Modern Xiaomi smartphones have many smart features designed to make it easier to interact with the device, but sometimes the standard behavior of the system is puzzling. One of these situations is the inability to lock the screen during a phone conversation. Many device owners notice that the screen goes out on its own when you lift it to the ear, but if the phone is lying on the table, the screen continues to burn, and the attempt to press the lock button is often ignored by the system.
This is not a defect or a breakdown, but rather a feature of the logic of the MIUI shell or HyperOS. The operating system believes that if an active call is made, the user may need quick access to the keyboard for the set of tone code, contacts or recording of the conversation. However, there are situations where access to the screen needs to be limited, for example, to avoid accidental cheek pressing or to put the smartphone in his pocket without interrupting.
In this article, we will discuss in detail why the touch screen behaves this way during a call, how the proximity sensor works, and what legal ways are there to force the display to lock, and we will also look at settings that may interfere with the correct operation of the system, and offer solutions for various use cases.
The principle of operation of the proximity and lock sensor
The main mechanism that turns off the screen during a conversation is the proximity sensor. This small module, usually located at the top of the smartphone body next to the speaker, uses infrared radiation to determine the distance to the object. When you hold the phone to the ear, the sensor detects the proximity of the foreign object and signals the system to turn off the display.
If the sensor is working correctly, the screen goes off automatically, and any touches on it are blocked so that the cheek does not reset the bell or turn on the microphone. However, if the phone is on the table and you do not close the top of the screen, the system keeps the display active, so that you can see the time of the conversation, information about the interlocutor and use additional functions.
Locking problems often arise from contamination of the sensor area or the use of low-transparency protective glasses at the top. If Xiaomi doesn't feel a close approach, it doesn't lock the screen. It's also worth noting that some models use a virtual proximity sensor that works on the basis of gyro and accelerometer data, which can lead to false positives or, conversely, ignoring the ear pad.
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Use dry soft cloth to wipe the top of the screen. Fat spots can reduce the sensitivity of the infrared sensor, which will not go out when you bring the screen to the ear.
Understanding the physics of the process helps you realize that "screen locking" during a conversation is essentially an emulation of a situation where the phone is near the ear. If you want to lock the screen on the table, you either need to simulate an approach or use software crutches, since the regular power button in this mode often turns off the lock function.
Standard methods of blocking during a call
In standard MIUI, the developers didn't have an explicit lock button on the active interface, and the logic is that if the call is coming, the screen should be available, but there are ways to get around that limitation using the standard functionality of the system, and the first and easiest method is to use a physical power button, but with nuance.
On most Xiaomi models, a brief press of the power button while talking does nothing. However, if you hold the power button a little longer (about 1-2 seconds), you may see a shutdown menu or voice assistant, but the screen may still not go out completely, staying in standby mode. In some versions of Android and shells, prolonged retention still leads to lockdown, but this depends on the specific model and version of the software.
A more reliable standard method is to use the Pocket Mode function or similar security settings, although they are more often designed to protect against random dialing in the pocket, rather than manually locking. You can also try to switch the speaker to speaker and turn the phone down with the screen - in some configurations this leads to a darkening of the display, since the light sensor detects the absence of light.
- 📱 Try to press the power button twice quickly: on some models, this causes the screen to lock even during the time of the test.
- 🔇 Switch to speakerphone and put the phone screen down on a flat surface.
- 🛑 Complete and immediately lock the device if the urgency allows you to interrupt the conversation.
It's important to understand that the lack of a direct button is a conscious decision by Xiaomi engineers, which assumes that while the user is holding the phone to his ear (screen is off by the sensor) or looking at it (screen is on).
Using third-party applications to control the screen
Since the standard means to solve the problem is not always possible, the most effective solution is to install specialized applications from the Google Play store. There are many utilities that intercept the event of an active one and force the screen to be extinguished by pressing a floating button or by timer.
One of the popular types of apps is Screen Off, which creates a transparent or translucent button on top of the interface, and when you have to put your phone in your pocket or your bag, you press that button, and the screen goes out, and when you get an incoming call or you touch the screen, it lights up again, and this solves the problem of random tapping without having to close the sensor with your finger.
When selecting an app, pay attention to the permissions you request. The program will require screen control rights, access to the phone status (to know if it's coming), and the right to display over other windows. Without these permissions, the app will not be able to function correctly at the time.
| Title of the annex | Substantive function | Resource consumption | Advertising |
|---|---|---|---|
| Screen Off and Lock | Blocking by timer or button | Low. | It's in the free version. |
| Call Screen Off | Automatic quenching for | Average. | Minimum |
| Proximity Sensor Reset | Sensor calibration and control | Low. | Absent. |
| Black Screen (Pro) | Simulation of the screen off | High. | There is. |
Be careful with apps that completely replace the dialing interface, which can conflict with the Xiaomi system call, causing problems with sound or recording, and choose utilities that work as an add-on rather than a replacement for system components.
Security of Third Party Applications
Adjustment of the proximity sensor sensitivity
Often the problem of not being able to lock the screen or, conversely, turning it off spontaneously lies in the wrong calibration of the proximity sensor. Xiaomi smartphones have a hidden engineering menu that allows you to check the operation of the sensors and calibrate them.
To enter the engineering menu, you need to open the Phone app and enter a special code. On most Xiaomi devices, this is the combination ##6484#. Once you enter the code, the CIT menu will open.
Inside the test, you'll see a value that varies from 0 to 1 (or 0.0 to 5.0 depending on the model) when you cover the top of the screen with your hand. If the values don't change or change randomly, the sensor needs to be calibrated. Press the Calibrate button and follow the instructions on the screen, usually you need to remove your hand from the sensor and then close it.
☑️ Calibration of the sensor in CIT menu
If calibration doesn't work, it might be a software failure, which can help reset the sensor settings through the same menu or update the firmware to the current version, sometimes helping to disable the "Increased Pocket Mode" function in the main system settings, if it's on.
⚠️ Warning: Don't change the sensitivity values manually unless you're sure of your actions. Incorrect calibration can cause the screen to stop going out altogether or, conversely, to go out with any movement of the phone in your hand, making it impossible to do so.
The impact of protective accessories on the screen
One of the most common reasons Xiaomi's screen doesn't lock at time or locks incorrectly is security accessories.Cheap security glasses often have an opaque frame or black stripe at the top that overlaps the proximity sensor.
If the sensor is closed, it constantly "sees" the object nearby and can keep the screen off even when the phone is lying on the table. Or, if it is only partially closed, it can work unstable. Owners of smartphones with a cut-out drop or hole in the screen need to be especially careful when choosing protection.
There are also cases. Some bookcases have a magnetic fastener or a tight cover that, when attached loosely, can mechanically press on the sensor area or cause interference. If you notice a problem after buying a new case, try removing it and checking the screen.
- 🛡️ Use protective glass with a cutout under the sensor or completely transparent throughout the area.
- 🧹 Rub the top of the screen regularly, removing fat and dirt that distort the sensor readings.
- 📵 Remove the case for diagnosis: if the problem has disappeared, it is the accessory.
In some cases, the re-adjustment of the protective glass with more precise positioning helps. For models with a subscreen sensor (although more often a separate IR sensor is used), the quality of the sticker is critical.
Solving Problems with Program Conflicts
Sometimes, locking the screen is not possible because of application conflict, for example, if you have a recording app installed, it may block standard screen controls to ensure recording stability, and memory cleaners or antiviruses that aggressively control processes may also conflict.
To diagnose, try running your phone in Safe Mode, which only downloads system applications, and if the screen is locked normally (power button) or the sensor is working correctly, it's the third-party app's fault, and you'll have to eliminate the culprit.
It's also worth checking for system updates. Xiaomi regularly releases patches that fix interface bugs. Go to Settings → About Phone → MIUI version and check for updates. Sometimes the problem is solved only by resetting the settings to factory, but this is an extreme measure.
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If after resetting the settings and checking in safe mode the problem persists, there is a high probability of hardware malfunction of the proximity sensor or screen plume.