[英]java.lang.NullPointerException in xml
這段代碼可以在MainActivity中正常工作,但是我想將一些動畫方法放在不同的類中,然后從那里調用它,但是我遇到一個錯誤,我試圖理解,為什么它向我顯示一個錯誤?
public class AnimationClass extends MainActivity{
private static ImageButton heart_icon,bee_icon;
private static int kill_flag = 0;
private static Animation anim_heart, anim_bee;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
heart_icon=(ImageButton)findViewById(R.id.heart_icon);
bee_icon = (ImageButton)findViewById(R.id.bee_icon);
}
public static void loadAnimations(Activity activity){
anim_heart = AnimationUtils.loadAnimation(activity, R.anim.heart_anim);
heart_icon.startAnimation(anim_heart);
anim_bee = AnimationUtils.loadAnimation(activity, R.anim.bee_anim);
bee_icon.startAnimation(anim_bee);
}
}
動畫:
<set xmlns:android="http://schemas.android.com/apk/res/android"
android:interpolator="@android:anim/accelerate_decelerate_interpolator"
android:shareInterpolator="true">
<scale
android:fillAfter="true"
android:repeatCount="infinite"
android:repeatMode="reverse"
android:duration="1000"
android:fromXScale="1.0"
android:toXScale="1.2"
android:fromYScale="1.0"
android:toYScale="1.2"
android:pivotX="50%"
android:pivotY="50%"/>
<rotate
android:fillAfter="true"
android:repeatCount="infinite"
android:repeatMode="reverse"
android:duration="1200"
android:fromDegrees="-20"
android:toDegrees="15"
android:pivotX="80%"
android:pivotY="20%"/>
<translate
android:fillAfter="true"
android:repeatCount="infinite"
android:repeatMode="reverse"
android:duration="800"
android:toXDelta="5"
android:toYDelta="-5"/>
<alpha
android:fromAlpha="0"
android:toAlpha="1"
android:duration="1500"/>
</set>
中的錯誤: anim_heart = AnimationUtils.loadAnimation(activity, R.anim.heart_anim);
您似乎誤解了靜態變量和方法的工作方式。
當創建AnimationClass
的對象時:
new AnimationClass()
調用onCreate
並正確設置了兩個ImageButtons
。
但是,當您調用靜態方法loadAnimations
,ImageButton變量可能仍為null,這將引發NPE。
不同的解決方案:
檢查空變量:
public static void loadAnimations(Activity activity){ anim_heart = AnimationUtils.loadAnimation(activity, R.anim.heart_anim); if (heart_icon != null) { heart_icon.startAnimation(anim_heart); } anim_bee = AnimationUtils.loadAnimation(activity, R.anim.bee_anim); if (bee_icon != null) { bee_icon.startAnimation(anim_bee); } }
如果作為參數傳遞給loadAnimations
包含有問題的視圖,那么您可能希望在現場找到它們:
public static void loadAnimations(Activity activity){ heart_icon = (ImageButton) activity.findViewById(R.id.heart_icon); bee_icon = (ImageButton) activity.findViewById(R.id.bee_icon); anim_heart = AnimationUtils.loadAnimation(activity, R.anim.heart_anim); heart_icon.startAnimation(anim_heart); anim_bee = AnimationUtils.loadAnimation(activity, R.anim.bee_anim); bee_icon.startAnimation(anim_bee); }
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.