如何解决无法将图像分配给Nullable ImageView
如何将图像设置为ImageView?
我的应用程序的想法是根据RecyclerView中的数据类显示不同类型的RecyclerView的视图持有者。数据类如下:
abstract class Thing(open val title: String,open val body: String,open val pic: ImageView?)
data class Movie(override val title: String,override val body: String): Thing(title,body,pic = null)
data class Book(override val title: String,pic = null)
data class Game(override val title: String,override val body: String,override val pic: ImageView?): Thing(title,pic)
此外,我还有一个MainFragment,我在其中手动添加数据。在这里,我试图给出游戏的名称和描述,还将特定的图像设置为game_pic ImageView:
class MainFragment: Fragment() {
private val mMoviesBooksGames = listOf(
Game("Dixit","Give the perfect clue so most (not all) players guess the right surreal image card.",game_pic.setImageResource(R.drawable.alias) as ImageView)
}
}
我如何在game_pic
所在的位置声明GameViewHolder:
class GameViewHolder(inflater: LayoutInflater,parent: ViewGroup) :
ThingViewHolder(inflater.inflate(R.layout.game_list_item,parent,false)) {
private var mGameTitleView: TextView? = null
private var mGameDescriptionView: TextView? = null
private var mGamePicImageView: ImageView? = null
init {
mGameTitleView = itemView.findViewById(R.id.game_title)
mGameDescriptionView = itemView.findViewById(R.id.game_description)
mGamePicImageView = itemView.findViewById(R.id.game_pic)
}
override fun bind(dataToBind: Thing) {
mGameTitleView?.text = ">> Book ${dataToBind.title}"
mGameDescriptionView?.text = dataToBind.body
mGamePicImageView = dataToBind.pic
}
}
使用game_pic.setImageResource(R.drawable.alias) as ImageView
后出现的错误是:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.recyclerview,PID: 822
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.recyclerview/com.example.recyclerview.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setImageResource(int)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3555)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3707)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2220)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:237)
at android.app.ActivityThread.main(ActivityThread.java:8019)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1100)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setImageResource(int)' on a null object reference
at com.example.recyclerview.MainFragment.<init>(MainFragment.kt:33)
at com.example.recyclerview.MainFragment$Companion.newInstance(MainFragment.kt:67)
at com.example.recyclerview.MainActivity.createFragment(MainActivity.kt:4)
at com.example.recyclerview.MainActivity.createFragment(MainActivity.kt:3)
at com.example.recyclerview.SingleFragmentActivity.onCreate(SingleFragmentActivity.kt:25)
at android.app.Activity.performCreate(Activity.java:7957)
at android.app.Activity.performCreate(Activity.java:7946)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1307)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3530)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3707)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2220)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:237)
at android.app.ActivityThread.main(ActivityThread.java:8019)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1100)
I/Process: Sending signal. PID: 822 SIG: 9
解决方法
该错误表明您的game_pic
变量为空。
一种建议的解决方法是我看不到您的代码
private val mMoviesBooksGames = listOf( Game(
"Dixit","Give the perfect clue so most (not all) players guess the right surreal image card.",ImageView(this).apply { setImageResource(R.drawable.alias) })
)
构造ImageView并在非null实例上设置图像资源。
或者,您可以在game_pic
方法中的某个位置初始化onCreateView
,然后在此之后初始化mMoviesBooksGames
。
UPD:
- 您不应将您的视图声明为可为空。
- 您可以用其他方式设置图像资源。
首先,您在mGamePicImageView
中初始化init
,然后在bind
中重写它。其次,您只能将可绘制的数据传递给视图持有者,而不是整个ImageView。
我建议您重新设计数据类:
data class Game(
override val title: String,override val body: String,override val imageDrawable: Drawable)
然后在viewholder的bind方法中
mGamePicImageView.setImageDrawable(dataToBind.imageDrawable)
最后
private val mMoviesBooksGames = listOf( Game(
"Dixit",ContextCompat.getDrawable(this.activity,android.R.drawable.alias))
)
不是getDrawable
的第一个参数是上下文,因此在此处传递片段的父活动。第二个参数是drawable的ID,我不确定是否需要前缀android.
,因此也可以只尝试R.drawable.alias
。
data class Game(
override val title: String,override val image: Int)
像这样修改数据类
override fun bind(dataToBind: Thing) {
mGameTitleView?.text = ">> Book ${dataToBind.title}"
mGameDescriptionView?.text = dataToBind.body
mGamePicImageViewsetImageResource(dataToBind.pic)
}
写完之后,像这样将代码替换到您的视图持有器中
data class Game(
"Dixit",R.drawable.your_pic
)
然后尝试将此值放入您的游戏缺点中。
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