BARCELONA, Spain — Smartphones are going against one of the long-held rules in portable electronics, that smaller is better.

Year by year, computers, storage devices and music players have shed size and weight. And for decades, it has been happening with cellphones, too.

But now cellphones, and smartphones in particular, are going the way of the television: They just keep getting bigger and bigger. And people keep buying them.

The trend became even more apparent this week, as handset makers introduced a number of big-screen smartphones — from 5 diagonal inches to more than seven inches — at the Mobile World Congress trade show in Barcelona.

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Samsung Electronics, Sony and Chinese manufacturers Huawei and ZTE, among others, are all betting that consumers find images and video to be more vivid and engaging on a bigger screen, and that they may prefer to carry a larger phone instead of both a smartphone and a tablet.

The turn to bigger screens is a sharp departure from the dominant strategy of phone-makers just a few years ago, when critics often and loudly mocked devices with big screens, joking that people would never buy them because they would not fit in the pockets of tight hipster jeans, or because people would not want to be seen clutching big devices to their skulls.

But Samsung, the No. 1 phone-maker in the world, pushed hard on phones with bigger screens, and the effort has paid off with millions of units sold, particularly in Asia.

Samsung has said its research found that people liked bigger-screen phones because they wanted a device that was good for handwriting, drawing and sharing notes. Asian-language speakers found it easier to write characters on a device using a pen rather than typing.

Now Samsung and other phone-makers think they will find a more receptive audience outside Asia, too, including in the United States and Europe.

The most extreme example of a big phone announced this week came from Huawei, which introduced the MediaPad X1, a smartphone with a 7-inch screen, usually a size used in tablets. Because the device has a phone connection, Huawei calls it a phablet.

Roland Sladek, a vice president for international media affairs at Huawei, said the company found that people liked to spend at least an hour a day on mobile devices, and that has driven the demand for larger screens.

Other makers are pushing slightly smaller versions. Samsung this week introduced the Galaxy S5, its latest flagship smartphone, which, at 5.1 diagonal inches, is just a smidgen bigger than its predecessor. Sony unveiled the Xperia Z2, a 5.2-incher. ZTE introduced the Grand Memo II, a 6-inch phone; last month it introduced the Boost Max, a 5.7-incher that the company hopes will help it gain some traction among American buyers.

Rumors abound that Apple is planning to release at least one bigger iPhone this year. Starting with the sixth-generation iPhone, Apple increased the size of the iPhone screen to 4 inches, up from 3.5 inches in the earlier models — still considerably smaller than many devices coming from its Asian rivals.

Lenovo, the Chinese company that is buying the handset division of Motorola from Google, said that there seemed to be no turning back from supersizing smartphones in markets around the world.

Liu Jun, executive vice president for Lenovo’s mobile business group, said: “Simply put, more and more people are using their smartphones for entertainment, and people like viewing their photos, TV shows and movies on a larger handheld screen.”