Android 动画学习笔记

1、属性动画

使用 ObjectAnimator 的时候，有一点非常重要，那就是操纵的属性要具有 get，set 方法，不然ObjectAnimator 就无法起效。下面这些事一些常用的，可以直接使用属性动画的属性值。translationX ，translationY，scaleX，ScaleY，pivotX，pivotY，x，y，alpha。

但是，有些属性是没有 get set 方法的，那么难道我们就不能用了吗？不是的。

private static class WrapperView{
    private View mTarget;

    public WrapperView(View target){
        mTarget = target;
    }

    public getWidth(){
        return mTarget.getLayoutParams().width;
    }

    public void setWidth(int width){
        mTarget.getLayoutParams().width = width;
        mTarget.requestLayput();
    }
}

// 通过以上代码给属性包了一层，并给它提供了 get set 的方法。使用如下：

WrapperView wrapper = new WrapperView(mButton);
ObjectAnimator.ofInt(wrapper,"width",500).setDuration(5000).start();

类似的，如果想实现视图动画中的AnimationSet，在属性动画中可以使用 PropertyValuesHolder 来实现。

PropertyValuesHolder pvh1 = PropertyValuesHolder.ofFloat("translationX",300f);
PropertyValuesHolder pvh2 = PropertyValuesHolder.ofFloat("scaleX",1f, 0, 1f);
PropertyValuesHolder pvh3 = PropertyValuesHolder.ofFloat("scaleY",1f, 0, 1f);
PropertyValuesHolder pvh1 = PropertyValuesHolder.ofFloat("translationX",1f, 0, 1f);
ObjectAnimator.ofPropertyValuesHolder(view, pvh1, pvh2, pvh3).setDuration(1000).start();

实例：

只展示 activity 中的代码。点击之后，自身变淡，四个方向上弹出四个图标。再点击一次，收回四个图标。

public class PropertyTest extends Activity implements View.OnClickListener {

    private int[] mRes = {R.id.imageView_a, R.id.imageView_b, R.id.imageView_c,
            R.id.imageView_d, R.id.imageView_e};
    private List<ImageView> mImageViews = new ArrayList<ImageView>();
    private boolean mFlag = true;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.property);
        for (int i = 0; i < mRes.length; i++) {
            ImageView imageView = (ImageView) findViewById(mRes[i]);
            imageView.setOnClickListener(this);
            mImageViews.add(imageView);
        }
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.imageView_a:
                if (mFlag) {
                    startAnim();
                } else {
                    closeAnim();
                }
                break;
            default:
                Toast.makeText(PropertyTest.this, "" + v.getId(),
                        Toast.LENGTH_SHORT).show();
                break;
        }
    }

    private void closeAnim() {
        ObjectAnimator animator0 = ObjectAnimator.ofFloat(mImageViews.get(0),
                "alpha", 0.5F, 1F);
        ObjectAnimator animator1 = ObjectAnimator.ofFloat(mImageViews.get(1),
                "translationY", 200F, 0);
        ObjectAnimator animator2 = ObjectAnimator.ofFloat(mImageViews.get(2),
                "translationX", 200F, 0);
        ObjectAnimator animator3 = ObjectAnimator.ofFloat(mImageViews.get(3),
                "translationY", -200F, 0);
        ObjectAnimator animator4 = ObjectAnimator.ofFloat(mImageViews.get(4),
                "translationX", -200F, 0);
        AnimatorSet set = new AnimatorSet();
        set.setDuration(500);
        set.setInterpolator(new BounceInterpolator());
        set.playTogether(animator0, animator1, animator2, animator3, animator4);
        set.start();
        mFlag = true;
    }

    private void startAnim() {
        ObjectAnimator animator0 = ObjectAnimator.ofFloat(
                mImageViews.get(0),
                "alpha",
                1F,
                0.5F);
        ObjectAnimator animator1 = ObjectAnimator.ofFloat(
                mImageViews.get(1),
                "translationY",
                200F);
        ObjectAnimator animator2 = ObjectAnimator.ofFloat(
                mImageViews.get(2),
                "translationX",
                200F);
        ObjectAnimator animator3 = ObjectAnimator.ofFloat(
                mImageViews.get(3),
                "translationY",
                -200F);
        ObjectAnimator animator4 = ObjectAnimator.ofFloat(
                mImageViews.get(4),
                "translationX",
                -200F);
        AnimatorSet set = new AnimatorSet();
        set.setDuration(500);
        set.setInterpolator(new BounceInterpolator());
        set.playTogether(
                animator0,
                animator1,
                animator2,
                animator3,
                animator4);
        set.start();
        mFlag = false;
    }
}

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