if(v == btPre){
btPre.setBackgroundColor(0xffc0c0c0);
String s = tvLevel.getText().toString();
int level = Integer.parseInt(s);
--level;
level = (level-1+TetrisView.MAX_LEVEL) % TetrisView.MAX_LEVEL;
++level;
s = String.valueOf(level);
tvLevel.setText(s);
mLevel = level;
btPre.setBackgroundColor(0x80cfcfcf);
return;
}