can you help me with my android addition program?

Question

i have this simple beginners android program. it just ask 2 numbers and outputs the sum of the 2 numbers.

I HAVE 4 ERRORS

1.)in activity_plus.xml in line <EditText android:text="" it says"This text field does not specify an inputType or a hint"

2&3)in plus.java in line private void initControls() it says

Multiple markers at this line
    - Method breakpoint:Plus [entry] - initControls()
    - The method initControls() from the type Plus is never 
     used locally

4.)is when i run the program, i input 2 numbers. then i click computer it errors and the program shuts down.

here is my program:

activity_plus.xml

<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"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".Plus" >

<EditText android:id="@+id/edit_message"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:hint="@string/edit_message"  />

<EditText android:id="@+id/add_message"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:hint="@string/add_message"  />

<Button android:id="@+id/calculate" 
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:onClick="calculate"
    android:text="@string/calculate" />

<EditText  android:text=""
    android:id="@+id/tt"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"

   />

</LinearLayout>

plus.java

package com.example.add;

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;



public class Plus extends Activity {

     EditText amount1;
     EditText amount2;
     TextView tt;
     Button calculate;
     double x=0;
     double y=0;
     double z=0;

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


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.plus, menu);
        return true;
    }

    private void initControls()
    {
        amount1=(EditText)findViewById(R.id.edit_message);
        amount2=(EditText)findViewById(R.id.add_message);
        tt=(TextView)findViewById(R.id.tt);
        calculate=(Button)findViewById(R.id.calculate);
        calculate.setOnClickListener(new Button.OnClickListener()
        {public void onClick
        (View  v) { calculate();}});
    }

    public void calculate() {
           x=Double.parseDouble(amount1.getText().toString());
           y=Double.parseDouble(amount2.getText().toString());
           z=x+y;
           tt.setText(Double.toString(z));
    }



}

strings.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <string name="app_name">add</string>
    <string name="action_settings">Settings</string>
    <string name="edit_message">Enter number</string>
    <string name="hello_world">+</string>
    <string name="calculate">Compute</string>
    <string name="add_message">Enter number</string>
    <string name="tt">Answer</string>


</resources>

Answer 1

Add:

 initControls();

in your activity's onCreate method

Update:

also you set up an onclick attribute for your button in your xml android:onClick="calculate", so you should make use of it, change your code to this:

private void initControls()
{
    amount1=(EditText)findViewById(R.id.edit_message);
    amount2=(EditText)findViewById(R.id.add_message);
    tt=(TextView)findViewById(R.id.tt);
    calculate=(Button)findViewById(R.id.calculate);
}

public void calculate(View view) {
       x=Double.parseDouble(amount1.getText().toString());
       y=Double.parseDouble(amount2.getText().toString());
       z=x+y;
       tt.setText(Double.toString(z));
}

so you don't need the listener, just add view parameter to your calculate method.

Answer 2

In xml file you declare onclick as calculate so in java page you have to write as below

public void calculate(View v) { }

Answer 3

a. Call your initControls() in onCreate() of your activity.

b. Please use this clickListener in your onCreate not in private method

    calculate.setOnClickListener(new Button.OnClickListener()
    {
        public void onClick(View  v) {
            calculate();
        }
    });

c. It should be a TextView not an EditText

    <EditText  
       android:text=""
       android:id="@+id/tt"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"/>

use this

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

Answer 4

Call initControls inside the oncreate method like this

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