Android Tutorial

Android ImageView Example

In Android, you can use “android.widget.ImageView” class to display an image file. Image file is easy to use but hard to master, because of the various screen and dpi in Android devices.

Note
Please refer to this official Android’s “Drawable Resource” and “Screen Support” article for better understand of how image works in Android.

In this tutorial, we didn’t go in deep about dpi and various screen issue, we just use ImageView to display a “png” image, when user click on a button, it will change to another “png” image.

P.S This project is developed in Eclipse 3.7, and tested with Android 2.3.3.

1. Add Image to Resources

Put your images into folder “res/drawable-ldpi“, “res/drawable-mdpi” or “res/drawable-hdpi“.

See figure below, no matter which folder you put, Android will find your image automatically. In this case, both “android.png” and “android3d.png” images are used for demonstration.

2. Add ImageView

Open “res/layout/main.xml” file, just add an ImageView and Button for demonstration. By default, imageView1 will display “android.png”.

File : res/layout/main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >
 
    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/android" />
 
    <Button
        android:id="@+id/btnChangeImage"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Change Image" />
 
</LinearLayout>

3. Code Code

Simple, when button is clicked, change it to “android3d.png”.

File : MyAndroidAppActivity.java

package com.mkyong.android;
 
import android.app.Activity;
import android.os.Bundle;
import android.widget.Button;
import android.widget.ImageView;
import android.view.View;
import android.view.View.OnClickListener;
 
public class MyAndroidAppActivity extends Activity {
 
 Button button;
 ImageView image;
 
 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);
 
  addListenerOnButton();
 
 }
 
 public void addListenerOnButton() {
 
  image = (ImageView) findViewById(R.id.imageView1);
 
  button = (Button) findViewById(R.id.btnChangeImage);
  button.setOnClickListener(new OnClickListener() {
 
   @Override
   public void onClick(View arg0) {
    image.setImageResource(R.drawable.android3d);
   }
 
  });
 
 }
 
}

4. Demo

Run the application.

1. Result, “android.png” is displayed.

2. Click on the button, image will changed to “android3d.png”.