在EditText和Variables之间传递数字数据，反之亦然

Question

在下面的代码中，我试图将两个EditText字段中的数值数据传递给两个变量，执行计算（乘法），然后将结果显示在第三个EditText字段中。

我尝试过两种不同的场景，但每当我尝试运行代码时，程序崩溃了。以下是第一个场景：

package edu.arizona.uas.fonji.bmicalculator;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import java.text.DecimalFormat;


public class BmiCalculator extends ActionBarActivity {

Button reset_button, calculate_button;
EditText height_text;  
EditText weight_text; 
EditText bmi_text;





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

    EditText height_text = (EditText)findViewById(R.id.height);       //get value from height text box
    String height_string = height_text.getText().toString();          //convert to string
    final float height_value = Integer.parseInt(height_string);             //convert to number



    EditText weight_text = (EditText)findViewById(R.id.weight);   //get value from weight text box
    String weight_string = weight_text.getText().toString();      //convert to string
    final float weight_value = Integer.parseInt(weight_string);        //convert to number




    calculate_button.setOnClickListener(new View.OnClickListener(){

        @Override
        public void onClick(View v) {
            DecimalFormat df = new DecimalFormat("#.0");
            double adouble = weight_value*height_value;
            bmi_text.setText("Number is " + df.format(adouble));

        }


        });
    }









@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.bmi_calculator, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}
}

由于我试图收集数据并在OnClickListener（）之外转换（height_text和weight_text），导致可能没有收集任何数据我在下面的场景中对其进行了修改，并且我还试图保护从运行时异常，如无效输入，如下所示：

package edu.arizona.uas.fonji.bmicalculator;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import java.text.DecimalFormat;


public class BmiCalculator extends ActionBarActivity {

Button reset_button, calculate_button;
EditText height_text;  
EditText weight_text; 
EditText bmi_text;
TextView myTextView;




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





    calculate_button.setOnClickListener(new View.OnClickListener(){

        @Override
        public void onClick(View v) {
        float height_value = 0;
        float weight_value = 0;

            EditText height_text = (EditText)findViewById(R.id.height);       //get value from height text box

        try{
            String height_string = height_text.getText().toString();          //convert to string
            height_value = Integer.parseInt(height_string);             //convert to number
        }catch(Exception e){
            myTextView.setText("Error, invalid character");
        }


            EditText weight_text = (EditText)findViewById(R.id.weight);   //get value from weight text box

        try{
            String weight_string = weight_text.getText().toString();      //convert to string
            weight_value = Integer.parseInt(weight_string);        //convert to number
        }catch(Exception e){
            myTextView.setText("Error, Invalid character");
        }

            DecimalFormat df = new DecimalFormat("#.0");
            double adouble = weight_value*height_value;
            bmi_text.setText("Number is " + df.format(adouble));

        }


        });
    }



@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.bmi_calculator, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}
}

在任何一种情况下，我仍然无法使其正常工作。我该如何解决这个问题？ .xml代码如下所示：

<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="edu.arizona.uas.fonji.bmicalculator.BmiCalculator" >
<Button
    android:id="@+id/reset"
    android:layout_width="300dp"
    android:layout_height="wrap_content"
    android:layout_above="@+id/calculate"
    android:layout_alignParentLeft="true"
    android:layout_centerHorizontal="true"
    android:layout_marginBottom="26dp"
    android:text="reset" />

<Button
    android:id="@+id/calculate"
    android:layout_width="300dp"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:layout_alignParentLeft="true"
    android:layout_marginBottom="37dp"
    android:text="calculate" />

<EditText
    android:id="@+id/height"
    android:layout_width="100dp"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_marginTop="16dp"
    android:ems="10"
    android:inputType="number"
    android:hint="height"  >


</EditText>

<EditText
    android:id="@+id/weight"
    android:layout_width="100dp"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/height"
    android:layout_below="@+id/height"
    android:ems="10"
    android:hint="weight"
    android:inputType="number" 
    />

<EditText
    android:id="@+id/bmi"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/weight"
    android:layout_below="@+id/weight"
    android:layout_marginTop="36dp"
    android:ems="10" 
    android:hint="bmi">

    <requestFocus />
</EditText>

<TextView
    android:id="@+id/report_error"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignRight="@+id/reset"
    android:layout_alignTop="@+id/height"
    android:padding="24dp"
    />

</RelativeLayout>