Children of extended LinearLayout defined in XML do not show

问题

In my project I have screens where the same pattern is repeated a lot - it's basically a container for views consisting of a linear layout with the heading, image and specific background. To avoid copying and pasting the same sequence multiple times I thought I could create a compound view, extend LinearLayout and define all the "styling" there, and then just use that component in my layouts. I followed howto's and examples and got my compound view to work. However, all examples I've seen use the resulting view as follows:

<com.myproject.compound.myview
    ...some attrs...
/>

I.e. no children are added via XML. I need to use it like this:

<com.myproject.compound.myview
    ...some attrs...>
    <TextView 
        ..../>
    ...other views...

</com.myproject.compound.myview>

Since I'm extending LinearLayout I was expecting "myview" tag to work like LinearLayout too, but for some reason items I put inside do not get drawn. Is there something I need to do specially to get the inner views to draw?

My extended LinearLayout is very simple, I am not overriding any methods and just calling super in constructor and inflating the layout like this:

    LayoutInflater inflater = (LayoutInflater) context
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        inflater.inflate(R.layout.my_compound_view, this, true);

UPDATE: I thought I'd add an XML as a point of reference:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" 
android:background="@drawable/bg"
android:padding="12dp">
<TextView 
    android:id="@+id/section_title"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:textColor="#FF0000AA"        />
<ImageView
    android:layout_width="match_parent"
    android:layout_height="2dp"
        android:src="@drawable/line"        />
</LinearLayout>

回答1:

Actually found a more elegant solution. Just need to use merge tag instead of LinearLayout in the compound view. All boils down to:

<merge xmlns:android="http://schemas.android.com/apk/res/android"
    <TextView 
        android:id="@+id/section_title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="HEADING"
        android:textColor="#FF0000AA"        />
    <ImageView
        android:layout_width="match_parent"
        android:layout_height="2dp"
        android:src="@drawable/line"        />
</merge>

and

public class CompoundLayout extends LinearLayout{
    public CompoundLayout(Context context, AttributeSet attrs) {
        super(context, attrs);

        LayoutInflater inflater = (LayoutInflater) context
           .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        inflater.inflate(R.layout.compound_layout, this, true);
    }
}

Main layout:

<com.testbench.CompoundLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="#FFFFDDEE"
    android:orientation="vertical">
    <TextView 
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Inner text"
            android:layout_gravity="center_horizontal"/>        
</com.testbench.CompoundLayout>

回答2:

After reading through the Android source and examples I think I figured this one out. Basically in my case it's a hybrid of Compound View and Custom Layout. "Compound view" part takes care about laying out and drawing the content of the XML which specifies the "container". But items inside that container get inflated later on and in my implementation they didn't get laid out. One way is to follow the Custom Layout path - I'd have to implement onLayout() and onMeasure() to properly calculate my children (and I did during my research, it worked). But since I really do not need anything different than what LinearLayout does already and I don't want to copy/paste it's code (those methods are huge there), I just decided to override the method onFinishInflate() and added my "container view" there. Here is the whole code, please comment is something can be improved.

public class CompoundLayout extends LinearLayout{
View mView;
public CompoundLayout(Context context, AttributeSet attrs) {
    super(context, attrs);

    LayoutInflater inflater = (LayoutInflater) context
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        mView = inflater.inflate(R.layout.compound_layout, this, false);
}

@Override
public void onFinishInflate(){
    super.onFinishInflate();
    addView(mView, 0);
}
}

Then in Activity's main layout I just use my custom layout the same way I would use LinearLayout. It renders the same, but always with those TextView and ImageView on top.

来源：https://stackoverflow.com/questions/15488776/children-of-extended-linearlayout-defined-in-xml-do-not-show