ImageView Widget in Android

What you should already KNOW?

You should be familiar with:

1) Creating, building, and running apps in Android Studio

2) Basics of android widgets

Explanation: Image View widget is used to insert the image into an activity. Their are several attributes of the Image View widget. With the help of android:srcCompat attribute we can set the source of the image we want to insert into an activity.

Example:

Xml File:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="169dp"
        app:srcCompat="@mipmap/ic_launcher" />
</RelativeLayout>

In the srcCompat Attribute physical address of the image is passes.

Java file:

package com.youtubevideoplayer.android.imageview;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageView;
public class MainActivity extends AppCompatActivity {
   public ImageView imageView;  // instance of ImageView class is declared as public
   public Boolean flag;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        imageView=(ImageView)findViewById(R.id.imageView);
        flag=true;
        imageView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(flag==true) {
                    imageView.setImageResource(R.mipmap.ic_launcher_round);//changes the image source
                    flag=false;
                }
                else {
                    imageView.setImageResource(R.mipmap.ic_launcher);//changes the image source
                    flag=true;
                }
            }
        });
    }
}

Image view does not requires an java file to be touched(Strictly while working with android studio). But to change the source of the image at the run time of the application java file is used.

Step by step explanation of the java code:

1) Create an instance variable of ImageView class inside the mainActivity class.

2) Assign the ImageView object to the imageView instance like this inside the onCreate() method.

 imageView=(ImageView)findViewById(R.id.imageView);

3) Use method setImageResource of ImageView class to change :

imageView.setImageResource(R.mipmap.ic_launcher_round);

Output Screen: