android 全屏 屏蔽返回键 代码

public class Algorithm extends Activity {
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// 设置无标题栏
requestWindowFeature(Window.FEATURE_NO_TITLE);
//全屏
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
setContentView(R.layout.algorithm);

}
//屏蔽返回键
public boolean onKeyDown(int keyCode, KeyEvent event) {

switch (keyCode) {
case KeyEvent.KEYCODE_BACK:
return true;
}
return super.onKeyDown(keyCode, event);
}

}