Android 手写百分比布局

百分比布局:通过设定百分比参数,自动适应手机屏幕,有时候还是比较实用的!
思路:
1:Android 自定义xmlns,百分比布局有2个自定义参数 所有要自定义 ximls
2:自定义百分比布局 继承 相对布局,重写LayoutParams 内部类(这里增加 2个百分比参数)
3:重写 onMeasure( )方法,在onMeasure 里获取容器的宽高,然后获得所有子控件,判断子空间的 LayoutParams 是否为 百分比布局的 LayoutParams,相同则 读取子控件的 长宽百分比 参数,然后计算出实际的长宽参数!

实现:
1: 自定义xmlns,首先 在 res下创建 attr.xml文件 声明一个styleable

<resources>
    <declare-styleable name="percentLayout">
        <attr name="layout_widthPercent" format = "float"> </attr>
         <attr name="layout_heightPercent" format = "float"> </attr>
    </declare-styleable>

</resources>

在 布局文件中添加自定义属性:
eclipse 这样写

http://schemas.android.com/apk/res/你的自定义View所在的包路径.

stuido 使用统一默认的

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

然后 在需要使用的子控件添加 百分比属性

<Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="nice" 
        app:layout_widthPercent="0.6"
        app:layout_heightPercent="0.8"
        android:background="#00ff00"
        />

整个自定义 xmlns 就完成了,接下来实现自定义控件

public class PercentLayout extends RelativeLayout{


    public PercentLayout(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        // TODO Auto-generated constructor stub
    }

    public PercentLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
        // TODO Auto-generated constructor stub
    }

    public PercentLayout(Context context) {
        super(context);
        // TODO Auto-generated constructor stub
    }

    /***
     * 测量容器的宽高
     */
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        // 获取容器的宽高
        int width = MeasureSpec.getSize(widthMeasureSpec);
        int height = MeasureSpec.getSize(heightMeasureSpec);
        //测量子控件的宽高，然后进行改变

        int childCount = getChildCount();
        for (int i = 0; i < childCount; i++) {
            View child = getChildAt(i);
            float widthPercent = 0;
            float heightPercent = 0;
            //获得子控件的布局参数
            ViewGroup.LayoutParams params = child.getLayoutParams();
            //判断是否为百分比布局
            if(params instanceof LayoutParams){
                widthPercent = ((LayoutParams) params).getWidthPercent();
                heightPercent = ((LayoutParams) params).getHeightPerccent();
            }
            if(widthPercent!=0){
                params.width = (int) (width*widthPercent);
                params.height = (int) (height*heightPercent);
            }
        }

        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }

    /***
     * 排列摆放子控件
     */
    @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);
    }

    //布局参数内部类,xml解析会自动关联对应的布局参数
    class LayoutParams extends RelativeLayout.LayoutParams{
        private float widthPercent;
        private float heightPerccent;
        public float getWidthPercent() {
            return widthPercent;
        }

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

        public float getHeightPerccent() {
            return heightPerccent;
        }

        public void setHeightPerccent(float heightPerccent) {
            this.heightPerccent = heightPerccent;
        }

        public LayoutParams(Context arg0, AttributeSet arg1) {
            super(arg0, arg1);
            TypedArray array = arg0.obtainStyledAttributes(arg1, R.styleable.percentLayout);
            widthPercent = array.getFloat(R.styleable.percentLayout_layout_widthPercent, widthPercent);
            heightPerccent = array.getFloat(R.styleable.percentLayout_layout_heightPercent, heightPerccent);
            array.recycle();
        }

        public LayoutParams(int arg0, int arg1) {
            super(arg0, arg1);
        }

        public LayoutParams(ViewGroup.LayoutParams arg0) {
            super(arg0);
        }


        public LayoutParams(MarginLayoutParams arg0) {
            super(arg0);
        }

    }


}

这个自定义控件代码,下面是 整个页面布局

<go.lqb.com.nettest.dn_sindy_layout.PercentLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="400dp"
    android:layout_height="600dp"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    >

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="nice" 
        app:layout_widthPercent="0.6"
        app:layout_heightPercent="0.8"
        android:background="#00ff00"
        />

</go.lqb.com.nettest.dn_sindy_layout.PercentLayout>