第7讲用户界面菜单和对话框

1、第7讲 用户界面（4）菜单和对话框一、对话框AlertDialog 教材P49例子：按下程序退出键，弹出是否退出对话框方法一、匿名内部类写对话框确定按钮的事件响应public class MainActivity extends ActionBarActivity Overridepublic boolean onKeyDown(int keyCode, KeyEvent event) / 监听键盘事件if(keyCode = KeyEvent.KEYCODE_BACK) /判断按下的是否退出键/弹出询问是否退出的对话框AlertDialog.Builder builder = new Ale

2、rtDialog.Builder(this);builder.setIcon(R.drawable.ic_launcher);builder.setTitle(系统提示);builder.setMessage(确定要退出么?);builder.setPositiveButton(确定, new OnClickListener() Overridepublic void onClick(DialogInterface dialog, int which) / 关闭ActivityMainActivity.this.finish(););builder.setNegativeButton(取消,

3、null);builder.show();return super.onKeyDown(keyCode, event);方法二、实例化一个内部类，作为事件监听器类注意：对话框的事件监听器类是：DialogInterface.OnClickListener，需要import android.content.DialogInterface.OnClickListener;而不是import android.view.View.OnClickListener;public class MainActivity extends ActionBarActivity Overridepublic bool

4、ean onKeyDown(int keyCode, KeyEvent event) / 监听键盘事件if(keyCode = KeyEvent.KEYCODE_BACK) /判断按下的是否退出键/弹出询问是否退出的对话框AlertDialog.Builder builder = new AlertDialog.Builder(this);builder.setIcon(R.drawable.ic_launcher);builder.setTitle(系统提示);builder.setMessage(确定要退出么?);builder.setPositiveButton(确定, listener

5、);builder.setNegativeButton(取消, listener);builder.show();return super.onKeyDown(keyCode, event);DialogInterface.OnClickListener listener = new DialogInterface.OnClickListener()Overridepublic void onClick(DialogInterface dialog, int which) /注意和按钮事件的OnClickListener区别switch(which)case AlertDialog.BUTTO

6、N_POSITIVE: /按下的是确定按钮MainActivity.this.finish();break;case AlertDialog.BUTTON_NEGATIVE:break;default:break;二、菜单一个菜单包含多个菜单项和子菜单，子菜单其实也是菜单，因为它实现了Menu接口，因此子菜单也可以包含多个菜单项菜单分三类：（1）选项菜单步骤1、定义选项菜单的布局文件Res/menu/main.xml步骤2、将菜单显示在Activity上Overridepublic boolean onCreateOptionsMenu(Menu menu) / Inflate the men

7、u; this adds items to the action bar if it is present.getMenuInflater().inflate(R.menu.main, menu);return true;步骤3、设置菜单的事件响应Overridepublic boolean onOptionsItemSelected(MenuItem item) / Handle action bar item clicks here. The action bar will/ automatically handle clicks on the Home/Up button, so lon

8、g/ as you specify a parent activity in AndroidM id = item.getItemId();switch(id)case R.id.exit:MainActivity.this.finish();break;case R.id.menuItem_red:tv_hello.setTextColor(Color.RED);break;case R.id.menuItem_blue:tv_hello.setTextColor(Color.BLUE);break;return super.onOptionsItemSelec

9、ted(item);（2）上下文菜单步骤1、设置上下文菜单，覆盖Activity的onCreateContextMenu方法public class MainActivity extends Activity private final int CONTEXT_MENU_RED=Menu.FIRST;private final int CONTEXT_MENU_GREEN=Menu.FIRST+1;private final int CONTEXT_MENU_BLUE=Menu.FIRST+2;/创建上下文菜单Overridepublic void onCreateContextMenu(Co

10、ntextMenu menu, View v,ContextMenuInfo menuInfo) / TODO Auto-generated method stubmenu.add(0, CONTEXT_MENU_BLUE, 0, 蓝色);menu.add(0, CONTEXT_MENU_GREEN, 0, 绿色);menu.add(0, CONTEXT_MENU_RED, 0, 红色);/super.onCreateContextMenu(menu, v, menuInfo);步骤2、将上下文菜单注册到组件上protected void onCreate(Bundle savedInstan

11、ceState) super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);tv_hello = (TextView) this.findViewById(R.id.tv_hello);layout = (RelativeLayout) this.findViewById(R.id.layout);/将上下文菜单加到layout上this.registerForContextMenu(layout);步骤3、编写上下文菜单的事件响应，覆盖Activity的onContextItemSelected方法 /

12、上下文菜单的事件响应Overridepublic boolean onContextItemSelected(MenuItem item) / TODO Auto-generated method stubswitch(item.getItemId()case CONTEXT_MENU_RED:layout.setBackgroundColor(Color.RED);break;case CONTEXT_MENU_BLUE:layout.setBackgroundColor(Color.BLUE);break;case CONTEXT_MENU_GREEN:layout.setBackgrou

13、ndColor(Color.GREEN);break;return super.onContextItemSelected(item);（3）Overflow Menu：没有物理menu键的手机，可以通过ActionBar的overflow按钮，来代替menu键。ActionBar：操作栏，替代了以前的标题栏（1）程序的图标（2）选项菜单的图标按钮（3）overflow按钮，里面存放了不常用的选项菜单如何定义ActionBar右边的菜单项（和选项菜单类似）步骤1、定义一个描述菜单的xml文件注意: android:showAsAction属性never：不会放在ActionBar ，只会出现在

14、底部菜单，使用物理的Menu键调出ifRoom：如果菜单项有图标和文字，如果有空间，就会将图标直接显示在ActionBar上always：一直显示在ActionBar上withText：只显示文字，折叠进overflow按钮中，通过按下右边的三点，弹出菜单项。 步骤2、将xml文件通过onCreateOptionsMenu设置到Activity上去（和原始的选项菜单的做法一样的）Overridepublic boolean onCreateOptionsMenu(Menu menu) / Inflate the menu; this adds items to the action bar i

15、f it is present.MenuInflater inflater = getMenuInflater(); inflater.inflate(R.menu.main, menu);return true;步骤3、事件响应（和原始的选项菜单的做法一样的）onOptionsItemSelected步骤4、强制显示overflow按钮在Activity中定义方法，然后在Activity中去调用这个方法/强制显示overflow的三点private void getOverFlowMenu()ViewConfiguration viewConfig = ViewConfiguration.g

16、et(this);try Field overflowMenuField = ViewConfiguration.class.getDeclaredField(sHasPermanentMenuKey);if(null != overflowMenuField)overflowMenuField.setAccessible(true);overflowMenuField.setBoolean(viewConfig, false); catch (Exception e) / TODO Auto-generated catch blocke.printStackTrace();Overrideprotected void onCreate(Bundle savedInstanceState) super.onCreate(savedInstanceState);setContentView(