Android - BMI App範例

今天要來撰寫一個簡單計算BMI值的Android App，

這個範例可以練習的基本的Button, TextView應用，

與Button的Click事件，

以下是範例程式碼：

MainActivity.java

package com.example.bmicalculator;

import java.text.DecimalFormat;

import com.example.sqlitetest.R;

import android.os.Bundle;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.graphics.Color;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

 private Button calculateBtn;
 private TextView BMIResult;
 private EditText heightValue;
 private EditText weightValue;
 
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  
  findViewIds();
  setActionListeners();
 }

 @Override
 public boolean onCreateOptionsMenu(Menu menu) {
  // Inflate the menu; this adds items to the action bar if it is present.
  getMenuInflater().inflate(R.menu.main, menu);
  return true;
 }
 
 // 對應元件與其View中的ID
 private void findViewIds() {
  calculateBtn = (Button)findViewById(R.id.CalculateBtn);
  BMIResult = (TextView)findViewById(R.id.BMIResult);
  heightValue = (EditText)findViewById(R.id.HeightValue);
  weightValue = (EditText)findViewById(R.id.WeightValue);
 }
 
 // 設定元件的觸發事件
 private void setActionListeners() {
  calculateBtn.setOnClickListener(
   new OnClickListener() {
    
    @SuppressLint("ShowToast")
    @Override
    public void onClick(View v) {
     // TODO Auto-generated method stub
     
     double height = Double.parseDouble(heightValue.getText().toString());
     double weight = Double.parseDouble(weightValue.getText().toString());
     if(checkValue(new double[]{ height, weight })) {
      doBMIAction(calculateBMI(height, weight));
     } else{
      Toast.makeText(v.getContext(), "Invalid value! Please Check values you enter.",
        Toast.LENGTH_SHORT).show();
     }
    }
   }
  );
 }
 
 // 檢查輸入的值是否正確
 private boolean checkValue(double[] values) {
  boolean isValid = true;
  for(int i = 0; i < values.length; i++) {
   if(values[i] < 0) {
    isValid = false;
    break;
   }
  }
  return isValid;
 }
 
 // 計算BMI值
 private double calculateBMI(double height, double weight) {
  double BMI = 0;
  BMI = weight / Math.pow((height / 100), 2);
  return BMI;
 }
 
 // 根據BMI值顯示顏色
 private void doBMIAction(double BMI) {
  BMIResult.setText((new DecimalFormat("0.0")).format(BMI));
  int color;
  if(BMI > 24) {
   color = Color.RED;
  } else if(BMI < 18.5) {
   color = Color.BLUE;
  } else {
   color = Color.GREEN;
  }
  BMIResult.setTextColor(color);
 }
}

activity_main.xml

<relativelayout android:layout_height="match_parent" android:layout_width="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=".MainActivity" xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools">

    <linearlayout android:layout_alignparentleft="true" android:layout_alignparenttop="true" android:layout_height="wrap_content" android:layout_width="match_parent" android:orientation="vertical">
        <textview android:id="@+id/textView1" android:layout_height="wrap_content" android:layout_width="wrap_content" android:text="@string/HeightText" android:textsize="20dp">
        <edittext android:ems="10" android:id="@+id/HeightValue" android:inputtype="numberDecimal" android:layout_height="wrap_content" android:layout_width="match_parent">
            <requestfocus>
        </requestfocus></edittext>
        <textview android:id="@+id/textView2" android:layout_height="wrap_content" android:layout_width="wrap_content" android:text="@string/WeightText" android:textsize="20dp">
        <edittext android:ems="10" android:id="@+id/WeightValue" android:inputtype="numberDecimal" android:layout_height="wrap_content" android:layout_width="match_parent">
        <button android:id="@+id/CalculateBtn" android:layout_height="wrap_content" android:layout_width="match_parent" android:text="Calculate" android:textsize="20dp">
        <textview android:id="@+id/BMIResult" android:layout_height="match_parent" android:layout_width="match_parent" android:textsize="50dp">
    </textview></button></edittext></textview></textview></linearlayout>
</relativelayout>

因為沒有加其他的Activity或開啟權限，
所以AndroidManifest.xml檔沒有更動。

執行結果：