Fragment newInstance

Since the Android system uses the default no-arg constructor when recreating a fragment, we should not pass values over an overloaded constructor with arguments when we instantiate it. Otherwise we get a warning that says “Avoid non-default constructors in fragments: use a default constructor plus Fragment setArguments(Bundle) instead” or we even get an InstantiationException.
The correct way to instantiate a new fragment and passing values to it, is by creating a bundle, setting arguments on this bundle and then passing it to our fragment. Inside the fragment we then retrieve this bundle and get the values out of it. A clean way to do this is by creating a so called “factory method”.

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example_fragment.xmlExampleFragment.javaactivity_main.xmlMainActivity.java
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/holo_green_light"
    android:gravity="center"
    android:orientation="vertical">

    <TextView
        android:id="@+id/text_view_fragment"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Fragment Text"
        android:textSize="20sp" />

</LinearLayout>
package com.codinginflow.newinstanceexample;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;


public class ExampleFragment extends Fragment {
    private static final String ARG_TEXT = "argText";
    private static final String ARG_NUMBER = "argNumber";

    private String text;
    private int number;

    public static ExampleFragment newInstance(String text, int number) {
        ExampleFragment fragment = new ExampleFragment();
        Bundle args = new Bundle();
        args.putString(ARG_TEXT, text);
        args.putInt(ARG_NUMBER, number);
        fragment.setArguments(args);
        return fragment;
    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.example_fragment, container, false);
        TextView textView = v.findViewById(R.id.text_view_fragment);

        if (getArguments() != null) {
            text = getArguments().getString(ARG_TEXT);
            number = getArguments().getInt(ARG_NUMBER);
        }

        textView.setText(text + number);

        return v;
    }
}
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.codinginflow.newinstanceexample.MainActivity" />
package com.codinginflow.newinstanceexample;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

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

        ExampleFragment fragment = ExampleFragment.newInstance("example text ", 123);

        getSupportFragmentManager().beginTransaction().replace(R.id.container, fragment).commit();
    }
}