android - ScrollView设置layoutParams后无法滚动

问题描述

问 题

ScrollView中包含一个高度远超屏幕的LinearLayout，可以正常滚动。当使用ObjectAnimator把ScrollView向上平移100个px，在updateLisnter中重设ScrollView的高度后，Scrollview没有完全显示，也无法滚动，这是什么原因呢？
代码：

    ll_wrap.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    ObjectAnimator objectAnimator = ObjectAnimator.ofFloat(scrollview, "translationY", -100f);
                    objectAnimator.setDuration(500);
                    objectAnimator.start();
    
                    objectAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
                        @Override
                        public void onAnimationUpdate(ValueAnimator valueAnimator) {
                            //重设ScrollView高度
                            ViewGroup.LayoutParams params = scrollview.getLayoutParams();
                    params.height = (int) (scrollview.getHeight() - (float) valueAnimator.getAnimatedValue());
                    scrollview.setLayoutParams(params);
                        }
                    });
                }
            });
            
布局代码：
<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <LinearLayout
        android:id="@+id/ll_wrap"
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">


        <FrameLayout
            android:background="@color/colorAccent"
            android:layout_width="match_parent"
            android:layout_height="400dp">

        </FrameLayout>
        <FrameLayout
            android:background="@android:color/darker_gray"
            android:layout_width="match_parent"
            android:layout_height="400dp">

        </FrameLayout>
    </LinearLayout>

</ScrollView>

解决方案

首先,很遗憾的告诉你,你的属性动画方法弄错了,translationY这个属性View有,也就是所有的View及其子类都会有,你设置了属性名称,那么它会自动去调用对应的Set方法,比如,你现在这样写,那么它会自动调用View.setTranslationY(float translationY)方法,所以你无需再执行下面的代码:

objectAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
                        @Override
                        public void onAnimationUpdate(ValueAnimator valueAnimator) {
                            ViewGroup.LayoutParams params = scrollview.getLayoutParams();
                            params.height = (int) (params.height + (float)valueAnimator.getAnimatedValue());
                            scrollview.setLayoutParams(params);
                        }
                    });

其次还有个问题,LayoutParams.height 对应的有

        public static final int FILL_PARENT = -1;

        /**
         * Special value for the height or width requested by a View.
         * MATCH_PARENT means that the view wants to be as big as its parent,
         * minus the parent's padding, if any. Introduced in API Level 8.
         */
        public static final int MATCH_PARENT = -1;

        /**
         * Special value for the height or width requested by a View.
         * WRAP_CONTENT means that the view wants to be just large enough to fit
         * its own internal content, taking its own padding into account.
         */
        public static final int WRAP_CONTENT = -2;

你的代码执行起来后,设置的LayoutParams.height<-2,这很明显是不对的,一般都是大于0的.
删掉这段代码块后,如果你希望每次点击都网上平移100px,那么你可以这样写:

ll_wrap.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                float curTranslationY = scrollview.getTranslationY();
                Log.e("test","curTranslationY: "+curTranslationY);
                ObjectAnimator objectAnimator = ObjectAnimator.ofFloat(scrollview, "translationY", curTranslationY,curTranslationY-100f);
                objectAnimator.setDuration(500);
                objectAnimator.start();


            }
        });

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