java - Android Studio 带有微调器选择的多个数字

Question

因此，我尝试使用一个微调器，您可以在其中选择要从英镑转换为的货币，输入英镑值，然后按按钮从微调器转换为所选货币。转换后的值将出现在下面的 TextView 中

这是我正在使用的转换 Activity 中的以下代码，该应用程序在尝试从主菜单切换到此布局时崩溃，但在我尝试添加乘法代码之前它正在工作。提前致谢。

public class Convert extends AppCompatActivity {


final EditText currency_input = (EditText) findViewById(R.id.editText_currency_input);
final TextView answer = (TextView) findViewById(R.id.textView_convert_to);

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

    Spinner spinner_convert_from = (Spinner) findViewById(R.id.spinner_convert_from);
    ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this,
            R.array.currency_array, android.R.layout.simple_spinner_item);
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinner_convert_from.setAdapter(adapter);
}



private void USD() {
    answer.setText(String.valueOf(Double.valueOf(String.valueOf(currency_input.getText()))*1.2798));
}

private void EUR() {
    answer.setText(String.valueOf(Double.valueOf(String.valueOf(currency_input.getText()))*1.14502));
}

private void AUD() {
    answer.setText(String.valueOf(Double.valueOf(String.valueOf(currency_input.getText()))*1.71911));
}

private void CAD() {
    answer.setText(String.valueOf(Double.valueOf(String.valueOf(currency_input.getText()))*1.7226));
}

private void JPY() {
    answer.setText(String.valueOf(Double.valueOf(String.valueOf(currency_input.getText()))*142.482));
}

private void CHF() {
    answer.setText(String.valueOf(Double.valueOf(String.valueOf(currency_input.getText()))* 1.24662));
}

private void CNY() {
    answer.setText(String.valueOf(Double.valueOf(String.valueOf(currency_input.getText()))* 8.7714));
}

private void KRW() {
    answer.setText(String.valueOf(Double.valueOf(String.valueOf(currency_input.getText()))*1430.8));
}

private void SEK() {
    answer.setText(String.valueOf(Double.valueOf(String.valueOf(currency_input.getText()))* 11.1187));
}


public class planOnClickListener implements AdapterView.OnItemSelectedListener {
    @Override
    public void onItemSelected(AdapterView<?> parent, View v, int pos,
                               long id) {
        parent.getItemAtPosition(pos);

        if (pos == 0) {
            USD();
        } else if (pos == 1) {
            EUR();
        } else if (pos == 2) {
            AUD();
        } else if (pos == 3) {
            CAD();
        } else if (pos == 4) {
            JPY();
        } else if (pos == 5) {
            CHF();
        } else if (pos == 6) {
            CNY();
        } else if (pos == 7) {
            KRW();
        } else if (pos == 8) {
            SEK();
        }
    }

    @Override
    public void onNothingSelected(AdapterView<?> arg0) {

    }
}

}

Answer 1

您的代码中存在一些常见错误。我已经更新了您的代码。

这是工作代码:

//Convert.java

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;

public class Convert extends AppCompatActivity {

    EditText currency_input ;
    TextView answer;

    String input;

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

        // Views
        currency_input = (EditText) findViewById(R.id.editText_currency_input);
        answer = (TextView) findViewById(R.id.textView_convert_to);

        // Default value
        currency_input.setText("0.0");

        Spinner spinner_convert_from = (Spinner) findViewById(R.id.spinner_convert_from);
        ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this,
                R.array.currency_array, android.R.layout.simple_spinner_item);
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner_convert_from.setAdapter(adapter);

        // Add item selected listener
        spinner_convert_from.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> parent, View v, int pos,
                                       long id) {

                // Get input text 
                input = currency_input.getText().toString();

                if (pos == 0) {
                    USD();
                } else if (pos == 1) {
                    EUR();
                } else if (pos == 2) {
                    AUD();
                } else if (pos == 3) {
                    CAD();
                } else if (pos == 4) {
                    JPY();
                } else if (pos == 5) {
                    CHF();
                } else if (pos == 6) {
                    CNY();
                } else if (pos == 7) {
                    KRW();
                } else if (pos == 8) {
                    SEK();
                }
            }

            @Override
            public void onNothingSelected(AdapterView<?> adapterView) {

            }
        });

    }

    private void USD() {
        answer.setText(String.valueOf(Double.valueOf(input)*1.2798));
    }

    private void EUR() {
        answer.setText(String.valueOf(Double.valueOf(input)*1.14502));
    }

    private void AUD() {
        answer.setText(String.valueOf(Double.valueOf(input)*1.71911));
    }

    private void CAD() {
        answer.setText(String.valueOf(Double.valueOf(input)*1.7226));
    }

    private void JPY() {
        answer.setText(String.valueOf(Double.valueOf(input)*142.482));
    }

    private void CHF() {
        answer.setText(String.valueOf(Double.valueOf(input)* 1.24662));
    }

    private void CNY() {
        answer.setText(String.valueOf(Double.valueOf(input)* 8.7714));
    }

    private void KRW() {
        answer.setText(String.valueOf(Double.valueOf(input)*1430.8));
    }

    private void SEK() {
        answer.setText(String.valueOf(Double.valueOf(input)* 11.1187));
    }
}

这是您的布局 XML:

// convert.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:orientation="vertical"
    android:layout_margin="16dp"
    tools:context="com.ferdous.stackoverflowanswer.Convert">

    <TextView
        android:id="@+id/textView_convert_to"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="24dp"/>

    <Spinner
        android:id="@+id/spinner_convert_from"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp">

    </Spinner>

    <EditText
        android:id="@+id/editText_currency_input"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"/>

</LinearLayout>

输出: