Source

Our Hello, Safari app

MainActivity.java

package com.oreilly.hellosafari;

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

public class MainActivity extends AppCompatActivity {
    private static final String TAG = "XYZ";

    private TextView textView;
    private EditText editText;

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

        textView = findViewById(R.id.textView);
        editText = findViewById(R.id.editText);

        Button helloButton = findViewById(R.id.helloButton);
//        helloButton.setOnClickListener(new View.OnClickListener() {
//            @Override
//            public void onClick(View v) {
//                sayHello(v);
//            }
//        });
        helloButton.setOnClickListener(this::sayHello);
        Log.i(TAG, "onCreate");

        if (savedInstanceState != null) {
            textView.setText(savedInstanceState.getString("greeting"));
        }
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putString("greeting", textView.getText().toString());
    }

    public void sayHello(View v) {
        String name = editText.getText().toString();
        textView.setText(String.format("Hello, %s!", name));

        Intent intent = new Intent(this, WelcomeActivity.class);
        intent.putExtra(Intent.EXTRA_TEXT, name);
        startActivity(intent);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.say_hello:
                sayHello(null);
                return true;
            case R.id.about:
                Toast.makeText(this, "A simple Hello, World app", Toast.LENGTH_LONG).show();
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }


    @Override
    protected void onPause() {
        super.onPause();
        Log.i(TAG, "onPause");
    }

    @Override
    protected void onStart() {
        super.onStart();
        Log.i(TAG, "onStart");
    }

    @Override
    protected void onStop() {
        super.onStop();
        Log.i(TAG, "onStop");
    }

    @Override
    protected void onResume() {
        super.onResume();
        Log.i(TAG, "onResume");
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.i(TAG, "onDestroy");
    }

    @Override
    protected void onRestart() {
        super.onRestart();
        Log.i(TAG, "onRestart");
    }
}

WelcomeActivity.java

package com.oreilly.hellosafari;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;

public class WelcomeActivity extends AppCompatActivity {

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

        if (getSupportActionBar() != null) {
            getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        }

        Intent intent = getIntent();
        String name = intent.getStringExtra(Intent.EXTRA_TEXT);

        TextView welcomeView = findViewById(R.id.welcomeText);
        welcomeView.setText(String.format("Hello, %s!", name));
    }

    // Send message via implicit intent
    public void shareMessage(String message) {
        // Create the text message with a string
        Intent sendIntent = new Intent();
        sendIntent.setAction(Intent.ACTION_SEND);
        sendIntent.putExtra(Intent.EXTRA_TEXT, message);
        sendIntent.setType("text/plain");

        // Verify that the intent will resolve to an activity
        if (sendIntent.resolveActivity(getPackageManager()) != null) {
            startActivity(sendIntent);
        }
    }

    // Open web site via implicit intent
    private void viewSite() {
        Intent intent = new Intent(
                Intent.ACTION_VIEW,
                Uri.parse("https://www.safaribooksonline.com"));
        if (intent.resolveActivity(getPackageManager()) != null) {
            startActivity(intent);
        }

    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.welcome, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.about:
                Toast.makeText(this, "A simple Hello, World app", Toast.LENGTH_LONG).show();
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="24sp"
        android:text="Hello World!" />

    <EditText
        android:id="@+id/editText"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:inputType="textPersonName"
        android:hint="@string/name_hint"
        tools:ignore="Autofill" />

    <Button
        android:id="@+id/helloButton"
        android:text="@string/hello_button_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <Button
        android:onClick="sayHello"
        android:text="@string/hi_button_label"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</LinearLayout>

activity_welcome.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".WelcomeActivity">

    <TextView
        android:id="@+id/welcomeText"
        android:textSize="24sp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="" />
</LinearLayout>

strings.xml

<resources>
    <string name="app_name">HelloSafari</string>
    <string name="name_hint">Please enter your name</string>
    <string name="hello_button_name">Say Hello</string>
    <string name="hi_button_label">Say Hi</string>
</resources>

AndroidManifest.xml

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme"
        tools:ignore="AllowBackup,GoogleAppIndexingWarning">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".WelcomeActivity"
            android:parentActivityName=".MainActivity" />
    </application>

</manifest>

main.xml (in src/main/res/menu)

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <item android:id="@+id/say_hello"
        android:title="@string/say_hello"
        android:icon="@android:drawable/ic_media_play"
        app:showAsAction="ifRoom|withText" />
    <item android:id="@+id/about"
        android:title="@string/about_app"
        app:showAsAction="never" />
</menu>

welcome.xml (in src/main/res/menu)

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <item android:id="@+id/about"
        android:title="@string/about_app"
        app:showAsAction="never" />
</menu>