lang.NullPointerException：尝试调用接口方法尝试调用接口方法'void android.text.TextWatcher.beforeTextChanged

Question

java.lang.NullPointerException: Attempt to invoke interface method 'void  android.text.TextWatcher.beforeTextChanged(java.lang.CharSequence, int, int, int)' on a  null object reference

我在我的 Android 应用程序中将 TextWatcher 添加到 TextInputEditText 中，当我开始输入文本或返回到片段时，应用程序抛出此异常并崩溃，我仍然不明白为什么。

这是我的代码，应用程序抛出异常：

class LoginView(
     private val binding: FragmentLoginBinding,
     private val callback: LoginViewCallback,
) {

    init {
        initViews()
    }

    private fun initViews() = with(binding) {
        btnLogin.setOnClickListener {
            callback.onLoginClick(
                UserLoginParams(
                    etLogin.text.toString(),
                    etPassword.text.toString().computedMD5Hash()
                )
            )
        }
        btnOfferToRegister.setOnClickListener { callback.onOfferToRegisterClick() }
    
        etLogin.addTextChangedListener(loginTextWatcher)
        etPassword.addTextChangedListener(loginTextWatcher)
    }

    fun bind(loginViewState: LoginViewState?) = with(binding) {
        loginViewState ?: return
    
        tvError.setTextByReference(loginViewState.loginError?.textReference)
    
        progressBar.setViewVisibility(loginViewState.progressBarVisibility)
        btnLogin.setViewVisibility(loginViewState.buttonVisibility)
    }

    private val loginTextWatcher = object : TextWatcher {
     
        override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {
        }
    
        override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {
            callback.onInputFieldsChanged()
        }
    
        override fun afterTextChanged(s: Editable?) {
        }
    
    }

}

提前谢谢您

Answer 1

我不知道如何解决这个问题，但如果它只是有时发生，你可以这样做

class LoginView(
     private val binding: FragmentLoginBinding,
     private val callback: LoginViewCallback,
) {

    init {
        initViews()
    }

    private fun initViews() = with(binding) {
        btnLogin.setOnClickListener {
            callback.onLoginClick(
                UserLoginParams(
                    etLogin.text.toString(),
                    etPassword.text.toString().computedMD5Hash()
                )
            )
        }
        btnOfferToRegister.setOnClickListener { callback.onOfferToRegisterClick() }
    
        etLogin.addTextChangedListener(loginTextWatcher)
        etPassword.addTextChangedListener(loginTextWatcher)
    }

    fun bind(loginViewState: LoginViewState?) = with(binding) {
        loginViewState ?: return
    
        tvError.setTextByReference(loginViewState.loginError?.textReference)
    
        progressBar.setViewVisibility(loginViewState.progressBarVisibility)
        btnLogin.setViewVisibility(loginViewState.buttonVisibility)
    }

    private val loginTextWatcher = object : TextWatcher {
     
        override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {
        }
    
        override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {
            callback.onInputFieldsChanged()
        }
    
        override fun afterTextChanged(s: Editable?) {
        }
    
    }

}