android动态添加布局时，布局参数不生效

增加父类布局，即要添加到的布局，如下：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

RelativeLayout rl = (RelativeLayout)findViewById(R.id.rl);
RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(
LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
params.width = 200;
params.height = 200;
params.topMargin = 200;
params.leftMargin = 200;

ImageView view = new ImageView(getApplicationContext());
view.setBackgroundResource(R.drawable.ic_launcher);
rl.addView(view, params);
}