A tentative study of animation (II.)

alphaanimation is a transparency transform animation. It is a subclass of animation, animation is too big, after the next, first look at alphaanimation.

First, Alphaanimation has two attributes:

    Private float Mfromalpha;     Private float Mtoalpha;

See from Mfromalpha change to Mtoalpha. In fact, Alphaanimation's construction method is to set these two functions.

Second, the construction method of Alphaanimation:

1)

    /*** Constructor used when an alphaanimation are loaded from a resource. *      * @paramContext Application Context to use *@paramattrs Attribute set from which to read values*/     Publicalphaanimation (Context context, AttributeSet attrs) {Super(context, attrs); TypedArray a=context.obtainstyledattributes (Attrs, com.android.internal.r.styleable.alphaanimation); Mfromalpha= A.getfloat (Com.android.internal.r.styleable.alphaanimation_fromalpha, 1.0f); Mtoalpha= A.getfloat (Com.android.internal.r.styleable.alphaanimation_toalpha, 1.0f);    A.recycle (); }

This constructor has two input parameters, one is the context, and the other is the set parameter of the component. This setting parameter comes from the configuration of the XML file, and then uses the method inside the Typedarray to take out the parameters set in the XML and assigns values to the attributes. As you can see, if I do not configure Xml,mfromalpha and Mtoalpha will take the default value of 1.0f, the equivalent of a new animation without any changes.

2)

    /**      * Constructor to building a alphaanimation from code     *      @param  fromalpha Star Ting Alpha value for the animation, where 1.0 means     *        fully opaque and 0.0 means fully transparent.      @param Toalpha ending alpha value for the animation.      */     Public Alphaanimation (floatfloat  toalpha) {        = fromalpha;         = toalpha;    }

This is another way to construct alphaanimation. This is easier to understand, which is to assign values directly to Mfromalpha and Mtoalpha.

Third, other methods of alphaanimation.

1,applytransformation:

    /**      * Changes the Alphaproperty of the supplied {@link  Transformation}     * /    @Override     protected void applytransformation (float  interpolatedtime, transformation t) {          Finalfloat alpha = mfromalpha;         + ((mtoalpha-alpha) * interpolatedtime));    }

Visible applytransformation () method is the implementation of the animation, the system will be a relatively high frequency to call this method, I test the frequency of the call is about 40+fps.

We can inherit the alphaanimation class and rewrite the applytransformation () method, if the animation is a function of the horizontal axis for the time, the vertical is the transparency, by default this function is a straight line, We can set the calculation of the mapping of the public test. The system takes dozens of interpolatedtime values per second, and we can list a formula to calculate the transparency of each interpolatedtime mapping.

It's too late for the pit to dig here first.

A tentative study of animation (II.)