Pass parameter to the second Activity

Question

I am trying to pass some parameter to another Activity, but the application hangs on the second screen. The name of the application is calculator. The error that says on the second screen is: Calculator stopped.

Follow the codes:

xml of the main Activity:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
    xmlns:tools="http://schemas.android.com/tools"  
    android:layout_width="match_parent"  
    android:layout_height="match_parent"  
    android:orientation="vertical"  
    tools:context="${relativePackage}.${activityClass}">  

    <TextView 
        android:id="@+id/tx1"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
    android:text="valor 1"/>  

    <EditText  
        android:id="@+id/edt1"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:inputType="numberDecimal"/>  

    <TextView  
        android:id="@+id/tx2"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:text="valor 2"/>  

    <EditText  
        android:id="@+id/edt2"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:inputType="numberDecimal"/>  

    <Button  
        android:id="@+id/btn1"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:text="calcular"/>  

</LinearLayout>  

Class of the Activity:

package com.estudos.calculadora;  

import android.app.Activity;  
import android.content.Intent;  
import android.os.Bundle;  
import android.view.View;  
import android.view.View.OnClickListener;  
import android.widget.Button;  
import android.widget.EditText;  
import android.widget.TextView;  

public class MainActivity extends Activity {  

@Override  
protected void onCreate(Bundle savedInstanceState) {  
super.onCreate(savedInstanceState);  
setContentView(R.layout.activity_main);  
final TextView tx1 = (TextView)findViewById(R.id.tx1);  

final EditText edt1 =(EditText)findViewById(R.id.edt1);  

TextView tx2 = (TextView)findViewById(R.id.tx2);  

final EditText edt2 =(EditText)findViewById(R.id.edt2);  

Button calcular =(Button)findViewById(R.id.btn1);  

calcular.setOnClickListener(new OnClickListener() {  

@Override  
public void onClick(View v) {  
double valor1=Double.parseDouble(edt1.getText().toString());  
double valor2=Double.parseDouble(edt2.getText().toString());  
Double soma=valor1+valor2;  

Intent intent = new Intent(MainActivity.this, Activity_tela2.class);  

intent.putExtras("soma", soma);  

        startActivity(intent);  
}  
});  
}  

}  

xml of the second acitivy:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
    xmlns:tools="http://schemas.android.com/tools"  
    android:layout_width="match_parent"  
    android:layout_height="match_parent"  
    android:orientation="vertical"  
    tools:context="${relativePackage}.${activityClass}">  

    <TextView  
        android:id="@+id/resultado"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:text="resultado"/>  

    <Button  
        android:id="@+id/vtn_volta"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:text="voltar"/>  

</LinearLayout>  

class code:

package com.estudos.calculadora;  

import android.app.Activity;  
import android.content.Intent;  
import android.os.Bundle;  
import android.view.View;  
import android.view.View.OnClickListener;  
import android.widget.Button;  
import android.widget.TextView;  

public class Activity_tela2 extends Activity {  

@Override  
protected void onCreate(Bundle savedInstanceState) {  
super.onCreate(savedInstanceState);  
setContentView(R.layout.activity_tela2);  

Intent intent = getIntent();  

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

Button btn_volta =(Button)findViewById(R.id.btn_volta);  
}  

}  

I still haven’t treated the onclick of the back button. I just want to understand why I still can’t go to the second screen.

Answer 1

When creating Intent do so:

Intent i = new Intent(v.getContext(), Classe_Tela2.class); i.putExtra("soma", soma); startActivity(i);

And on Monday, do the following:

Bundle receptor = getActivity().getExtras(); //depois é só receber os valores usando Bundle (receptor)

Answer 2

You got that line wrong, buddy:

Intent intent = new Intent(MainActivity.this, Activity_tela2.class);

It must be so:

Intent intent = new Intent();
intent.setClass(MainActivity.this, Activity_tela2.class);
startActivity(intent);

That is, first Voce creates a new Intent with the method new Intent(), only then use the method setClass to set the current Activity and which Activity Voce you want to go to.

Answer 3

In Java, "value is different from Value" and "Value is different from VALUE" . On that line where you declare the sum variable, you put Double, try to put double.

Type: *double* soma = valor1 + valor2; And not *Double* soma = valor1 + valor2;