content: package com.alexjlockwood.example.delight;
  
  import android.os.Bundle;
  import android.support.v7.app.AppCompatActivity;
  import android.view.View;
  import android.widget.ImageView;
  
  import butterknife.BindView;
  import butterknife.ButterKnife;
  import butterknife.OnClick;
  
  public class AnimalsActivity extends AppCompatActivity {
    private static final int[] STATE_SET_HIPPO =
        {R.attr.state_hippo, -R.attr.state_buffalo, -R.attr.state_elephant};
    private static final int[] STATE_SET_BUFFALO =
        {-R.attr.state_hippo, R.attr.state_buffalo, -R.attr.state_elephant};
    private static final int[] STATE_SET_ELEPHANT =
        {-R.attr.state_hippo, -R.attr.state_buffalo, R.attr.state_elephant};
  
    @BindView(R.id.icon) ImageView iconView;
    @BindView(R.id.hippo) View hippoButton;
    @BindView(R.id.buffalo) View buffaloButton;
    @BindView(R.id.elephant) View elephantButton;
  
    @Override
    protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_animals);
      ButterKnife.bind(this);
    }
  
    @OnClick(R.id.hippo)
    void setHippo() {
      hippoButton.setEnabled(false);
      buffaloButton.setEnabled(true);
      elephantButton.setEnabled(true);
      iconView.setImageState(STATE_SET_HIPPO, true);
    }
  
    @OnClick(R.id.buffalo)
    void setBuffalo() {
      hippoButton.setEnabled(true);
      buffaloButton.setEnabled(false);
      elephantButton.setEnabled(true);
      iconView.setImageState(STATE_SET_BUFFALO, true);
    }
  
    @OnClick(R.id.elephant)
    void setElephant() {
      hippoButton.setEnabled(true);
      buffaloButton.setEnabled(true);
      elephantButton.setEnabled(false);
      iconView.setImageState(STATE_SET_ELEPHANT, true);
    }
  }
  