Android Basic Components-activity

• What is activity

1. In the Android program, each Activity inherits from Android.app.Activity,
2. There is an XML layout file that corresponds to it,
3. One interface corresponds to an activity,
4. Each activity needs to be registered in the Androidmanifest.xml
5. Activity organizes controls by layout management

• Get control in activity

1. The controls in each activity will correspond to the R files.
2. defined in the XML layout file, android:id= "@+id/thisisbutton"
3. Each control in the layout file has a corresponding class, with the button example, in the layout file for <button/> Its corresponding class as button
4. Use button button = (button) Findviewbyid (R.id.thisisbutton) reference in activity

• Jumps between the activity

1. Use the startactivity (Intent Intent) method to open another activity
2. Before opening, you can pass parameters by storing variables in the intent.
3. Create a new activity to jump to
4. To bind a button to an event

5. Create a new intent and point to the corresponding activity to complete the page jump

6. You can populate the intent with data before jumping

   Normal types can be passed between activity, and wrapper classes cannot be passed.

7. Complete

• Activity life cycle

Method	Call timing
OnCreate	Called when an activity is created
OnStart	Immediately after the call is created, the activity is about to become visible
Onrestart	Called when it is back to activity, and then calls start after the call is completed.
Onresume	The activity is ready to be called when user action is accepted
OnPause	To switch to another activity call, which is particularly useful for saving some of the current activity's data
OnStop	Called when the current activity is overwritten by another activity
OnDestroy	Called when the activity is destroyed

• Activity Life Cycle Classification
  • Full life cycle
    • OnCreate () OnDestroy ()
  • Visual life cycle
    • OnStart () OnStop ()
  • Foreground life cycle
    • Onresume () OnPause ()
• Activity and Task

Accessing multiple activity forms an activity chain in order, called task,android, to manipulate tasks in the form of a stack.

Activity is run according to the rules of the stack.

Android Basic Components-activity