kotlin中使用Java接口,报错Parameter specified as non-null is null
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简述
kotlin中使用Java接口,报错Parameter specified as non-null is null
问题
2021-07-06 09:33:35.053 2317-2317/com.lqbs.piot E/androidRuntime: FATAL EXCEPTION: main
Process: com.lqbs.piot, PID: 2317
java.lang.NullPointerException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkNotNullParameter, parameter hittingNode
原因分析
有一个接口TreeViewControlListener.class
public interface TreeViewControlListener {
int MIN_SCALE = -1;
int FREE_SCALE = 0;
int MAX_SCALE = 1;
void onScaling(int state, int percent);
void onDragMoveNodesHit(NodeModel<?> draggingNode,NodeModel<?> hittingNode,View draggingView,View hittingView);
}
对应实现
binding!!.baseTreeView.setTreeViewControlListener(object : TreeViewControlListener {
override fun onScaling(state: Int, percent: Int) {
...
}
override fun onDragMoveNodesHit(
draggingNode: NodeModel<*>,
hittingNode: NodeModel<*>,
draggingView: View,
hittingView: View
) {
...
}
})
当在java中调用’onDragMoveNodesHit’方法传入null参数时,会crash。如下
if(listener!=null){
listener.onDragMoveNodesHit(draggingNode,null,draggingView,null);
}
解决方案
首先,在java接口中添加@Nullable
注解,这样在自动生成Kotlin实现接口代码时,就会可空,所以改为如下
TreeViewControlListener.class
public interface TreeViewControlListener {
int MIN_SCALE = -1;
int FREE_SCALE = 0;
int MAX_SCALE = 1;
void onScaling(int state, int percent);
void onDragMoveNodesHit(@Nullable NodeModel<?> draggingNode, @Nullable NodeModel<?> hittingNode, @Nullable View draggingView, @Nullable View hittingView);
}
根据实际情况,实现接口代码,添加?
表示可空
override fun onDragMoveNodesHit(
draggingNode: NodeModel<*>?,
hittingNode: NodeModel<*>?,
draggingView: View?,
hittingView: View?
) {
....
}
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