尝试忽略电话号码开头的零时出错？

如何解决尝试忽略电话号码开头的零时出错？

//getting data
String _phoneNumber = number.getEditText().getText().toString().trim();
String _password = password.getEditText().getText().toString().trim();

if (_phoneNumber.charat(0) == '0') {
    _phoneNumber = _phoneNumber.substring(1);
}

Caused by: java.lang.reflect.InvocationTargetException
    at java.lang.reflect.Method.invoke(Native Method)
    at androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:409)
    at android.view.View.performClick(View.java:7125)
    at android.view.View.performClickInternal(View.java:7102)
    at android.view.View.access$3500(View.java:801)
    at android.view.View$PerformClick.run(View.java:27336)
    at android.os.Handler.handleCallback(Handler.java:883)
    at android.os.Handler.dispatchMessage(Handler.java:100)
    at android.os.Looper.loop(Looper.java:214)
    at android.app.ActivityThread.main(ActivityThread.java:7356)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
    Caused by: java.lang.Stringindexoutofboundsexception: length=0; index=0
    at java.lang.String.charat(Native Method)

解决方法

确保您的字符串不是空字符串。您可能对使用 startsWith() 方法而不是 charAt() 感兴趣：

String _phoneNumber = number.getEditText().getText().toString().trim();
String _password = password.getEditText().getText().toString().trim();

if (_phoneNumber.length > 0 && _phoneNumber.startsWith('0')) {
    _phoneNumber = _phoneNumber.substring(1);
}

如果您有兴趣，这里是 startsWith() 文档的链接：https://developer.android.com/reference/java/lang/String#startsWith(java.lang.String)