以编程方式更改Android的查看属性

Question

In general, I'm trying to understand if it's possible in Android to arbitrarily change the properties of a view programmatically.

I understand that there are many properties that can be changed via methods (eg TextView.setBackgroundColor() among many others) but there aren't methods for every possible property.

Specifically, I'm interested in instantiating a custom View and then changing the layout_weight. I'm interested in learning how to do this, but in general I want to know how I'm supposed to create a custom View if I can't change it's properties programmatically. I understand I can change all its properties in xml (including custom xml properties) but I want to be able to instantiate the view at run-time.

Answer 1

layout_ attributes are actually slightly different than most other things as explained in this pro-tip : they're instructions to the parent ViewGroup and are stored in their LayoutParams .

For example, layout_weight in a LinearLayout would be found in LinearLayout.LayoutParams . This means you can change them by doing

LinearLayout.LayoutParams params = 
    (LinearLayout.LayoutParams) yourCustomView.getLayoutParams();
// Set the weight however you like
params.weight = 4.0f;

Creating the view allows you to do this as well:

LinearLayout parentLayout = ...;
YourCustomView yourCustomView = ...;
LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
    LayoutParams.MATCH_PARENT, // width
    LayoutParams.WRAP_CONTENT, // height
    1.0f); // weight
parentLayout.addView(yourCustomView, params);