Android for Game Developers - Beginning Android Games - page 142

The KeyEvent class is similar to the MotionEvent class. It has two methods that are relevant
for us:
ï?® KeyEvent.getAction() : This returns KeyEvent.ACTION_DOWN , KeyEvent.ACTION_UP ,
and KeyEvent.ACTION_MULTIPLE . For our purposes, we can ignore the last
key event type. The other two will be sent when a key is either pressed or
released.
ï?® KeyEvent.getUnicodeChar() : This returns the Unicode character the key
would produce in a text field. Say we hold down the Shift key and press
the A key. This would be reported as an event with a key code of
KeyEvent.KEYCODE_A , but with a Unicode character A . We can use this
method if we want to do text input ourselves.
To receive keyboard events, a View must have the focus. This can be forced with the following
method calls:
View.setFocusableInTouchMode(true);
View.requestFocus();
The first method will guarantee that the View can be focused. The second method requests that
the specific View gets the focus.
Let's implement a simple test activity to see how this works in combination. We want to get key
events and display the last one we received in a TextView . The information we'll display is the
key event type, along with the key code and the Unicode character, if one would be produced.
Note that some keys do not produce a Unicode character on their own, but only in combination
with other characters. Listing 4-5 demonstrates how we can achieve all of this in a small number
of code lines.
Listing 4-5. KeyTest.Java; Testing the Key Event API
package com.badlogic.androidgames;
import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.KeyEvent;
import android.view.View;
import android.view.View.OnKeyListener;
import android.widget.TextView;
public class KeyTest extends Activity implements OnKeyListener {
StringBuilder builder = new StringBuilder();
TextView textView;
public void onCreate(Bundle savedInstanceState) {
super .onCreate(savedInstanceState);
textView = new TextView( this );
textView.setText("Press keys (if you have some)!");
textView.setOnKeyListener( this );