Android ListView动画上的NullPointerError

我有一个

列表视图

嵌入在

线性布局

中，它位于

框架布局

中。我能够在

线性布局

中的其他视图上执行

ObjectAnimation的

，但在

列表视图

上执行动画时收到空指针错误。随附详细信息和错误日志：

所讨论的

列表视图

位于所附布局内：

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/frame"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <!-- CalendarView and ListView -->
    <LinearLayout
        android:id="@+id/layout_contents"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        android:animateLayoutChanges="true" >

        <CalendarView
          android:id="@+id/calendarView1"
          android:layout_width="match_parent"
          android:layout_height="0dp"
          android:layout_weight="3"
          android:background="@drawable/color_border"
         />

        <RelativeLayout
            android:id="@+id/button_relative"
            android:layout_width="match_parent"
            android:layout_height="0dp"
          android:layout_weight="0.3"
            android:background="#807FE817" >

            <ImageButton
                android:id="@+id/change_cols_btn"
                style="?android:attr/buttonStyleSmall"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_centerInParent="true"
                android:background="@drawable/ic_btn_round_more_normal" />

        </RelativeLayout>

        <ListView
            android:id="@+id/listview1"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="3" >
        </ListView>

    </LinearLayout>

    <!-- Header consisting of Month and Day abbreviations -->
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:background="#FFFFFFFF"  >

        <TextView
            android:id="@+id/month_txt"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:text="January"
            android:textSize="20sp"
            android:textStyle="bold"
            android:paddingTop="10dp" />

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            android:paddingTop="10dp" >

            <TextView
                android:id="@+id/sunday_txt"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:gravity="center_horizontal"
                android:text="S" />

            <TextView
                android:id="@+id/monday_txt"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:gravity="center_horizontal"
                android:text="M" />

        </LinearLayout>
    </LinearLayout>
</FrameLayout>

动画在clickListener中运行，代码如下：

expand_btn = (ImageButton)view.findViewById(R.id.change_cols_btn);
expand_btn.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {

int calendarHeight = calendarView1.getHeight();
final float translateBy = calendarHeight * 0.6f;
ObjectAnimator animator;

if (expanded) {

animator = ObjectAnimator.ofFloat(listView, "translationY", - translateBy);
                        animator.setDuration(300);
                        animator.start();

Logcat

中接收到的错误为：

09-18 16:03:15.506: E/AndroidRuntime(24637): FATAL EXCEPTION: main
09-18 16:03:15.506: E/AndroidRuntime(24637): java.lang.NullPointerException
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.animation.PropertyValuesHolder.setupSetterAndGetter(PropertyValuesHolder.java:505)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.animation.ObjectAnimator.initAnimation(ObjectAnimator.java:392)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.animation.ValueAnimator.setCurrentPlayTime(ValueAnimator.java:502)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.animation.ValueAnimator.start(ValueAnimator.java:913)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.animation.ValueAnimator.start(ValueAnimator.java:923)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.animation.ObjectAnimator.start(ObjectAnimator.java:370)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at com.example.eventsmockup.ShowEvents$3.onClick(ShowEvents.java:195)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.view.View.performClick(View.java:4354)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.view.View$PerformClick.run(View.java:17961)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.os.Handler.handleCallback(Handler.java:725)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.os.Handler.dispatchMessage(Handler.java:92)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.os.Looper.loop(Looper.java:137)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.app.ActivityThread.main(ActivityThread.java:5328)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at java.lang.reflect.Method.invokeNative(Native Method)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at java.lang.reflect.Method.invoke(Method.java:511)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at dalvik.system.NativeStart.main(Native Method)

---

非常感谢您的帮助

这是由于代码重复造成的。

您能说得更具体些吗？你是在两次启动动画吗？

09-18 16:03:15.506: E/AndroidRuntime(24637): FATAL EXCEPTION: main
09-18 16:03:15.506: E/AndroidRuntime(24637): java.lang.NullPointerException
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.animation.PropertyValuesHolder.setupSetterAndGetter(PropertyValuesHolder.java:505)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.animation.ObjectAnimator.initAnimation(ObjectAnimator.java:392)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.animation.ValueAnimator.setCurrentPlayTime(ValueAnimator.java:502)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.animation.ValueAnimator.start(ValueAnimator.java:913)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.animation.ValueAnimator.start(ValueAnimator.java:923)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.animation.ObjectAnimator.start(ObjectAnimator.java:370)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at com.example.eventsmockup.ShowEvents$3.onClick(ShowEvents.java:195)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.view.View.performClick(View.java:4354)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.view.View$PerformClick.run(View.java:17961)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.os.Handler.handleCallback(Handler.java:725)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.os.Handler.dispatchMessage(Handler.java:92)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.os.Looper.loop(Looper.java:137)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at android.app.ActivityThread.main(ActivityThread.java:5328)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at java.lang.reflect.Method.invokeNative(Native Method)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at java.lang.reflect.Method.invoke(Method.java:511)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
09-18 16:03:15.506: E/AndroidRuntime(24637):    at dalvik.system.NativeStart.main(Native Method)