Step 03 - The 'Donate' Button

Place a button directly on to the activity - attached to the bottom of the screen as shown:

Following a similar procedure as in the previous step, rename the button and add an id, both called donateButton If all goes as expected, your xml files should be like this:

activity_donate.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto" android:layout_width="match_parent"
    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:showIn="@layout/activity_donate" tools:context=".Donate">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="@string/donateTitle"
        android:id="@+id/donateTitle"
        android:layout_alignParentTop="true"
        android:layout_alignParentStart="true"
        android:layout_alignParentEnd="true" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:text="@string/donateSubtitle"
        android:id="@+id/donateSubtitle"
        android:layout_below="@+id/donateTitle"
        android:layout_alignParentStart="true"
        android:layout_marginTop="27dp"
        android:layout_alignEnd="@+id/donateTitle" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/donateButton"
        android:id="@+id/donateButton"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="47dp" />
</RelativeLayout>

strings.xml

<resources>
    <string name="app_name">Donation.1.0</string>
    <string name="action_settings">Settings</string>
    <string name="donateTitle">Welcome Homer</string>
    <string name="donateSubtitle">Please Give Generously</string>
    <string name="donateButton">Donate</string>
</resources>

If there is a deviation from the above - retrace your steps (delete the button) until you can match the above.

We can now switch our attention to the Java Activity class Donate:

package ie.app;

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;

public class Donate extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_donate);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_donate, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

For any 'controls' a user can interact with we usually find it useful to associate a class member with that object. Currently we only have one - a Button. The text fields we don't consider 'interactive' as such, so we will not include those.

Insert the following new field into the class:

  private Button donateButton;

The class will have to be imported. The class name will always match the name in the Palette:

We are free to call the variable anything we like. However, in order to keep confusion to a minimum, always call the variable by the same name you used in the Outline view:

In onCreate - we need to initialise this variable:

    donateButton = (Button) findViewById(R.id.donateButton);

We might also add a logging message so we can have some feedback as the app launches:

    if (donateButton != null)
        {
            Log.v("Donate", "Really got the donate button");
        }

This is the complete activity class:

package ie.app;

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;

public class Donate extends AppCompatActivity {

    private Button donateButton;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_donate);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

        donateButton = (Button) findViewById(R.id.donateButton);

        if (donateButton != null)
        {
            Log.v("Donate", "Really got the donate button");
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_donate, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

Finding the log message can be very difficult, unless you set a filter. In the 'LogCat' view in Android Studio, create a filter like this:

Choose "Edit Filter Configuration" on the right-hand-side of the LogCat View

Enter the name and filter as below

and if you then select the filter, we should see our message:

Run the app again, and verify the above message appears.