How to Set Opacity (Alpha) for View in Android

Question

I have a button as in the following:

<Button android:text="Submit" android:id="@+id/Button01" android:layout_width="fill_parent" android:layout_height="wrap_content"></Button>

In my onCreate event, I am calling Button01 like this:

setContentView(R.layout.main);

View Button01 = this.findViewById(R.id.Button01);
Button01.setOnClickListener(this);

There is a background in the application, and I want to set an opacity on this submit button. How can I set an opacity for this view? Is it something that I can set on the java side, or can I set in the main.xml file?

On the java side I tried Button01.mutate().SetAlpha(100), but it gave me an error.

Thank you.

Answer 1

android:background="@android:color/transparent"

The above is something that I know... I think creating a custom button class is the best idea

Answer 2

I just found your question while having the similar problem with a TextView. I was able to solve it, by extending TextView and overriding onSetAlpha. Maybe you could try something similar with your button:

import android.content.Context;
import android.util.AttributeSet;
import android.widget.TextView;

public class AlphaTextView extends TextView {

  public AlphaTextView(Context context) {
    super(context);
  }

  public AlphaTextView(Context context, AttributeSet attrs) {
    super(context, attrs);
  }

  public AlphaTextView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
  }

  @Override
  public boolean onSetAlpha(int alpha) {
    setTextColor(getTextColors().withAlpha(alpha));
    setHintTextColor(getHintTextColors().withAlpha(alpha));
    setLinkTextColor(getLinkTextColors().withAlpha(alpha));
    return true;
  }
}