* 作 者: 雷恒鑫
* 完成日期: 2012 年 08 月 09 日
* 版 本 号: V1.0
* 对任务及求解方法的描述部分
* 输入描述:
* 问题描述:
* 程序输出:
* 程序头部的注释结束
*/
①Toast页面组件:
Toast页面组件的作用是弹出一个消息框,快速在屏幕上显示一小段信息。
openOptionsDialog()函数增加的代码如下:
private void openOptionsDialog(){
Toast.makeText(Bmi.this, "BMI 计算器", Toast.LENGTH_SHORT).show();
/*注释掉原本的对话框
new AlertDialog.Builder(Bmi.this)
.setTitle(R.string.about_title)
.setMessage(R.string.about_msg)
.setPositiveButton(R.string.ok_lable,
new DialogInterface.OnClickListener(){
public void onClick(
DialogInterface dialoginterface,int i){
}
})
.show();
*/
}
调用“show()”方法来将Taost组件显示在屏幕上
运行结果:
②错误处理:
前面使用XML说明文件定义界面时,在字段的属性中添加了只能输入数字的限制。现在我们将体重(weight)输入的限制移除,允许输入除了整数之外的其他符号(为了可以输入小数点位数的体重)。
打开“res/layout/main.xml”文件,把说明文件中的语句从原本的:
改为:
以上代码增加了“android:singleLine="true"”单行输入的属性。
注意:这样改有一个缺点:当用户在“体重”字段输入了非整数也非浮点数的值时,整个程序就崩溃了 。
因此在下面的程序改进中,使用“try......catch”语句做错误处理,利用“Toast”组件来通知用户他们的输入有误。
try......catch插入的位置如下:
private Button.OnClickListener calcBMI = new Button.OnClickListener() {
public void onClick(View v) {
DecimalFormat nf = new DecimalFormat("0.00");
try{
//EditText fieldheight = (EditText) findViewById(R.id.height);
//EditText fieldweight = (EditText) findViewById(R.id.weight);
double height = Double
.parseDouble(field_height.getText().toString()) / 100;
double weight = Double
.parseDouble(field_weight.getText().toString());
double BMI = weight / (height * height);
//TextView result = (TextView) findViewById(R.id.result);
//result.setText("Your BMI is " + nf.format(BMI));
//Present result
view_result.setText(getText(R.string.bmi_result)+nf.format(BMI));
// Give health advice
// TextView fieldsuggest = (TextView) findViewById(R.id.suggest);
if (BMI > 25) {
view_result.setText(R.string.advice_heavy);
} else if (BMI < 20) {
view_result.setText(R.string.advice_light);
} else {
view_result.setText(R.string.advice_average);
}
openOptionsDialog();
}catch(Exception obj){
Toast.makeText(Bmi.this, "打错了吗?只能输入数字喔", Toast.LENGTH_SHORT).show();
}
};
};
运行结果:
③提取字符串:
为了更好的重用,继续把字符串提取到“res/values/string.xml”中:
............
打错了吗?只能输入数字喔
然后在程序中使用“R.string.inputerror”来取得字符串:
Toast.makeText(Bmi.this, "BMI 计算器", Toast.LENGTH_SHORT).show();
一下是修改后完整的“Bmi.java文件代码:
package com.demo.android.bmi;
import java.text.DecimalFormat;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.res.ColorStateList;
import android.content.res.Resources;
import android.content.res.XmlResourceParser;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnTouchListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class Bmi extends Activity {
/**
* Called when the activity is first created.
*
* @param
*/
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
findViews();
setListensers();
// Listen for button clicks
//Button button = (Button) findViewById(R.id.submit);
//button.setOnClickListener(calcBMI);
}
private Button button_calc;
private EditText field_height;
private EditText field_weight;
private TextView view_result;
private TextView view_suggest;
private void findViews(){
button_calc = (Button)findViewById(R.id.submit);
field_height = (EditText)findViewById(R.id.height);
field_weight = (EditText)findViewById(R.id.weight);
view_result = (TextView)findViewById(R.id.result);
view_suggest = (TextView)findViewById(R.id.suggest);
}
// Listen for button clicks
private void setListensers(){
button_calc.setOnClickListener(calcBMI);
}
private Button.OnClickListener calcBMI = new Button.OnClickListener() {
public void onClick(View v) {
DecimalFormat nf = new DecimalFormat("0.00");
try{
//EditText fieldheight = (EditText) findViewById(R.id.height);
//EditText fieldweight = (EditText) findViewById(R.id.weight);
double height = Double
.parseDouble(field_height.getText().toString()) / 100;
double weight = Double
.parseDouble(field_weight.getText().toString());
double BMI = weight / (height * height);
//TextView result = (TextView) findViewById(R.id.result);
//result.setText("Your BMI is " + nf.format(BMI));
//Present result
view_result.setText(getText(R.string.bmi_result)+nf.format(BMI));
// Give health advice
// TextView fieldsuggest = (TextView) findViewById(R.id.suggest);
if (BMI > 25) {
view_result.setText(R.string.advice_heavy);
} else if (BMI < 20) {
view_result.setText(R.string.advice_light);
} else {
view_result.setText(R.string.advice_average);
}
openOptionsDialog();
}catch(Exception obj){
Toast.makeText(Bmi.this, R.string.input_error, Toast.LENGTH_SHORT).show();
}
}
};
private void openOptionsDialog(){
Toast.makeText(Bmi.this, "BMI 计算器", Toast.LENGTH_SHORT).show();
/*注释掉原本的对话框
new AlertDialog.Builder(Bmi.this)
.setTitle(R.string.about_title)
.setMessage(R.string.about_msg)
.setPositiveButton(R.string.ok_lable,
new DialogInterface.OnClickListener(){
public void onClick(
DialogInterface dialoginterface,int i){
}
})
.show();
*/
}
}
运行结果: