Question

我想做一个动画，我将图像视图从下到上移动。到目前为止我有这个代码

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login_screen);

    if (savedInstanceState == null) {
        getFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment()).commit();
    }

    ImageView bubbles = (ImageView) findViewById(R.id.bubbles);
    //bubbles.setVisibility(View.GONE);


    Animation animContentUp = AnimationUtils.loadAnimation(this, R.anim.slide_up_service);

    animContentUp.setAnimationListener(new AnimationListener() {
        @Override
        public void onAnimationStart(Animation animation) {
        }

        @Override
        public void onAnimationRepeat(Animation animation) {
        }

        @Override
        public void onAnimationEnd(Animation animation) {
        }
    });

    bubbles.startAnimation(animContentUp);  // line 48
}

slide_up_service.xml

<?xml version="1.0" encoding="utf-8"?>
<translate xmlns:android="http://schemas.android.com/apk/res/android"
      android:duration="700" 
      android:fromXDelta="0%p" 
      android:toXDelta="0%p"
      android:fromYDelta="0%"
      android:toYDelta="120%">
</translate>

但是当我打电话给bubbles.startAnimation(animContentUp);时，它会崩溃。

有谁知道问题是什么？

此外，xml来自一个帖子，询问如何从上到下移动，我怎样才能从头到尾？

由于

05-31 16:49:31.035: E/AndroidRuntime(3026): FATAL EXCEPTION: main
05-31 16:49:31.035: E/AndroidRuntime(3026): java.lang.RuntimeException: Unable to start activity ComponentInfo{android.arin/android.arin.LoginScreen}: java.lang.NullPointerException
05-31 16:49:31.035: E/AndroidRuntime(3026):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2110)
05-31 16:49:31.035: E/AndroidRuntime(3026):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2135)
05-31 16:49:31.035: E/AndroidRuntime(3026):     at android.app.ActivityThread.access$700(ActivityThread.java:143)
05-31 16:49:31.035: E/AndroidRuntime(3026):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1241)
05-31 16:49:31.035: E/AndroidRuntime(3026):     at android.os.Handler.dispatchMessage(Handler.java:99)
05-31 16:49:31.035: E/AndroidRuntime(3026):     at android.os.Looper.loop(Looper.java:137)
05-31 16:49:31.035: E/AndroidRuntime(3026):     at android.app.ActivityThread.main(ActivityThread.java:4950)
05-31 16:49:31.035: E/AndroidRuntime(3026):     at java.lang.reflect.Method.invokeNative(Native Method)
05-31 16:49:31.035: E/AndroidRuntime(3026):     at java.lang.reflect.Method.invoke(Method.java:511)
05-31 16:49:31.035: E/AndroidRuntime(3026):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1004)
05-31 16:49:31.035: E/AndroidRuntime(3026):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:771)
05-31 16:49:31.035: E/AndroidRuntime(3026):     at dalvik.system.NativeStart.main(Native Method)
05-31 16:49:31.035: E/AndroidRuntime(3026): Caused by: java.lang.NullPointerException
05-31 16:49:31.035: E/AndroidRuntime(3026):     at android.arin.LoginScreen.onCreate(LoginScreen.java:48)
05-31 16:49:31.035: E/AndroidRuntime(3026):     at android.app.Activity.performCreate(Activity.java:5177)
05-31 16:49:31.035: E/AndroidRuntime(3026):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1094)
05-31 16:49:31.035: E/AndroidRuntime(3026):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2074)
05-31 16:49:31.035: E/AndroidRuntime(3026):     ... 11 more

Answer 1

NullPointerException可能是指气泡，因此findViewById()找不到您的ImageView。你的身份证了吗？

Answer 2

您无法使用当前布局中不存在的视图。findViewById(R.id.bubbles)这将返回null，因为它位于fragment_loginscreen中，而不是您用作activity_loginscreen的{{1}}活动中的布局

<强>溶液

将您的图片视图放入activity_loginscreen版面，或者只是将活动的布局更改为fragment_loginscreen

Answer 3

bubbles为空，因为在View布局中没有@id/bubbles代码为activity_login_screen的内容。

Android动画崩溃

3 个答案: