我正在尝试在按下 FAB 时对卡片视图进行动画处理。我想获得圆形动画。最初，"卡片视图"设置为"不可见"。但是，它在CardView.setVisibility上拖曳空对象引用。
public class FeedFragment extends Fragment {
private FloatingActionButton floatingBtn;
private CardView cardView;
boolean flag = true;
public FeedFragment() {
// Required empty public constructor
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_feed, container, false);
floatingBtn = view.findViewById(R.id.floatBtn);
cardView = view.findViewById(R.id.cardView);
floatingBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if(flag) {
// Check if the runtime version is at least Lollipop
if (Build.VERSION.SDK_INT == Build.VERSION_CODES.LOLLIPOP) {
// get the center for the clipping circle
int cx = cardView.getWidth() / 2;
int cy = cardView.getHeight() / 2;
// get the final radius for the clipping circle
float finalRadius = (float) Math.hypot(cx, cy);
// create the animator for this view (the start radius is zero)
Animator anim =
ViewAnimationUtils.createCircularReveal(cardView, cx, cy, 0, finalRadius);
// make the view visible and start the animation
cardView.setVisibility(View.VISIBLE);
anim.start();
} else {
// set the view to visible without a circular reveal animation below Lollipop
cardView.setVisibility(View.VISIBLE);
}
flag = false;
} else {
// Check if the runtime version is at least Lollipop
if (Build.VERSION.SDK_INT == Build.VERSION_CODES.LOLLIPOP) {
// get the center for the clipping circle
int cx = cardView.getWidth() / 2;
int cy = cardView.getHeight() / 2;
// get the initial radius for the clipping circle
float initialRadius = (float) Math.hypot(cx, cy);
// create the animation (the final radius is zero)
Animator anim =
ViewAnimationUtils.createCircularReveal(cardView, cx, cy, initialRadius, 0);
// make the view invisible when the animation is done
anim.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
super.onAnimationEnd(animation);
cardView.setVisibility(View.INVISIBLE);
}
});
// start the animation
anim.start();
} else {
// set the view to visible without a circular reveal animation below Lollipop
cardView.setVisibility(View.VISIBLE);
}
flag = true;
}
}
});
return view;
}
}
这是 XML 代码
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
tools:context="com.authent.authentication.FeedFragment">
<!-- TODO: Update blank fragment layout -->
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:layout_gravity="bottom">
<android.support.v7.widget.CardView
android:id="@+id/cardView"
android:layout_width="match_parent"
android:layout_height="208dp"
android:layout_gravity="bottom"
android:layout_marginBottom="8dp"
android:layout_marginEnd="16dp"
android:layout_marginRight="16dp"
android:layout_marginStart="16dp"
app:cardCornerRadius="20dp"
android:visibility="gone">
<LinearLayout
android:id="@+id/linearReveal"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:visibility="gone">
<Button
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:background="@color/white"
android:text="Ask a Query"
android:textSize="24dp"
android:textAllCaps="false"
android:textColor="#00ccff"/>
<View
android:layout_width="match_parent"
android:layout_height="1dp"
android:background="@android:color/darker_gray"/>
<Button
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:background="@color/white"
android:text="Share Something"
android:textSize="24dp"
android:textAllCaps="false"
android:textColor="#ff3300"/>
<View
android:layout_width="match_parent"
android:layout_height="1dp"
android:background="@android:color/darker_gray"/>
<Button
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:background="@color/white"
android:text="Post an MCQ"
android:textSize="24dp"
android:textAllCaps="false"
android:textColor="#cc9900"/>
</LinearLayout>
</android.support.v7.widget.CardView>
<android.support.design.widget.FloatingActionButton
android:id="@+id/floatBtn"
android:layout_width="56dp"
android:layout_height="56dp"
android:layout_gravity="end"
android:layout_marginEnd="16dp"
android:layout_marginBottom="16dp"
android:layout_marginRight="16dp"
android:src="@drawable/edit_nick_name" />
</LinearLayout>
有人帮助如何实现圆形动画。我是编程新手。我还尝试使LinearLayout不可见，它也在空对象引用上抛出LinearLayout.setVisibility上的NullPointerException。提前谢谢。
您的CardView为空。根据您的代码，您正在尝试从接收onClick的视图中获取CardView，即FloatingButton。
尝试在侦听器之前在外部调用初始化。理想情况下，与初始化FloatingButton的位置处于同一级别。
在"clickListener"之外灌输卡片视图。
您只需要删除此行cardView = view.findViewById(R.id.cardView);
并粘贴之前
floatingBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
return view;
}