所以这是我的指示：
从以下位置检索当前货币转换率：
http://api.fixer.io例如，要将美元兑换成英镑，请致电：
http://api.fixer.io/latest?base=USD&symbols=GBP2-提供两种旋转器，其中包含您选择的5种货币。
3 - 对转换查找使用异步调用，它们不应该阻塞 UI线程。
现在我已经从JSON API中提取值并使其成功显示1美元到1英镑的转换率（这是通过硬编码以美元和英镑从JSON API中提取来完成的。但是现在我正在努力试图让硬编码的货币从一对包含5种不同货币的纺纱厂中拉出来。此外，我很难让费率乘以用户指定的金额（例如，如果价格是0.69并且用户想要将10USD转换为GBP应用程序应该报告转换量为6.90GBP）但是目前我得到的是“运营商*不能应用于双倍” 目前，该应用程序在发布时崩溃，我的首要任务是让它运行并将1个货币单位转换为等量的另一个货币单位。
这是我的FetchConversionRateTask.java文件
以及Android Studio引发错误的地方
package edu.ggc.tkeating.currencyconverter;
import android.content.Context;
import android.media.MediaPlayer;
import android.os.AsyncTask;
import android.util.Log;
import android.widget.EditText;
import android.widget.TextView;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedInputStream;
import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.text.DecimalFormat;
import java.util.Scanner;
/**
* Created by T3P0 on 6/9/2016.
*/
//http://api.fixer.io/latest?base=USD&symbols=GBP
public class FetchConversionRateTask extends AsyncTask<String, String, Double> {
private HttpURLConnection conn;
private TextView tv;
private Context context;
private EditText amount;
private TextView conversionTV;
public FetchConversionRateTask(Context _context, TextView _tv, EditText _amount){
this.tv = _tv;
this.context = _context;
this.amount = _amount;
}
private final static String TAG = "CurrencyConverter";
@Override
protected void onPreExecute() {
super.onPreExecute();
MediaPlayer tingMP = MediaPlayer.create(context, R.raw.ting);
tingMP.start();
}
@Override
protected Double doInBackground(String... currencies){
String from = currencies[0];
String to = currencies[1];
double rate = 0.0d;
double conversion = 0.0d;
try{
URL url = new URL("http://api.fixer.io/latest?base="+ from +
"&symbols="+ to);
conn = (HttpURLConnection) url.openConnection();
Scanner scanner = null;
scanner = new Scanner(new BufferedInputStream(conn.getInputStream()));
String rslt ="";
while (scanner.hasNext()) rslt += scanner.nextLine();
Log.i(TAG, rslt);
// {"base":"USD","date":"2016-06-09","rates":{"GBP":0.69151}}
rate = new JSONObject(rslt).getJSONObject("rates").getDouble(to);
conversion = new JSONObject(rslt).getJSONObject("conversion").getDouble(String.valueOf(amount));
scanner.close();
return conversion;
} catch (IOException | JSONException e){
e.printStackTrace();
}
return rate;
}
@Override
protected void onPostExecute(Double rate){
super.onPostExecute(rate);
MediaPlayer tingMP = MediaPlayer.create(context, R.raw.ting);
tingMP.start();
DecimalFormat format = new DecimalFormat("###.##");
String msg = "rate=" + format.format(rate);
Log.i(TAG, msg);
tv.setText(msg);
}
}
这是我的MainActivity.java
package edu.ggc.tkeating.currencyconverter;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
private TextView result;
private EditText amount;
private String fromCurr;
private String toCurr;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button button = (Button) findViewById(R.id.btnConvert);
result = (TextView) findViewById(R.id.tvResult);
amount = (EditText) findViewById(R.id.amount);
Spinner spinner2 = (Spinner) findViewById(R.id.spinnerFrom);
fromCurr = spinner2.getSelectedItem().toString();
Spinner spinner = (Spinner) findViewById(R.id.spinnerTo);
toCurr = spinner.getSelectedItem().toString();
// Create an ArrayAdapter using the string array and a default spinner layout
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this,
R.array.currency_array, android.R.layout.simple_spinner_item);
// Specify the layout to use when the list of choices appears
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
// Apply the adapter to the spinner
spinner.setAdapter(adapter);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
new FetchConversionRateTask(getApplicationContext(), result,
amount).execute(fromCurr, toCurr);
}
});
}
}
activity_main.xml中
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context="edu.ggc.tkeating.currencyconverter.MainActivity">
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="@style/AppTheme.AppBarOverlay">
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:popupTheme="@style/AppTheme.PopupOverlay"/>
</android.support.design.widget.AppBarLayout>
<include layout="@layout/content_main"/>
</android.support.design.widget.CoordinatorLayout>
的AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="edu.ggc.tkeating.currencyconverter">
<uses-permission android:name="android.permission.INTERNET"/>
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity
android:name=".MainActivity"
android:label="@string/app_name"
android:theme="@style/AppTheme.NoActionBar">
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
</application>
</manifest>
content_main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context="edu.ggc.tkeating.currencyconverter.MainActivity"
tools:showIn="@layout/activity_main">
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Convert"
android:id="@+id/btnConvert"
android:layout_centerVertical="true"
android:layout_centerHorizontal="true"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Result"
android:id="@+id/tvResult"
android:layout_marginTop="44dp"
android:layout_below="@+id/btnConvert"
android:layout_centerHorizontal="true" />
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:inputType="numberDecimal"
android:ems="10"
android:id="@+id/amount"
android:layout_above="@+id/btnConvert"
android:layout_centerHorizontal="true"
android:layout_marginBottom="79dp"
android:hint="How much do you want to convert?"/>
<Spinner
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/spinnerTo"
android:spinnerMode="dropdown"
android:layout_above="@+id/btnConvert"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"
android:layout_toRightOf="@+id/tvResult"
android:layout_toEndOf="@+id/tvResult"/>
<Spinner
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/spinnerFrom"
android:spinnerMode="dropdown"
android:layout_above="@+id/btnConvert"
android:layout_toLeftOf="@+id/btnConvert"
android:layout_toStartOf="@+id/btnConvert"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Result"
android:id="@+id/conversionTV"
android:layout_marginTop="22dp"
android:layout_below="@+id/tvResult"
android:layout_centerHorizontal="true"/>
</RelativeLayout>
我觉得我错过了一些非常简单明了的东西，我希望新鲜的眼睛（以及更有经验的程序员）能够想出这个代码。先谢谢你了