addView() method use experience
The addView method can meet the needs of dynamically adding layouts, so it seems that after the layout is added, it is not the effect we want. I began to think that my sub-layout set some attributes, but I looked at the layout and found that there was nothing wrong, so I guessed it was probably There was a problem with addView.
My use is as follows:
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);
View ViewGroup source code addView() method
The ViewGroup class provides five overloaded methods of addView as follows
/**
* <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);
}
Looking at it, I found that these five methods are all written together. It is very easy to find. I believe that when you see this, you will suddenly realize like me. That is the case, usually I use the method of addView (View) as a parameter, if we don’t specify it Constraints, the system will add constraints for us by default,
/**
* 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);
}
We call addView (view) without specifying constraints, and finally call the above method, and finally call
/**
* 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);
}
The layout we added to specify this constraint by default.
use correctly
llIntegral.addView(view,new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT));
Of course, we can also specify the width and height, and the system has specifically approved this method for us.