F21 Pro 5G Smartphone
Troubleshooting
User Manual
Hang issue
1.1 Definition and symptom
Definition
Hanging is about animation drop frame, and pause when clicking a certain key, icon, or sliding widget.
Symptom
Slow reaction
- Slow Reaction While App Initiates/Stops/Runs
- Slow Screen-on While Pressing Power Key
Run unsmoothly
- System Runs unsmoothly
- Hang in App running (hang in sliding)
- Stuck in App running (stuck in the launcher)
- White screen for a long time/ black screen for a short time
Slow Internet Speed
Crash and Reboot
ANR
App stops running
1.2 Cause
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3rd Part Abnormality | ANR Hanging will occur sometime before the application does not respond. ANR： Application Not Responding | ROOT After the phone is rooted, system files will be altered and the application may not apply for resources. | Low Memory Running memory was largely occupied by apps, resulting in small capacity and thus the system keeps recovering memory and occupying CPU. | Under locking Excess temperature causes low CPU frequency and nuclear number, insufficient resource. | System Abnormality |
1.3 Android Memory Management Mechanism
1.4 Troubleshooting steps
Battery drains and overheat
2.1 Cause for battery drains
Criteria 
A1:In the state of being standby, more than 2% per hour of power consumption can be determined as abnormal;
–> mostly applied in SCREEN OFF and STANDBY mode.
A2:Comparison test: use the same model(good sample), and set the same setting conditions (the default time unit: hour), if the power difference between the test sample and user machine is more than 5%, it can be judged to be abnormal consumption.
–>mostly applied in OPERATION mode。
* Note：
- The standby conditions in criteria A1 are no background APPs, GPS/WIFI/BT/GPRS/low power mode off.
Common Causes 
- Battery capacity limitation; high hardware configuration; battery aging(Capacity will averagely reduce 12% with the condition of charging and discharging 300 times.)
- Large working current(Such as long-time reading books, playing games, and watching videos.)
- The phone cannot sleep when the screen is off and on standby(The third application fault causes the CPU keeps running and never sleep.)
- Hardware problem(Mainboard electric leakage)
- Users do not have good habits(cellular network is on for a long time, too many background apps)
- Power consumed by screen(ex: adjust the screen brightness to the highest level, screen timeout period too long)
- Others (hotspot, sunshine directly, etc.)
2.2 Cause for battery drains
However,
in irregular working conditions, system software can cause power consumption faults too.
 | Screen off misoperation like turn on the screen, camera, flashlight, and music carelessly |
 | Poor network signal In comparison with the good condition, the power consumption of standby and call will relatively increase. |
 | Poor Wi-Fi signal Wi-Fi signal connection is poor, often disconnected again |
2.3 Phone overheat
Standard 
The heat of the smartphone is closely related to how to use it and what’s the status of the device, such as playing video. The different degrees the CPU is being used can definitely cause different heat produced by smartphones. A simple example like playing games at room temperature and being exposed to the hot sun will not have the same heat results.
Why phone gets heated 
The working principle of the processor of smartphones and computers is the same. When the processor is in an operation state, it will generate heat. The computer can be mounted cooling fan, and heat can be discharged in a timely manner, but a big-screen smartphone chip is within a compact space, so it is impossible to discharge heat like a computer, and can only rely on a shell. So when the phone is being used, the heat will be discharged by the shell and felt by users
2.4 Troubleshooting steps
THANKS
