问题描述
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() {@Overridepublic void onClick(View view) { ObjectAnimator objectAnimator = ObjectAnimator.ofFloat(scrollview, 'translationY', -100f); objectAnimator.setDuration(500); objectAnimator.start();objectAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {@Overridepublic 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: android:layout_width='match_parent' android:layout_height='match_parent'> <LinearLayoutandroid: 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>
问题解答
回答1：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() {@Overridepublic 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(); }});
