Teach my Apprentice Introduction to Android Development (II)

Objective:

The previous period achieved a simple QQ login effect, this period continues to expand the previous issue

Knowledge points in this issue:

Toast Popup, three ways to implement button click event Monitoring

Body:

Toast Pop-up is simple, make a toast in Android studio, and then press TAB to quickly generate a toast

Toast. Maketext (currentactivity.   Toast.  Length_short). Show ();
The three parameters in parentheses, the first is the context (context, where the toast is displayed), the second is a string string, which is what the toast shows, and the third is the time the toast is displayed, short is the meaning

This will enable the popup toast, I changed the previous popup dialog code into the following code, this refers to the current activity, so that can be omitted to write

About listening to events, maybe I didn't explain it too clearly, take the example above , we let the current activity implemented a listening interface, and then copy its OnClick method, through Findviewbyid find the button instance, Call Setonclicklistener to bind the listener , and then, when the user taps the button, it goes into the OnClick method, By V.getid the ID of the view that the current user clicked, and then into a switch branch statement, the ID is the same as R.id.button, and the branch is executed, that is, a toast is popped, not just the button, the other TextView, LinearLayout the control or the root layout can also set the listener's

I've summed up five ways to implement a time listener, which may not be correct, but it's okay to know the way, not to dwell on the details.

Ways to implement event listeners:

• Inner class Form
• External class Form
• Activity itself as an event listener class
• Anonymous inner class form
• Bind directly to a label

Inner class form

Defines the event listener class within the current class

　　

PublicClass TestExtendsactivity{@OverrideProtectedvoid OnCreate (@Nullable Bundle savedinstancestate) { Span style= "color: #0000ff;" >super.oncreate (Savedinstancestate); Setcontentview (R.layout.activity_main); Button button =new Mybuttonlistener (); Button.setonclicklistener (listener); } class mybuttonlistener implements view.onclicklistener{@Override public void OnClick (View v) {// related event handling             /span>   

Class form of outer class

Test class

Extends activity{    @Override    voidSuperonCreate (savedinstancestate); Setcontentview ( R.layout.activity_main); Button button =new mybuttonlistener (); Button.setonclicklistener (listener);}}     

Mybuttonlistener class

Implements View.onclicklistener {    @Override    void// event handling }}    

activity itself as an event listener class

The activity itself as the event listener class

　　

PublicClass Testextends Activity implements  view.onclicklistener{@Override protected void OnCreate (@Nullable Bundle savedinstancestate) {.oncreate (Savedinstancestate); Setcontentview (R.layout.activity_main); Button button =this); } @Override public void// event handling             /span>    

anonymous inner class form

Publicclass Test extendsprotected void OnCreate (@Nullable Bundle savedinstancestate) {super . OnCreate (Savedinstancestate); Setcontentview (R.layout.activity_main); Button button =new View.onclicklistener () {@Override public void//  event handling  

bind directly to a label

Add the onclick attribute to the XML layout file and set the relevant method

Define a method, remember that the parameter is the view

Want to know more about this one can also look at this: Android development based on the monitoring of event processing

Teach my Apprentice Introduction to Android Development (II)