自定义百分比布局PercentRelativeLayout

随着Android系统版本的不断迭代升级，支持的设备也越来越多，从最初的手机，到现在覆盖watch，TV等，应用越来越广泛，但是暴露出的碎片化问题也愈发突出，设备适配也变成了一个复杂的任务，基于以上问题，编写具有百分比的自定义布局适配各中不同设备显得十分必要。

• 自定义布局首先是自定义属性：

• 其次是继承Relativelayout布局，并重写里面对应的方法:

public class PercentRelativelayout extends RelativeLayout {

    public PercentRelativelayout(Context context) {
        super(context);
    }

    public PercentRelativelayout(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public PercentRelativelayout(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int width = View.MeasureSpec.getSize(widthMeasureSpec);
        int height = View.MeasureSpec.getSize(heightMeasureSpec);

        //测量子控件的高度进行改变
        int childCount = this.getChildCount();
        for (int i = 0; i < childCount; i++) {
            View child = this.getChildAt(i);//每一个子控件
            ViewGroup.LayoutParams layoutParams = child.getLayoutParams();
            //解析自定义进行替换
            float widthPercent = 0;
            float heightPercent = 0;
            if (layoutParams instanceof PercentRelativelayout.LayoutParams) {
                widthPercent = ((LayoutParams) layoutParams).getWidthPercent();
                heightPercent = ((LayoutParams) layoutParams).getHeightPercent();
            }
            if (widthPercent != 0) {
                layoutParams.width = (int) (width * widthPercent);
            }
            if (heightPercent != 0) {
                layoutParams.height = (int) (height * heightPercent);
            }
        }

        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        super.onLayout(changed, l, t, r, b);
    }

    @Override
    public LayoutParams generateLayoutParams(AttributeSet attrs) {
        return new LayoutParams(getContext(), attrs);
    }

    public static class LayoutParams extends RelativeLayout.LayoutParams {

        private float widthPercent;
        private float heightPercent;

        public float getWidthPercent() {
            return widthPercent;
        }

        public void setWidthPercent(float widthPercent) {
            this.widthPercent = widthPercent;
        }

        public float getHeightPercent() {
            return heightPercent;
        }

        public void setHeightPercent(float heightPercent) {
            this.heightPercent = heightPercent;
        }

        public LayoutParams(Context c, AttributeSet attrs) {
            super(c, attrs);
            TypedArray typedArray = c.obtainStyledAttributes(attrs, R.styleable.PercentRelativelayout);
            widthPercent = typedArray.getFloat(R.styleable.PercentRelativelayout_layout_widthPercent, widthPercent);
            heightPercent = typedArray.getFloat(R.styleable.PercentRelativelayout_layout_heightPercent, heightPercent);
            typedArray.recycle();
        }

        public LayoutParams(int w, int h) {
            super(w, h);
        }

        public LayoutParams(ViewGroup.LayoutParams source) {
            super(source);
        }

        public LayoutParams(MarginLayoutParams source) {
            super(source);
        }

        @TargetApi(Build.VERSION_CODES.KITKAT)
        public LayoutParams(RelativeLayout.LayoutParams source) {
            super(source);
        }
    }
}

在该类中重写了onMeasure，generateLayoutParams方法，其中LayoutParams 继承自RelativeLayout.LayoutParams,将百分比布局的属性widthPercent,heightPercent初始化，并封装。
在generateLayoutParams方法中回调LayoutParams 方法，在onMeasure方法中获取并测量子布局大小，若自定义属性widthPercent ，heightPercent 为非空时，设置子布局大小。

• 布局引用：

需要自定义命名空间xmlns:app="http://schemas.android.com/apk/res-auto"， 设置app:layout_widthPercent="0.5" app:layout_heightPercent="0.8"，显示效果如下：

显示效果