我有一个带有数据绑定布局的CustomView类,它接受一个变量.在包含CustomView的布局中,我想将一个属性传递给CustomView,并让该CustomView将该属性传递给它自己的布局绑定.这就是我所拥有的：
public class CustomView extends LinearLayout
{
public CustomView(Context inContext,AttributeSet inAttrs)
{
super(inContext,inAttrs);
inflate(inContext,R.layout.custom_view,null);
}
@BindingAdapter({"app:variable"})
public static void SetVariable(CustomView inCustomView,VariableType inMyVariable)
{
CustomViewBinding binding = DataBindingUtil.getBinding(inCustomView);
binding.setMyVariable(inMyVariable);
}
}
这崩溃试图从视图中提取绑定.这有可能吗？这是堆栈跟踪：
java.lang.NullPointerException: Attempt to invoke virtual method 'void xxx.databinding.CustomViewBinding.setVariableType(xxx.VariableType)' on a null object reference
at xxx.CustomView.SetDynamicList(CustomView.java:32)
at xxx.MyFragmentBinding.executeBindings(MyFragmentBinding.java:116)
at android.databinding.ViewDataBinding.executePendingBindings(ViewDataBinding.java:350)
at android.databinding.ViewDataBinding$6.run(ViewDataBinding.java:167)
at android.databinding.ViewDataBinding$7.doFrame(ViewDataBinding.java:233)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:856)
at android.view.Choreographer.doCallbacks(Choreographer.java:670)
at android.view.Choreographer.doFrame(Choreographer.java:603)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
如果我改变了
DataBindingUtil.getBinding(inCustomView)
至
DataBindingUtil.bind(inCustomView)
然后我明白了：
java.lang.IllegalArgumentException: View is not a binding layout
at android.databinding.DataBindingUtil.bind(DataBindingUtil.java:166)
at android.databinding.DataBindingUtil.bind(DataBindingUtil.java:140)
at xxx.CustomView.SetDynamicList(CustomView.java:30)
- at xxx.databinding.MyFragmentBinding.executeBindings(MyFragmentBinding.java:116)
at android.databinding.ViewDataBinding.executePendingBindings(ViewDataBinding.java:350)
at android.databinding.ViewDataBinding$6.run(ViewDataBinding.java:167)
at android.databinding.ViewDataBinding$7.doFrame(ViewDataBinding.java:233)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:856)
at android.view.Choreographer.doCallbacks(Choreographer.java:670)
at android.view.Choreographer.doFrame(Choreographer.java:603)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
解决方法
您必须绑定膨胀视图以创建数据绑定.在您的示例中,您将绑定布局的容器.
您可以通过多种方式完成此操作.最容易的是将其作为通胀的一部分来约束：
public class CustomView extends LinearLayout
{
CustomViewBinding mBinding;
public CustomView(Context inContext,AttributeSet inAttrs)
{
super(inContext,inAttrs);
LayoutInflater inflater = LayoutInflater.from(inContext);
// I assume you want it inflated into this ViewGroup
mBinding = CustomViewBinding.inflate(inflater,this,true);
}
public void setVariable(CustomView inCustomView,VariableType inMyVariable) {
mBinding.setVariable(inMyVariable);
}
...
}
除非您不希望将setter作为自定义视图的一部分,否则您实际上不需要绑定适配器.在这种情况下,你仍然需要一种方法来获得绑定,所以你需要添加这样的东西：
public CustomViewBinding getBinding() { return mBinding; }
以便您的绑定适配器工作.
如果您知道LinearLayout内容全部来自膨胀视图,您可以使用如下的绑定适配器：
@BindingAdapter({"app:variable"})
public static void setVariable(CustomView inCustomView,VariableType inMyVariable)
{
if (inCustomView.getChildCount() == 0) {
return;
}
View boundView = inCustomView.getChildAt(0);
CustomViewBinding binding = DataBindingUtil.getBinding(boundView);
binding.setMyVariable(inMyVariable);
}
<include layout="@layout/custom_view" app:variable="@{myVariableValue}"/>
当然,您必须将LinearLayout移动到custom_view.xml中.