我有一段代码，我一直在处理四种转换比率，具体取决于微调器中选择的单位转换选项。根据用户选择的内容，我将如何调用每个单独的比率。
例如，如果在微调器中选择了选项 1，则要使用的转换将是Miles to Kilometers或resultOutput = userInput * 1.6093由于转换将是用户输入的英里数，则公里结果为miles * 1.6093. 现在我如何将那个和多个其他 if 语句注入到这个源代码中？我会创建一个新方法还是直接在里面做public void onItemSelected？
我会输入： if(conversionType = list.get(0)){ resultOutput = userInput * 1.6093 ?
我只需要一个大致的方向，因为我已经坚持了几天。感谢您提供任何帮助！
主活动.java :
package com.example.corey.unitconversionappbycoreywhitlow;
import java.util.ArrayList;
import java.util.List;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity implements OnItemSelectedListener {
Spinner spinnerConversions;
TextView conversionFrom, conversionTo, outputResult;
EditText userInput;
List<String> list = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
conversionFrom = findViewById(R.id.fromValue);
conversionTo = findViewById(R.id.toValue);
outputResult = findViewById(R.id.resultOutput);
userInput = findViewById(R.id.numInput);
}
public void onItemSelected(AdapterView<?> parent, View view, int pos, long id){
spinnerConversions = findViewById(R.id.conversionSpinner);
spinnerConversions.setOnItemSelectedListener(this);
list.add("Miles to Kilometers");
list.add("Kilometers to Miles");
list.add("Inches to Centimeters");
list.add("Centimeters to Inches");
ArrayAdapter<String> adapter = new ArrayAdapter<>(this, android.R.layout.simple_spinner_item, list);
adapter.setDropDownViewResource
(android.R.layout.simple_spinner_dropdown_item);
spinnerConversions.setAdapter(adapter);
String conversionType = list.get(1);
String[] units = conversionType.split("to");
String conFrom = units[0].trim();
String conTo = units[1].trim();
conversionFrom.setText(conFrom);
conversionTo.setText(conTo);
}
public void onNothingSelected(AdapterView<?> parent){}
}
我对您的代码进行了更改：
public class MainActivity extends AppCompatActivity implements OnItemSelectedListener {
Spinner spinnerConversions;
TextView conversionFrom, conversionTo, outputResult;
EditText userInput;
List<String> list = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
conversionFrom = findViewById(R.id.fromValue);
conversionTo = findViewById(R.id.toValue);
outputResult = findViewById(R.id.resultOutput);
userInput = findViewById(R.id.numInput);
spinnerConversions = findViewById(R.id.conversionSpinner);
list.add("Miles to Kilometers");
list.add("Kilometers to Miles");
list.add("Inches to Centimeters");
list.add("Centimeters to Inches");
ArrayAdapter<String> adapter = new ArrayAdapter<>(this, android.R.layout.simple_spinner_item, list);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinnerConversions.setAdapter(adapter);
String conversionType = list.get(0);
String[] units = conversionType.split("to");
String conFrom = units[0].trim();
String conTo = units[1].trim();
conversionFrom.setText(conFrom);
conversionTo.setText(conTo);
spinnerConversions.setOnItemSelectedListener(this);
}
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
Double d = 0.0;
try {
d = Double.parseDouble(userInput.getText().toString().trim());
} catch (NumberFormatException e) {
e.printStackTrace();
}
switch (position){
case 0:
outputResult.setText(d * 1.6093 + "");
break;
case 1:
//Do something
break;
case 2:
//Do something
break;
case 3:
//Do something
break;
}
}
@Override
public void onNothingSelected(AdapterView<?> parent){}
}
你有很多的初始化代码onItemSelected，但它应该被放置在您的活动的onCreate()
该switch语句允许您选择如何处理用户的选择做。您将在那里进行所需的转换。
在onCreate()你把所有的初始化代码：变量和观点的声明，设置适配器和听众微调等。
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