Question

我有代码来简单计算复利。当用户在EditText视图中编辑值时，计算将更改。

public class CompoundInterest extends AppCompatActivity {

    TextView mCompBalance;
    TextView mBalance;
    EditText mYears;
    Integer balance;
    Integer years;
    Double compbalance;
    Double interest;
    boolean isNumber;



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

        interest = 0.025;

        mBalance = (TextView) findViewById(R.id.tv_savingsbalance);
        mCompBalance = (TextView) findViewById(R.id.tv_interestbalance);
        mYears = (EditText) findViewById(R.id.et_years);
        System.out.println(mYears.getText().toString());

        Resources res = getResources();
        balance = Integer.valueOf(res.getString(R.string.savings_balance));
        mBalance.setText("£"+ balance);


        mYears.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {

            }

            @Override
            public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {
                if (mYears.getText().toString().matches("\\d+(?:\\.\\d+)?")){
                    years = Integer.valueOf(mYears.getText().toString());
                    System.out.println(years);
                    isNumber =true;
                } else {
                    isNumber =false;
                }

                if (isNumber){
                    compbalance = balance*Math.pow(1+interest, years);
                    mCompBalance.setText("£"+String.format("%.2f", compbalance));
                }

            }

            @Override
            public void afterTextChanged(Editable editable) {

            }
        });


    }
}

当我尝试编辑设置计算年数的EditText视图时 - 我收到此错误并且应用程序崩溃：

java.lang.NullPointerException：尝试调用虚方法＆＃39; int java.lang.Integer.intValue（）＆＃39;在null对象引用上 at com。###。android.citiapp.CompoundInterest $ 1.onTextChanged（CompoundInterest.java:63）在android.widget.TextView.sendOnTextChanged（TextView.java:8187）在android.widget.TextView.handleTextChanged（TextView.java:8249）在android.widget.TextView $ ChangeWatcher.onTextChanged（TextView.java:10371）在android.text.SpannableStringBuilder.sendTextChanged（SpannableStringBuilder.java:1208）在android.text.SpannableStringBuilder.replace（SpannableStringBuilder.java:578）在android.text.SpannableStringBuilder.delete（SpannableStringBuilder.java:230）在android.text.SpannableStringBuilder.delete（SpannableStringBuilder.java:229）在android.view.inputmethod.BaseInputConnection.deleteSurroundingText（BaseInputConnection.java:251） at com.android.internal.view.IInputConnectionWrapper.executeMessage（IInputConnectionWrapper.java:459） at com.android.internal.view.IInputConnectionWrapper $ MyHandler.handleMessage（IInputConnectionWrapper.java:93）在android.os.Handler.dispatchMessage（Handler.java:102）在android.os.Looper.loop（Looper.java:154）在android.app.ActivityThread.main（ActivityThread.java:6119） at java.lang.reflect.Method.invoke（Native Method）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:886）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:776）

我不确定发生了什么。

Answer 1

在charSequence.toString()功能中使用mYears.getText().toString()代替onTextChanged。希望它能帮助或准确指出NullPointerException的确切位置？

带有文本更改侦听器android

1 个答案: