How does findViewById work?

Question

package com.example.dell.helloworld;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.v         


        

Answer 1

The root view in an Activity is determined by setContentView(int layoutId) or setContentView(View rootView).

In your case, it is

setContentView(R.layout.activity_main);

Therefore, any call you make to findViewById will lookup the id from activity_main.xml.

If it is unable to find the id that you have specified, it will return null.

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It is worth mentioning that that you aren't calling that method and this is typically how a Toast is made.

Toast.makeText(getApplicationContext(), "Hello toast!", Toast.LENGTH_SHORT).show();