I am trying to make a Simultaneous equation solver. But my code i wrote so far gives me the error Unable to instantiate Componentinfo NullPointerException. I don't know where I am null referencing.
Here's my MainActivity.java
package com.dulanga.solver;
import android.os.Bundle;
import android.app.Activity;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.Menu;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.TableLayout;
import android.widget.TableRow;
import android.widget.TextView;
public class MainActivity extends Activity implements TextWatcher {
EditText unknowns;
TableRow equationRows;
LinearLayout mainLayout;
TextView eqnNumber;
EditText eqn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void onResume(){
super.onResume();
equationRows=new TableRow(this);
eqnNumber=new TextView(this);
eqn=new EditText(this);
unknowns =(EditText) findViewById(R.id.unknowns);
unknowns.addTextChangedListener(this);
mainLayout=(TableLayout)findViewById(R.id.LinearLayout1);
equationRows.addView(eqn,1);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
@Override
public void afterTextChanged(Editable arg0) {
// TODO Auto-generated method stub
}
@Override
public void beforeTextChanged(CharSequence arg0, int arg1, int arg2,
int arg3) {
// TODO Auto-generated method stub
}
@Override
public void onTextChanged(CharSequence arg0, int arg1, int arg2, int arg3) {
// TODO Auto-generated method stub
int number=Integer.parseInt(arg0.toString());
mainLayout.removeViews(1, mainLayout.getChildCount()-1);
//equationRows.removeAllViews();
for(int i=0;i<number;i++){
if (i==0)
eqnNumber.setText((i+1)+"st");
else if (i==1)
eqnNumber.setText((i+1)+"nd");
else if (i==2)
eqnNumber.setText((i+1)+"rd");
else
eqnNumber.setText((i+1)+"th");
equationRows.addView(eqnNumber,0);
mainLayout.addView(equationRows);
equationRows.removeViewAt(0);
}
}
}
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.dulanga.solver"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="7"
android:targetSdkVersion="17" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.dulanga.solver.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
activity_main.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/LinearLayout1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity" >
<TableRow
android:id="@+id/tableRow1"
android:layout_width="wrap_content"
android:layout_height="wrap_content" >
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="No. of Unknowns"
android:textAppearance="?android:attr/textAppearanceMedium"
android:paddingRight="25dp" />
<EditText
android:id="@+id/unknowns"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:ems="10"
android:inputType="number" >
<requestFocus />
</EditText>
</TableRow>
</LinearLayout>
Please can anyone help me.