Inflating ImageButton programatically changes width & height params to wrap_content. Why?

Question

In my app I'm using android.support.v7.widget.Toolbar.

Left half of the toolbar always acts as back button.

Right half is different for different activities. Sometimes it's just text, sometimes a button. So I inflate the right half with views programmatically.

Toolbar

<android.support.v7.widget.Toolbar>
...
... <LinearLayout
        android:id="@+id/left_LL"/>
...
<LinearLayout
        android:id="@+id/right_LL"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_centerVertical="true"
        android:orientation="horizontal" />

</android.support.v7.widget.Toolbar>

I'm inflating this view in right_LL:

child_button.xml

<?xml version="1.0" encoding="utf-8"?>
<ImageButton xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/right_IB"
android:layout_width="30dp"
android:layout_height="30dp"
android:src="@drawable/save"
android:background="@null"
android:onClick="onRightHeaderButton"
android:scaleType="fitXY" />

I'm adding it programatically like this:

right_LL.addView(inflater.inflate(R.layout.child_button,
                    null, false));

So the problem is that the button occupies half the screen. It's original dimensions are 512x512.

I thought that maybe the LayoutParams are somehow getting reset, so I also tried

final float scale = getResources().getDisplayMetrics().density;
int pixels = (int) (30 * scale + 0.5f);

right_IB = (ImageButton) right_LL.findViewById(R.id.right_IB);
right_IB.setLayoutParams(new ViewGroup.LayoutParams(
                    pixels,pixels));

it gave this exception:

java.lang.ClassCastException: android.view.ViewGroup$LayoutParams cannot be cast to android.widget.LinearLayout$LayoutParams

Any help will be greatly appreciated.

Answer 1

When you call inflater.inflate(R.layout.child_button, null, false), you are passing in null for the parent view - this causes any layout_ attributes to be ignored (as those attributes are only used by the parent view) - see this Google+ post for more details.

Instead, you should use

inflater.inflate(R.layout.child_button, right_LL, true));

This causes your child_button layout to be inflated properly for its parent layout, right_LL, and automatically added (that's what the true does).

Answer 2

Just by chance I decided to surround my ImageButton with a LinearLayout & it worked!!! So the issue is resolved.

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content">

<ImageButton
    android:id="@+id/right_IB"
    android:layout_width="30dp"
    android:layout_height="30dp"
    android:background="@null"
    android:onClick="onRightHeaderButton"
    android:scaleType="fitXY"
    android:src="@drawable/ic_launcher" />
</LinearLayout>

I don't really know why, but it did. If someone can give me proper explanation for that I'll be great.