Android Studio Development Note Five

1.activity: An application component that provides a user interface to interact with the program
2.android Four components:
--activity--service--broadcastreceiver--content Provider
3. How to create a usage activity
(1) Acivity classes that inherit Android
(2) Override method
(3) Setting the display layout
(4) in the Androidmanifest file, register the activity
4.activity life cycle: Create---> Destroy
OnCreate () Create OnStart () run Onresume () Get focus
OnPause () lost Focus onStop () pause OnDestroy () Destroy Onrestart ()
OnCreate ()->onstart ()->onresume ()->onpause ()->onstop ()->ondestroy ()
Four states of 5.activity:
(1) Active status: Activity at the top of the interface, get focus
(2) Pause state: Activity loses focus, but visible to user, program pauses
(3) Stop state: activity is completely obscured but retains all status and member information
For example, back to the home screen, the program runs in the background
(4) Inactive: activity is stopped

Intent
1. Intent to assist in the completion of communication between various components of Andro
2. Implement the Jump mode:
(1) >startactivity (Intent)--no return result
(2) >startactivityforresult (Intent,requestcode)
--there is a return result, that is, two pages can be exchanged for data
>onactivityresult ()
>setresult ()
Code:
Manifest file:
<?xml version= "1.0" encoding= "Utf-8"?>
<manifest xmlns:android= "Http://schemas.android.com/apk/res/android"
Package= "Com.example.administrator.myintent" >
<application
Android:allowbackup= "true"
android:icon= "@mipmap/ic_launcher"
Android:label= "@string/app_name"
Android:supportsrtl= "true"
Android:theme= "@style/apptheme" >
<activity android:name= ". Mainactivity ">
</activity>
<activity android:name= ". Factivity ">
The following code, which represents this as the first page
<intent-filter>
<action android:name= "Android.intent.action.MAIN"/>
<category android:name= "Android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
<activity android:name= ". Sactivity ">
</activity>

</application>

</manifest>

The code for the first page:
public class Factivity extends Activity {
Private Button bt1;
Private Button BT2;
Private TextView TV;
@Override
protected void OnCreate (Bundle saveinstancestate) {
Super.oncreate (saveinstancestate);
Setcontentview (r.layout.factivity);
/*
Implement a jump between pages by clicking BT1
1.startactivity Way to achieve
1.> Initialize Intent
*/
bt1= (Button) Findviewbyid (R.id.button1_first);
Bt2= (Button) Findviewbyid (R.id.button2_first);
tv= (TextView) Findviewbyid (R.ID.TEXTVIEW1);
Bt1.setonclicklistener (New View.onclicklistener () {
/*
First parameter: Context this
Second parameter: Destination file
*/
@Override
public void OnClick (View v) {
Intent intent=new Intent (factivity.this,sactivity.class);
StartActivity (Intent);
}
});
/*
Implemented through Startactivityforresult
*/
Bt2.setonclicklistener (New View.onclicklistener () {
@Override
public void OnClick (View v) {
Intent intent=new Intent (factivity.this,sactivity.class);
/*
The first parameter is the intent parameter
The second parameter is an identity of the request, which is an integer type
*/
Startactivityforresult (intent,1);
}
});
}
/*
Jump through Startactivityforresult, accept the returned data
First parameter: The identity of the request
Second parameter: The identity returned by the second page, that is, to know which page to return from.
Third parameter: Data returned from the second page
*/
@Override
protected void Onactivityresult (int requestcode,int resultcode,intent data) {
Super.onactivityresult (Requestcode,requestcode,data);
if (requestcode==1&&resultcode==2) {
String Content=data.getstringextra ("data");
Tv.settext (content);
}
}
}
The code for the second page:
public class Sactivity extends Activity {
Private Button BT;
Private String content= "This is the data returned by the second page";
@Override
protected void OnCreate (Bundle hinstace) {
Super.oncreate (Hinstace);
Setcontentview (r.layout.sactivity);
/*
When does the second page begin to return data?
The data that is passed back to the first page is actually a intent object
*/
bt= (Button) Findviewbyid (R.id.button1_second);
Bt.setonclicklistener (New View.onclicklistener () {
@Override
public void OnClick (View v) {
Intent data=new Intent ();
Data.putextra ("Data", content);
Callback Data
Setresult (2,data);
End Current Page
Finish ();
}
});
}
}

Android Studio Development Note Five