Android Button setAlpha

Question

There are a set of buttons, I want to get the result:

When I click one of them, first I divide them into two parts: the clicked one and the others. I\'m trying to se

Answer 1

Button btn;

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);   
    setContentView(R.layout.main);  
    btn = (Button) findViewById(R.id.main_btn);  
    Drawable d = getResources().getDrawable(R.drawable.imagen);  
    d.setAlpha(60);  
    btn.setBackgroundDrawable(d);  
}

This works for me :)

Answer 2

Thanks for the question and the answer. This really helped me out.

For my solution, I needed to set the alpha of a button without seeing any animation effect, but the button.setAlpha(x) was failing sporadically. Using animations instead did the trick, but I had to set the duration to zero to get the automatic effect.

alphaDown = new AlphaAnimation(1.0f, 0.3f);
alphaUp = new AlphaAnimation(0.3f, 1.0f);
alphaDown.setDuration(0);
alphaUp.setDuration(0);
alphaDown.setFillAfter(true);
alphaUp.setFillAfter(true);

I use this for player controls in a media application, so I had something like this:

    boolean bInitPrevEnabled = m_btPrev.isEnabled();
    boolean bInitNextEnabled = m_btNext.isEnabled();
    boolean bInitPlayEnabled = m_btPlay.isEnabled();

    m_btPrev.setEnabled(true);
    m_btNext.setEnabled(true);
    m_btPlay.setEnabled(true);

    // Process enabling of the specific buttons depending on the state

    if (bInitPrevEnabled != m_btPrev.isEnabled())
            m_btPrev.startAnimation((m_btPrev.isEnabled()) ? alphaUp : alphaDown);

    if (bInitNextEnabled != m_btNext.isEnabled())
            m_btNext.startAnimation((m_btNext.isEnabled()) ? alphaUp : alphaDown);

    if (bInitPlayEnabled != m_btPlay.isEnabled())
            m_btPlay.startAnimation((m_btPlay.isEnabled()) ? alphaUp : alphaDown);

Answer 3

public void setAlpha (int alpha) - deprecated

public void setAlpha (float alpha) (0f < alpha < 1f) Added in API level 11

Answer 4

Using AlphaAnimation should work; verified on my device.

public class Test extends Activity implements OnClickListener {

    private AlphaAnimation alphaDown;
    private AlphaAnimation alphaUp;
    private Button b1;
    private Button b2;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        LinearLayout ll = (LinearLayout) findViewById(R.id.linear_layout);

        b1 = new Button(this);
        b1.setText("Button 1");
        b1.setOnClickListener(this);
        ll.addView(b1);

        b2 = new Button(this);
        b2.setText("Button 2");
        b2.setOnClickListener(this);
        ll.addView(b2);

        alphaDown = new AlphaAnimation(1.0f, 0.3f);
        alphaUp = new AlphaAnimation(0.3f, 1.0f);
        alphaDown.setDuration(1000);
        alphaUp.setDuration(1000);
        alphaDown.setFillAfter(true);
        alphaUp.setFillAfter(true);
    }

    public void onClick(View v) {
        if (v == b1) {
            b1.startAnimation(alphaUp);
            b2.startAnimation(alphaDown);
        } else {
            b1.startAnimation(alphaDown);
            b2.startAnimation(alphaUp);
        }
    }
}

The key is calling setFillAfter(true) so that the alpha change persists.