Android Tip - Displaying App Icons

You often need to display icons in your Android apps. Instead of designing your own, the Android system comes with a set of icons that you can use in your application.

The application icons that come bundled with Android is accessible through the android.R.drawable class.  For example, if you want to display a Share icon on your ImageButton, you simple use the setImageResource() method of the view, like this:

        btnShare = (ImageButton) findViewById(R.id.btnShare);

        btnShare.setImageResource(

            android.R.drawable.ic_menu_share);

The following code snippet shows how you can use Reflection to go through the list of constants defined in the android.R.drawable class and display each icon:

package net.learn2develop.appicons.appicons;

import android.graphics.Color;

import android.support.v7.app.ActionBarActivity;

import android.os.Bundle;

import android.view.Menu;

import android.view.MenuItem;

import android.widget.ImageButton;

import android.widget.LinearLayout;

import android.widget.TextView;

import java.lang.reflect.Field;

public class MainActivity extends ActionBarActivity {

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        //---display all the icons defined in

        // android.R.drawable---

        DisplayDrawables(android.R.drawable.class);

    }

    //---use reflection to examine the fields in a class---

    public void DisplayDrawables(Class _class){

        LinearLayout linearLayout = (LinearLayout)

            findViewById(R.id.linearLayout);

        LinearLayout.LayoutParams lp = new

            LinearLayout.LayoutParams(

                LinearLayout.LayoutParams.WRAP_CONTENT,

                LinearLayout.LayoutParams.WRAP_CONTENT);

        final Field[] fields = _class.getDeclaredFields();

        for (Field field : fields) {

            final int drawableId;

            try {

                drawableId = field.getInt(_class);

                ImageButton imageButton = new

                    ImageButton(this);

                imageButton.setImageResource(drawableId);

                imageButton.setLayoutParams(lp);

                imageButton.setBackgroundColor(

                    Color.TRANSPARENT);

                linearLayout.addView(imageButton);

                TextView txtView = new TextView(this);

                txtView.setText(field.getName());

                imageButton.setLayoutParams(lp);

                imageButton.setBackgroundColor(

                    Color.TRANSPARENT);

                linearLayout.addView(txtView);

            } catch (Exception e) {

                continue;

            }

        }

    }

In the activity_main.xml, you use a ScrollView to contain a LinearLayout:

<ScrollView xmlns:android=

    "http://schemas.android.com/apk/res/android"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent">

    <LinearLayout

        xmlns:tools="http://schemas.android.com/tools"

        android:id="@+id/linearLayout"

        android:layout_width="match_parent"

        android:layout_height="match_parent"

        android:paddingLeft=

            "@dimen/activity_horizontal_margin"

        android:paddingRight=

            "@dimen/activity_horizontal_margin"

        android:paddingTop="@dimen/activity_vertical_margin"

        android:paddingBottom=

            "@dimen/activity_vertical_margin"

        android:orientation="vertical"

        tools:context=

           "net.learn2develop.appicons.appicons.MainActivity">

    </LinearLayout>

</ScrollView>

The following screenshot shows the application icons and their corresponding names: