在Android 2.3(Gingerbread) 系统的时候，我写过一篇关于“Android 震动马达系统“的文章，当时的Linux内核还是2.6版本的。写那篇文章的目的，是想彻底的了解从硬件到驱动，再到应用的运作流程。完成了之后，文章一直仍在草稿箱里面没发表；今天看到，决定整理一下，重新发表。目的是想和大家分享自己对Android系统的一点认识：以马达为代表，来考究“Android是如何一步步工作的。它从硬件设计，到Linux驱动，再到HAL，再到JNI，再到Framework，最后到被应用调用，这整套的流程到底是怎么样的！”
转载请注明出处：http://www.cnblogs.com/skywang12345/p/3404808.html
Part 1 马达的硬件设计
马达的震动原理很简单，给马达通电，马达就能震动。至于马达是如何工作，如何将电能转化为机械能，这不是我们关心的重点。但是，我们要需要了解如何控制马达的通电。在硬件上，我们是通过一个IO口(GPIO)去控制；对于马达而言，我们可以将IO理解为一个开关。当开关合上时，马达震动；开关断开，马达停止震动。
GPIO(General Purpose Input Output)，称为通用输入/输出。它可以被配置为中断、输入、输出等类型，从而对各个IO进行控制。对于马达而已，GPIO就相当于一个开关。下面看看硬件原理图中的马达部分，如下图：
注：上面原理图对应CPU是“三星A8”。不同平台的马达，马达的接法和GPIO都不一样；但原理都是类似的。
原理图中红线标注部分的含义：GPH3_3是马达的GPIO。三星A8中有很多组GPIO，而马达对应和GPH3_3连接。
Part 2 马达的驱动代码
知道马达的硬件设计之后，我们就可以进行Linux Driver开发工作，也就是编写马达的驱动。Linux的一个非常重要的特点，一切都是文件！而我们进行Linux Driver开发的目的，就是将硬件设备映射成一个文件；然后，我们可以通过操作文件，来操作对应的硬件设备。
OK！理解了驱动的作用和原理之后，我们接下来开发讲解马达的驱动开发。
1. Datasheet中相关信息
我们知道，马达是通过GPIO去控制；接下来，我们就是找到马达对应的GPIO信息，然后控制该GPIO即可。
通过马达的原理图，我们知道马达和GPH3_3相连接。我们查阅“三星A8 的Datasheet”，查找GPH3_3的相关信息。
所谓Datasheet，就是CPU芯片的数据手册。
上面记载了CPU的功能特性和操作方式等信息。任何一个厂家在发布它的芯片时，都会提供对应的Datasheet给它的客户；客户根据Datasheet上面所描述的CPU的特性，就可以进行相关的开发(当然，实际开发中可能还需要芯片厂商的支持)。例如，国内手机都是采用MTK平台，对于MTK方案开发商来说，它要开发MTK6577的产品。那么首先，MTK原厂会提供一份MTK6577的BSP包，BSP包中包括了MTK6577的Datasheet，也就是该芯片的数据手册。方案开发商有任何关于MTK6577的问题，都可以查阅该Datasheet。
说明：
(01) GPH3_3对应CPU中的寄存器是GPH3CON[3]。
(02) [15:12] 表示寄存器的第12~15位，一个寄存器共32 bits。而第三列的 0000, 0001, 0010, 0011, 1111表示“寄存器取不同值的时候，该GPIO的功能”。
例如， 0000表示将该GPIO作为输入，0001表示将GPIO作为输出，1111表示将该GPIO作为中断。
前面，我们已经说过，操作马达就是相当与将它作为一个开关操作。因此，我们需要将马达的GPIO设为“输入”类型；然后输入1，相当于开启马达；输入0，则是关闭马达！
下面，我们需要做的就是在Driver中将GPH3_3(也就是GPH3CON[3])映射为一个文件节点，并将它配置为“输入”类型，即将GPH3CON[3]的寄存器值设为0000。
2. 马达的驱动
我们编写马达驱动(drivers/misc/misc_sysfs.c)，将马达(vibrator)注册道platform总线上。源码如下：
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/platform_device.h>
#include <linux/delay.h>
#include <linux/irq.h>
#include <linux/interrupt.h>
#include <linux/sysfs.h>
#include <linux/input.h>
#include <mach/gpio.h> // vibrator 对应的GPIO
#define VIBRATOR_POWER_PORT (S5PV210_GPH3(3)) typedef struct combo_module__t {
unsigned char status_vibrator;
} combo_module_t ; static combo_module_t combo_module; /*
* vibrator初始化函数：申请GPIO，并初始化vibrator状态。
*/
static void combo_module_init(void)
{
if(gpio_request(VIBRATOR_POWER_PORT, "vibrator power")) {
printk("misc_sysfs.c request vibrator gpio failse.\n");
}
gpio_pull_updown(VIBRATOR_POWER_PORT, PullDisable);
gpio_direction_output(VIBRATOR_POWER_PORT, GPIO_LOW); combo_module.status_vibrator = ;
} /*
* vibrator控制函数
*/
staticvoid combo_module_control(void)
{
if(combo_module.status_vibrator)
{
gpio_direction_output(VIBRATOR_POWER_PORT, GPIO_HIGH);
}
else
{
gpio_direction_output(VIBRATOR_POWER_PORT, GPIO_LOW);
} } /////////////////////////////////////////////////////////////////////////////////////////////////////////// static ssize_t show_vibrator_onoff (struct device *dev, struct device_attribute *attr, char *buf)
{
return sprintf(buf, "%d\n", combo_module.status_vibrator);
} static ssize_t set_vibrator_onoff (struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
unsigned int val; if(!(sscanf(buf, "%u\n", &val))) return -EINVAL; //printk("set_vibrator_onoff:%d\n",val); if(!val )
{
combo_module.status_vibrator = ;
combo_module_control();
}
else
{
combo_module.status_vibrator = ;
combo_module_control(); msleep(val); combo_module.status_vibrator = ;
combo_module_control();
} return count;
} static ssize_t show_vibrator_onoff (struct device *dev, struct device_attribute *attr, char *buf);
static ssize_t set_vibrator_onoff (struct device *dev, struct device_attribute *attr, const char *buf, size_t count);
// 将vibrator注册到sysfs文件系统。
// 参数说明：
// vibrator_onoff : vibrator对应在sysfs下的文件节点名称
// S_IRWXUGO : 文件节点的属性
// show_vibrator_onoff : 对应的读函数
// set_vibrator_onoff : 对应的写函数
static DEVICE_ATTR(vibrator_onoff, S_IRWXUGO, show_vibrator_onoff, set_vibrator_onoff); static struct attribute *control_sysfs_entries[] = {
&dev_attr_vibrator_onoff.attr,
NULL
}; static struct attribute_group control_sysfs_attr_group = {
.name = NULL,
.attrs = control_sysfs_entries,
}; static int control_sysfs_probe(struct platform_device *pdev)
{
printk("vibrator probe");
combo_module_init();
combo_module_control();
return sysfs_create_group(&pdev->dev.kobj, &control_sysfs_attr_group);
} staticint control_sysfs_remove(struct platform_device *pdev)
{
sysfs_remove_group(&pdev->dev.kobj, &control_sysfs_attr_group); return ;
} #ifdef CONFIG_PM
static int control_sysfs_resume(struct platform_device *dev)
{ combo_module_control(); return ;
} static int control_sysfs_suspend(struct platform_device *dev, pm_message_t state)
{ combo_module_control(); return ;
}
#else
#define control_sysfs_suspend NULL
#define control_sysfs_resume NULL
#endif static struct platform_driver control_sysfs_driver = {
.driver = {
.name = "misc_ctl",
.owner = THIS_MODULE,
},
.probe = control_sysfs_probe,
.remove = control_sysfs_remove,
.suspend = control_sysfs_suspend,
.resume = control_sysfs_resume,
}; static int __init control_sysfs_init(void)
{
// 将vibrator注册到platform总线
printk("vibrator init");
return platform_driver_register(&control_sysfs_driver);
} static void __exit control_sysfs_exit(void)
{
platform_driver_unregister(&control_sysfs_driver);
} module_init(control_sysfs_init);
module_exit(control_sysfs_exit); MODULE_DESCRIPTION("misc control driver");
MODULE_AUTHOR("other");
MODULE_LICENSE("GPL");
说明：
若您熟悉驱动开发，应该很容易理解上面的代码。不熟悉也不要紧，您只需要了解“Linux系统中，一切都是文件”，上面代码的作用是，
将马达(vibrator)映射到“/sys/devices/platform/misc_ctl/vibrator_onoff”文件上，我们可以通过读写vibrator_onoff来操作马达的开启和关闭。
有了马达的源码之后，我们还需要将该源码编译到Linux内核中。这就是通过Kconfig和Makefile来完成的，关于Kconfig和Makefile的知识，这里就不过多说明了。目前您只需要了解，通过Kconfig和Makefile，我们能将马达驱动编译到内核中，该驱动会在驱动加载的时候自动运行就可以了！
马达对应的Kconfig(driver/misc/Kconfig)内容如下：
config MISC_VIBRATOR
tristate"misc vabrator"
default y
马达对应的Makefile(driver/misc/Makefile)内容如下：
obj-$(CONFIG_MISC_VIBRATOR) += misc_sysfs.o
至此，我们已经完成马达的驱动开发了！也就是说，我们已经成功的将马达映射到文件节点上；接下来，我们通过操作文件节点，就可以操作马达了。下面从HAL层到Framework曾，都是基于Android4.2系统进行说明的。
Part 3 马达的HAL实现
HAL (Hardware Abstraction Layer), 又称为“硬件抽象层”。在Linux驱动中，我们已经将马达设为映射为文件了；而该HAL层的存在的意义，就是“对设备文件进行操作，从而相当于硬件进行操作”。HAL层的作用，一是操作硬件设备，二是操作接口封装，外界能方便的使用HAL提供的接口直接操作硬件设备。
理解了HAL之后，我们看看Android中如何在HAL层对马达进行操作。
在Android系统中，我们在libhardware_legacy中，实现马达的HAL层控制。
马达在HAL中的代码路径：hardware/libhardware_legacy/vibrator/vibrator.c
vibrator.c的代码如下：
/*
* Copyright (C) 2008 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.
*/
#include <hardware_legacy/vibrator.h>
#include "qemu.h" #include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h> #define THE_DEVICE "/sys/devices/platform/misc_ctl/vibrator_onoff" int vibrator_exists()
{
int fd; #ifdef QEMU_HARDWARE
if (qemu_check()) {
return ;
}
#endif fd = open(THE_DEVICE, O_RDWR);
if(fd < )
return ;
close(fd);
return ;
} static int sendit(int timeout_ms)
{
int nwr, ret, fd;
char value[]; #ifdef QEMU_HARDWARE
if (qemu_check()) {
return qemu_control_command( "vibrator:%d", timeout_ms );
}
#endif fd = open(THE_DEVICE, O_RDWR);
if(fd < )
return errno; nwr = sprintf(value, "%d\n", timeout_ms);
ret = write(fd, value, nwr); close(fd); return (ret == nwr) ? : -;
} int vibrator_on(int timeout_ms)
{
/* constant on, up to maximum allowed time */
return sendit(timeout_ms);
} int vibrator_off()
{
return sendit();
}
在kernel的驱动中，我们已经将马达注册到sys文件系统中(/sys/devices/platform/misc_ctl/vibrator_onoff)。在vibrator.c中，我们就是通过读写“vibrator_onoff文件节点”来实现对马达的操作。
Part 4 马达的JNI部分
1 马达的JNI实现
JNI(Java Native Interface)，中文是“Java本地接口”。
JNI是Java中一种技术，它存在的意义，是保证本地代码(C/C++代码)能在任何Java虚拟机下工作。简单点说，Java通过JNI接口，能够调用到C/C++代码。 关于“JNI的更多内容”，请参考“Android JNI和NDK学习系列文章”。
在了解了vibrator的HAL层实现之后，我们再来看看android是如何通过JNI将震动马达注册到android系统中。马达对应的JNI层代码路径如下：frameworks/base/services/jni/com_android_server_VibratorService.cpp
com_android_server_VibratorService.cpp的源码如下：
/*
* Copyright (C) 2009 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.
*/ #define LOG_TAG "VibratorService" #include "jni.h"
#include "JNIHelp.h"
#include "android_runtime/AndroidRuntime.h" #include <utils/misc.h>
#include <utils/Log.h>
#include <hardware_legacy/vibrator.h> #include <stdio.h> namespace android
{ static jboolean vibratorExists(JNIEnv *env, jobject clazz)
{
return vibrator_exists() > ? JNI_TRUE : JNI_FALSE;
} static void vibratorOn(JNIEnv *env, jobject clazz, jlong timeout_ms)
{
// ALOGI("vibratorOn\n");
vibrator_on(timeout_ms);
} static void vibratorOff(JNIEnv *env, jobject clazz)
{
// ALOGI("vibratorOff\n");
vibrator_off();
} static JNINativeMethod method_table[] = {
{ "vibratorExists", "()Z", (void*)vibratorExists },
{ "vibratorOn", "(J)V", (void*)vibratorOn },
{ "vibratorOff", "()V", (void*)vibratorOff }
}; int register_android_server_VibratorService(JNIEnv *env)
{
return jniRegisterNativeMethods(env, "com/android/server/VibratorService",
method_table, NELEM(method_table));
} };
下面，对这部分的JNI代码进行简单说明。
(01) 通过 jniRegisterNativeMethods()，我们将method_table中的方法注册到 com.android.server.VibratorService.java 中。配对表格如下：
---------------------------------------------------++++-------------------------------------------
VibratorService.java com_android_server_VibratorService.cpp
native static boolean vibratorExists(); static jboolean vibratorExists(JNIEnv *env, jobject clazz)
native static void vibratorOn(long milliseconds); static void vibratorOn(JNIEnv *env, jobject clazz, jlong timeout_ms)
native static void vibratorOff(); static void vibratorOff(JNIEnv *env, jobject clazz)
通过JNI，我们就能将Java层和HAL层的代码联系起来。
以vibratorOff()来说，我们在VibratorService.java中调用vibratorOff()；实际上会调用到com_android_server_VibratorService.cpp中的vibratorOff()函数；进一步会调用到vibrator_off()函数，而vibrator_off()是我们在 “HAL层的vibrator.c中的接口”。
2 马达的JNI如何和HAL关联方式
在继续接下来的研究之前，我们先搞清楚：JNI如何和HAL层代码关联起来的。即com_android_server_VibratorService.cpp是如何调用到vibrator.c中的代码的。
实际上道理很简单，我们先将vibrator.c封装成.so库；然后在com_android_server_VibratorService.cpp中导入该库，就可以调用vibrator.c的接口了。下面，看看Android中具体是如何做到的。
(01) vibrator.c封装到libhardware_legacy.so中的步骤
在hardware/libhardware_legacy/vibrator/Android.mk中，会将vibrator.c添加到 LOCAL_SRC_FILES 变量中。
hardware/libhardware_legacy/vibrator/Android.mk源码如下：
LOCAL_SRC_FILES += vibrator/vibrator.c
在hardware/libhardware_legacy/Android.mk中，它会调用子目录的Android.mk并将它们导入当前的Android.mk中。
hardware/libhardware_legacy/Android.mk源码如下：
legacy_modules := power uevent vibrator wifi qemu qemu_tracing SAVE_MAKEFILES := $(call all-named-subdir-makefiles,$(legacy_modules))
LEGACY_AUDIO_MAKEFILES := $(call all-named-subdir-makefiles,audio) include $(SAVE_MAKEFILES) ... LOCAL_MODULE:= libhardware_legacy include $(BUILD_SHARED_LIBRARY)
在“我们编译Android系统”或“通过 mmm hardware/libhardware_legacy进行模块编译”的时候，就会生成库libhardware_legacy.so；而且vibrator.c被包含在该库中。
(02) 在 com_android_server_VibratorService.cpp 对应的Android.mk中，会导入libhardware_legacy.so。
com_android_server_VibratorService.cpp 对应的frameworks/base/services/jni/Android.mk 的源码如下：
LOCAL_SRC_FILES:= \
com_android_server_VibratorService.cpp \
... LOCAL_SHARED_LIBRARIES := \
libhardware_legacy \
... LOCAL_MODULE:= libandroid_servers include $(BUILD_SHARED_LIBRARY)
Part 5 马达的Framework层实现
应用层操作马达，是通过马达服务进行操作的。而马达服务是通过aidl实现的，aidl是Android进程间的通信方式。关于aidl的更多说明可以参考“Android Service总结06 之AIDL”。
马达服务涉及的主要文件如下：
frameworks/base/services/java/com/android/server/SystemServer.java
frameworks/base/services/java/com/android/server/VibratorService.java
frameworks/base/core/java/android/os/IVibratorService.aidl
frameworks/base/core/java/android/os/Vibrator.java
frameworks/base/core/java/android/os/SystemVibrator.java
下面，对这几个文件的功能进行简要说明。
文件1: SystemServer.java
它是系统服务，作用是启动、管理系统服务，包括“马达服务、Wifi服务、Activity管理服务”等等。
SystemServer是通过Zygote启动的，而Zygote又是在init中启动的，init则是kernel加载完毕之后启动的第一个进程。在这里，我们只需要知道“SystemServer是用来启动/管理马达服务即可。”
文件2: IVibratorService.aidl
它是马达服务对应的aidl配置文件。我们在aidl中定义了其它进程可以访问的外部接口；然后再通过VibratorService.java实现这些接口。
文件3: VibratorService.java
它是马达服务对应的aidl接口的实现程序。它实现IVibratorService.aidl的接口，从而实现马达服务；它的函数接口，是通过调用JNI层对应的马达控制函数来实现的。
文件4: Vibrator.java
它是马达服务开放给应用层的调用类。理论上讲，我们完全可以通过aidl直接调用马达服务，而不需要Vibrator.java类。但是！既然它存在，就肯定有它的理由。事实的确如此，Google之所以这么做。有以下几个原因：
第一，提供统一而且方便的服务调用方式。这里的“统一”，是指和所有其它的系统服务一样，我们调用服务时，需先通过getSystemService()获取服务，然后再调用服务的函数接口。这里的“方便”，是指若我们直接通过aidl调用，操作比较繁琐(若你用过aidl就会知道，需要先实现ServiceConnection接口以获取IBinder对象，然后再通过IBinder对象调用aidl的接口)； 而Vibrator.java封装之后的接口，将许多细节都隐藏了，非常便于应用者调用！
第二，基于安全的考虑。Vibrator.java封装隐藏了许多细节，而这些都是应用开发者不必要知道的。
第三，Vibrator是抽象类。它便于我们支持不同类型的马达：包括“将马达直接映射到文件”以及“将马达注册到输入子系统”中。
文件5: SystemVibrator.java
它是Vibrator.java的子类，实现了马达的服务接口。
下面，我们继续Read The Fucking Source Code，加深对上面知识的理解。
1 SystemServer.java
在frameworks/base/services/java/com/android/server/SystemServer.java中关于马达的代码如下：
{
VibratorService vibrator = null;
Slog.i(TAG, "Vibrator Service");
vibrator = new VibratorService(context);
ServiceManager.addService("vibrator", vibrator);
...
try {
vibrator.systemReady();
} catch (Throwable e) {
reportWtf("making Vibrator Service ready", e);
}
}从中，我们知道：
(01) SystemServer中会通过VibratorService()新建马达服务，并将其添加到ServiceManager中。
(02) 在Android系统启动完成之后，SystemServer会调用vibrator.systemReady()。
2 IVibratorService.aidl
在查看VibratorService.java之前，我们先看看它对应的aidl文件。frameworks/base/core/java/android/os/IVibratorService.aidl源码如下：
package android.os;
/** {@hide} */
interface IVibratorService
{
boolean hasVibrator();
void vibrate(long milliseconds, IBinder token);
void vibratePattern(in long[] pattern, int repeat, IBinder token);
void cancelVibrate(IBinder token);
}3 VibratorService.java
frameworks/base/services/java/com/android/server/VibratorService.java源码如下：
/*
* Copyright (C) 2008 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 com.android.server; import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.pm.PackageManager;
import android.database.ContentObserver;
import android.hardware.input.InputManager;
import android.os.Handler;
import android.os.IVibratorService;
import android.os.PowerManager;
import android.os.Process;
import android.os.RemoteException;
import android.os.IBinder;
import android.os.Binder;
import android.os.SystemClock;
import android.os.UserHandle;
import android.os.Vibrator;
import android.os.WorkSource;
import android.provider.Settings;
import android.provider.Settings.SettingNotFoundException;
import android.util.Slog;
import android.view.InputDevice; import java.util.ArrayList;
import java.util.LinkedList;
import java.util.ListIterator; public class VibratorService extends IVibratorService.Stub
implements InputManager.InputDeviceListener {
private static final String TAG = "VibratorService"; private final LinkedList<Vibration> mVibrations;
private Vibration mCurrentVibration;
private final WorkSource mTmpWorkSource = new WorkSource();
private final Handler mH = new Handler(); private final Context mContext;
private final PowerManager.WakeLock mWakeLock;
private InputManager mIm; volatile VibrateThread mThread; // mInputDeviceVibrators lock should be acquired after mVibrations lock, if both are
// to be acquired
private final ArrayList<Vibrator> mInputDeviceVibrators = new ArrayList<Vibrator>();
private boolean mVibrateInputDevicesSetting; // guarded by mInputDeviceVibrators
private boolean mInputDeviceListenerRegistered; // guarded by mInputDeviceVibrators native static boolean vibratorExists();
native static void vibratorOn(long milliseconds);
native static void vibratorOff(); private class Vibration implements IBinder.DeathRecipient {
private final IBinder mToken;
private final long mTimeout;
private final long mStartTime;
private final long[] mPattern;
private final int mRepeat;
private final int mUid; Vibration(IBinder token, long millis, int uid) {
this(token, millis, null, 0, uid);
} Vibration(IBinder token, long[] pattern, int repeat, int uid) {
this(token, 0, pattern, repeat, uid);
} private Vibration(IBinder token, long millis, long[] pattern,
int repeat, int uid) {
mToken = token;
mTimeout = millis;
mStartTime = SystemClock.uptimeMillis();
mPattern = pattern;
mRepeat = repeat;
mUid = uid;
} public void binderDied() {
synchronized (mVibrations) {
mVibrations.remove(this);
if (this == mCurrentVibration) {
doCancelVibrateLocked();
startNextVibrationLocked();
}
}
} public boolean hasLongerTimeout(long millis) {
if (mTimeout == 0) {
// This is a pattern, return false to play the simple
// vibration.
return false;
}
if ((mStartTime + mTimeout)
< (SystemClock.uptimeMillis() + millis)) {
// If this vibration will end before the time passed in, let
// the new vibration play.
return false;
}
return true;
}
} VibratorService(Context context) {
// Reset the hardware to a default state, in case this is a runtime
// restart instead of a fresh boot.
vibratorOff(); mContext = context;
PowerManager pm = (PowerManager)context.getSystemService(
Context.POWER_SERVICE);
mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "*vibrator*");
mWakeLock.setReferenceCounted(true); mVibrations = new LinkedList<Vibration>(); IntentFilter filter = new IntentFilter();
filter.addAction(Intent.ACTION_SCREEN_OFF);
context.registerReceiver(mIntentReceiver, filter);
} public void systemReady() {
mIm = (InputManager)mContext.getSystemService(Context.INPUT_SERVICE); mContext.getContentResolver().registerContentObserver(
Settings.System.getUriFor(Settings.System.VIBRATE_INPUT_DEVICES), true,
new ContentObserver(mH) {
@Override
public void onChange(boolean selfChange) {
updateInputDeviceVibrators();
}
}, UserHandle.USER_ALL); mContext.registerReceiver(new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
updateInputDeviceVibrators();
}
}, new IntentFilter(Intent.ACTION_USER_SWITCHED), null, mH); updateInputDeviceVibrators();
} public boolean hasVibrator() {
return doVibratorExists();
} public void vibrate(long milliseconds, IBinder token) {
if (mContext.checkCallingOrSelfPermission(android.Manifest.permission.VIBRATE)
!= PackageManager.PERMISSION_GRANTED) {
throw new SecurityException("Requires VIBRATE permission");
}
int uid = Binder.getCallingUid();
// We're running in the system server so we cannot crash. Check for a
// timeout of 0 or negative. This will ensure that a vibration has
// either a timeout of > 0 or a non-null pattern.
if (milliseconds <= 0 || (mCurrentVibration != null
&& mCurrentVibration.hasLongerTimeout(milliseconds))) {
// Ignore this vibration since the current vibration will play for
// longer than milliseconds.
return;
} Vibration vib = new Vibration(token, milliseconds, uid);
synchronized (mVibrations) {
removeVibrationLocked(token);
doCancelVibrateLocked();
mCurrentVibration = vib;
startVibrationLocked(vib);
}
} private boolean isAll0(long[] pattern) {
int N = pattern.length;
for (int i = 0; i < N; i++) {
if (pattern[i] != 0) {
return false;
}
}
return true;
} public void vibratePattern(long[] pattern, int repeat, IBinder token) {
if (mContext.checkCallingOrSelfPermission(android.Manifest.permission.VIBRATE)
!= PackageManager.PERMISSION_GRANTED) {
throw new SecurityException("Requires VIBRATE permission");
}
int uid = Binder.getCallingUid();
// so wakelock calls will succeed
long identity = Binder.clearCallingIdentity();
try {
if (false) {
String s = "";
int N = pattern.length;
for (int i=0; i<N; i++) {
s += " " + pattern[i];
}
Slog.i(TAG, "vibrating with pattern: " + s);
} // we're running in the server so we can't fail
if (pattern == null || pattern.length == 0
|| isAll0(pattern)
|| repeat >= pattern.length || token == null) {
return;
} Vibration vib = new Vibration(token, pattern, repeat, uid);
try {
token.linkToDeath(vib, 0);
} catch (RemoteException e) {
return;
} synchronized (mVibrations) {
removeVibrationLocked(token);
doCancelVibrateLocked();
if (repeat >= 0) {
mVibrations.addFirst(vib);
startNextVibrationLocked();
} else {
// A negative repeat means that this pattern is not meant
// to repeat. Treat it like a simple vibration.
mCurrentVibration = vib;
startVibrationLocked(vib);
}
}
}
finally {
Binder.restoreCallingIdentity(identity);
}
} public void cancelVibrate(IBinder token) {
mContext.enforceCallingOrSelfPermission(
android.Manifest.permission.VIBRATE,
"cancelVibrate"); // so wakelock calls will succeed
long identity = Binder.clearCallingIdentity();
try {
synchronized (mVibrations) {
final Vibration vib = removeVibrationLocked(token);
if (vib == mCurrentVibration) {
doCancelVibrateLocked();
startNextVibrationLocked();
}
}
}
finally {
Binder.restoreCallingIdentity(identity);
}
} private final Runnable mVibrationRunnable = new Runnable() {
public void run() {
synchronized (mVibrations) {
doCancelVibrateLocked();
startNextVibrationLocked();
}
}
}; // Lock held on mVibrations
private void doCancelVibrateLocked() {
if (mThread != null) {
synchronized (mThread) {
mThread.mDone = true;
mThread.notify();
}
mThread = null;
}
doVibratorOff();
mH.removeCallbacks(mVibrationRunnable);
} // Lock held on mVibrations
private void startNextVibrationLocked() {
if (mVibrations.size() <= 0) {
mCurrentVibration = null;
return;
}
mCurrentVibration = mVibrations.getFirst();
startVibrationLocked(mCurrentVibration);
} // Lock held on mVibrations
private void startVibrationLocked(final Vibration vib) {
if (vib.mTimeout != 0) {
doVibratorOn(vib.mTimeout);
mH.postDelayed(mVibrationRunnable, vib.mTimeout);
} else {
// mThread better be null here. doCancelVibrate should always be
// called before startNextVibrationLocked or startVibrationLocked.
mThread = new VibrateThread(vib);
mThread.start();
}
} // Lock held on mVibrations
private Vibration removeVibrationLocked(IBinder token) {
ListIterator<Vibration> iter = mVibrations.listIterator(0);
while (iter.hasNext()) {
Vibration vib = iter.next();
if (vib.mToken == token) {
iter.remove();
unlinkVibration(vib);
return vib;
}
}
// We might be looking for a simple vibration which is only stored in
// mCurrentVibration.
if (mCurrentVibration != null && mCurrentVibration.mToken == token) {
unlinkVibration(mCurrentVibration);
return mCurrentVibration;
}
return null;
} private void unlinkVibration(Vibration vib) {
if (vib.mPattern != null) {
// If Vibration object has a pattern,
// the Vibration object has also been linkedToDeath.
vib.mToken.unlinkToDeath(vib, 0);
}
} private void updateInputDeviceVibrators() {
synchronized (mVibrations) {
doCancelVibrateLocked(); synchronized (mInputDeviceVibrators) {
mVibrateInputDevicesSetting = false;
try {
mVibrateInputDevicesSetting = Settings.System.getIntForUser(
mContext.getContentResolver(),
Settings.System.VIBRATE_INPUT_DEVICES, UserHandle.USER_CURRENT) > 0;
} catch (SettingNotFoundException snfe) {
} if (mVibrateInputDevicesSetting) {
if (!mInputDeviceListenerRegistered) {
mInputDeviceListenerRegistered = true;
mIm.registerInputDeviceListener(this, mH);
}
} else {
if (mInputDeviceListenerRegistered) {
mInputDeviceListenerRegistered = false;
mIm.unregisterInputDeviceListener(this);
}
} mInputDeviceVibrators.clear();
if (mVibrateInputDevicesSetting) {
int[] ids = mIm.getInputDeviceIds();
for (int i = 0; i < ids.length; i++) {
InputDevice device = mIm.getInputDevice(ids[i]);
Vibrator vibrator = device.getVibrator();
if (vibrator.hasVibrator()) {
mInputDeviceVibrators.add(vibrator);
}
}
}
} startNextVibrationLocked();
}
} @Override
public void onInputDeviceAdded(int deviceId) {
updateInputDeviceVibrators();
} @Override
public void onInputDeviceChanged(int deviceId) {
updateInputDeviceVibrators();
} @Override
public void onInputDeviceRemoved(int deviceId) {
updateInputDeviceVibrators();
} private boolean doVibratorExists() {
// For now, we choose to ignore the presence of input devices that have vibrators
// when reporting whether the device has a vibrator. Applications often use this
// information to decide whether to enable certain features so they expect the
// result of hasVibrator() to be constant. For now, just report whether
// the device has a built-in vibrator.
//synchronized (mInputDeviceVibrators) {
// return !mInputDeviceVibrators.isEmpty() || vibratorExists();
//}
return vibratorExists();
} private void doVibratorOn(long millis) {
synchronized (mInputDeviceVibrators) {
final int vibratorCount = mInputDeviceVibrators.size();
if (vibratorCount != 0) {
for (int i = 0; i < vibratorCount; i++) {
mInputDeviceVibrators.get(i).vibrate(millis);
}
} else {
vibratorOn(millis);
}
}
} private void doVibratorOff() {
synchronized (mInputDeviceVibrators) {
final int vibratorCount = mInputDeviceVibrators.size();
if (vibratorCount != 0) {
for (int i = 0; i < vibratorCount; i++) {
mInputDeviceVibrators.get(i).cancel();
}
} else {
vibratorOff();
}
}
} private class VibrateThread extends Thread {
final Vibration mVibration;
boolean mDone; VibrateThread(Vibration vib) {
mVibration = vib;
mTmpWorkSource.set(vib.mUid);
mWakeLock.setWorkSource(mTmpWorkSource);
mWakeLock.acquire();
} private void delay(long duration) {
if (duration > 0) {
long bedtime = duration + SystemClock.uptimeMillis();
do {
try {
this.wait(duration);
}
catch (InterruptedException e) {
}
if (mDone) {
break;
}
duration = bedtime - SystemClock.uptimeMillis();
} while (duration > 0);
}
} public void run() {
Process.setThreadPriority(Process.THREAD_PRIORITY_URGENT_DISPLAY);
synchronized (this) {
int index = 0;
long[] pattern = mVibration.mPattern;
int len = pattern.length;
int repeat = mVibration.mRepeat;
long duration = 0; while (!mDone) {
// add off-time duration to any accumulated on-time duration
if (index < len) {
duration += pattern[index++];
} // sleep until it is time to start the vibrator
delay(duration);
if (mDone) {
break;
} if (index < len) {
// read on-time duration and start the vibrator
// duration is saved for delay() at top of loop
duration = pattern[index++];
if (duration > 0) {
VibratorService.this.doVibratorOn(duration);
}
} else {
if (repeat < 0) {
break;
} else {
index = repeat;
duration = 0;
}
}
}
mWakeLock.release();
}
synchronized (mVibrations) {
if (mThread == this) {
mThread = null;
}
if (!mDone) {
// If this vibration finished naturally, start the next
// vibration.
mVibrations.remove(mVibration);
unlinkVibration(mVibration);
startNextVibrationLocked();
}
}
}
}; BroadcastReceiver mIntentReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
if (intent.getAction().equals(Intent.ACTION_SCREEN_OFF)) {
synchronized (mVibrations) {
doCancelVibrateLocked(); int size = mVibrations.size();
for(int i = 0; i < size; i++) {
unlinkVibration(mVibrations.get(i));
} mVibrations.clear();
}
}
}
};
}
其中，VibratorService实际上是通过“本地方法”去控制马达的。例如，hasVibratora()最终是通过vibratorExists()来判断马达是否存在的。
4 Vibrator.java
frameworks/base/core/java/android/os/Vibrator.java源码如下：
package android.os;
import android.content.Context;
public abstract class Vibrator {
public Vibrator() {
}
public abstract boolean hasVibrator();
public abstract void vibrate(long milliseconds);
public abstract void vibrate(long[] pattern, int repeat);
public abstract void cancel();
}5 SystemVibrator.java
frameworks/base/core/java/android/os/SystemVibrator.java源码如下：
/*
* Copyright (C) 2012 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.os; import android.util.Log; /**
* Vibrator implementation that controls the main system vibrator.
*
* @hide
*/
public class SystemVibrator extends Vibrator {
private static final String TAG = "Vibrator"; private final IVibratorService mService;
private final Binder mToken = new Binder(); public SystemVibrator() {
mService = IVibratorService.Stub.asInterface(
ServiceManager.getService("vibrator"));
} @Override
public boolean hasVibrator() {
if (mService == null) {
Log.w(TAG, "Failed to vibrate; no vibrator service.");
return false;
}
try {
return mService.hasVibrator();
} catch (RemoteException e) {
}
return false;
} @Override
public void vibrate(long milliseconds) {
if (mService == null) {
Log.w(TAG, "Failed to vibrate; no vibrator service.");
return;
}
try {
mService.vibrate(milliseconds, mToken);
} catch (RemoteException e) {
Log.w(TAG, "Failed to vibrate.", e);
}
} @Override
public void vibrate(long[] pattern, int repeat) {
if (mService == null) {
Log.w(TAG, "Failed to vibrate; no vibrator service.");
return;
}
// catch this here because the server will do nothing. pattern may
// not be null, let that be checked, because the server will drop it
// anyway
if (repeat < pattern.length) {
try {
mService.vibratePattern(pattern, repeat, mToken);
} catch (RemoteException e) {
Log.w(TAG, "Failed to vibrate.", e);
}
} else {
throw new ArrayIndexOutOfBoundsException();
}
} @Override
public void cancel() {
if (mService == null) {
return;
}
try {
mService.cancelVibrate(mToken);
} catch (RemoteException e) {
Log.w(TAG, "Failed to cancel vibration.", e);
}
}
}
说明：
(01) 在构造函数SystemVibrator()中，我们通过 IVibratorService.Stub.asInterface(ServiceManager.getService("vibrator")) 获取马达服务，实际上获取的是VibratorService对象。
(02) SystemVibrator的接口都是调用VibratorService接口实现的。
在讲解“应用层如何通过getSystemService(VIBRATOR_SERVICE)获取马达服务，然后进一步的操作马达”之前，我们先看看应用层的马达操作示例！
Part 6 马达的应用示例
1 权限
调用马达服务，需要在manifest中添加相应的权限：
<!-- 震动马达权限 -->
<uses-permission android:name="android.permission.VIBRATE"/>
2 源码
源码如下：
package com.test; import android.app.Activity;
import android.os.Bundle;
import android.os.Vibrator;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ToggleButton;
import android.util.Log; public class VibratorTest extends Activity {
private static final String TAG = "skywang-->VibratorTest"; private Vibrator mVibrator;
private Button mOnce = null;
private ToggleButton mEndless = null; @Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main); // 获取震动马达服务
mVibrator= (Vibrator) getSystemService(VIBRATOR_SERVICE); mOnce = (Button) findViewById(R.id.vib_once);
mOnce.setOnClickListener(new View.OnClickListener() { @Override
public void onClick(View view) {
//震动指定时间
mVibrator.vibrate(100);
}
}); mEndless = (ToggleButton) findViewById(R.id.vib_endless);
mEndless.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
if (mEndless.isChecked()) {
//等待100ms后，按数组所给数值间隔震动；其后为重复次数，-1为不重复，0一直震动
mVibrator.vibrate(new long[]{100,20,100,40,100,60}, 0);
} else {
// 取消震动
mVibrator.cancel();
}
}
}); } @Override
protected void onStop() {
super.onStop();
if (mVibrator != null)
mVibrator= null;
}
}
点击下载：Android马达应用代码
Part 7 马达的应用如何调用到马达服务的
接下来，我们分析一下如何获取马达服务的：即 mVibrator= (Vibrator) getSystemService(VIBRATOR_SERVICE) 的工作原理。
1. Context.java中的getSystemService()
getSystemService()定义在frameworks/base/core/java/android/content/Context.java中，源码如下：
public abstract Object getSystemService(String name);
Context.java中的getSystemService() 是个抽象方法，它的实现在ContextImpl.java中。
2. ContextImpl.java中的getSystemService()
frameworks/base/core/java/android/app/ContextImpl.java中的 getSystemService() 源码如下：
@Override
public Object getSystemService(String name) {
ServiceFetcher fetcher = SYSTEM_SERVICE_MAP.get(name);
return fetcher == null ? null : fetcher.getService(this);
}
3. ContextImpl.java中的SYSTEM_SERVICE_MAP
SYSTEM_SERVICE_MAP是一个HashMap对象，它的相关代码如下：
private static final HashMap<String, ServiceFetcher> SYSTEM_SERVICE_MAP =
new HashMap<String, ServiceFetcher>(); SYSTEM_SERVICE_MAP的初始化，是在ContextImpl.java通过static静态模块完成的。源码如下：
static { ... // 注册“传感器服务”
registerService(SENSOR_SERVICE, new ServiceFetcher() {
public Object createService(ContextImpl ctx) {
return new SystemSensorManager(ctx.mMainThread.getHandler().getLooper());
}}); // 注册其它服务 ... // 注册马达服务
registerService(VIBRATOR_SERVICE, new ServiceFetcher() {
public Object createService(ContextImpl ctx) {
return new SystemVibrator();
}}); ...
}
说明：在上面的static静态模块中，会通过registerService()注册一系列的服务，包括马达服务。注册服务是通过registerService()实现的，下面我们看看registerService()的定义。
private static int sNextPerContextServiceCacheIndex = 0;
private static void registerService(String serviceName, ServiceFetcher fetcher) {
if (!(fetcher instanceof StaticServiceFetcher)) {
fetcher.mContextCacheIndex = sNextPerContextServiceCacheIndex++;
}
SYSTEM_SERVICE_MAP.put(serviceName, fetcher);
}
从中，我们知道，在registerService()中，会通过 SYSTEM_SERVICE_MAP.put(serviceName, fetcher) 将serviceName和fetcher添加到哈希表SYSTEM_SERVICE_MAP中。
对马达服务而言，添加到哈希表SYSTEM_SERVICE_MAP中的key-value中的key是VIBRATOR_SERVICE，value则是ServiceFetcher对象；而且该匿名ServiceFetcher对象的createService()方法会“通过new SystemVibrator()”返回SystemVibrator对象。而SystemVibrator我们在前面已经介绍过了，它是马达服务对外提供接口的类。
OK，接着往下看。
3. ContextImpl.java中的fetcher.getService(this)
public Object getSystemService(String name) {
ServiceFetcher fetcher = SYSTEM_SERVICE_MAP.get(name);
return fetcher == null ? null : fetcher.getService(this);
}我们已经知道SYSTEM_SERVICE_MAP是哈希表，通过SYSTEM_SERVICE_MAP.get(name)返回的是ServiceFetcher对象。
由于fetcher不为null，所以，getSystemService()会返回fetcher.getService(this)。我们看看ServiceFetcher中getService()源码：
static class ServiceFetcher {
int mContextCacheIndex = -1;
public Object getService(ContextImpl ctx) {
ArrayList<Object> cache = ctx.mServiceCache;
Object service;
synchronized (cache) {
if (cache.size() == 0) {
// “服务对象”缓冲
for (int i = 0; i < sNextPerContextServiceCacheIndex; i++) {
cache.add(null);
}
} else {
service = cache.get(mContextCacheIndex);
if (service != null) {
return service;
}
}
service = createService(ctx);
cache.set(mContextCacheIndex, service);
return service;
}
}
public Object createService(ContextImpl ctx) {
throw new RuntimeException("Not implemented");
}
}从中，我们发现，getService()实际上返回的是“通过createService(ctx)创建的service对象”。
而在registerService()注册马达服务时，我们匿名实现了createService()方法：它实际上是通过 new SystemVibrator() 返回SystemVibrator对象。
至此，我们知道：getSystemService(VIBRATOR_SERVICE) 返回的是 SystemVibrator对象！SystemVibrator前面已经分析过，这里就不再说明了。