android 如何计算Content-Length android:columncount

GridLayout表格布局以  行x列 的形式管理UI组件，

XMLandroid:columnCount="5" //设置列数 android:rowCount="5"//设置行数
android:layout_columnSpan="4" //横向跨几列
android:layout_rowSpan="4"
代码

mGridLayout.setColumnCount(int);//设置列数 
mGridLayout.setRowCount(int);//设置行数

package shortcut.song.com.myapplication;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Gravity;
import android.widget.Button;
import android.widget.GridLayout;

public class GridLayoutActivity extends AppCompatActivity {

    GridLayout mGridLayout;

    String[]  chars = new String[]
            {
                    "7", "8", "9", "/",
                    "4", "5", "6", "*",
                    "1", "2", "3", "-",
                    ".", "0", "=", "+"
            };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_grid_layout);

        mGridLayout = (GridLayout)findViewById(R.id.gridlayout1);
        for( int i=0; i<chars.length; i++ )
        {
            Button btn = new Button(this);
            btn.setText(chars[i]);
            btn.setTextSize(40);
            btn.setMinWidth(30);
            btn.setPadding(5, 35, 5, 35);

            //指定该组件所在的行
            GridLayout.Spec rowSpec = GridLayout.spec(i / 4 + 2);
            //指定该组件所在的列
            GridLayout.Spec columnSpec = GridLayout.spec(i % 4);
            GridLayout.LayoutParams params = new GridLayout.LayoutParams(rowSpec, columnSpec);
            params.setGravity(Gravity.FILL);
            mGridLayout.addView(btn, params);

        }

    }
}

<?xml version="1.0" encoding="utf-8"?>
<GridLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:columnCount="4"
    android:rowCount="6"
    android:id="@+id/gridlayout1"
    >
    <TextView
        android:id="@+id/val_text"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_columnSpan="4"
        android:layout_marginLeft="2pt"
        android:layout_marginRight="2pt"
        android:layout_gravity="right"
        android:padding="3pt"
        android:text="0"
        />
    <Button
        android:id="@+id/clear_btn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_columnSpan="4"
        android:text="Clear"
        />
</GridLayout>