android ObjectAnimator基本应用

上篇博客讲过了ObjectAnimator是继承了ValueAnimator,所以ValueAnimator类方法ObjectAnimator类都可以使用,比如我只想让view在y轴方向平移,如果是纯用动画实现,ValueAnimator是做不了的,而ObjectAnimator就能实现针对View的一些属性进行动画操作,

比如让一个textview透明

ObjectAnimator animator = ObjectAnimator.ofFloat(tv_object_animator,"alpha",1,0,0.5f);
animator.setDuration(2000);
animator.start();

ofFloat()是ObjectAnimator类的静态方法,看下它的方法以及说明

/**
 * Constructs and returns an ObjectAnimator that animates between float values. A single
 * value implies that that value is the one being animated to. Two values imply starting
 * and ending values. More than two values imply a starting value, values to animate through
 * along the way, and an ending value (these values will be distributed evenly across
 * the duration of the animation).
 *
 * @param target The object whose property is to be animated. This object should
 * have a public method on it called setName(), where name is
 * the value of the propertyName parameter.
 * @param propertyName The name of the property being animated.
 * @param values A set of values that the animation will animate between over time.
 * @return An ObjectAnimator object that is set up to animate between the given values.
 */
public static ObjectAnimator ofFloat(Object target, String propertyName, float... values) {
    ObjectAnimator anim = new ObjectAnimator(target, propertyName);
    anim.setFloatValues(values);
    return anim;
}

第一个参数：target是指你应用动画到那个控件上

第二个参数:propertyName是属性的名称,就是你作用于那个view上的动画属性

第二个参数values:是一个可变参数,表示propertyName这个属性值的变化从哪变到哪

现在第一个和第三个值都好说,就是第二个值有时候不知道传啥,我刚开始以为这个属性值都是在ObjectAnimator类中,后来在源码中找了一下没有,然后想想它既然在textview上能起作用,而我们动画作用于view是任意的,所以就想到了这个属性值名称应该在view上,只要在view中找到和动画相关的set方法,把它的形参拷贝进去就行,

比如这样：

public void setTranslationX(float translationX) {
    if (translationX != getTranslationX()) {
        invalidateViewProperty(true, false);
        mRenderNode.setTranslationX(translationX);
        invalidateViewProperty(false, true);

        invalidateParentIfNeededAndWasQuickRejected();
        notifySubtreeAccessibilityStateChangedIfNeeded();
    }
}

只要把translationX当做上面的第二个参数就行,总结下view中常用的和动画有关的set方法

透明度

public void setAlpha(float alpha) {}

旋转

public void setRotation(float rotation) {}

public void setRotationX(float rotationX) {}

public void setRotationY(float rotationY) {}

平移

public void setTranslationX(float translationX) {}

public void setTranslationY(float translationY) {}

缩放

public void setScaleX(float scaleX) {}

public void setScaleY(float scaleY) {}