Java 从适配器类获取不同活动中的EditText值

我是Android的新手，我正在尝试构建一个货币转换器应用程序。我很难理解如何从CurrencyRateAdapter.java内部访问activity_main.xml中的EditText。我尝试过膨胀视图-代码构建时没有错误，但在选中复选框、输入值，然后按convert后崩溃

编辑

---

更改了“int amount=mainActivity.getAmount（）；”至“int amount=activity.getAmount（）；”它运行时不会崩溃，但应用程序中不会显示结果

生成错误：错误：（55,40）错误：无法从静态上下文引用非静态方法getAmount（）

我提供了以下代码作为上下文：

MainActivity.java

import android.content.Context;
import android.graphics.Color;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    CheckBox USchk, UKchk, AUSchk, JAPchk, CHINAchk, SINGchk, THAIchk, INDIAchk;
    EditText inputAmount;
    Button convertButton;
    int count = 0, checkedBoxes = 0;
    TextView MYR;
    CheckBox[] checkBoxArray;
    ArrayList<CurrencyRate> currencyRates;
    CurrencyRateAdapter currencyRateAdapter;
    ArrayList<CurrencyRate> resultRows;

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

        initUI();
        inputAmount.setEnabled(false);
        checkBoxArray = new CheckBox[]{
                (CheckBox)findViewById(R.id.chkUS),
                (CheckBox)findViewById(R.id.chkUK),
                (CheckBox)findViewById(R.id.chkAUS),
                (CheckBox)findViewById(R.id.chkJAP),
                (CheckBox)findViewById(R.id.chkCHINA),
                (CheckBox)findViewById(R.id.chkSING),
                (CheckBox)findViewById(R.id.chkTHAI),
                (CheckBox)findViewById(R.id.chkINDIA)
        };

        for (CheckBox cb: checkBoxArray) {
            cb.setOnCheckedChangeListener(cbListener);
        }

        currencyRates = new ArrayList<CurrencyRate>();
        currencyRates.add(new CurrencyRate("USD",4.25,"1 USD = 4.25 MYR"));
        currencyRates.add(new CurrencyRate("GBP",5.60,"1 GBP = 5.60 MYR"));
        currencyRates.add(new CurrencyRate("AUS",3.30,"1 AUD = 3.30 MYR"));
        currencyRates.add(new CurrencyRate("JPY",0.0394,"1 JYP = 0.0394 MYR"));
        currencyRates.add(new CurrencyRate("CNY",0.633,"1 CNY = 0.633 MYR"));

        currencyRates.add(new CurrencyRate("SGD",3.10,"1 SGD = 3.10 MYR"));
        currencyRates.add(new CurrencyRate("THB",0.128,"1 THB = 0.128 MYR"));
        currencyRates.add(new CurrencyRate("INR",0.067,"1 INR = 0.067 MYR"));

        resultRows = new ArrayList<CurrencyRate>();

        //invokeAdapter();
        //DECLARE ADAPTER
        currencyRateAdapter = new CurrencyRateAdapter(this, resultRows);
        ListView listView = (ListView) findViewById(resultListView);
        listView.setAdapter(currencyRateAdapter);
    }


    private View.OnClickListener convertListener = new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            checkedBoxes = countCheckboxes();

            Toast.makeText(getApplicationContext(),"CLICKED CONVERT",Toast.LENGTH_SHORT).show();

            int crBeforeCalc =  currencyRates.size();
            String crStrBCalc = Integer.toString(crBeforeCalc);
            Log.i("crStrBCalc",crStrBCalc);

            resultRows.clear();

            //Execute Calculate function
            calculateTotal(inputAmount,checkBoxArray,currencyRates);

            int crAfterCalc =  currencyRates.size();
            String crStrACalc = Integer.toString(crAfterCalc);
            Log.i("crStrACalc",crStrACalc);
        }
    };


    //Calculate rates
    private void calculateTotal(EditText inputAmount,CheckBox checkBoxArray[], ArrayList<CurrencyRate> currencyRates)
    {
        for(int i = 0; i < 8; i++) {

            Log.i("THISTAG", "PRINT TIMES PRINTED LOOP");
            if(checkBoxArray[i].isChecked())
            {
                Log.i("ifRuns","ifRuns");

                resultRows.add(currencyRates.get(i));
            }
        }

        //currencyRateAdapter.addAll(resultRows);

        int rrDSize =  resultRows.size();
        String rrDStringSize = Integer.toString(rrDSize);
        Log.i("rrDStringSize",rrDStringSize);

        //currencyRateAdapter.notifyDataSetChanged();

        int rrASize =  resultRows.size();
        String rrAStringSize = Integer.toString(rrASize);
        Log.i("rrAStringSize",rrAStringSize);
    }

    public void initUI() {

        USchk = (CheckBox) findViewById(R.id.chkUS);
        UKchk = (CheckBox) findViewById(R.id.chkUK);
        AUSchk = (CheckBox) findViewById(R.id.chkAUS);
        JAPchk = (CheckBox) findViewById(R.id.chkJAP);

        CHINAchk = (CheckBox) findViewById(R.id.chkCHINA);
        SINGchk = (CheckBox) findViewById(R.id.chkSING);
        THAIchk = (CheckBox) findViewById(R.id.chkTHAI);
        INDIAchk = (CheckBox) findViewById(R.id.chkINDIA);

        MYR = (TextView) findViewById(R.id.MYR);

        convertButton = (Button) findViewById(R.id.convertButton);
        inputAmount = (EditText) findViewById(R.id.amountInput);

        convertButton.setOnClickListener(convertListener);
    }

    CompoundButton.OnCheckedChangeListener cbListener = new CompoundButton.OnCheckedChangeListener() {
        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
            disableChkWhenMax(checkBoxArray);
            inputAmount.setText("");

            //Clear all textbox rows
            resultRows.clear();

        }
    };

    private void disableChkWhenMax(CheckBox checkBoxes[]){

        int countChecked =0;

        inputAmount.setEnabled(false);

        for (CheckBox cb:checkBoxes){
            cb.setEnabled(true);
            if (cb.isChecked()) countChecked++;
        }

        if(1<= countChecked)
        {
            inputAmount.setEnabled(true);
        }

        if (3 <= countChecked) {
            for (CheckBox cb:checkBoxes){
                if (!cb.isChecked())cb.setEnabled(false);
            }
        }
    }

public int getAmount() {
    int value=0;
    if (inputAmount != null) {
        return Integer.parseInt(inputAmount.getText().toString().trim());
    } else {
        return 0;
    }
}
    private int countCheckboxes()
    {
        if (USchk.isChecked()) {
            count++;
        }
        if (UKchk.isChecked()){
            count++;
        }
        if (AUSchk.isChecked()){
            count++;
        }

        if(JAPchk.isChecked()){
            count++;
        }

        if(CHINAchk.isChecked()){
            count++;
        }

        if(SINGchk.isChecked()){
            count++;
        }

        if(THAIchk.isChecked()){
            count++;
        }

        if(INDIAchk.isChecked()){
            count++;
        }

        return count;
    }

}

public class CurrencyRate {

    private String mcurrencyCode;
    private double mresultValue;
    private String conversionDescription;

    public CurrencyRate(String mcurrencyCode, Double mresultValue, String conversionDescription) {
        this.mcurrencyCode = mcurrencyCode;
        this.mresultValue = mresultValue;
        this.conversionDescription = conversionDescription;
    }

    public String getMcurrencyCode() {
        return mcurrencyCode;
    }

    public double getMresultValue() {
        return mresultValue;
    }

    public String getConversionDescription() {
        return conversionDescription;
    }


}

import android.app.Activity;
import android.content.Context;
import android.graphics.Color;
import android.graphics.Typeface;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.text.Layout;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.RelativeLayout;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.Collection;


public class CurrencyRateAdapter extends ArrayAdapter<CurrencyRate> {

    MainActivity activity;

    public CurrencyRateAdapter(Context context, ArrayList<CurrencyRate> resultRows){
        super(context,0,resultRows);
        activity=(MainActivity)activity;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

            View listItemView = convertView;

        try {

            if (listItemView == null) {
                listItemView = LayoutInflater.from(getContext()).inflate(
                        R.layout.list_item, parent, false);
            }

            CurrencyRate currentCurrencyRate = getItem(position);

            TextView currencyCodeTextView = (TextView) listItemView.findViewById(R.id.currency_code);
            currencyCodeTextView.setText(currentCurrencyRate.getMcurrencyCode());
            currencyCodeTextView.setTextColor(Color.parseColor("#FF0000"));
            String currencyCode = currencyCodeTextView.toString();

            TextView convDesTextView = (TextView) listItemView.findViewById(R.id.conversion_description);
            convDesTextView.setText(currentCurrencyRate.getConversionDescription());

            TextView resultValueTextView = (TextView) listItemView.findViewById(R.id.result_value);

            Double result = currentCurrencyRate.getMresultValue();

            int amount= activity.getAmount();

            switch (currencyCode) {
                case "USD":
                    result = amount * currentCurrencyRate.getMresultValue();
                    break;
                case "GBP":
                    result = amount * currentCurrencyRate.getMresultValue();
                    break;
                case "AUS":
                    result = amount * currentCurrencyRate.getMresultValue();
                    break;
                case "JPY":
                    result = amount * currentCurrencyRate.getMresultValue();
                    break;
                case "CNY":
                    result = amount * currentCurrencyRate.getMresultValue();
                    break;
                case "SGD":
                    result = amount * currentCurrencyRate.getMresultValue();
                    break;
                case "THB":
                    result = amount * currentCurrencyRate.getMresultValue();
                    break;
                case "INR":
                    result = amount * currentCurrencyRate.getMresultValue();
                    break;
                default:
                    break;
            }


            String resultV = String.valueOf(result);
            resultValueTextView.setText(resultV);

        } catch (Exception e) {
            Log.e("APP_TAG", "STACKTRACE");
            Log.e("APP_TAG", Log.getStackTraceString(e));
        }

        return listItemView;

    }

}

CurrencyRateAdapter.java

import android.content.Context;
import android.graphics.Color;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    CheckBox USchk, UKchk, AUSchk, JAPchk, CHINAchk, SINGchk, THAIchk, INDIAchk;
    EditText inputAmount;
    Button convertButton;
    int count = 0, checkedBoxes = 0;
    TextView MYR;
    CheckBox[] checkBoxArray;
    ArrayList<CurrencyRate> currencyRates;
    CurrencyRateAdapter currencyRateAdapter;
    ArrayList<CurrencyRate> resultRows;

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

        initUI();
        inputAmount.setEnabled(false);
        checkBoxArray = new CheckBox[]{
                (CheckBox)findViewById(R.id.chkUS),
                (CheckBox)findViewById(R.id.chkUK),
                (CheckBox)findViewById(R.id.chkAUS),
                (CheckBox)findViewById(R.id.chkJAP),
                (CheckBox)findViewById(R.id.chkCHINA),
                (CheckBox)findViewById(R.id.chkSING),
                (CheckBox)findViewById(R.id.chkTHAI),
                (CheckBox)findViewById(R.id.chkINDIA)
        };

        for (CheckBox cb: checkBoxArray) {
            cb.setOnCheckedChangeListener(cbListener);
        }

        currencyRates = new ArrayList<CurrencyRate>();
        currencyRates.add(new CurrencyRate("USD",4.25,"1 USD = 4.25 MYR"));
        currencyRates.add(new CurrencyRate("GBP",5.60,"1 GBP = 5.60 MYR"));
        currencyRates.add(new CurrencyRate("AUS",3.30,"1 AUD = 3.30 MYR"));
        currencyRates.add(new CurrencyRate("JPY",0.0394,"1 JYP = 0.0394 MYR"));
        currencyRates.add(new CurrencyRate("CNY",0.633,"1 CNY = 0.633 MYR"));

        currencyRates.add(new CurrencyRate("SGD",3.10,"1 SGD = 3.10 MYR"));
        currencyRates.add(new CurrencyRate("THB",0.128,"1 THB = 0.128 MYR"));
        currencyRates.add(new CurrencyRate("INR",0.067,"1 INR = 0.067 MYR"));

        resultRows = new ArrayList<CurrencyRate>();

        //invokeAdapter();
        //DECLARE ADAPTER
        currencyRateAdapter = new CurrencyRateAdapter(this, resultRows);
        ListView listView = (ListView) findViewById(resultListView);
        listView.setAdapter(currencyRateAdapter);
    }


    private View.OnClickListener convertListener = new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            checkedBoxes = countCheckboxes();

            Toast.makeText(getApplicationContext(),"CLICKED CONVERT",Toast.LENGTH_SHORT).show();

            int crBeforeCalc =  currencyRates.size();
            String crStrBCalc = Integer.toString(crBeforeCalc);
            Log.i("crStrBCalc",crStrBCalc);

            resultRows.clear();

            //Execute Calculate function
            calculateTotal(inputAmount,checkBoxArray,currencyRates);

            int crAfterCalc =  currencyRates.size();
            String crStrACalc = Integer.toString(crAfterCalc);
            Log.i("crStrACalc",crStrACalc);
        }
    };


    //Calculate rates
    private void calculateTotal(EditText inputAmount,CheckBox checkBoxArray[], ArrayList<CurrencyRate> currencyRates)
    {
        for(int i = 0; i < 8; i++) {

            Log.i("THISTAG", "PRINT TIMES PRINTED LOOP");
            if(checkBoxArray[i].isChecked())
            {
                Log.i("ifRuns","ifRuns");

                resultRows.add(currencyRates.get(i));
            }
        }

        //currencyRateAdapter.addAll(resultRows);

        int rrDSize =  resultRows.size();
        String rrDStringSize = Integer.toString(rrDSize);
        Log.i("rrDStringSize",rrDStringSize);

        //currencyRateAdapter.notifyDataSetChanged();

        int rrASize =  resultRows.size();
        String rrAStringSize = Integer.toString(rrASize);
        Log.i("rrAStringSize",rrAStringSize);
    }

    public void initUI() {

        USchk = (CheckBox) findViewById(R.id.chkUS);
        UKchk = (CheckBox) findViewById(R.id.chkUK);
        AUSchk = (CheckBox) findViewById(R.id.chkAUS);
        JAPchk = (CheckBox) findViewById(R.id.chkJAP);

        CHINAchk = (CheckBox) findViewById(R.id.chkCHINA);
        SINGchk = (CheckBox) findViewById(R.id.chkSING);
        THAIchk = (CheckBox) findViewById(R.id.chkTHAI);
        INDIAchk = (CheckBox) findViewById(R.id.chkINDIA);

        MYR = (TextView) findViewById(R.id.MYR);

        convertButton = (Button) findViewById(R.id.convertButton);
        inputAmount = (EditText) findViewById(R.id.amountInput);

        convertButton.setOnClickListener(convertListener);
    }

    CompoundButton.OnCheckedChangeListener cbListener = new CompoundButton.OnCheckedChangeListener() {
        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
            disableChkWhenMax(checkBoxArray);
            inputAmount.setText("");

            //Clear all textbox rows
            resultRows.clear();

        }
    };

    private void disableChkWhenMax(CheckBox checkBoxes[]){

        int countChecked =0;

        inputAmount.setEnabled(false);

        for (CheckBox cb:checkBoxes){
            cb.setEnabled(true);
            if (cb.isChecked()) countChecked++;
        }

        if(1<= countChecked)
        {
            inputAmount.setEnabled(true);
        }

        if (3 <= countChecked) {
            for (CheckBox cb:checkBoxes){
                if (!cb.isChecked())cb.setEnabled(false);
            }
        }
    }

public int getAmount() {
    int value=0;
    if (inputAmount != null) {
        return Integer.parseInt(inputAmount.getText().toString().trim());
    } else {
        return 0;
    }
}
    private int countCheckboxes()
    {
        if (USchk.isChecked()) {
            count++;
        }
        if (UKchk.isChecked()){
            count++;
        }
        if (AUSchk.isChecked()){
            count++;
        }

        if(JAPchk.isChecked()){
            count++;
        }

        if(CHINAchk.isChecked()){
            count++;
        }

        if(SINGchk.isChecked()){
            count++;
        }

        if(THAIchk.isChecked()){
            count++;
        }

        if(INDIAchk.isChecked()){
            count++;
        }

        return count;
    }

}

public class CurrencyRate {

    private String mcurrencyCode;
    private double mresultValue;
    private String conversionDescription;

    public CurrencyRate(String mcurrencyCode, Double mresultValue, String conversionDescription) {
        this.mcurrencyCode = mcurrencyCode;
        this.mresultValue = mresultValue;
        this.conversionDescription = conversionDescription;
    }

    public String getMcurrencyCode() {
        return mcurrencyCode;
    }

    public double getMresultValue() {
        return mresultValue;
    }

    public String getConversionDescription() {
        return conversionDescription;
    }


}

import android.app.Activity;
import android.content.Context;
import android.graphics.Color;
import android.graphics.Typeface;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.text.Layout;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.RelativeLayout;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.Collection;


public class CurrencyRateAdapter extends ArrayAdapter<CurrencyRate> {

    MainActivity activity;

    public CurrencyRateAdapter(Context context, ArrayList<CurrencyRate> resultRows){
        super(context,0,resultRows);
        activity=(MainActivity)activity;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

            View listItemView = convertView;

        try {

            if (listItemView == null) {
                listItemView = LayoutInflater.from(getContext()).inflate(
                        R.layout.list_item, parent, false);
            }

            CurrencyRate currentCurrencyRate = getItem(position);

            TextView currencyCodeTextView = (TextView) listItemView.findViewById(R.id.currency_code);
            currencyCodeTextView.setText(currentCurrencyRate.getMcurrencyCode());
            currencyCodeTextView.setTextColor(Color.parseColor("#FF0000"));
            String currencyCode = currencyCodeTextView.toString();

            TextView convDesTextView = (TextView) listItemView.findViewById(R.id.conversion_description);
            convDesTextView.setText(currentCurrencyRate.getConversionDescription());

            TextView resultValueTextView = (TextView) listItemView.findViewById(R.id.result_value);

            Double result = currentCurrencyRate.getMresultValue();

            int amount= activity.getAmount();

            switch (currencyCode) {
                case "USD":
                    result = amount * currentCurrencyRate.getMresultValue();
                    break;
                case "GBP":
                    result = amount * currentCurrencyRate.getMresultValue();
                    break;
                case "AUS":
                    result = amount * currentCurrencyRate.getMresultValue();
                    break;
                case "JPY":
                    result = amount * currentCurrencyRate.getMresultValue();
                    break;
                case "CNY":
                    result = amount * currentCurrencyRate.getMresultValue();
                    break;
                case "SGD":
                    result = amount * currentCurrencyRate.getMresultValue();
                    break;
                case "THB":
                    result = amount * currentCurrencyRate.getMresultValue();
                    break;
                case "INR":
                    result = amount * currentCurrencyRate.getMresultValue();
                    break;
                default:
                    break;
            }


            String resultV = String.valueOf(result);
            resultValueTextView.setText(resultV);

        } catch (Exception e) {
            Log.e("APP_TAG", "STACKTRACE");
            Log.e("APP_TAG", Log.getStackTraceString(e));
        }

        return listItemView;

    }

}

---

不要在适配器中再次膨胀活动xml。这不是访问editText的正确方法

删除这些代码行

    LayoutInflater inflater = LayoutInflater
            .from(parent.getContext());
    View view = inflater.inflate(R.layout.activity_main,null);


    EditText inputAmount = (EditText)view.findViewById(R.id.amountInput);

    String amountString = inputAmount.toString();
    int i = Integer.parseInt(amountString);

而是创建一个方法来获取activity类中editText的值

  public int getAmount() {
     if (inputAmount != null) {
        return Integer.parseInt(inputAmount.getText().toString().trim());
    } else {
        return 0;
     }
   }

并在适配器中传递活动引用

MainActivity activity;

//Constructor
public CurrencyRateAdapter(Context context, ArrayList<CurrencyRate> resultRows){
    super(context,0,resultRows);
    activity=(MainActivity)activity;
}

---

不要在适配器中再次膨胀活动xml。这不是访问editText的正确方法

删除这些代码行

    LayoutInflater inflater = LayoutInflater
            .from(parent.getContext());
    View view = inflater.inflate(R.layout.activity_main,null);


    EditText inputAmount = (EditText)view.findViewById(R.id.amountInput);

    String amountString = inputAmount.toString();
    int i = Integer.parseInt(amountString);

而是创建一个方法来获取activity类中editText的值

  public int getAmount() {
     if (inputAmount != null) {
        return Integer.parseInt(inputAmount.getText().toString().trim());
    } else {
        return 0;
     }
   }

并在适配器中传递活动引用

MainActivity activity;

//Constructor
public CurrencyRateAdapter(Context context, ArrayList<CurrencyRate> resultRows){
    super(context,0,resultRows);
    activity=(MainActivity)activity;
}

换行

  String resultV = String.valueOf(result);

换行

  String resultV = String.valueOf(result);

---

发布异常堆栈跟踪。@LeoAso已经这样做了，谢谢。正如我所说，您的editText中没有任何值。发布异常堆栈跟踪。@LeoAso已经这样做了，谢谢。正如我所说，您的editText中没有任何值谢谢您的帮助！我收到以下错误：java.lang.NullPointerException:尝试在com.example.user.assignment2task3_v2.MainActivity.getAmount（）上对com.example.user.assignment2task3_v2.CurrencyRateAdapter.getView上的空对象引用调用虚拟方法'int com.example.user.assignment2task3_v2'（CurrencyRateAdapter.java:87）确保inputAmount不为null并且它有内容，您正在向edittext添加值否？现在获取此信息：-错误：（59,37）错误：非静态方法getAmount（）无法从静态上下文引用。这是否意味着将方法声明为静态？除非需要，否则不要将任何内容写入静态。将上下文保持为静态有时会导致内存泄漏。因此，将上下文设置为非静态，问题就解决了：）更改了“int amount=mainActivity.getAmount（）；”至“int amount=activity.getAmount（）；”它运行时没有崩溃，但是没有显示结果。谢谢你的帮助！我收到以下错误：java.lang.NullPointerException:尝试在com.example.user.assignment2task3_v2.MainActivity.getAmount（）上对com.example.user.assignment2task3_v2.CurrencyRateAdapter.getView上的空对象引用调用虚拟方法'int com.example.user.assignment2task3_v2'（CurrencyRateAdapter.java:87）确保inputAmount不为null并且它有内容，您正在向edittext添加值否？现在获取此信息：-错误：（59,37）错误：非静态方法getAmount（）无法从静态上下文引用。这是否意味着将方法声明为静态？除非需要，否则不要将任何内容写入静态。将上下文保持为静态有时会导致内存泄漏。因此，将上下文设置为非静态，问题就解决了：）更改了“int amount=mainActivity.getAmount（）；”至“int amount=activity.getAmount（）；”它运行时没有崩溃，但没有显示任何结果。您好，您已经这样做了，但我收到了错误：NullPointerException:尝试对空对象引用调用虚拟方法“int com.example.user.assignment2task3_v2.MainActivity.getAmount（）”，您好，已执行此操作，但我收到错误：NullPointerException:尝试对null对象引用调用虚拟方法“int com.example.user.assignment2task3_v2.MainActivity.getAmount（）”