No RelativeLayout id in R.id while Getting dimensions of RelativeLayout

问题

I am trying to get the dimensions of my RelativeLayout.

I am told by many to use the following codes:

    RelativeLayout relativeLayout = (RelativeLayout) findViewById(R.id.myRelativeLayout);
    int layoutWidth = relativeLayout.getWidth();
    int layoutHeight = relativeLayout.getHeight();

My problem is that all the ids I can find in my R.id are all buttons, text views, and all that kind. There is nothing like layout id at all!

Then I try to write:

relativeLayout = (RelativeLayout) findViewById(R.layout.main_activity); 

relativeLayout is null when run. So it is also incorrect.

Do I need to add the layout id manually into R.id? I don't think so.

But why there is no id for the layout in R.id?

回答1:

That depends on what layout do you mean. By default, when you create an activity or a XML layout, it will be stored as R.layout.xxx . But lets say, inside a layout, you have another layout (nested layout in this case), you have to manually "id" the layout that you want to refer to.

For example:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <RelativeLayout
        android:id="@+id/CallMe"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="139dp"
        android:layout_marginTop="130dp" >
    </RelativeLayout>

    <RelativeLayout
        android:layout_width="@+layout/test"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/CallMe"
        android:layout_below="@+id/CallMe"
        android:layout_marginTop="64dp" >
    </RelativeLayout>

</RelativeLayout>

You can then refer to the first relative layout by R.id.CallMe and the second one by R.layout.test

You can name it anything, it doesn't has to be layout or id. Hope that helps

来源：https://stackoverflow.com/questions/17646188/no-relativelayout-id-in-r-id-while-getting-dimensions-of-relativelayout