ImageSwitcher安卓NullPointerException
ImageSwitcher安卓NullPointerException
提问于 2018-06-25 18:16:30
我正在使用ImageSwitcher视图在3张图片之间创建一个无限循环。每秒钟都会在视图中显示另一个图像。
我的代码如下..
我收到以下错误消息：
"java.lang.NullPointerException:尝试在空对象引用上调用虚方法'void android.widget.ImageView.setImageResource(int)‘’“
这意味着我没有实例化ImageSwitcher，而我相信我是实例化了。我遗漏了什么？
public class SecAct_Foto_Fragment extends Fragment {
int counter = 0;
View rootView;
private ImageSwitcher pic_image_switch;
private Handler pic_image_switch_handler;
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
rootView = inflater.inflate(R.layout.sec_act_photo_layout, container, false);
pic_image_switch = (ImageSwitcher) rootView.findViewById(R.id.foto_groot_imageswitch);
pic_image_switch_handler = new Handler(Looper.getMainLooper());
pic_image_switch_handler.post(new Runnable() {
@Override
public void run() {
switch (counter) {
case 0:
pic_image_switch.setImageResource(R.drawable.run_mount);
break;
case 1:
pic_image_switch.setImageResource(R.drawable.run_away);
break;
case 2:
pic_image_switch.setImageResource(R.drawable.run_rocks);
break;
}
counter += 1;
if (counter == 3) {
counter = 0;
}
pic_image_switch.postDelayed(this, 1000);
}
});
return rootView;
}
}片段XML：
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:background="@color/white"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageSwitcher
android:id="@+id/foto_groot_imageswitch"
android:layout_width="match_parent"
android:layout_height="220dp"
android:background="@color/black"
android:contentDescription="@string/topscreen_picture_secondactivity"
android:padding="3dp"
android:scaleType="fitXY"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="@drawable/run_rocks"
/>
<ImageView
android:id="@+id/knoppen"
android:layout_width="120dp"
android:layout_height="25dp"
android:layout_marginBottom="264dp"
android:contentDescription="@string/threebuttons_secondact"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintHorizontal_bias="0.501"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:srcCompat="@drawable/but_left" />
</android.support.constraint.ConstraintLayout>回答 2
Stack Overflow用户
回答已采纳
发布于 2018-06-25 18:50:59
val pic_image_switch = findViewById(R.id.imageswitch) as ImageSwitcher
pic_image_switch.setFactory(object : ViewSwitcher.ViewFactory {
override fun makeView(): View {
val imageview = ImageView(this@MainActivity)
return imageview;
}
})
pic_image_switch_handler = Handler();
pic_image_switch_handler!!.post(object : Runnable {
override fun run() {
when (counter) {
0 -> mBinding.imageswitch.setImageResource(R.drawable.ic_pic_one)
1 -> mBinding.imageswitch.setImageResource(R.drawable.ic_pic_two)
2 -> mBinding.imageswitch.setImageResource(R.drawable.ic_pic_three)
}
counter += 1
if (counter === 3) {
counter = 0
}
pic_image_switch_handler!!.postDelayed(this, 1000)
}
})Stack Overflow用户
发布于 2018-06-25 18:42:34
我找到了答案..忘记调用setFactory()方法..为我工作的是什么..
public class SecAct_Foto_Fragment extends Fragment {
int counter = 0;
View rootView;
private ImageSwitcher pic_image_switch;
private Handler pic_image_switch_handler;
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
rootView = inflater.inflate(R.layout.sec_act_photo_layout, container, false);
/*Animation anim_in = AnimationUtils.loadAnimation(getActivity(), R.anim.enter_from_left);
pic_image_switch.setInAnimation(anim_in);*/
//pic_image_switch = new ImageSwitcher(getActivity());
pic_image_switch = (ImageSwitcher) rootView.findViewById(R.id.foto_groot_imageswitch);
pic_image_switch.setFactory(new ViewSwitcher.ViewFactory() {
@Override
public View makeView() {
ImageView imageView = new ImageView(getActivity());
imageView.setScaleType(ImageView.ScaleType.FIT_CENTER);
imageView.setLayoutParams(new ImageSwitcher.LayoutParams(LinearLayout.LayoutParams.FILL_PARENT, LinearLayout.LayoutParams.FILL_PARENT));
return imageView;
}
});
pic_image_switch_handler = new Handler(Looper.getMainLooper());
pic_image_switch_handler.post(new Runnable() {
@Override
public void run() {
switch (counter) {
case 0:
pic_image_switch.setImageResource(R.drawable.run_mount);
break;
case 1:
pic_image_switch.setImageResource(R.drawable.run_away);
break;
case 2:
pic_image_switch.setImageResource(R.drawable.run_rocks);
break;
}
counter += 1;
if (counter == 3) {
counter = 0;
}
pic_image_switch.postDelayed(this, 1000);
}
});
return rootView;
}
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/51021073
复制相关文章
相似问题