设置TextView部分文字的颜色和背景(高亮显示)

public class Test extends Activity {
private String strs="我的心太乱ewrwer了，给我点空白。"; 
    private TextView textview; 
    private Button btn1, btn2;
    private SpannableStringBuilder style;
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
        super.onCreate(savedInstanceState); 
        setContentView(R.layout.main); 
       
        loadView(); 
    } 
    private void loadView(){
    btn1 = (Button) findViewById(R.id.btn1);
    btn2 = (Button) findViewById(R.id.btn2);
    textview = (TextView) findViewById(R.id.tv);
    style=new SpannableStringBuilder(strs); 
    btn1.setText("蓝色");
    btn2.setText("红色");
        btn1.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
        style.setSpan(new BackgroundColorSpan(Color.BLUE),0,strs.length(),Spannable.SPAN_EXCLUSIVE_EXCLUSIVE); 
        textview.setText(style); 
}
});
        btn2.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
        style.setSpan(new BackgroundColorSpan(Color.RED),0,strs.length(),Spannable.SPAN_EXCLUSIVE_EXCLUSIVE); 
        textview.setText(style); 
}
});
    }
}