  - log some message
}
else {
  while(c.moveToNext()){
    Log.w("...Provider...",c.getString(0)+"-"+c.getString(1)+"-"+c.getString(2));
  } 
}

Answer 2

而不是这个

btnp.setOnClickListener(new View.OnClickListener

尝试

btnp.setOnClickListener(this)

并将onClickListner实现到Activity。

简而言之，不是将onClickListener强制转换为按钮，而是将其实现到整个活动并尝试。

Android - Content Provider查询游标

2 个答案: