Get specific drawable from state list drawable

问题

I have a state list drawable, and i want to get a specific drawable from the state list drawable:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android" xmlns:kplus="http://schemas.android.com/apk/res-auto">


    <item kplus:key_type_space_alt="true" android:state_pressed="true" android:drawable="@drawable/space_1_pressed" />
    <item kplus:key_type_space_alt="true" android:drawable="@drawable/space_1_normal" />

    <!-- TopNav keys. -->

    <item kplus:key_type_topnav="true" android:state_pressed="true" android:drawable="@drawable/tab_down" />
    <item kplus:key_type_topnav="true" android:state_selected="true" android:drawable="@drawable/tab_down" />
    <item kplus:key_type_topnav="true" android:drawable="@drawable/tab_normal" />

    <!-- TopRow keys. -->

    <item kplus:key_type_toprow="true" android:state_pressed="true" android:drawable="@drawable/numeric_presseed" />
    <item kplus:key_type_toprow="true" android:drawable="@drawable/numeric_normal" />
</selector>

I select the correct drawable state for each key, something like this:

if (keyIsNumbers) {
    if (KPlusInputMethodService.sNumbersState == 2) {
        drawableState = mDrawableStatesProvider.KEY_STATE_TOPNAV_CHECKED;
    }
}

Now the states are defined like this:

KEY_STATE_TOPNAV_NORMAL = new int[] {keyTypeTopNavAttrId};
KEY_STATE_TOPNAV_PRESSED = new int[] {keyTypeTopNavAttrId, android.R.attr.state_pressed};
KEY_STATE_TOPNAV_CHECKED = new int[] {keyTypeTopNavAttrId, android.R.attr.state_selected};

Now my question is how to extract the correct drawable for each state ? I need to get the 9patch padding of the drawable, because if the state have different padding on 9patch it will get the padding only for the top drawable, and i want to set the padding manually for each key (drawable.getPadding(rect)).

回答1:

There is no public API to get the drawable from the state.

There are some methods in StateListDrawable but they are @hide with the comment "pending API council".

You can invoke them by reflection... but it's at your own risk !!!. (it may change in future releases)

Those methods are :

• getStateDrawableIndex
• getStateDrawable

Here is how to proceed (exceptions omitted) :

int[] currentState = view.getDrawableState();
StateListDrawable stateListDrawable = (StateListDrawable)view.getBackground();
Method getStateDrawableIndex = StateListDrawable.class.getMethod("getStateDrawableIndex", int[].class);
Method getStateDrawable = StateListDrawable.class.getMethod("getStateDrawable", int.class);
int index = (int) getStateDrawableIndex.invoke(stateListDrawable,currentState);
Drawable drawable = (Drawable) getStateDrawable.invoke(stateListDrawable,index);

来源：https://stackoverflow.com/questions/26713618/get-specific-drawable-from-state-list-drawable