自定义的 AutoAlphaView

/**
 * Created by GuDong on 2017/3/10 15:47.
 * Contact with ruibin.mao@moji.com.
 */

public class AutoAlphaView extends TextView {
    private static final String TAG = "AutoAlphaView";
    private static final float DEFAULT_ALPHA_VALUE = 0.7f;
    private float mPressedAlphaValue = DEFAULT_ALPHA_VALUE;

    public AutoAlphaView(Context context) {
        this(context, null);
    }

    public AutoAlphaView(Context context, @Nullable AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public AutoAlphaView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init(context, attrs, defStyleAttr);
    }

    private void init(Context context, AttributeSet attrs, int defStyleAttr) {
        final TypedArray attributes = context.getTheme().obtainStyledAttributes(attrs, R.styleable.AutoAlphaView, defStyleAttr, 0);
        mPressedAlphaValue = attributes.getFloat(R.styleable.AutoAlphaView_pressed_alpha_value, DEFAULT_ALPHA_VALUE);
        attributes.recycle();
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                setBackgroundByAlpha(getAlpha(mPressedAlphaValue));
                break;
            case MotionEvent.ACTION_UP:
                setBackgroundByAlpha(255);
                break;
            case MotionEvent.ACTION_CANCEL:
                setBackgroundByAlpha(255);
                break;
        }
        return super.onTouchEvent(event);
    }

    public static int getAlpha(@FloatRange(from = 0, to = 1) float alpha) {
        return (int) (255 * alpha);
    }

    private void setBackgroundByAlpha(@IntRange(from = 0, to = 255) int alpha) {
        Drawable drawableUp = getBackground();
        drawableUp.setAlpha(alpha);
        setBackgroundDrawable(drawableUp);
    }
}

The issue only provides an AutoAlphaView Java snippet and does not name a repository file, test, or requested change. Clarify the intended Android change and its acceptance criteria before locating the relevant entry point and deciding what test or behavior will demonstrate completion.