Android 2018-side question

"One" Activity

1. Life cycle

OnCreate: Indicates that activity is being created (this method can do some initial chemical work)

Onrestart: Indicates that the activity is being restarted and is called when the active activity is visible from invisible

OnStart: Activity is being started, activity is visible, but not in foreground, unable to interact with user

Onresume: The activity is already visible, located in the foreground and can interact with the user

OnPause: Indicates activity is stopping

OnStop

Ondestory:

2. Life cycle analysis under abnormal conditions

When the activity terminates in an abnormal situation, the system calls Onsaveinstancestate to maintain the current activity status;

After the activity is re-created, the system calls Onrestoreinstancestate and passes the bundle objects saved as arguments to the OnCreate and Onrestoreinstancestate methods as parameters while the activity is destroyed.

3.activity Load Mode

Standard: Default mode

Singletop: Stack top mode (activity is reused at the top of the stack, not rebuilt): The display page of the push message

Singletask: There will be no duplicate instance in the stack, reuse will dry turn on all the activity to adapt to the scene: The entrance of the program, used in the Start page and the homepage

SingleInstance: Single-instance mode re-opens new task stack adaptation scenarios: Pages separated from the program (Alerts like alarms)

"Two" broadcast

The broadcast can come from the system and can also come from other apps;

Broadcast is divided into orderly broadcasting and disordered broadcasting;

Intent is used to send the broadcast, Broadcastreceiver is to accept the broadcast.

Dynamic registration must wait until the app starts to receive the broadcast, static registration can be implemented without launching the application can also accept the broadcast;

　　

"Three" service

1. Properties of the manifest file

Exported: Whether the representation can be implicitly invoked by another application

Process: Whether you need to run in a separate process

Enable: Whether it can be instantiated by the system

2. How to ensure that the service is not killed

Kill service due to low memory: You can set the return value of the Onstartcommand method to Start_sticky, which means that the service will recover when memory resources are tight and then restore when memory resources are sufficient, or you can set the service as a foreground service with a higher comparison level This will not be killed when the memory resources are tense.

User manual intervention Kill service: The non-mandatory shutdown service, will walk the life cycle, the Ondestory method will be called, you can send a broadcast in this method, restart (for the program more robust, we can open two services, mutual monitoring, mutual start, service a monitor B broadcast to start B, Service B listens on A's broadcast to start a)

　　

Android 2018-side question