What are the ways to call system functions in Android system?

what are the ways to call system functions in p>Android system?

Android system is an open source mobile operating system, which provides rich system functions for developers to call. When developing Android applications, we often need to call these system functions to complete various functions, such as making phone calls, sending text messages, calling cameras and so on. So, what are the ways to call system functions in Android system? This article will introduce it to you.

1. using JavaAPI

in Android development, JavaAPI is often used to call system functions. Android system provides many Java classes to realize various system functions, such as TelephonyManager class for managing calls (including making and answering calls, incoming number, etc.), SmsManager class for sending short messages, etc.

For example, if we want to make a phone call, we can use the following code:

`

Intent Intent = New Intent (Intent. Action _ Call);

intent.setData(Uri.parse(tel:186));

startActivity(intent);

`

This code uses the Intent class and Uri class provided by Android to realize the function of calling.

2. using JNI

in some cases, we may need to access some low-level system functions, which cannot be accessed directly through the JavaAPI. At this time, we can use JNI(JavaNativeInterface) to realize it.

JNI is a way for Java to interact with local codes (such as C, C++, etc.). Through JNI, we can call the functions in the local code in Java code to realize some advanced or complex functions.

For example, if we want to implement a custom camera application, we can use the following code:

`

static {

system. loadlibrary (native-lib);

}

publicnativevoidopenCamera();

publicnativevoidcloseCamera();

publicnativevoidstartPreview();

publicnativevoidstopPreview();

`

This code uses JNI to call the underlying system functions to open, close, start and stop the camera preview.

3. using system services

in addition to JavaAPI and JNI, we can also use the system services that come with the Android system to call system functions.

Android system provides many system services, such as ActivityManager, WindowManager, MediaScannerService and so on. These system services provide various system-level functions, through which we can call the underlying system functions.

For example, if we want to get the current electricity information, we can use the following codes:

`

BatteryManagerBatteryManager = (Battery Manager) getSystemService (Battery _ Service);

intbatteryLevel=batteryManager.getIntProperty(BatteryManager.BATTERY_PROPERTY_CAPACITY);

`

This code uses the BatteryManager system service provided by the Android system to obtain the current power information.

Summary

Through the above three ways, we can call various system functions in the Android system to realize the functions we need. Of course, in actual development, we need to choose an appropriate way to call system functions according to specific needs. At the same time, we also need to pay attention to some security issues and rights management issues to ensure the normal operation of applications and the safety of users.