Use the interface callback to implement the communication between fragment and activity.

Use the interface callback to implement the communication between fragment and activity.

Fragment and activity transmit data to each other as follows:

1. The Activity transmits data to Fragment: Creates a Bundle data packet in the Activity (if the transmission involves an object, serialization of the object is required), and CALLS setArguments (Bundle bundle) of Fragment) this method can be used to send Bundle data packets to Fragment, which is easy to implement.

2. But if, in turn, when we click to trigger the Fragment event, we want to return the data to the Activity. The Activity obtains the data for subsequent operations, that is, Fragment actively transmits data to the Activity, this is what will be explained in detail in this blog post. You can use the interface callback to implement the communication between fragment and activity.

Now let's assume that Fragment1 displays some News windows. Now we need to click the news window (this news window is an Android component, the following code assumes that it is a Button and binds it to the corresponding URL.) return the corresponding uir to Activity and Activity to get the URL of the news window information clicked by the user, then call Fragment2 of the specific news to display the specific News (send the URL to Fragment2 and let Fragment2 load the specific News ).

Core Implementation of Fragment1:

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1. Class Fragment1 extends Fragment {
3. -------
4. Button button;
5. // Bind the button to the website url
6. Button. setText ("www.baidu.com ");
7. -------
8. -------
9. OnMyclikListener myListener;
10. // Define the callback Interface
11. Interface OnMyclikListener {
12. Public void onclik (View v );
13. }
15. // Define the function for the Activity to call
16. Public void setOnclikListener (OnMyclikListener onMyclikListener ){
17. This. myListener = onMyclikListener;
18. }
20. Button. setOnClickListener (new OnClickListener (){
22. @ Override
23. Public void onClick (View v ){
24. // TODO Auto-generated method stub

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1. // Here, the clicked news window (v) is passed to the Activity

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1. System. out. println ("and me ");
2. }
3. });
4. -------
5. -------
6. -------
8. }

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1. Core Implementation of Activity

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1. Class MyActivity extends Activity {
2. -------
3. // Define Fragment1 and add Fragment to Activity.
4. Fragment1 fragment;
5. -------
6. -------
7. // Call the Fragment public function in the Activity. This function is defined above.
8. Fragment. setOnclikListener (new OnMyclikListener ){
9. @ Override
10. Public void onClick (View v ){
11. // TODO Auto-generated method stub
12. // Note that this parameter v is actually the handle of the button in Fragment1. We can use it to access the url bound to the button.
13. Button button = (Button) v;
14. String url = button. getText (). toString ();
15. }
16. }
17. -------
18. -------
19. -------
20. -------
21. }

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1. Sort execution order

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1. 1. First, when we click the button in Fragment1, execute one of the functions in Fragment1.

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1. Button. setOnClickListener (new OnClickListener (){
3. @ Override
4. Public void onClick (View v ){
5. // TODO Auto-generated method stub
6. // Here, the clicked news window (v) is passed to the Activity
7. MyListener. onclik (v );

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1. System. out. println ("and me ");

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1. }
2. );

That is, execute

Public void onClick (View v)

Function, but when

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1. // Here, the clicked news window (v) is passed to the Activity
2. MyListener. onclik (v );

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1. In this statement, the interface function of the defined interface is called and v is used as a parameter. This v is the handle of the clicked button.

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1. Let's take a look at the implementation of this interface function, which is implemented in the Activity, and then executed to the Activity

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1. 2. As mentioned above, the execution is transferred to the Activity, that is, the function of the Activity.

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1. // Call the Fragment public function in the Activity. This function is defined above.
2. Fragment. setOnclikListener (new OnMyclikListener ){
3. @ Override
4. Public void onClick (View v ){
5. // TODO Auto-generated method stub
6. // Note that this parameter v is actually the handle of the button in Fragment1. We can use it to access the url bound to the button.
7. Button button = (Button) v;
8. String url = button. getText (). toString ();
9. }
10. }

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1. After the execution, the Activity obtains the Url passed by Fragment1, enabling Fragment1 to actively pass data to the Activity.

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1. After this function is executed, return to 1 </span>

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1. Button. setOnClickListener (new OnClickListener (){
3. @ Override
4. Public void onClick (View v ){
5. // TODO Auto-generated method stub
6. // Here, the clicked news window (v) is passed to the Activity
7. MyListener. onclik (v );

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1. System. out. println ("and me ");

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1. }
2. );

3. Return to 1 and continue execution

As shown in

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1. In short

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1. 1. The button click event in Fragment1 enables Fragment1 to actively pass the Data Url to the Activity. After the Activity obtains the url, it can perform subsequent operations.

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1. 2. Does the reader actually feel that the interface callback method is similar to the component listener method? Yes, the Android component listening interface is also the callback interface, which is also implemented in this way.