PTBR FATAL EXCPETION: main java.lang.RuntimeException - window get call back

package com.example.deadsec.gerflores;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class inicio extends AppCompatActivity {

    //identificando o botão
    Button botaoestoque = (Button) findViewById(R.id.btn_estoque);

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

        //configurando o botão estoque
        botaoestoque.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View arg0) {

                Intent trocatela = new Intent(inicio.this,carrinho.class);
                inicio.this.startActivity(trocatela);
                inicio.this.finish();

            }
        });
    }



}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.deadsec.gerflores">

    <uses-permission android:name="android.permission.CAMERA" />
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/Theme.MyTheme">



        <activity android:name=".inicio">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>


        <activity android:name=".carrinho"
            android:label="carrinho">
        </activity>


        <activity android:name=".prateleira"
            android:label="prateleira">
        </activity>


        <activity android:name=".cocho"
            android:label="cocho">
        </activity>


        <activity android:name=".qrcodereader"
            android:label="qrcodereader">
            <meta-data android:name="com.google.android.gms.vision.DEPENDENCIES"
                android:value="barcode"/>
        </activity>

        <activity android:name=".toolbar"
            android:label="toolbar">
        </activity>


    </application>
</manifest>