Detailed explanation of the basic knowledge of Android call

Call is a commonly used call function. The most basic functions are incoming call, outgoing call and hangupcall. Generally speaking, the caller becomes the calling party and the receiver is the called party. Some terms commonly used in call module are:

1. dialing call

Dialing is the state when the caller is waiting to be handed over for listening when the other party has not answered the call

2. active call

Active call: a normal call between two parties

3. hold call

Hold call: hang up the current call, and neither the caller nor the called party can hear the other party's voice

4. mute call

Mute: after mute, the other party cannot hear the voice of the mute initiator, but the mute initiator can hear the other party's voice

5. waiting call

In the process of a call, a third-party call comes in. For the user who is currently talking, the third-party is a waiting call waiting for the incoming call

6. end all

End Call

7. Auto redial

Automatic redial: this function generally allows the user to select whether to turn it on or off in call setting. If it is turned on, the device will automatically dial the number again after the first call fails. Generally, it can redial 7 times or more automatically. In addition, the interval between the first two automatic redials is short and the following times are long

8. Quick dial

Speed dialing: set a key (usually a number key) in call setting to correspond to a common number. Long press the key in the idle interface to display the number and dial it normally

9. Answer mode：

Answer mode: it is the user's answer method for incoming calls. By default, you can answer by pressing the answer key. This option is generally available in call setting, and users can choose freely.

a. Automatic response: generally, the phone will be connected automatically after ringing for about 5 seconds

b. Press any key to answer: any key except hang up key and power key can answer the incoming call

10. call waiting

Call waiting: this function needs to be supported and enabled by the operator. Generally, the card supports this function and the operator is enabled by default. Generally, the mobile phone will have an option to turn this function on or off in call setting, and the user can choose freely. If the user sets call waiting, it can be realized that during a call, if there is an incoming call from a third party, there will be a prompt tone and prompt screen. At this time, you can choose to answer, reject or ignore the call. If you choose to answer a third party call, the original call will be held without being hung up. Of course, you can also choose to answer and hang up the original call. If you refuse, the third-party call will be hung up and the original call will not be affected.

11. call forwarding

Call transfer: call transfer is a function of transferring incoming calls to other phones, which needs the support and activation of the operator. Not all SIM / USIM cards have this function. The transferred numbers can be mobile phone numbers or fixed phone numbers, including:

a. Unconditional transfer: that is, any incoming call will be transferred to the set good horse

b. No response transfer: if the incoming call is not answered, after a period of time (the length of this time period is determined by the network segment, usually about 25 seconds), the phone will be transferred to the set phone number

c. Unable to connect transfer: when no phone cannot be connected (such as shutdown, no signal, etc.), the phone will be transferred to the set phone number

d. Transfer when the line is busy: if the phone is in a call, another call will be transferred to the set phone number

12. call barring

Call restriction: call restriction is to restrict outgoing or incoming calls. Not all SIM / USIM cards support this function. As far as I know, only China Mobile's global card with international call function supports this function. Specifically include:

a. All outgoing calls: the mobile phone will not be able to make any calls. Generally, there will be a prompt that the call is restricted

b. All incoming calls: the phone will not be able to access any incoming calls

c. All international outgoing calls: no overseas calls can be made

d. All international calls: any international calls will not be connected

e. Local incoming and outgoing calls only: all local incoming and outgoing calls will be prohibited

13. multi-party

Multi party call (not all cards support this function): the precondition of multi-party call is that this card must support call waiting and the call waiting function must be enabled.

When another call is made during the call, the third-party phone is connected to form a multi-party call. At this time, the original call is suspended (i.e. in the hold state). At this time, the held call will not hear any sound here. The new call is connected to the active state, and the hold and active states can be switched to each other. Therefore, generally, multi-party calls have a menu option, which includes: mute, hold / activate, join the conference call, hang up the current, hang up hold and other call related options

Multi party calls also include conference calls: when there are multi-party calls, you can choose to join the conference call. All parties participating in the conference call can hear each other's voices and have multi-party talks. The menu options of teleconference generally include: join / exit teleconference (select any member), mute, teleconference member list, hang up all, hang up a certain distance, etc. if hang up all, the hang up interface of each call will appear one by one, and the time of teleconference shall be subject to the earliest established time. Multi party calls include conference calls. The maximum number of seven way calls is supported. There is also a number limit for teleconference. The maximum number varies with different operators. When the maximum limit is reached, you will not be able to join the teleconference.

14. Processing status of call

A phone has and only has three calls, ringcall, forgroundcall and backgroundcall. It can be simply understood that each call corresponds to four states (the state differences between the three calls are not concerned here) ring, active, hold and idle. At the same time, three calls can only have one ring state (ringcall), one active state (forgroundcall) and one hold state (backgroundcall) can have three idle states at the same time, so it involves how to switch between call states.

Handling of single card in Android:

a. When there is a ring call, switching between hold and active is not allowed;

b. When there is both ring call and hold call, hanging up the ring call will hang up together with the hold call.

c. There are both active call and hold call. When hanging up, hang up active call first and then hold call

In fact, in our code, it is not a call, but a connection. Ringcall can only establish one connection, while forgroundcall and backgroundcall can establish multiple connections at the same time, especially when there are multi-party calls or conference calls, up to seven connections can be established in the three states at the same time.

The above is the whole content of this article. I hope the content of this article can bring some help to your study or work. At the same time, I also hope to support a lot of programming tips!