假设我有一个垂直线性布局:

[v1]
[v2]

默认情况下,v1已经可见= GONE。我想用一个展开动画显示v1,同时下推v2。

我是这样做的:

Animation a = new Animation()
{
    int initialHeight;

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t) {
        final int newHeight = (int)(initialHeight * interpolatedTime);
        v.getLayoutParams().height = newHeight;
        v.requestLayout();
    }

    @Override
    public void initialize(int width, int height, int parentWidth, int parentHeight) {
        super.initialize(width, height, parentWidth, parentHeight);
        initialHeight = height;
    }

    @Override
    public boolean willChangeBounds() {
        return true;
    }
};

但是用这个解决方案,当动画开始时我有一个眨眼。我认为这是由于v1在应用动画之前显示全尺寸。

用javascript,这是一行jQuery!android有什么简单的方法吗?


当前回答

我改编了汤姆·埃斯特兹(Tom Esterez)目前接受的答案,这个答案有效,但动画起伏不定,不太流畅。我的解决方案基本上是用ValueAnimator替换动画,它可以与你选择的Interpolator相匹配,以实现各种效果,如超调、反弹、加速等。

这个解决方案非常适用于具有动态高度的视图(即使用WRAP_CONTENT),因为它首先测量实际所需的高度,然后动画到该高度。

public static void expand(final View v) {
    v.measure(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
    final int targetHeight = v.getMeasuredHeight();

    // Older versions of android (pre API 21) cancel animations for views with a height of 0.
    v.getLayoutParams().height = 1;
    v.setVisibility(View.VISIBLE);

    ValueAnimator va = ValueAnimator.ofInt(1, targetHeight);
    va.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
        public void onAnimationUpdate(ValueAnimator animation) {
            v.getLayoutParams().height = (Integer) animation.getAnimatedValue();
            v.requestLayout();
        }
    });
    va.addListener(new Animator.AnimatorListener() {
        @Override
        public void onAnimationEnd(Animator animation) {
            v.getLayoutParams().height = ViewGroup.LayoutParams.WRAP_CONTENT;
        }

        @Override public void onAnimationStart(Animator animation) {}
        @Override public void onAnimationCancel(Animator animation) {}
        @Override public void onAnimationRepeat(Animator animation) {}
    });
    va.setDuration(300);
    va.setInterpolator(new OvershootInterpolator());
    va.start();
}

public static void collapse(final View v) {
    final int initialHeight = v.getMeasuredHeight();

    ValueAnimator va = ValueAnimator.ofInt(initialHeight, 0);
    va.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
        public void onAnimationUpdate(ValueAnimator animation) {
            v.getLayoutParams().height = (Integer) animation.getAnimatedValue();
            v.requestLayout();
        }
    });
    va.addListener(new Animator.AnimatorListener() {
        @Override
        public void onAnimationEnd(Animator animation) {
            v.setVisibility(View.GONE);
        }

        @Override public void onAnimationStart(Animator animation) {}
        @Override public void onAnimationCancel(Animator animation) {}
        @Override public void onAnimationRepeat(Animator animation) {}
    });
    va.setDuration(300);
    va.setInterpolator(new DecelerateInterpolator());
    va.start();
}

然后你只需调用expand(myView);或崩溃(myView);。

其他回答

我试图做一个我认为非常相似的动画,并找到了一个优雅的解决方案。这段代码假设你总是从0->h或h->0 (h是最大高度)。三个构造函数参数是view =要动画的视图(在我的例子中是webview), targetHeight =视图的最大高度,以及down =一个布尔值,用于指定方向(true =展开,false =折叠)。

public class DropDownAnim extends Animation {
    private final int targetHeight;
    private final View view;
    private final boolean down;

    public DropDownAnim(View view, int targetHeight, boolean down) {
        this.view = view;
        this.targetHeight = targetHeight;
        this.down = down;
    }

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t) {
        int newHeight;
        if (down) {
            newHeight = (int) (targetHeight * interpolatedTime);
        } else {
            newHeight = (int) (targetHeight * (1 - interpolatedTime));
        }
        view.getLayoutParams().height = newHeight;
        view.requestLayout();
    }

    @Override
    public void initialize(int width, int height, int parentWidth,
            int parentHeight) {
        super.initialize(width, height, parentWidth, parentHeight);
    }

    @Override
    public boolean willChangeBounds() {
        return true;
    }
}

好吧,我刚刚发现了一个非常丑陋的解决方案:

public static Animation expand(final View v, Runnable onEnd) {
    try {
        Method m = v.getClass().getDeclaredMethod("onMeasure", int.class, int.class);
        m.setAccessible(true);
        m.invoke(
            v,
            MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED),
            MeasureSpec.makeMeasureSpec(((View)v.getParent()).getMeasuredHeight(), MeasureSpec.AT_MOST)
        );
    } catch (Exception e){
        Log.e("test", "", e);
    }
    final int initialHeight = v.getMeasuredHeight();
    Log.d("test", "initialHeight="+initialHeight);

    v.getLayoutParams().height = 0;
    v.setVisibility(View.VISIBLE);
    Animation a = new Animation()
    {
        @Override
        protected void applyTransformation(float interpolatedTime, Transformation t) {
            final int newHeight = (int)(initialHeight * interpolatedTime);
            v.getLayoutParams().height = newHeight;
            v.requestLayout();
        }

        @Override
        public boolean willChangeBounds() {
            return true;
        }
    };
    a.setDuration(5000);
    v.startAnimation(a);
    return a;
}

请随意提出一个更好的解决方案!

这是非常简单的droidQuery。首先,考虑这样的布局:

<LinearLayout
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="vertical" >
    <LinearLayout
        android:id="@+id/v1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" >
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" 
            android:text="View 1" />
    </LinearLayout>
    <LinearLayout
        android:id="@+id/v2"
        android:layout_width="wrap_content"
        android:layout_height="0dp" >
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" 
            android:text="View 2" />
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" 
            android:text="View 3" />
    </LinearLayout>
</LinearLayout>

我们可以使用下面的代码将高度动画到所需的值-比如100dp:

//convert 100dp to pixel value
int height = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 100, getResources().getDisplayMetrics());

然后使用droidQuery进行动画。最简单的方法是:

$.animate("{ height: " + height + "}", new AnimationOptions());

为了让动画更吸引人,可以考虑添加一个easing:

$.animate("{ height: " + height + "}", new AnimationOptions().easing($.Easing.BOUNCE));

你也可以使用duration()方法改变AnimationOptions上的持续时间,或者处理动画结束时发生的事情。对于一个复杂的例子,试试:

$.animate("{ height: " + height + "}", new AnimationOptions().easing($.Easing.BOUNCE)
                                                             .duration(1000)
                                                             .complete(new Function() {
                                                                 @Override
                                                                 public void invoke($ d, Object... args) {
                                                                     $.toast(context, "finished", Toast.LENGTH_SHORT);
                                                                 }
                                                             }));

是的,我同意上面的评论。事实上,它似乎是正确的(或者至少是最简单的?)事情要做的是指定(在XML中)一个初始布局高度“0px”——然后你可以传递另一个参数“toHeight”(即“最终高度”)到你的自定义动画子类的构造函数,例如,在上面的例子中,它看起来像这样:

    public DropDownAnim( View v, int toHeight ) { ... }

不管怎样,希望这能有所帮助!:)

public static void expand(final View v, int duration, int targetHeight) {
        v.measure(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
        v.getLayoutParams().height = 0;
        v.setVisibility(View.VISIBLE);
        ValueAnimator valueAnimator = ValueAnimator.ofInt(0, targetHeight);
        valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                v.getLayoutParams().height = (int) animation.getAnimatedValue();
                v.requestLayout();
            }
        });
        valueAnimator.setInterpolator(new DecelerateInterpolator());
        valueAnimator.setDuration(duration);
        valueAnimator.start();
    }
public static void collapse(final View v, int duration, int targetHeight) {
    ValueAnimator valueAnimator = ValueAnimator.ofInt(0, targetHeight);
    valueAnimator.setInterpolator(new DecelerateInterpolator());
    valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
        @Override
        public void onAnimationUpdate(ValueAnimator animation) {
            v.getLayoutParams().height = (int) animation.getAnimatedValue();
            v.requestLayout();
        }
    });
    valueAnimator.setInterpolator(new DecelerateInterpolator());
    valueAnimator.setDuration(duration);
    valueAnimator.start();
}