程式學習紀錄

@HasNativeInterpolator
public class AccelerateInterpolator extends BaseInterpolator implements NativeInterpolatorFactory {
    private final float mFactor;
    private final double mDoubleFactor;

    public AccelerateInterpolator() {
        mFactor = 1.0f;
        mDoubleFactor = 2.0;
    }

    /**
     * Constructor
     *
     * @param factor Degree to which the animation should be eased. Seting
     *        factor to 1.0f produces a y=x^2 parabola. Increasing factor above
     *        1.0f  exaggerates the ease-in effect (i.e., it starts even
     *        slower and ends evens faster)
     */
    public AccelerateInterpolator(float factor) {
        mFactor = factor;
        mDoubleFactor = 2 * mFactor;
    }

    public AccelerateInterpolator(Context context, AttributeSet attrs) {
        this(context.getResources(), context.getTheme(), attrs);
    }

    public AccelerateInterpolator(Resources res, Theme theme, AttributeSet attrs) {
        TypedArray a;
        if (theme != null) {
            a = theme.obtainStyledAttributes(attrs, R.styleable.AccelerateInterpolator, 0, 0);
        } else {
            a = res.obtainAttributes(attrs, R.styleable.AccelerateInterpolator);
        }

        mFactor = a.getFloat(R.styleable.AccelerateInterpolator_factor, 1.0f);
        mDoubleFactor = 2 * mFactor;
        setChangingConfiguration(a.getChangingConfigurations());
        a.recycle();
    }

    public float getInterpolation(float input) {
        if (mFactor == 1.0f) {
            return input * input;
        } else {
            return (float)Math.pow(input, mDoubleFactor); // y = t^2f, default f=1, mDoubleFactor=2
        }
    }

    @Override
    public long createNativeInterpolator() {
        return NativeInterpolatorFactoryHelper.createAccelerateInterpolator(mFactor);
    }
}