Websql排队执行 - iOS6 Mobile Safari

时间:2012-09-26 19:17:49

标签: javascript ios html5 mobile web-sql

自iOS6发布以来,我的网络应用程序遇到了一系列错误,其中最糟糕的是我几乎100%肯定的是webql事务正在排队。当我第一次在移动safari(ipad)中加载应用程序时,交易正常。然后,如果我关闭safari并再次打开它,则事务似乎排队并且永远不会执行。

如果我打开开发工具并运行一个简单的alert,方法将触发,如果我只是重新加载事务也可以正常工作,或者如果我将数据库事务的运行延迟1秒或者某事它的工作正常。

我不想运行setTimeout来运行事务。

这是safari现在实施后的缓存问题吗?

如果有人对如何解决这个问题有任何好的想法,请在下面回答。

提前致谢。

2 个答案:

答案 0 :(得分:0)

可能不是错误。您可能不必要地使用一系列交易。您可以为每个事务使用多个请求。 onsuccess回调,您可以重复使用该事务。它应该工作。同时,限制每个事务的请求数。永远不应该setTimeout

以下是使用单个事务插入多个对象的方法

/**
* @param {goog.async.Deferred} df
* @param {string} store_name table name.
* @param {!Array.<!Object>} objects object to put.
 * @param {!Array.<(Array|string|number)>=} opt_keys
*/
ydn.db.req.WebSql.prototype.putObjects = function (df, store_name, objects, opt_keys) {

  var table = this.schema.getStore(store_name);
  if (!table) {
    throw new ydn.db.NotFoundError(store_name);
  }

  var me = this;
  var result_keys = [];
  var result_count = 0;

  /**
   * Put and item at i. This ydn.db.core.Storage will invoke callback to df if all objects
   * have been put, otherwise recursive call to itself at next i+1 item.
   * @param {number} i
   * @param {SQLTransaction} tx
   */
  var put = function (i, tx) {

    // todo: handle undefined or null object

    var out;
    if (goog.isDef(opt_keys)) {
      out = table.getIndexedValues(objects[i], opt_keys[i]);
    } else {
      out = table.getIndexedValues(objects[i]);
    }
    //console.log([obj, JSON.stringify(obj)]);

    var sql = 'INSERT OR REPLACE INTO ' + table.getQuotedName() +
        ' (' + out.columns.join(', ') + ') ' +
        'VALUES (' + out.slots.join(', ') + ');';

    /**
     * @param {SQLTransaction} transaction transaction.
     * @param {SQLResultSet} results results.
     */
    var success_callback = function (transaction, results) {
      result_count++;
      result_keys[i] = goog.isDef(out.key) ? out.key : results.insertId;
      if (result_count == objects.length) {
        df.callback(result_keys);
      } else {
        var next = i + ydn.db.req.WebSql.RW_REQ_PER_TX;
        if (next < objects.length) {
          put(next, transaction);
        }
      }
    };

    /**
     * @param {SQLTransaction} tr transaction.
     * @param {SQLError} error error.
     */
    var error_callback = function (tr, error) {
      if (ydn.db.req.WebSql.DEBUG) {
        window.console.log([sql, out, tr, error]);
      }
      df.errback(error);
      return true; // roll back
    };

    //console.log([sql, out.values]);
    tx.executeSql(sql, out.values, success_callback, error_callback);
  };

  if (objects.length > 0) {
    // send parallel requests
    for (var i = 0; i < ydn.db.req.WebSql.RW_REQ_PER_TX && i < objects.length; i++) {
      put(i, this.getTx());
    }
  } else {
    df.callback([]);
  }
};

关于事务队列,最好由应用程序处理,而不是由SQLite处理以获得健壮性。基本上我们可以在开始新事务之前观察事务complete事件。只要它们受到控制,运行多个事务也很好。失控将在循环下打开交易。一般来说,我只会开几笔交易。

以下是交易排队的方式:

/**
 * Create a new isolated transaction. After creating a transaction, use
 * {@link #getTx} to received an active transaction. If transaction is not
 * active, it return null. In this case a new transaction must re-create.
 * @export
 * @param {Function} trFn function that invoke in the transaction.
 * @param {!Array.<string>} store_names list of keys or
 * store name involved in the transaction.
 * @param {ydn.db.TransactionMode=} opt_mode mode, default to 'readonly'.
 * @param {function(ydn.db.TransactionEventTypes, *)=} oncompleted
 * @param {...} opt_args
 * @override
 */
ydn.db.tr.TxStorage.prototype.transaction = function (trFn, store_names, opt_mode, oncompleted, opt_args) {

  //console.log('tr starting ' + trFn.name);
  var scope_name = trFn.name || '';

  var names = store_names;
  if (goog.isString(store_names)) {
    names = [store_names];
  } else if (!goog.isArray(store_names) ||
    (store_names.length > 0 && !goog.isString(store_names[0]))) {
    throw new ydn.error.ArgumentException("storeNames");
  }
  var mode = goog.isDef(opt_mode) ? opt_mode : ydn.db.TransactionMode.READ_ONLY;
  var outFn = trFn;
  if (arguments.length > 4) { // handle optional parameters
    var args = Array.prototype.slice.call(arguments, 4);
    outFn = function () {
      // Prepend the bound arguments to the current arguments.
      var newArgs = Array.prototype.slice.call(arguments);
       //newArgs.unshift.apply(newArgs, args); // pre-apply
      newArgs = newArgs.concat(args); // post-apply
      return trFn.apply(this, newArgs);
    }
  }
  outFn.name = scope_name;

  var me = this;

  if (this.mu_tx_.isActive()) {
    //console.log(this + ' active')
    this.pushTxQueue(outFn, store_names, mode, oncompleted);
  } else {
    //console.log(this + ' not active')
    var transaction_process = function (tx) {

      me.mu_tx_.up(tx, scope_name);

      // now execute transaction process
      outFn(me);

      me.mu_tx_.out(); // flag transaction callback scope is over.
      // transaction is still active and use in followup request handlers
    };

    var completed_handler = function (type, event) {
      me.mu_tx_.down(type, event);
      /**
       * @preserve_try
       */
      try {
        if (goog.isFunction(oncompleted)) {
          oncompleted(type, event);
        }
      } catch (e) {
        // swallow error. document it publicly.
        // this is necessary to continue transaction queue
        if (goog.DEBUG) {
          throw e;
        }
      } finally {
        me.popTxQueue_();
      }
    };

    if (ydn.db.tr.TxStorage.DEBUG) {
      window.console.log(this + ' transaction ' + mode + ' open for ' + JSON.stringify(names) + ' in ' + scope_name);
    }
    this.storage_.newTransaction(transaction_process, names, mode, completed_handler);
  }

};

答案 1 :(得分:0)

事实证明,在websql导致问题之前初始化Facebook。在评论FB后,应用程序运行正常,这就是setTimeout也解决了这个问题的原因; fb api准备好了。我不知道如何阻止执行的线程。

所以,对任何使用FB然后尝试执行websql事务的人来说......延迟FB!

虽然,websql在safari加载上的运行速度仍然有点......