Android 自定义百分比布局

效果图：

思路：
1、编写xml文件，声明自定义属性
2、继承RelativeLayout
3、根据自定义ViewGroup的思想我们一般会在继承之后，创建构造器，然后重写onMeasure、onLayout和onDraw三个方法。这里对onLayout和onDraw方法都不需要进行特别的操作。因为百分比布局，是以该布局作为容器，子控件的宽度跟高度以百分比布局为参考设定。比如你的容器宽200px，子控件设置占容器宽度的0.5则子控件宽度为100px。所以主要是在onMeasure方法中编写代码。
为了支持margin、padding属性重写了generateLayoutParams()方法，并通过返回new LayoutParams(getContext(),attrs)对象解析到自定义的属性，最后在omMeasure方法中获取容器宽和高，遍历子控件，如果子控件的widthPercent或者heightPercent属性不为0就为该子控件的宽度或者高度重新赋值
4、使用自定义布局
代码：
1、声明自定义属性：

<?xml version="1.0" encoding="utf-8"?>
<resources>
<declare-styleable name="percentLayout">
<attr name="widthPercent" format="float"></attr>
<attr name="heightPercent" format="float"></attr>
</declare-styleable>
</resources>

2、自定义百分比布局
（1）定义属性、解析属性 、返回给generateLayoutParams
（2）onMeasure中对子控件遍历、获取属性值、设置宽度或者高度

public class PercentLayout extends RelativeLayout {
public PercentLayout(Context context) {
super(context);
    }

public PercentLayout(Context context, AttributeSet attrs) {

super(context, attrs);

    }
//测量容器宽高
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int width = View.MeasureSpec.getSize(widthMeasureSpec);
int height=View.MeasureSpec.getSize(heightMeasureSpec);
//测量出子控件的宽高
int childcount=getChildCount();
for (int i=0;i<childcount;i++){
            View child=this.getChildAt(i);
            LayoutParams params= (LayoutParams) child.getLayoutParams();
//默认不设置是为0
float widthPercent=0;
float heightPercent=0;
if(params instanceof PercentLayout.LayoutParams){
                widthPercent=((LayoutParams) params).getWidthPercent();
                heightPercent=((LayoutParams) params).getHeightPercent();
if(widthPercent!=0){
//不为0时重新设置宽度
                  params.width= (int) (width*widthPercent);
                }
if(heightPercent!=0){
                    params.height= (int) (height*heightPercent);
                }
            }

        }
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }

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


public  static  class LayoutParams extends RelativeLayout.LayoutParams{
//定义属性
private float widthPercent;
private float heightPercent;

public float getWidthPercent() {
return widthPercent;
        }

public float getHeightPercent() {
return heightPercent;
        }

public LayoutParams(Context context, AttributeSet attrs) {
super(context, attrs);
//解析自己定义的属性
            TypedArray array=context.obtainStyledAttributes(attrs,R.styleable.percentLayout);
             widthPercent=array.getFloat(R.styleable.percentLayout_widthPercent,widthPercent);
             heightPercent=array.getFloat(R.styleable.percentLayout_heightPercent,getHeightPercent());
            array.recycle();

        }

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

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

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


    }
//用于对子控件进行布局
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
super.onLayout(changed, l, t, r, b);
    }
}

3、使用
注意：添加这行代码（AndroidStudio如下，如果是ecplise：xmlns:app="http://schemas.android.com/apk/res/包名+类名）：

 xmlns:app="http://schemas.android.com/apk/res-auto"

使用例子：

<com.df.percentlayout.androidpercentlayout.PercentLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
  >
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:widthPercent="0.8"
        app:heightPercent="0.8"
        android:layout_centerInParent="true"
        android:background="#00ff00"
        android:text="Hello World!" />
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:widthPercent="0.5"
        app:heightPercent="0.3"
        android:layout_centerInParent="true"
        android:background="#ff0000"
        android:text="Hello World!" />

</com.df.percentlayout.androidpercentlayout.PercentLayout>