Android program design logic analysis-user Event Response-Use of callback Functions

 

Note: this series of articles focuses on instance analysis and can be run directly after completing the steps.

 

Example: Add two integers and display the result.

 

1. Create an Android project.

 

2. Edit res/layout/main. xml. Design interface elements.

 

<? Xml version = "1.0" encoding = "UTF-8"?>

<LinearLayout xmlns: android = "http://schemas.android.com/apk/res/android"

Android: orientation = "vertical"

Android: layout_width = "fill_parent"

Android: layout_height = "fill_parent"

>

<EditText

Android: id = "@ + id/int1"

Android: layout_width = "100px"

Android: layout_height = "wrap_content"

Android: text = "0"

/>

 

<EditText

Android: id = "@ + id/int2"

Android: layout_width = "100px"

Android: layout_height = "wrap_content"

Android: text = "0"

/>

<Button

Android: id = "@ + id/submit"

Android: layout_width = "wrap_content"

Android: layout_height = "wrap_content"

Android: text = "executed"

/>

<LinearLayout

Android: orientation = "vertical"

Android: layout_width = "fill_parent"

Android: layout_height = "wrap_content"

>

<TextView

Android: layout_width = "wrap_content"

Android: layout_height = "wrap_content"

Android: text = "The result is"

/>

<TextView

Android: id = "@ + id/result"

Android: layout_width = "wrap_content"

Android: layout_height = "wrap_content"

Android: text = "0"

/>

</LinearLayout>

</LinearLayout>

3. Edit the source file in the src directory.

 

Package com. taisen. android;

 

Import android. app. Activity;

Import android. OS. Bundle;

Import android. view. View;

Import android. view. View. OnClickListener;

Import android. widget. Button;

Import android. widget. TextView;

 

Public class CallBackAddMethodActivity extends Activity {

Public void onCreate (Bundle savedInstanceState ){

Super. onCreate (savedInstanceState );

SetContentView (R. layout. main );

Button B = (Button) findViewById (R. id. submit );

OnClickListener l = new OnClickListener (){

Public void onClick (View v ){

// TODO Auto-generated method stub

TextView int1 = (TextView) findViewById (R. id. int1 );

TextView int2 = (TextView) findViewById (R. id. int2 );

TextView result = (TextView) findViewById (R. id. result );

Int a, B;

A = Integer. parseInt (int1.getText (). toString ());

B = Integer. parseInt (int2.getText (). toString ());

Result. setText (String. valueOf (a + B ));

}

};

B. setOnClickListener (l );

}

}

 

The class that inherits the Activity completes the user-clicked event response.

 

OnClickListener is called to implement the unique onClick (View v) method ). Finally, use setOnClickListener () to map the object to the View.

 

From Yanyun's column