从源码分析addView子控件match_parent失效问题

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

  /**
     * 
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.
     *
     * 
Note: 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.
     *
     * @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.
     *
     * 
Note: 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.
     *
     * @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.
     *
     * 
Note: 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.
     *
     * @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.
     *
     * 
Note: 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.
     *
     * @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.
     *
     * 
Note: 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.
     *
     * @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.
     *
     * 
Note: 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.
     *
     * @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。