布局参数对requestLayout的调用时机？

[qianlima210210]

各位老师：Android代码布局时，为什么红色部分在设置宽度后不调用requestLayout()，二绿色部分必须调用呢？


Button button = new Button(this);
button.setText("Go");
layout.addView(button);

RelativeLayout.LayoutParams btnLayoutParams = (RelativeLayout.LayoutParams)button.getLayoutParams();

btnLayoutParams.width = RelativeLayout.LayoutParams.MATCH_PARENT;
btnLayoutParams.height = RelativeLayout.LayoutParams.WRAP_CONTENT;

btnLayoutParams.addRule(RelativeLayout.BELOW, 14);

button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {

RelativeLayout.LayoutParams btnLayoutParams = (RelativeLayout.LayoutParams)v.getLayoutParams();
btnLayoutParams.width = RelativeLayout.LayoutParams.WRAP_CONTENT;

//更新布局
v.requestLayout();
}
});

[qianlima210210]

楼上真理楼上真理楼上真理

[jklwan]

参考https://blog.csdn.net/cauchyweierstrass/article/details/41445769 可以用setLayoutParams，也可以用requestLayout，否则设置了宽高却并没有重新测量绘制，布局并不会立即改变大小。