How do I make Button work only if Edittext is filled in?

Question

I just want to push the button after all the EditText's are filled in

package com.example.marcosnogueira.appnote;


import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.*;
import android.content.*;

public class Principal extends AppCompatActivity {

    private EditText nome;
    private EditText nomlojcli;
    private EditText endereco;
    private EditText cpf;
    private EditText cnpj;
    private EditText tel;
    private Button cadastrar;

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_principal);

        nome = (EditText) findViewById(R.id.nome);
        nomlojcli = (EditText) findViewById(R.id.nomlojcli);
        endereco = (EditText) findViewById(R.id.endereco);
        cpf = (EditText) findViewById(R.id.cpf)
        cnpj = (EditText) findViewById(R.id.cnpj);
        tel = (EditText) findViewById(R.id.tel);
        cadastrar = (Button) findViewById(R.id.button);

        cadastrar.setOnClickListener (new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                AlertDialog.Builder mensagem = new AlertDialog.Builder(Principal.this);
                mensagem.setMessage("Cadastrado com Sucesso");
                mensagem.setNeutralButton("Ok",null);
                mensagem.show();


            }
        });
    }
}

Answer 1

Thinking here I managed to find two ways to do this.

1. The first (which I think best by explaining the "error", but not exactly what you asked for) is to leave the clickable button and click to make a condição checking whether all the EditText.length (size) are different from zero, if yes, shows the AlertDialog, if not, shows a Toast saying that information is lacking.

   eTNome = (EditText)findViewById(R.id.eTNome);
   eTCidade = (EditText)findViewById(R.id.eTCidade);
   btnSave = (Button)findViewById(R.id.btnSave);
   
   btnSave.setOnClickListener(new View.OnClickListener() {
       @Override
       public void onClick(View v) {
           if(eTCidade.length() != 0 && eTNome.length() != 0){
               //Mensagem avisando "cadastro feito com sucesso"!
           } else {
               //Avisando pra colocar mais informações
           }
       }
   });
   

2. The other solution (which is what you want) would be every change in one EditText check that they are all filled and if they are leaving the clickable button, we can use the addTextChangedListener, with it you can do actions before, during and after the text is changed, overwriting the methods beforeTextChanged, onTextChanged and afterTextChanged, I only used the after, but I think in any one it serves, the code below:

   public class MainActivity extends AppCompatActivity {
       Button btnSave;
       EditText eTNome;
       EditText eTCidade;
   
       @Override
       protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           setContentView(R.layout.activity_main);
   
           eTNome = (EditText)findViewById(R.id.eTNome);
           eTCidade = (EditText)findViewById(R.id.eTCidade);
           btnSave = (Button)findViewById(R.id.btnSave);
           btnSave.setEnabled(false);
           btnSave.setClickable(false);
   
           eTNome.addTextChangedListener(MudarTexto);
           eTCidade.addTextChangedListener(MudarTexto);
       }
       private TextWatcher MudarTexto = new TextWatcher(){
           @Override
           public void beforeTextChanged(CharSequence s, int start, int count, int after) {
           }
   
           @Override
           public void onTextChanged(CharSequence s, int start, int before, int count) {
           }
   
           @Override
           public void afterTextChanged(Editable s) {
               AoMudarTexto();
           }
       };
       private void AoMudarTexto(){
           if(eTCidade.length() != 0 && eTNome.length() != 0) {
               btnSave.setEnabled(true);
               btnSave.setClickable(true);
           } else {
               btnSave.setEnabled(false);
               btnSave.setClickable(false);
           }
       }
   }