用代码来实现selector

       平常我们都是用xml来创建编写selector，最近由于项目需要，需要加载网络图片，问题来了，既要设置drawableTop又要动态加载网络图片？一开始想想没招，后面查找了资料，发现我们平常写的selector.xml其实也可以用代码实现，以下就是相关介绍：

selector.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_pressed="true" android:drawable="@drawable/woman_icon_select"/>
<item android:state_pressed="false" android:drawable="@drawable/woman_icon_default"/>
</selector>

采用代码实现：

StateListDrawable drawable = new StateListDrawable();
Drawable selected = context.getResources().getDrawable(R.drawable.woman_icon_select);
Drawable unSelected = context.getResources().getDrawable(R.drawable.woman_icon_default);
drawable.addState(new int[]{android.R.attr.state_pressed},
selected);
drawable.addState(new int[]{-android.R.attr.state_pressed},
unSelected);
tv.setCompoundDrawablesWithIntrinsicBounds(null, drawable, null, null);

-android.R.attr.state_presses前面加负号代表xml中android:state_pressed="false"

注意里面的“-”号，当XML的设定是false时，就需要使用资源符号的负值来设定。


加载网络图片，记得不能主线程里加载转化为Drawable，否则会导致异常：

new AsyncTask<Void, Void, Drawable>() {

@Override
protected Drawable doInBackground(Void... params) {
StateListDrawable drawable = new StateListDrawable();
Drawable selected = loadImageFromNetwork("http://img0.imgtn.bdimg.com/it/u=919099284,2188508604&fm=15&gp=0.jpg");
Drawable unSelected = loadImageFromNetwork("http://img14.360buyimg.com/n4/g15/M00/04/01/rBEhWlLorJcIAAAAAAKhgJm7YvkAAIPwAI8vyUAAqGY603.jpg");
drawable.addState(new int[]{android.R.attr.state_pressed},
selected);
drawable.addState(new int[]{},
unSelected);
return drawable;
}

@Override
protected void onPostExecute(Drawable drawable) {
super.onPostExecute(drawable);
tv.setCompoundDrawablesWithIntrinsicBounds(null, drawable, null, null);
}

}.execute();

//通过网络地址转为Drawable

private Drawable loadImageFromNetwork(String address) {
Drawable drawable = null;
try {
drawable = Drawable.createFromStream(new URL(address).openStream(), "image.jpg");
} catch (IOException e) {
Log.d("test", e.getMessage());
}
return drawable;
}