Cannot resolve constructor 'ImageButton()'

user_9440466 0
Viewed 109

My goal is to create an image button and be able to change the background image each time the button is clicked. I was having trouble accessing the ImageButton that I designed inside the activity_main.xml file.

This is the MainActivity.java file

package com.example.imageButtonTest;

import androidx.appcompat.app.AppCompatActivity;
import android.view.View;
import android.os.Bundle;
import android.util.Log;
import android.widget.ImageButton;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void foo(View v) {

        ImageButton myButton = new ImageButton(); //error here, might have to pass something inside Imagebutton()

        if(v.getId() == R.id.image_1) { //check if button is clicked
            myButton.setImageResource(R.drawable.imageName); //update to new image (imageName)
        }
    }
}

And this is the activity_main.xml where the ImageButton is declared:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <ImageButton
        android:id="@+id/image_1"
        android:tag="12"
        android:onClick="foo"
        android:background="@drawable/image_1"
        android:layout_width="50dp"
        android:layout_height="50dp">
    </ImageButton>

 </LinearLayout>

This is the error:

Cannot resolve constructor 'ImageButton()'

How can I properly initialize ImageButton so I can change its android:background each time the button is clicked?

android-studio android xml java
2 Answers

ImageButton doesn't have a 0 argument constructor. No View does. They all take a Context at a minimum. new ImageButton(this) would compile. It still wouldn't do what you want though. There is no reason to create a new view here at all. Instead what you want to do is

public void foo(View v) {
    ImageButton myButton = (ImageButton)v;
    myButton.setImageResource(R.drawable.imageName)
}

This will change the image of the existing view. Creating a new button and setting the image on that would do nothing, as your new view isn't in the displayed view root.

user_16311930

This is further to Gabe's detailed answer on the error.

My approach assumes you want to change the ImageButton's background between 2 images say image_one and image_two.

You need to declare a variable to hold the state of the button and toggle the Button - think of on and off switch.

    public class MainActivity extends AppCompatActivity {
    //declare ImageButton here
    ImageButton imageButton;

    //variable for toggling state
    boolean isClicked = false;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //initialize ImageButton here
        imageButton = findViewById(R.id.image_1);
    }

    public void foo(View v) {

        //if statement to check state of the button
        if (isClicked) {

            imageButton.setImageResource(R.drawable.image_one);

            //reverse button state
            isClicked = false;
        } else {
            imageButton.setImageResource(R.drawable.image_two);

            //reverse button state
            isClicked = true;
        }

    }

}

If you have multiple images to set on the button you can go for the Switch Statement instead of If-Statement.

user_78395180
Related