addView（）方法使用心得
addView方法可以满足动态添加布局需求，于是乎就出现了布局加进去后不是我们想要的效果，我开始以为是我子布局设置了什么属性，仔细看了布局却发现没什么错误，所以猜想大概是addView时出了问题。
我的使用如下：
View view = null;
LayoutInflater layoutInflater = LayoutInflater.from(getContext());
if (true) {
view = layoutInflater.inflate(R.layout.layout_operate_bar_has, null);
} else {
view = layoutInflater.inflate(R.layout.layout_operate_bar_no, null);
}
if (llIntegral.getChildCount() != 0) {
llIntegral.removeAllViews();
}
llIntegral.addView(view);
查看ViewGroup源码addView()方法
ViewGroup 类提供了addView五个重载方法分别如下
/**
* <p>Adds a child view. If no layout parameters are already set on the child, the
* default parameters for this ViewGroup are set on the child.</p>
*
* <p><strong>Note:</strong> do not invoke this method from
* {@link #draw(android.graphics.Canvas)}, {@link #onDraw(android.graphics.Canvas)},
* {@link #dispatchDraw(android.graphics.Canvas)} or any related method.</p>
*
* @param child the child view to add
*
* @see #generateDefaultLayoutParams()
*/
public void addView(View child) {
addView(child, -1);
}
/**
* Adds a child view. If no layout parameters are already set on the child, the
* default parameters for this ViewGroup are set on the child.
*
* <p><strong>Note:</strong> do not invoke this method from
* {@link #draw(android.graphics.Canvas)}, {@link #onDraw(android.graphics.Canvas)},
* {@link #dispatchDraw(android.graphics.Canvas)} or any related method.</p>
*
* @param child the child view to add
* @param index the position at which to add the child
*
* @see #generateDefaultLayoutParams()
*/
public void addView(View child, int index) {
if (child == null) {
throw new IllegalArgumentException("Cannot add a null child view to a ViewGroup");
}
LayoutParams params = child.getLayoutParams();
if (params == null) {
params = generateDefaultLayoutParams();
if (params == null) {
throw new IllegalArgumentException("generateDefaultLayoutParams() cannot return null");
}
}
addView(child, index, params);
}
/**
* Adds a child view with this ViewGroup's default layout parameters and the
* specified width and height.
*
* <p><strong>Note:</strong> do not invoke this method from
* {@link #draw(android.graphics.Canvas)}, {@link #onDraw(android.graphics.Canvas)},
* {@link #dispatchDraw(android.graphics.Canvas)} or any related method.</p>
*
* @param child the child view to add
*/
public void addView(View child, int width, int height) {
final LayoutParams params = generateDefaultLayoutParams();
params.width = width;
params.height = height;
addView(child, -1, params);
}
/**
* Adds a child view with the specified layout parameters.
*
* <p><strong>Note:</strong> do not invoke this method from
* {@link #draw(android.graphics.Canvas)}, {@link #onDraw(android.graphics.Canvas)},
* {@link #dispatchDraw(android.graphics.Canvas)} or any related method.</p>
*
* @param child the child view to add
* @param params the layout parameters to set on the child
*/
@Override
public void addView(View child, LayoutParams params) {
addView(child, -1, params);
}
/**
* Adds a child view with the specified layout parameters.
*
* <p><strong>Note:</strong> do not invoke this method from
* {@link #draw(android.graphics.Canvas)}, {@link #onDraw(android.graphics.Canvas)},
* {@link #dispatchDraw(android.graphics.Canvas)} or any related method.</p>
*
* @param child the child view to add
* @param index the position at which to add the child or -1 to add last
* @param params the layout parameters to set on the child
*/
public void addView(View child, int index, LayoutParams params) {
if (DBG) {
System.out.println(this + " addView");
}
if (child == null) {
throw new IllegalArgumentException("Cannot add a null child view to a ViewGroup");
}
// addViewInner() will call child.requestLayout() when setting the new LayoutParams
// therefore, we call requestLayout() on ourselves before, so that the child's request
// will be blocked at our level
requestLayout();
invalidate(true);
addViewInner(child, index, params, false);
}
查看发现这五个方法都写在一起，挺好找的，相信看到这里，你也会和我一样恍然大悟，原来如此，通常我都是使用addView（View）一个参数的方法,如果我们不指定约束条件，系统就会默认为我们添加约束，
/**
* Adds a child view. If no layout parameters are already set on the child, the
* default parameters for this ViewGroup are set on the child.
*
* <p><strong>Note:</strong> do not invoke this method from
* {@link #draw(android.graphics.Canvas)}, {@link #onDraw(android.graphics.Canvas)},
* {@link #dispatchDraw(android.graphics.Canvas)} or any related method.</p>
*
* @param child the child view to add
* @param index the position at which to add the child
*
* @see #generateDefaultLayoutParams()
*/
public void addView(View child, int index) {
if (child == null) {
throw new IllegalArgumentException("Cannot add a null child view to a ViewGroup");
}
LayoutParams params = child.getLayoutParams();
if (params == null) {
params = generateDefaultLayoutParams();
if (params == null) {
throw new IllegalArgumentException("generateDefaultLayoutParams() cannot return null");
}
}
addView(child, index, params);
}
我们调用addView（view）不指定约束，最后就会调用上面这个方法，最后会调用
/**
* Returns a set of default layout parameters. These parameters are requested
* when the View passed to {@link #addView(View)} has no layout parameters
* already set. If null is returned, an exception is thrown from addView.
*
* @return a set of default layout parameters or null
*/
protected LayoutParams generateDefaultLayoutParams() {
return new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
}
给我们加进去的布局默认指定这个约束。
正确使用
llIntegral.addView(view,new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT));
当然我们也可以指定宽高，系统也为我们特意准了这个方法。