Basic Android: page Jump and value passing (activity jump and value passing)

An Android ApplicationProgramThere is rarely one activity object. It is a basic requirement to jump between multiple activities and pass values to each other.

Here we will talk about several methods of page Jump and value passing in Android!

Activity jump and value passing mainly connects multiple activities through the intent class and transmits data through the bundle class.

The most common and common page JumpCode, Very simple, as follows:

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Intent intent = new intent (A. This, B. Class );
Startactivity (intent );
 

You can also write as follows:

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Intent intent = new intent ();
Intent. setclass (A. This, B. Class );
Startactivity (intent );
 

With these two sentences, you can jump from page a to page B. (A and B inherit from activity)

Sometimes, data needs to be transferred when the page is redirected. How can this problem be solved?

If the data volume is small, for example, you only need to pass a name, then you only need to add "intent. putextra (" name "," feng88724 ");", the Code is as follows:

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Intent intent = new intent ();
Intent. setclass (A. This, B. Class );
Intent. putextra ("name", "feng88724 ");
Startactivity (intent );
 

If there is a large amount of data, you need to use the bundle class. The Code is as follows: (for more information, see annotations)

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Intent intent = new intent (A. This, B. Class );

/* Use the bundle object to store the data to be transferred */
Bundle bundle = new bundle ();
/* Character, String, Boolean, byte array, floating point, and so on can all be passed */
Bundle. putstring ("name", "feng88724 ");
Bundle. putboolean ("ismale", true );

/* Assign the bundle object assign to intent */
Intent. putextras (bundle );

Startactivity (intent );
 

We are talking about how to perform page Jump and data transmission. How should we receive data on another page B?

On page A, objects are encapsulated by bundle. On page B, encapsulated data is also unbound by bundle. You can use the "getintent (). getextras ()" method to obtain the bundle and then obtain data from the bundle. You can also use the "this. getintent (). getstringextra (" name ");" method to directly obtain data from intent.

Code for getting data from bundle:

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@ Override
Public void oncreate (bundle savedinstancestate ){
Super. oncreate (savedinstancestate );
/* Load the page */
Setcontentview (R. layout. Main );

/* Get the bundle object in intent */
Bundle bundle = This. getintent (). getextras ();

/* Obtain the data in the bundle. Pay attention to the type and key */
String name = bundle. getstring ("name ");
Boolean ismale = bundle. getboolean ("ismale ");

}

Sometimes, after a page Jump, you need to return to the previous page and retain the user's previous information. What should you do at this time?

After the page jumps, the previous activity has been destroy. To return and display data, You must wake up the previous activity and call a method to obtain and display data.

To achieve this effect, perform the following steps:

1. When you jump from page a to page B, you cannot use the "startactivity ()" method, but the "startactivityforresult" method.

2. In the activity on page A, you must override the onactivityresult method.

 
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@ Override
Protected void onactivityresult (INT requestcode, int resultcode, intent data ){

Switch (requestcode ){
Case result_ OK:
/* Obtain the data from page B and display it to the screen */
Bundle bundle = data. getextras ();

/* Obtain the data in the bundle. Pay attention to the type and key */
String name = bundle. getstring ("name ");
Boolean ismale = bundle. getboolean ("ismale ");
}
}
 

3. Add a return button on page B and write the following code in the event:

 
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/* Return the result to the previous activity */
B. This. setresult (result_ OK, intent );
/* End the activity */
B. This. Finish ();
 

This is the case.