Good question! I am wondering the same. Having a good preview in layout editor is really really difficult and it seems to be quite little documentation about what you can and you can't do when "isineditmode" is true (for example, analise custom XML attributes in the incoming AttributeSet on the constructor of the views doesn't seem to work, etc, etc.).
I even have problems with finding views by ID in a custom view. A simple thing like
mTextView = (TextView)myLayout.findViewById(R.id.view_id);
after inflating my custom view layout returns null only when running the layout from the editor (i.e. isineditmode() == true). When running the app on a phone it works.
I leave you here what helped me when trying to better preview my layouts in the layout editor:
1- Finding the views: I use the TAG property, as the findViewWithTag() function does work when in edit mode. So I use the Id for the TAG
<TextView
android:id="@+id/myTextViewId"
android:layout_width="match_parent"
android:layout_height="wrap_content"
...
android:tag="mytextViewId" />
and then find the views using the tag:
if(isineditmode()){
((TextView)myLayout.findViewWithTag("myTextViewId")).setText("Test text");
}
2- Checking some values to know why sometimes my custom view cannot be instantiated in edit mode, or checking if some proerties can be queried in edit mode and know their value. I use a especial textview in the parent layout in which my custom view will be placed, and I leave it hidden and with a special tag:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
...
<com.example.myCustomView ... />
...
<TextView
android:id="@+id/DebugView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:tag="debug"
android:textSize="16sp"
android:textColor="#FFFFFF"
android:visibility="gone"
/>
</LinearLayout>
This linear layout would be the parent of my custom view, and the one I need to open in the layout editor in order to preview my custom view. The "debug" textview visibilty is "gone" so I won't disturb if no needed.
Then, when I need to check something I do the following in the java code of my custom view:
if(isineditmode()){
TextView wDebugView = (TextView)this.getRootView().findViewWithTag("debug");
wDebugView.setVisibility(View.VISIBLE);
wDebugView.setText(Integer.valueOf(getPaddingTop()).toString());
}
In this example I check a property of the view, like the top padding.
Important note: you need to manually convert to String the value to show in the "debug" view, otherwise it will crash and give you an error.
Hope it helps.
And if anyone has some idea of why finding views by id doesn't work, any help would be appreciated.
