AndroidView v3.0 - Referencing Views in Resource Files

Android Tutorials - Herong's Tutorial Examples

∟AndroidView v3.0 - Referencing Views in Resource Files

This section provides a tutorial example on how to identify and reference layouts or views defined the layout resource file. This is needed to mix layouts and views created in Java code with those defined in the resource file.

With AndroidView version 3, I want to try the mixed approach to develop the UI layout, where major UI layouts and views are defined layout resource files and minor ones are created in Java class code.

In order to mix UI layouts and views defined in the layout resource file to those created in the Java code, I need to learn two 2 new features provided in the Android SDK:

1. Assigning a ID to the layout or view defined in the layout resource file. This can be done using the "id" attribute as shown in the following example:

<someView android:id="@+id/someID"/>

2. Obtaining the reference to the layout or view object defined in the layout resource file. This can be done using the findviewById() method as shown in the following example:

findViewById(R.id.someID);

The next question is what layouts and views should be defined in the layout resource file and what should be created in the Java code. The answer depends on the nature of the application. For my AndroidView version 3, here is what I want:

The screen should display an input form with three blocks: a contact information block, an address block, and an action button block.
The layout of these blocks should be defined in the layout resource file so I can re-arrange it easily later.
Detail fields in each block should be created in the Java code so I can control them with program logics.

So I enhanced .\src\com\herongyang\view\AndroidView.java as follows:

/* AndroidView.java
 * Version 3.0 - Mixing View objects with Layouts from resource file
 * Copyright (c) 2015, HerongYang.com, All Rights Reserved.
 */
package com.herongyang.view;

import android.app.Activity;
import android.os.Bundle;
import android.widget.LinearLayout;
import android.widget.Button;
import android.widget.TextView;
public class AndroidView extends Activity {
   @Override
   public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);

      // Set the top layout as the activity content
      setContentView(R.layout.main);

      // Build detail fields
      LinearLayout l;
      l = (LinearLayout) findViewById(R.id.lContact);
      buildContact(l);
      l = (LinearLayout) findViewById(R.id.lAddress);
      buildAddress(l);
      l = (LinearLayout) findViewById(R.id.lAction);
      buildAction(l);
   }
   public void buildContact(LinearLayout l) {
      TextView v = new TextView(this);
      v.setText("First name: Herong");
      l.addView(v);

      v = new TextView(this);
      v.setText("Last name: Yang");
      l.addView(v);
   }
   public void buildAddress(LinearLayout l) {
      TextView v = new TextView(this);
      v.setText("City: Paris");
      l.addView(v);

      v = new TextView(this);
      v.setText("Country: France");
      l.addView(v);
   }
   public void buildAction(LinearLayout l) {
      Button b = new Button(this);
      b.setText("Submit");
      l.addView(b);

      b = new Button(this);
      b.setText("Cancel");
      l.addView(b);
   }
}

See next tutorials on how to create layout resource file to display the final form. The resource file will define 3 layouts identified as lContact, lAddress and lAction.