计算圆的半径

计应111 杨惠

import java.text.DecimalFormat;

//import org.w3c.dom.Text;

import android.app.Activity;

import android.os.Bundle;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.EditText;

import android.widget.TextView;

public class FormActivity extends Activity implements OnClickListener {

    /** Called when the activity is first created. */

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

        btnOK=(Button) findViewById(R.id.btnOK);

        lbArea=(TextView) findViewById(R.id.lbArea);

        txtR=(EditText) findViewById(R.id.txtR);

        btnOK.setOnClickListener(this);

    }

        Button btnOK;

    TextView lbArea;

    EditText txtR;

 public void onClick(View arg0) {

  // TODO Auto-generated method stub   float r,a;

  r=Float.parseFloat(txtR.getText().toString())

;   a=3.1415f*r*r;

  DecimalFormat df=new DecimalFormat("0.00");

  lbArea.setText(df.format(a));

 }

}

实现框架如下：

计算结果如下：