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POInstantiation problems with id
 

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  1. POInstantiation problems with id
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    <p>I've followed a tutorial to realise a calculator. It seems that my buttons objects that i define, and instantiate with the ID are not instantiated because when i add a listener on them, they return a null pointer exception. here's the java code:</p> <pre><code>package com.example.calculette; import android.app.Activity; import android.os.Bundle; import android.view.Menu; import android.view.View; import android.widget.Button; import android.widget.EditText; public class MainActivity extends Activity { //Variables declaration Button b0; Button b1; Button b2; Button b3; Button b4; Button b5; Button b6; Button b7; Button b8; Button b9; Button bC; Button bCE; Button bEgal; Button bPlus; Button bMoins; Button bDiviser; Button bMultiplier; EditText saisie; private double number1 = 0; private boolean clicOperateur = false; private boolean update = true; private String operateur = ""; //onCreate is the first procedure called by the activity @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); b0 = (Button) findViewById(R.id.button0); b1 = (Button) findViewById(R.id.button1); b2 = (Button) findViewById(R.id.button2); b3 = (Button) findViewById(R.id.button3); b4 = (Button) findViewById(R.id.button4); b5 = (Button) findViewById(R.id.button5); b6 = (Button) findViewById(R.id.button6); b7 = (Button) findViewById(R.id.button7); b8 = (Button) findViewById(R.id.button8); b9 = (Button) findViewById(R.id.button9); bC = (Button) findViewById(R.id.buttonC); bCE = (Button) findViewById(R.id.buttonCE); bEgal = (Button) findViewById(R.id.buttonEgal); bPlus = (Button) findViewById(R.id.buttonPlus); bMoins = (Button) findViewById(R.id.buttonMoins); bDiviser = (Button) findViewById(R.id.buttonDiviser); bMultiplier = (Button) findViewById(R.id.buttonMultiplier); saisie = (EditText) findViewById(R.id.EditText01); //Listeners declaration b0.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub numberClick("0"); } }); </code></pre> <p>(i don't link the whole code because it's still the same for the 9 buttons and after it's simple methods).</p> <p>here you can see the XML associated:</p> <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt; &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="wrap_content" &gt; &lt;TableLayout android:layout_width="fill_parent" android:layout_height="wrap_content" android:stretchColumns="3"&gt; &lt;EditText android:id="@+id/EditText01" android:layout_width="fill_parent" android:layout_height="80px" android:textSize="20px" android:editable="false" android:cursorVisible="false" /&gt; &lt;View android:layout_height="3dip" android:background="#FF999999" /&gt; &lt;TableRow&gt; &lt;Button android:id="@+id/buttonCE" android:text="CE" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_span="2" style="@style/button_text" android:background="@drawable/button" /&gt; &lt;Button android:id="@+id/buttonC" android:text="C" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_span="2" style="@style/button_text" android:background="@drawable/button" /&gt; &lt;/TableRow&gt; &lt;TableRow&gt; &lt;Button android:id="@+id/button7" android:text="7" android:layout_width="wrap_content" android:layout_height="wrap_content" style="@style/button_text" android:background="@drawable/button" /&gt; &lt;Button android:id="@+id/button8" android:text="8" android:layout_width="wrap_content" android:layout_height="wrap_content" style="@style/button_text" android:background="@drawable/button" /&gt; &lt;Button android:id="@+id/button9" android:text="9" android:layout_width="wrap_content" android:layout_height="wrap_content" style="@style/button_text" android:background="@drawable/button" /&gt; &lt;Button android:id="@+id/buttonPlus" android:text="+" android:layout_width="fill_parent" android:layout_height="wrap_content" style="@style/button_text" android:background="@drawable/button" /&gt; &lt;/TableRow&gt; &lt;TableRow&gt; &lt;Button android:id="@+id/button4" android:text="4" android:layout_width="wrap_content" android:layout_height="wrap_content" style="@style/button_text" android:background="@drawable/button" /&gt; &lt;Button android:id="@+id/button5" android:text="5" android:layout_width="wrap_content" android:layout_height="wrap_content" style="@style/button_text" android:background="@drawable/button" /&gt; &lt;Button android:id="@+id/button6" android:text="6" android:layout_width="wrap_content" android:layout_height="wrap_content" style="@style/button_text" android:background="@drawable/button" /&gt; &lt;Button android:id="@+id/buttonMoins" android:text="-" android:layout_width="fill_parent" android:layout_height="wrap_content" style="@style/button_text" android:background="@drawable/button" /&gt; &lt;/TableRow&gt; &lt;TableRow&gt; &lt;Button android:id="@+id/button1" android:text="1" android:layout_width="wrap_content" android:layout_height="wrap_content" style="@style/button_text" android:background="@drawable/button" /&gt; &lt;Button android:id="@+id/button2" android:text="2" android:layout_width="wrap_content" android:layout_height="wrap_content" style="@style/button_text" android:background="@drawable/button" /&gt; &lt;Button android:id="@+id/button3" android:text="3" android:layout_width="wrap_content" android:layout_height="wrap_content" style="@style/button_text" android:background="@drawable/button" /&gt; &lt;Button android:id="@+id/buttonMultiplier" android:text="*" android:layout_width="fill_parent" android:layout_height="wrap_content" style="@style/button_text" android:background="@drawable/button" /&gt; &lt;/TableRow&gt; &lt;TableRow&gt; &lt;Button android:id="@+id/button0" android:text="0" android:layout_width="wrap_content" android:layout_height="wrap_content" style="@style/button_text" android:background="@drawable/button" /&gt; &lt;Button android:id="@+id/buttonPoint" android:text="." android:layout_width="wrap_content" android:layout_height="wrap_content" style="@style/button_text" android:background="@drawable/button" /&gt; &lt;Button android:id="@+id/buttonEgal" android:text="=" android:layout_width="wrap_content" android:layout_height="wrap_content" style="@style/button_text" android:background="@drawable/button" /&gt; &lt;Button android:id="@+id/buttonDiviser" android:text="/" android:layout_width="fill_parent" android:layout_height="wrap_content" style="@style/button_text" android:background="@drawable/button" /&gt; &lt;/TableRow&gt; &lt;/TableLayout&gt; &lt;ImageView android:layout_height="fill_parent" android:layout_width="fill_parent" android:src="@drawable/logosafran" android:id="@+id/imageView1" &gt;&lt;/ImageView&gt; &lt;/LinearLayout&gt; </code></pre> <p>The logcat says that i have a nullPointerException on the first listener declaration with b0.</p> <p>Thank you guys!</p>
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    1. USEydolol
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    1. COIs this the activity_main.xml?
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    2. COnop it's a button_classical.xml that i've defined to create my tableLayout with all buttons in
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      1. USEydolol
 

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