编码设置FrameLayout子View的layout_gravity,gravity

方法：

setLayoutParams: 用来设置带有layout前缀的属性，所有子View attach到父View都会有LayoutParams，但是parentView.addView(childView)之前，childView.getLayoutParams（）会返回null。

根据源码：

    public void setLayoutParams(ViewGroup.LayoutParams params) {
        if (params == null) {
            throw new NullPointerException("Layout parameters cannot be null");
        }
        mLayoutParams = params;
        resolveLayoutParams();
        if (mParent instanceof ViewGroup) {
            ((ViewGroup) mParent).onSetLayoutParams(this, params);
        }
        requestLayout();
    }

可以看出要想使setlayoutParams生效，必须有父View，就是调用了addView

setGravity：用来设置内部的子View。

代码：

	mTitleBar = new LinearLayout(context);
    	mTitleBar.setLayoutParams(new LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, 200));
    	mTitleBar.setBackgroundColor(Color.BLACK);

    	TextView textView = new TextView(context);
    	textView.setText("lfjasodijfaodjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj");
    	mTitleBar.addView(textView);
    	LinearLayout.LayoutParams textParams = new LinearLayout.LayoutParams(
    			ViewGroup.LayoutParams.MATCH_PARENT,ViewGroup.LayoutParams.WRAP_CONTENT);
    	textView.setLayoutParams(textParams);
    	textView.setGravity(Gravity.END);

    	mBottomBar = new LinearLayout(context);
    	TextView bottomTV = new TextView(context);
    	bottomTV.setText("lfjasodijfaodjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj");
    	mBottomBar.addView(bottomTV);

    	this.addView(mTitleBar);
    	this.addView(mBottomBar);

    	FrameLayout.LayoutParams frameLayoutParams = new FrameLayout.LayoutParams(FrameLayout.LayoutParams.MATCH_PARENT, 70);
    	frameLayoutParams.gravity = Gravity.TOP;
    	mTitleBar.setLayoutParams(frameLayoutParams);

    	FrameLayout.LayoutParams frameLayoutParams2 = new FrameLayout.LayoutParams(FrameLayout.LayoutParams.MATCH_PARENT, 70);
    	frameLayoutParams2.gravity = Gravity.BOTTOM;
    	mBottomBar.setLayoutParams(frameLayoutParams2);
    	

效果是：

两个TextView，在两个LinearLayout中，上面的TextView gravity是右边。两个LinearyLayout在FrameLayout中layout_gravity一个Top一个Bottom

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