How to get parent id on Android?

Question

I've tried to get parent id of RadioButton (id of RadioGroup) by

RadioGroup rg = (RadioGroup) arg0.getParent();

but it failed. Following construction

RadioGroup rg = (RadioGroup) findViewById(R.id.radiogr);

works well. How can I get parent id at runtime?

fails with these logs:

12-26 17:11:05.205: E/AndroidRuntime(912): FATAL EXCEPTION: main
12-26 17:11:05.205: E/AndroidRuntime(912): java.lang.ClassCastException: android.widget.LinearLayout
12-26 17:11:05.205: E/AndroidRuntime(912):  at com.letmedraw.shopcart.ShopCartActivity.onCheckedChanged(ShopCartActivity.java:96)
12-26 17:11:05.205: E/AndroidRuntime(912):  at android.widget.RadioGroup.setCheckedId(RadioGroup.java:172)
12-26 17:11:05.205: E/AndroidRuntime(912):  at android.widget.RadioGroup.access$600(RadioGroup.java:52)
12-26 17:11:05.205: E/AndroidRuntime(912):  at android.widget.RadioGroup$CheckedStateTracker.onCheckedChanged(RadioGroup.java:342)
12-26 17:11:05.205: E/AndroidRuntime(912):  at android.widget.CompoundButton.setChecked(CompoundButton.java:127)
12-26 17:11:05.205: E/AndroidRuntime(912):  at android.widget.CompoundButton.toggle(CompoundButton.java:86)
12-26 17:11:05.205: E/AndroidRuntime(912):  at android.widget.RadioButton.toggle(RadioButton.java:69)
12-26 17:11:05.205: E/AndroidRuntime(912):  at android.widget.CompoundButton.performClick(CompoundButton.java:98)
12-26 17:11:05.205: E/AndroidRuntime(912):  at android.view.View$PerformClick.run(View.java:8816)
12-26 17:11:05.205: E/AndroidRuntime(912):  at android.os.Handler.handleCallback(Handler.java:587)
12-26 17:11:05.205: E/AndroidRuntime(912):  at android.os.Handler.dispatchMessage(Handler.java:92)
12-26 17:11:05.205: E/AndroidRuntime(912):  at android.os.Looper.loop(Looper.java:123)
12-26 17:11:05.205: E/AndroidRuntime(912):  at android.app.ActivityThread.main(ActivityThread.java:4627)
12-26 17:11:05.205: E/AndroidRuntime(912):  at java.lang.reflect.Method.invokeNative(Native Method)
12-26 17:11:05.205: E/AndroidRuntime(912):  at java.lang.reflect.Method.invoke(Method.java:521)
12-26 17:11:05.205: E/AndroidRuntime(912):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
12-26 17:11:05.205: E/AndroidRuntime(912):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
12-26 17:11:05.205: E/AndroidRuntime(912):  at dalvik.system.NativeStart.main(Native Method)

Answer 1

android中的所有视图（控件）都是View类型，因此您可以使用getId()来查找id。

int parentId = ((View) arg0.getParent()).getId();

Answer 2

Because getParent() is not RadioGroup value, and not an id either. getParent() returns ViewParent type, not a View.

ViewParent is interface and View is a class.

Answer 3

Just to more clarify the accepted answer, You can get parent Id (in integer form) of view any view, Like this

int parentId = ((View) arg0.getParent()).getId();

And now you can compare id with R.id to take your action. Because ids of all views are saved in R file in Android in integer format.

if (parentId == R.id.your_id) { //
     // Do whatever you want
}

Answer 4

似乎arg0 parent是LinearLayout，而不是Radio组，你正在尝试将它转换为RadioGroup，这就是它抛出异常的原因。