<?xml version="1.0" encoding="utf-8"?>
<GridLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:orientation="vertical"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:rowCount="6"
 android:columnCount="4"
 android:id="@+id/root">
 
 <TextView
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:layout_columnSpan="4"
 android:textSize="50sp"
 android:layout_marginLeft="2pt"
 android:layout_marginRight="2pt"
 android:padding="3pt"
 android:layout_gravity="right"
 android:background="#eee"
 android:textColor="#000"
 android:text="0" />
 
 <Button
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:layout_columnSpan="4"
 android:text="清除"/>
 
</GridLayout>

package learn.li.com.learnthree;
 
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Gravity;
import android.widget.Button;
import android.widget.GridLayout;
import android.widget.TextView;
 
import java.util.Timer;
import java.util.TimerTask;
 
public class MainActivity extends AppCompatActivity {
 GridLayout gridLayout;
 String[] chars = new String[]{
  "7","8","9","÷",
  "4","5","6","x",
  "1","2","3","-",
  ".","0","=","="
 };
 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 gridLayout = (GridLayout)findViewById(R.id.root);
 for(int i = 0;i < chars.length;i++){
  Button bn = new Button(this);
  bn.setText(chars[i]);
  bn.setTextSize(40);
  bn.setPadding(5,35,5,35);
  GridLayout.Spec rowSpec = GridLayout.spec(i/4 + 2);
  GridLayout.Spec columnSpec = GridLayout.spec(i%4);
  GridLayout.LayoutParams params = new GridLayout.LayoutParams(rowSpec,columnSpec);
  params.setGravity(Gravity.FILL);
  gridLayout.addView(bn,params);
 
 }
 }
}