Android : why shape can not be appied to the textview in android

I am a newer to android, and I have got this problem:the shape drawable can not be applied to the textview. The java code in my textview as below:

shape = getResources().getDrawable(R.drawable.shape_tag_round_corner);
this.setBackgroundDrawable(shape);
this.setBackgroundColor(color);
this.setText(roleName);
this.setGravity(Gravity.CENTER);

shape xml file as below:

<shape xmlns:android="http://schemas.android.com/apk/res/android">
<corners android:radius="5dp"></corners>
<padding
    android:left="5dp"
    android:top="0dp"
    android:right="5dp"
    android:bottom="0dp"
/>
</shape>

finally,the textview didnot get the shape and the color setted int the code,why?