ch07 Android 回调方法
<div class="Section0">--------------------------------------------CallUp.java-------------------------------------package com.ch07.callback;
/**
*
* 项目名称：com.ch07.callback
* 类名称：CallUp
* 类描述： 打电话类
* 创建人：fy
* 创建时间：2012-11-9 下午6:28:38
* Copyright (c) 方勇-版权所有
*/
public class CallUp {
/* 打电话,回调方法 */
public void callme(OnCallBack onCallBack) {
onCallBack.execute();
}
/* 接口作为参数传递 */
public interface OnCallBack {
void execute();
}
}
--------------------------------------------TestCall.java-------------------------------------
package com.ch07.callback;
/**
*
* 场景描述：
*
* java回调函数
* 什么是回调？(What)
* 精妙比喻：我把手机号码给你，你通过手机号码联系我
* 具体解释：
* 我把我的手机号码给你，你通过电话号码打电话 联系我
* 我把我的手机号码给你，你通过电话号码发短信 联系我
* 共同的部分：
* 我把我的手机号码给你，你通过电话号码(****)联系我
* 不同的部分
* 每次在使用的时候，选择是打电话或是发短信。
* 回调都做了什么？
* 将变动与不变的代码分离，变动的代码在每次使用时确认
* 什么情况使用回调？为什么要使用回调？
* 步骤固定，但有一部分内容只有在使用的时候才能知道。
*
*/
public class TestCall {
public static void main(String[] args) {
/* 实例化电话类 */
CallUp callUp = new CallUp();
/* 拨打对方的电话,只需要知道对方的手机号码 */
callUp.callme(new CallUp.OnCallBack() {
@Override
public void execute() {
System.out.println("回调方法");
}
});
}
}
--------------------------------------------DatePickerDialog.java---------------------------------
/*
* Copyright (C) 2007 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.app;
import android.content.Context;
import android.content.DialogInterface;
import android.content.DialogInterface.OnClickListener;
import android.os.Bundle;
import android.text.format.DateUtils;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.DatePicker;
import android.widget.DatePicker.OnDateChangedListener;
import com.android.internal.R;
import java.util.Calendar;
/**
* A simple dialog containing an {@link android.widget.DatePicker}.
*
* <p>See the <a href="{@docRoot}resources/tutorials/views/hello-datepicker.html">Date Picker
* tutorial</a>.</p>
*/
public class DatePickerDialog extends AlertDialog implements OnClickListener,
OnDateChangedListener {
private static final String YEAR = "year";
private static final String MONTH = "month";
private static final String DAY = "day";
private final DatePicker mDatePicker;
private final OnDateSetListener mCallBack;
private final Calendar mCalendar;
private boolean mTitleNeedsUpdate = true;
/**
* The callback used to indicate the user is done filling in the date.
*/
public interface OnDateSetListener {
/**
* @param view The view associated with this listener.
* @param year The year that was set.
* @param monthOfYear The month that was set (0-11) for compatibility
* with {@link java.util.Calendar}.
* @param dayOfMonth The day of the month that was set.
*/
void onDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth);
}
/**
* @param context The context the dialog is to run in.
* @param callBack How the parent is notified that the date is set.
* @param year The initial year of the dialog.
* @param monthOfYear The initial month of the dialog.
* @param dayOfMonth The initial day of the dialog.
*/
public DatePickerDialog(Context context,
OnDateSetListener callBack,
int year,
int monthOfYear,
int dayOfMonth) {
this(context, 0, callBack, year, monthOfYear, dayOfMonth);
}
/**
* @param context The context the dialog is to run in.
* @param theme the theme to apply to this dialog
* @param callBack How the parent is notified that the date is set.
* @param year The initial year of the dialog.
* @param monthOfYear The initial month of the dialog.
* @param dayOfMonth The initial day of the dialog.
*/
public DatePickerDialog(Context context,
int theme,
OnDateSetListener callBack,
int year,
int monthOfYear,
int dayOfMonth) {
super(context, theme);
mCallBack = callBack;
mCalendar = Calendar.getInstance();
Context themeContext = getContext();
setButton(BUTTON_POSITIVE, themeContext.getText(R.string.date_time_done), this);
setIcon(0);
LayoutInflater inflater =
(LayoutInflater) themeContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View view = inflater.inflate(R.layout.date_picker_dialog, null);
setView(view);
mDatePicker = (DatePicker) view.findViewById(R.id.datePicker);
mDatePicker.init(year, monthOfYear, dayOfMonth, this);
updateTitle(year, monthOfYear, dayOfMonth);
}
public void onClick(DialogInterface dialog, int which) {
tryNotifyDateSet();
}
public void onDateChanged(DatePicker view, int year,
int month, int day) {
mDatePicker.init(year, month, day, this);
updateTitle(year, month, day);
}
/**
* Gets the {@link DatePicker} contained in this dialog.
*
* @return The calendar view.
*/
public DatePicker getDatePicker() {
return mDatePicker;
}
/**
* Sets the current date.
*
* @param year The date year.
* @param monthOfYear The date month.
* @param dayOfMonth The date day of month.
*/
public void updateDate(int year, int monthOfYear, int dayOfMonth) {
mDatePicker.updateDate(year, monthOfYear, dayOfMonth);
}
private void tryNotifyDateSet() {
if (mCallBack != null) {
mDatePicker.clearFocus();
mCallBack.onDateSet(mDatePicker, mDatePicker.getYear(),
mDatePicker.getMonth(), mDatePicker.getDayOfMonth());
}
}
@Override
protected void onStop() {
tryNotifyDateSet();
super.onStop();
}
private void updateTitle(int year, int month, int day) {
if (!mDatePicker.getCalendarViewShown()) {
mCalendar.set(Calendar.YEAR, year);
mCalendar.set(Calendar.MONTH, month);
mCalendar.set(Calendar.DAY_OF_MONTH, day);
String title = DateUtils.formatDateTime(mContext,
mCalendar.getTimeInMillis(),
DateUtils.FORMAT_SHOW_DATE
| DateUtils.FORMAT_SHOW_WEEKDAY
| DateUtils.FORMAT_SHOW_YEAR
| DateUtils.FORMAT_ABBREV_MONTH
| DateUtils.FORMAT_ABBREV_WEEKDAY);
setTitle(title);
mTitleNeedsUpdate = true;
} else {
if (mTitleNeedsUpdate) {
mTitleNeedsUpdate = false;
setTitle(R.string.date_picker_dialog_title);
}
}
}
@Override
public Bundle onSaveInstanceState() {
Bundle state = super.onSaveInstanceState();
state.putInt(YEAR, mDatePicker.getYear());
state.putInt(MONTH, mDatePicker.getMonth());
state.putInt(DAY, mDatePicker.getDayOfMonth());
return state;
}
@Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
int year = savedInstanceState.getInt(YEAR);
int month = savedInstanceState.getInt(MONTH);
int day = savedInstanceState.getInt(DAY);
mDatePicker.init(year, month, day, this);
}
}
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