Android 程式开发：（九）用户界面 —— 9.2 重写onKeyDown()

用户可以使用两种级别与你的UI进行交互，一种是activity级别，另一种是view级别。在activity级别，Activity类暴露了一些你可以重写的方法。有一些常用的方法，你可以在你的Activity中进行重写：

onKeyDown
onKeyUp
onMenuItemSelected
onMenuOpened
下面的例子重写了一些在activity中的方法，通过这个例子展示用户如何与众多的activity进行交互。

1、创建一个工程：UIActivity。

2、main.xml中的代码。

[html]
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <TextView
        android:layout_width="214dp"
        android:layout_height="wrap_content"
        android:text="Your Name"
        />
    <EditText
        android:id="@+id/txt1"
        android:layout_width="214dp"
        android:layout_height="wrap_content"
        />
    <Button
        android:id="@+id/btn1"
        android:layout_width="106dp"
        android:layout_height="wrap_content"
        android:text="OK"
        />
    <Button
        android:id="@+id/btn2"
        android:layout_width="106dp"
        android:layout_height="wrap_content"
        android:text="Cancel"
        />

</LinearLayout>
3、UIActivityActivity.java中的代码。
[java]
package net.learn2develop.UIActivity;

import android.app.Activity;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class UIActivityActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

    }

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event)
    {
        switch (keyCode)
        {
            case KeyEvent.KEYCODE_DPAD_CENTER:
                Toast.makeText(getBaseContext(),
                        "Center was clicked",
                        Toast.LENGTH_LONG).show();
                break;
            case KeyEvent.KEYCODE_DPAD_LEFT:
                Toast.makeText(getBaseContext(),
                        "Left arrow was clicked",
                        Toast.LENGTH_LONG).show();
                break;
            case KeyEvent.KEYCODE_DPAD_RIGHT:
                Toast.makeText(getBaseContext(),
                        "Right arrow was clicked",
                        Toast.LENGTH_LONG).show();
                break;
            case KeyEvent.KEYCODE_DPAD_UP:
                Toast.makeText(getBaseContext(),
                        "Up arrow was clicked",
                        Toast.LENGTH_LONG).show(); 、
                break;
            case KeyEvent.KEYCODE_DPAD_DOWN:
                Toast.makeText(getBaseContext(),
                        "Down arrow was clicked",
                        Toast.LENGTH_LONG).show();
                break;
     &nbs

补充：移动开发 , Android ,