Help my app crashes when using "implements onclicklistener"

[Android Question]

package com.example.toggle;

import android.app.Activity;

import android.os.Bundle;

import android.text.InputType;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.EditText;

import android.widget.ToggleButton;

public class MainActivity extends Activity implements OnClickListener
{
EditText input;
ToggleButton tb;
protected void onCreate(Bundle savedInstanceState)
{
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final EditText input=(EditText)findViewById(R.id.et1);
final ToggleButton tb=(ToggleButton)findViewById(R.id.tb1);
tb.setOnClickListener(this);
}
@override
public void onClick(View v) {
// TODO Auto-generated method stub
if(tb.isChecked())
{
input.setInputType(InputType.TYPE_CLASS_TEXT | InputType.TYPE_TEXT_VARIATION_PASSWORD);
}
else
{
input.setInputType(InputType.TYPE_CLASS_TEXT);
}
}
}