相关疑难解决方法(0)

根据https://developer.android.com/training/material/animations.html

通过该ViewAnimationUtils.createCircularReveal()方法,您可以设置剪贴圆的动画以显示或隐藏视图.

要使用此效果显示以前不可见的视图:

// previously invisible view
View myView = findViewById(R.id.my_view);

// get the center for the clipping circle
int cx = (myView.getLeft() + myView.getRight()) / 2;
int cy = (myView.getTop() + myView.getBottom()) / 2;

// get the final radius for the clipping circle
int finalRadius = Math.max(myView.getWidth(), myView.getHeight());

// create the animator for this view (the start radius is zero)
Animator anim =
    ViewAnimationUtils.createCircularReveal(myView, cx, cy, 0, finalRadius);

// make the view visible and start the …

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所以最近我试图实现一个 FAB，它将扩展到一个新的活动，但在按下 FAB 后它崩溃了。此外，从这个问题，我遵循了实现它的步骤：FloatingActionButton expand into a new Activity

日志猫：

Process: com.example.jovie.canteen, PID: 6953
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setVisibility(int)' on a null object reference
    at com.example.jovie.canteen.Home$1$2.run(Home.java:105)
    at android.os.Handler.handleCallback(Handler.java:739)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:148)
    at android.app.ActivityThread.main(ActivityThread.java:5417)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

主页.java

public class Home extends AppCompatActivity
    implements NavigationView.OnNavigationItemSelectedListener {
CoordinatorLayout homeLayout;

private GoogleApiClient client;
private Toolbar toolbar;
private TabLayout tabLayout;
private ViewPager viewPager;
private RevealLayout mRevealLayout;

View mViewToReveal;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState); …