android: how todivide linear layout elements equally

Question

I have a linear layout with two listviews and two dead buttons. How to divide the space equally between the list views. I got some suggestions like setting the height to 0dip but it didn't work. The graphical layout in eclipse shows a correct layout but when I add different number of elements to the lists they expand to different height. Here is the xml.

<?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:weightSum="2">

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:enabled="false"
        android:text="Installed engines" >
    </Button>

    <ListView
        android:id="@+id/primary"
        android:layout_width="match_parent"
        android:layout_height="0dp" 
        android:layout_weight="1" >
    </ListView>

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:enabled="false"
        android:text="Active engines" >
    </Button>

    <ListView
        android:id="@+id/secondary"
        android:layout_width="match_parent"
        android:layout_height="0dp" 
        android:layout_weight="1" >
    </ListView>

</LinearLayout>

thanks

Since no one believes me here is an image of what I am getting. Just the links since I don't have enough reputation to post pics :( ! run ! eclipse

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After all this may not be xml issue based on this answer Linear Layout and weight in Android

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This is correct for static XML layouts. If you're adding Views dynamically at runtime, you'll need to use addView with layout parameters like addView(button, new LinearLayout.LayoutParams(0, height, 1)); This is true even if you're inflating layouts with the correct width and weight values. – Nuthatch Sep 3 '11 at 21:41

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I do use the layout inflater to add my view to a tab. Maybe that is the problem .. xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Here is sample code that reproduces the problem when I use an inflator.

public class TestActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ParticipantsPanel p = new ParticipantsPanel(this);
        setContentView(p);
    }
}

class ParticipantsPanel extends LinearLayout {
    public ParticipantsPanel(Context ctx) {
        super(ctx);

        LayoutInflater li = LayoutInflater.from(ctx);
        View myView = li.inflate(R.layout.participants, null);
        final ListView primary = (ListView) myView.findViewById(R.id.primary);
        final ListView secondary = (ListView) myView.findViewById(R.id.secondary);
        final ArrayAdapter<String> primaryA = 
            new ArrayAdapter<String>(ctx,R.layout.lvtext);
        final ArrayAdapter<String> secondaryA = 
            new ArrayAdapter<String>(ctx,R.layout.lvtext);

        primaryA.add("hello1");
        primaryA.add("hello2");
        primaryA.add("hello3");
        primaryA.add("hello4");
        primaryA.add("hello5");
        primaryA.add("hello6");
        primaryA.add("hello7");
        primaryA.add("hello8");

        secondaryA.add("select1");
        secondaryA.add("select2");

        primary.setAdapter(primaryA);
        secondary.setAdapter(secondaryA);

        addView(myView);
    }
}

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Yet another update. I think the problem is as Nuthatch ( the guy I referred to from an old post) pointed out : addView() just messes up whatever layout you have in static xml, which is a valuable lesson imo. When I move the code in the ParticipantsPanel to the main activity, and set the view directly without out adding it to another linearlayout, it works as expected. I appreciate an explanation as to why that is the case, and how I may still put my code in a class and have desired behavior.

Answer 1

That code you posted is not a good example. The problem of the two ListViews that don't take equal space when you use the LayoutInflater is because you inflate the layout file without supplying a parent ViewGroup from which to take its LayoutParams.

If you use:

addView(myView, new LinearLayout.LayoutParams(
                LinearLayout.LayoutParams.MATCH_PARENT,
                LinearLayout.LayoutParams.MATCH_PARENT));

or modify the R.layout.participants and replace the parent LinearLayout with a merge tag and also setting:

        this.setOrientation(LinearLayout.VERTICAL);
        this.setWeightSum(2.0f);
        li.inflate(R.layout.participants, this, true);

for the ParticipantsPanel,

then all should be alright.

Answer 2

for vertical orientation , set the height of the weighted views to 0px (or 0dp , or whatver, 0 is a 0 in all units on android) . for horizontal orientation do the same but for width.