Android之 看“马达”如何贯通Android系统 (从硬件设计 --> 驱动 --> HAL --> JNI --> Framework --> Applicati
16lz
2021-01-25
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。 三星A8的Datasheet中，关于GPH3_3的信息如下：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：
1 #include <linux/kernel.h> 2 #include <linux/types.h> 3 #include <linux/module.h> 4 #include <linux/device.h> 5 #include <linux/platform_device.h> 6 #include <linux/delay.h> 7 #include <linux/irq.h> 8 #include <linux/interrupt.h> 9 #include <linux/sysfs.h> 10 #include <linux/input.h> 11 #include <mach/gpio.h> 12 13 // vibrator 对应的GPIO 14 #define VIBRATOR_POWER_PORT (S5PV210_GPH3(3)) 15 16 typedef struct combo_module__t { 17 unsigned char status_vibrator; 18 } combo_module_t ; 19 20 static combo_module_t combo_module; 21 22 /* 23 * vibrator初始化函数：申请GPIO，并初始化vibrator状态。 24 */ 25 static void combo_module_init(void) 26 { 27 if(gpio_request(VIBRATOR_POWER_PORT, "vibrator power")) { 28 printk("misc_sysfs.c request vibrator gpio failse.\n"); 29 } 30 gpio_pull_updown(VIBRATOR_POWER_PORT, PullDisable); 31 gpio_direction_output(VIBRATOR_POWER_PORT, GPIO_LOW); 32 33 combo_module.status_vibrator = 0; 34 } 35 36 /* 37 * vibrator控制函数 38 */ 39 staticvoid combo_module_control(void) 40 { 41 if(combo_module.status_vibrator) 42 { 43 gpio_direction_output(VIBRATOR_POWER_PORT, GPIO_HIGH); 44 } 45 else 46 { 47 gpio_direction_output(VIBRATOR_POWER_PORT, GPIO_LOW); 48 } 49 50 } 51 52 53 /////////////////////////////////////////////////////////////////////////////////////////////////////////// 54 55 static ssize_t show_vibrator_onoff (struct device *dev, struct device_attribute *attr, char *buf) 56 { 57 return sprintf(buf, "%d\n", combo_module.status_vibrator); 58 } 59 60 static ssize_t set_vibrator_onoff (struct device *dev, struct device_attribute *attr, const char *buf, size_t count) 61 { 62 unsigned int val; 63 64 if(!(sscanf(buf, "%u\n", &val))) return -EINVAL; 65 66 //printk("set_vibrator_onoff:%d\n",val); 67 68 if(!val ) 69 { 70 combo_module.status_vibrator = 0; 71 combo_module_control(); 72 } 73 else 74 { 75 combo_module.status_vibrator = 1; 76 combo_module_control(); 77 78 msleep(val); 79 80 combo_module.status_vibrator = 0; 81 combo_module_control(); 82 } 83 84 return count; 85 } 86 87 static ssize_t show_vibrator_onoff (struct device *dev, struct device_attribute *attr, char *buf); 88 static ssize_t set_vibrator_onoff (struct device *dev, struct device_attribute *attr, const char *buf, size_t count); 89 // 将vibrator注册到sysfs文件系统。 90 // 参数说明： 91 // vibrator_onoff : vibrator对应在sysfs下的文件节点名称 92 // S_IRWXUGO : 文件节点的属性 93 // show_vibrator_onoff : 对应的读函数 94 // set_vibrator_onoff : 对应的写函数 95 static DEVICE_ATTR(vibrator_onoff, S_IRWXUGO, show_vibrator_onoff, set_vibrator_onoff); 96 97 98 static struct attribute *control_sysfs_entries[] = { 99 &dev_attr_vibrator_onoff.attr,100 NULL101 };102 103 static struct attribute_group control_sysfs_attr_group = {104 .name = NULL,105 .attrs = control_sysfs_entries,106 };107 108 static int control_sysfs_probe(struct platform_device *pdev) 109 {110 printk("vibrator probe");111 combo_module_init();112 combo_module_control();113 return sysfs_create_group(&pdev->dev.kobj, &control_sysfs_attr_group);114 }115 116 staticint control_sysfs_remove(struct platform_device *pdev) 117 {118 sysfs_remove_group(&pdev->dev.kobj, &control_sysfs_attr_group);119 120 return 0;121 }122 123 #ifdef CONFIG_PM124 static int control_sysfs_resume(struct platform_device *dev)125 {126 127 combo_module_control();128 129 return 0;130 }131 132 static int control_sysfs_suspend(struct platform_device *dev, pm_message_t state)133 {134 135 combo_module_control();136 137 return 0;138 }139 #else140 #define control_sysfs_suspend NULL141 #define control_sysfs_resume NULL142 #endif143 144 145 static struct platform_driver control_sysfs_driver = {146 .driver = {147 .name = "misc_ctl",148 .owner = THIS_MODULE,149 },150 .probe = control_sysfs_probe,151 .remove = control_sysfs_remove,152 .suspend = control_sysfs_suspend,153 .resume = control_sysfs_resume,154 };155 156 static int __init control_sysfs_init(void)157 { 158 // 将vibrator注册到platform总线159 printk("vibrator init");160 return platform_driver_register(&control_sysfs_driver);161 }162 163 static void __exit control_sysfs_exit(void)164 {165 platform_driver_unregister(&control_sysfs_driver);166 }167 168 169 module_init(control_sysfs_init);170 module_exit(control_sysfs_exit);171 172 173 MODULE_DESCRIPTION("misc control driver");174 MODULE_AUTHOR("other");175 MODULE_LICENSE("GPL");View Code
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：
1 /* 2 * Copyright (C) 2008 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 *10 * Unless required by applicable law or agreed to in writing, software11 * distributed under the License is distributed on an "AS IS" BASIS,12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.13 * See the License for the specific language governing permissions and14 * limitations under the License.15 */16 #include <hardware_legacy/vibrator.h>17 #include "qemu.h"18 19 #include <stdio.h>20 #include <unistd.h>21 #include <fcntl.h>22 #include <errno.h>23 24 #define THE_DEVICE "/sys/devices/platform/misc_ctl/vibrator_onoff"25 26 int vibrator_exists()27 {28 int fd;29 30 #ifdef QEMU_HARDWARE31 if (qemu_check()) {32 return 1;33 }34 #endif35 36 fd = open(THE_DEVICE, O_RDWR);37 if(fd < 0)38 return 0;39 close(fd);40 return 1;41 }42 43 static int sendit(int timeout_ms)44 {45 int nwr, ret, fd;46 char value[20];47 48 #ifdef QEMU_HARDWARE49 if (qemu_check()) {50 return qemu_control_command( "vibrator:%d", timeout_ms );51 }52 #endif53 54 fd = open(THE_DEVICE, O_RDWR);55 if(fd < 0)56 return errno;57 58 nwr = sprintf(value, "%d\n", timeout_ms);59 ret = write(fd, value, nwr);60 61 close(fd);62 63 return (ret == nwr) ? 0 : -1;64 }65 66 int vibrator_on(int timeout_ms)67 {68 /* constant on, up to maximum allowed time */69 return sendit(timeout_ms);70 }71 72 int vibrator_off()73 {74 return sendit(0);75 }View Code
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：
1 /* 2 * Copyright (C) 2009 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 *10 * Unless required by applicable law or agreed to in writing, software11 * distributed under the License is distributed on an "AS IS" BASIS,12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.13 * See the License for the specific language governing permissions and14 * limitations under the License.15 */16 17 #define LOG_TAG "VibratorService"18 19 #include "jni.h"20 #include "JNIHelp.h"21 #include "android_runtime/AndroidRuntime.h"22 23 #include <utils/misc.h>24 #include <utils/Log.h>25 #include <hardware_legacy/vibrator.h>26 27 #include <stdio.h>28 29 namespace android30 {31 32 static jboolean vibratorExists(JNIEnv *env, jobject clazz)33 {34 return vibrator_exists() > 0 ? JNI_TRUE : JNI_FALSE;35 }36 37 static void vibratorOn(JNIEnv *env, jobject clazz, jlong timeout_ms)38 {39 // ALOGI("vibratorOn\n");40 vibrator_on(timeout_ms);41 }42 43 static void vibratorOff(JNIEnv *env, jobject clazz)44 {45 // ALOGI("vibratorOff\n");46 vibrator_off();47 }48 49 static JNINativeMethod method_table[] = {50 { "vibratorExists", "()Z", (void*)vibratorExists },51 { "vibratorOn", "(J)V", (void*)vibratorOn },52 { "vibratorOff", "()V", (void*)vibratorOff }53 };54 55 int register_android_server_VibratorService(JNIEnv *env)56 {57 return jniRegisterNativeMethods(env, "com/android/server/VibratorService",58 method_table, NELEM(method_table));59 }60 61 };View Code
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_tracingSAVE_MAKEFILES := $(call all-named-subdir-makefiles,$(legacy_modules))LEGACY_AUDIO_MAKEFILES := $(call all-named-subdir-makefiles,audio)include $(SAVE_MAKEFILES)...LOCAL_MODULE:= libhardware_legacyinclude $(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_serversinclude $(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：
1 frameworks/base/services/java/com/android/server/SystemServer.java2 frameworks/base/services/java/com/android/server/VibratorService.java3 frameworks/base/core/java/android/os/IVibratorService.aidl4 frameworks/base/core/java/android/os/Vibrator.java5 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：
1 { 2 VibratorService vibrator = null; 3 4 Slog.i(TAG, "Vibrator Service"); 5 vibrator = new VibratorService(context); 6 ServiceManager.addService("vibrator", vibrator); 7 8 ... 9 10 try {11 vibrator.systemReady();12 } catch (Throwable e) {13 reportWtf("making Vibrator Service ready", e);14 }15 }
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：
1 package android.os; 2 3 /** {@hide} */ 4 interface IVibratorService 5 { 6 boolean hasVibrator(); 7 void vibrate(long milliseconds, IBinder token); 8 void vibratePattern(in long[] pattern, int repeat, IBinder token); 9 void cancelVibrate(IBinder token);10 }
3 VibratorService.java
frameworks/base/services/java/com/android/server/VibratorService.java源码如下：
1 /* 2 * Copyright (C) 2008 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.android.server; 18 19 import android.content.BroadcastReceiver; 20 import android.content.Context; 21 import android.content.Intent; 22 import android.content.IntentFilter; 23 import android.content.pm.PackageManager; 24 import android.database.ContentObserver; 25 import android.hardware.input.InputManager; 26 import android.os.Handler; 27 import android.os.IVibratorService; 28 import android.os.PowerManager; 29 import android.os.Process; 30 import android.os.RemoteException; 31 import android.os.IBinder; 32 import android.os.Binder; 33 import android.os.SystemClock; 34 import android.os.UserHandle; 35 import android.os.Vibrator; 36 import android.os.WorkSource; 37 import android.provider.Settings; 38 import android.provider.Settings.SettingNotFoundException; 39 import android.util.Slog; 40 import android.view.InputDevice; 41 42 import java.util.ArrayList; 43 import java.util.LinkedList; 44 import java.util.ListIterator; 45 46 public class VibratorService extends IVibratorService.Stub 47 implements InputManager.InputDeviceListener { 48 private static final String TAG = "VibratorService"; 49 50 private final LinkedList<Vibration> mVibrations; 51 private Vibration mCurrentVibration; 52 private final WorkSource mTmpWorkSource = new WorkSource(); 53 private final Handler mH = new Handler(); 54 55 private final Context mContext; 56 private final PowerManager.WakeLock mWakeLock; 57 private InputManager mIm; 58 59 volatile VibrateThread mThread; 60 61 // mInputDeviceVibrators lock should be acquired after mVibrations lock, if both are 62 // to be acquired 63 private final ArrayList<Vibrator> mInputDeviceVibrators = new ArrayList<Vibrator>(); 64 private boolean mVibrateInputDevicesSetting; // guarded by mInputDeviceVibrators 65 private boolean mInputDeviceListenerRegistered; // guarded by mInputDeviceVibrators 66 67 native static boolean vibratorExists(); 68 native static void vibratorOn(long milliseconds); 69 native static void vibratorOff(); 70 71 private class Vibration implements IBinder.DeathRecipient { 72 private final IBinder mToken; 73 private final long mTimeout; 74 private final long mStartTime; 75 private final long[] mPattern; 76 private final int mRepeat; 77 private final int mUid; 78 79 Vibration(IBinder token, long millis, int uid) { 80 this(token, millis, null, 0, uid); 81 } 82 83 Vibration(IBinder token, long[] pattern, int repeat, int uid) { 84 this(token, 0, pattern, repeat, uid); 85 } 86 87 private Vibration(IBinder token, long millis, long[] pattern, 88 int repeat, int uid) { 89 mToken = token; 90 mTimeout = millis; 91 mStartTime = SystemClock.uptimeMillis(); 92 mPattern = pattern; 93 mRepeat = repeat; 94 mUid = uid; 95 } 96 97 public void binderDied() { 98 synchronized (mVibrations) { 99 mVibrations.remove(this);100 if (this == mCurrentVibration) {101 doCancelVibrateLocked();102 startNextVibrationLocked();103 }104 }105 }106 107 public boolean hasLongerTimeout(long millis) {108 if (mTimeout == 0) {109 // This is a pattern, return false to play the simple110 // vibration.111 return false;112 }113 if ((mStartTime + mTimeout)114 < (SystemClock.uptimeMillis() + millis)) {115 // If this vibration will end before the time passed in, let116 // the new vibration play.117 return false;118 }119 return true;120 }121 }122 123 VibratorService(Context context) {124 // Reset the hardware to a default state, in case this is a runtime125 // restart instead of a fresh boot.126 vibratorOff();127 128 mContext = context;129 PowerManager pm = (PowerManager)context.getSystemService(130 Context.POWER_SERVICE);131 mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "*vibrator*");132 mWakeLock.setReferenceCounted(true);133 134 mVibrations = new LinkedList<Vibration>();135 136 IntentFilter filter = new IntentFilter();137 filter.addAction(Intent.ACTION_SCREEN_OFF);138 context.registerReceiver(mIntentReceiver, filter);139 }140 141 public void systemReady() {142 mIm = (InputManager)mContext.getSystemService(Context.INPUT_SERVICE);143 144 mContext.getContentResolver().registerContentObserver(145 Settings.System.getUriFor(Settings.System.VIBRATE_INPUT_DEVICES), true,146 new ContentObserver(mH) {147 @Override148 public void onChange(boolean selfChange) {149 updateInputDeviceVibrators();150 }151 }, UserHandle.USER_ALL);152 153 mContext.registerReceiver(new BroadcastReceiver() {154 @Override155 public void onReceive(Context context, Intent intent) {156 updateInputDeviceVibrators();157 }158 }, new IntentFilter(Intent.ACTION_USER_SWITCHED), null, mH);159 160 updateInputDeviceVibrators();161 }162 163 public boolean hasVibrator() {164 return doVibratorExists();165 }166 167 public void vibrate(long milliseconds, IBinder token) {168 if (mContext.checkCallingOrSelfPermission(android.Manifest.permission.VIBRATE)169 != PackageManager.PERMISSION_GRANTED) {170 throw new SecurityException("Requires VIBRATE permission");171 }172 int uid = Binder.getCallingUid();173 // We're running in the system server so we cannot crash. Check for a174 // timeout of 0 or negative. This will ensure that a vibration has175 // either a timeout of > 0 or a non-null pattern.176 if (milliseconds <= 0 || (mCurrentVibration != null177 && mCurrentVibration.hasLongerTimeout(milliseconds))) {178 // Ignore this vibration since the current vibration will play for179 // longer than milliseconds.180 return;181 }182 183 Vibration vib = new Vibration(token, milliseconds, uid);184 synchronized (mVibrations) {185 removeVibrationLocked(token);186 doCancelVibrateLocked();187 mCurrentVibration = vib;188 startVibrationLocked(vib);189 }190 }191 192 private boolean isAll0(long[] pattern) {193 int N = pattern.length;194 for (int i = 0; i < N; i++) {195 if (pattern[i] != 0) {196 return false;197 }198 }199 return true;200 }201 202 public void vibratePattern(long[] pattern, int repeat, IBinder token) {203 if (mContext.checkCallingOrSelfPermission(android.Manifest.permission.VIBRATE)204 != PackageManager.PERMISSION_GRANTED) {205 throw new SecurityException("Requires VIBRATE permission");206 }207 int uid = Binder.getCallingUid();208 // so wakelock calls will succeed209 long identity = Binder.clearCallingIdentity();210 try {211 if (false) {212 String s = "";213 int N = pattern.length;214 for (int i=0; i<N; i++) {215 s += " " + pattern[i];216 }217 Slog.i(TAG, "vibrating with pattern: " + s);218 }219 220 // we're running in the server so we can't fail221 if (pattern == null || pattern.length == 0222 || isAll0(pattern)223 || repeat >= pattern.length || token == null) {224 return;225 }226 227 Vibration vib = new Vibration(token, pattern, repeat, uid);228 try {229 token.linkToDeath(vib, 0);230 } catch (RemoteException e) {231 return;232 }233 234 synchronized (mVibrations) {235 removeVibrationLocked(token);236 doCancelVibrateLocked();237 if (repeat >= 0) {238 mVibrations.addFirst(vib);239 startNextVibrationLocked();240 } else {241 // A negative repeat means that this pattern is not meant242 // to repeat. Treat it like a simple vibration.243 mCurrentVibration = vib;244 startVibrationLocked(vib);245 }246 }247 }248 finally {249 Binder.restoreCallingIdentity(identity);250 }251 }252 253 public void cancelVibrate(IBinder token) {254 mContext.enforceCallingOrSelfPermission(255 android.Manifest.permission.VIBRATE,256 "cancelVibrate");257 258 // so wakelock calls will succeed259 long identity = Binder.clearCallingIdentity();260 try {261 synchronized (mVibrations) {262 final Vibration vib = removeVibrationLocked(token);263 if (vib == mCurrentVibration) {264 doCancelVibrateLocked();265 startNextVibrationLocked();266 }267 }268 }269 finally {270 Binder.restoreCallingIdentity(identity);271 }272 }273 274 private final Runnable mVibrationRunnable = new Runnable() {275 public void run() {276 synchronized (mVibrations) {277 doCancelVibrateLocked();278 startNextVibrationLocked();279 }280 }281 };282 283 // Lock held on mVibrations284 private void doCancelVibrateLocked() {285 if (mThread != null) {286 synchronized (mThread) {287 mThread.mDone = true;288 mThread.notify();289 }290 mThread = null;291 }292 doVibratorOff();293 mH.removeCallbacks(mVibrationRunnable);294 }295 296 // Lock held on mVibrations297 private void startNextVibrationLocked() {298 if (mVibrations.size() <= 0) {299 mCurrentVibration = null;300 return;301 }302 mCurrentVibration = mVibrations.getFirst();303 startVibrationLocked(mCurrentVibration);304 }305 306 // Lock held on mVibrations307 private void startVibrationLocked(final Vibration vib) {308 if (vib.mTimeout != 0) {309 doVibratorOn(vib.mTimeout);310 mH.postDelayed(mVibrationRunnable, vib.mTimeout);311 } else {312 // mThread better be null here. doCancelVibrate should always be313 // called before startNextVibrationLocked or startVibrationLocked.314 mThread = new VibrateThread(vib);315 mThread.start();316 }317 }318 319 // Lock held on mVibrations320 private Vibration removeVibrationLocked(IBinder token) {321 ListIterator<Vibration> iter = mVibrations.listIterator(0);322 while (iter.hasNext()) {323 Vibration vib = iter.next();324 if (vib.mToken == token) {325 iter.remove();326 unlinkVibration(vib);327 return vib;328 }329 }330 // We might be looking for a simple vibration which is only stored in331 // mCurrentVibration.332 if (mCurrentVibration != null && mCurrentVibration.mToken == token) {333 unlinkVibration(mCurrentVibration);334 return mCurrentVibration;335 }336 return null;337 }338 339 private void unlinkVibration(Vibration vib) {340 if (vib.mPattern != null) {341 // If Vibration object has a pattern,342 // the Vibration object has also been linkedToDeath.343 vib.mToken.unlinkToDeath(vib, 0);344 }345 }346 347 private void updateInputDeviceVibrators() {348 synchronized (mVibrations) {349 doCancelVibrateLocked();350 351 synchronized (mInputDeviceVibrators) {352 mVibrateInputDevicesSetting = false;353 try {354 mVibrateInputDevicesSetting = Settings.System.getIntForUser(355 mContext.getContentResolver(),356 Settings.System.VIBRATE_INPUT_DEVICES, UserHandle.USER_CURRENT) > 0;357 } catch (SettingNotFoundException snfe) {358 }359 360 if (mVibrateInputDevicesSetting) {361 if (!mInputDeviceListenerRegistered) {362 mInputDeviceListenerRegistered = true;363 mIm.registerInputDeviceListener(this, mH);364 }365 } else {366 if (mInputDeviceListenerRegistered) {367 mInputDeviceListenerRegistered = false;368 mIm.unregisterInputDeviceListener(this);369 }370 }371 372 mInputDeviceVibrators.clear();373 if (mVibrateInputDevicesSetting) {374 int[] ids = mIm.getInputDeviceIds();375 for (int i = 0; i < ids.length; i++) {376 InputDevice device = mIm.getInputDevice(ids[i]);377 Vibrator vibrator = device.getVibrator();378 if (vibrator.hasVibrator()) {379 mInputDeviceVibrators.add(vibrator);380 }381 }382 }383 }384 385 startNextVibrationLocked();386 }387 }388 389 @Override390 public void onInputDeviceAdded(int deviceId) {391 updateInputDeviceVibrators();392 }393 394 @Override395 public void onInputDeviceChanged(int deviceId) {396 updateInputDeviceVibrators();397 }398 399 @Override400 public void onInputDeviceRemoved(int deviceId) {401 updateInputDeviceVibrators();402 }403 404 private boolean doVibratorExists() {405 // For now, we choose to ignore the presence of input devices that have vibrators406 // when reporting whether the device has a vibrator. Applications often use this407 // information to decide whether to enable certain features so they expect the408 // result of hasVibrator() to be constant. For now, just report whether409 // the device has a built-in vibrator.410 //synchronized (mInputDeviceVibrators) {411 // return !mInputDeviceVibrators.isEmpty() || vibratorExists();412 //}413 return vibratorExists();414 }415 416 private void doVibratorOn(long millis) {417 synchronized (mInputDeviceVibrators) {418 final int vibratorCount = mInputDeviceVibrators.size();419 if (vibratorCount != 0) {420 for (int i = 0; i < vibratorCount; i++) {421 mInputDeviceVibrators.get(i).vibrate(millis);422 }423 } else {424 vibratorOn(millis);425 }426 }427 }428 429 private void doVibratorOff() {430 synchronized (mInputDeviceVibrators) {431 final int vibratorCount = mInputDeviceVibrators.size();432 if (vibratorCount != 0) {433 for (int i = 0; i < vibratorCount; i++) {434 mInputDeviceVibrators.get(i).cancel();435 }436 } else {437 vibratorOff();438 }439 }440 }441 442 private class VibrateThread extends Thread {443 final Vibration mVibration;444 boolean mDone;445 446 VibrateThread(Vibration vib) {447 mVibration = vib;448 mTmpWorkSource.set(vib.mUid);449 mWakeLock.setWorkSource(mTmpWorkSource);450 mWakeLock.acquire();451 }452 453 private void delay(long duration) {454 if (duration > 0) {455 long bedtime = duration + SystemClock.uptimeMillis();456 do {457 try {458 this.wait(duration);459 }460 catch (InterruptedException e) {461 }462 if (mDone) {463 break;464 }465 duration = bedtime - SystemClock.uptimeMillis();466 } while (duration > 0);467 }468 }469 470 public void run() {471 Process.setThreadPriority(Process.THREAD_PRIORITY_URGENT_DISPLAY);472 synchronized (this) {473 int index = 0;474 long[] pattern = mVibration.mPattern;475 int len = pattern.length;476 int repeat = mVibration.mRepeat;477 long duration = 0;478 479 while (!mDone) {480 // add off-time duration to any accumulated on-time duration481 if (index < len) {482 duration += pattern[index++];483 }484 485 // sleep until it is time to start the vibrator486 delay(duration);487 if (mDone) {488 break;489 }490 491 if (index < len) {492 // read on-time duration and start the vibrator493 // duration is saved for delay() at top of loop494 duration = pattern[index++];495 if (duration > 0) {496 VibratorService.this.doVibratorOn(duration);497 }498 } else {499 if (repeat < 0) {500 break;501 } else {502 index = repeat;503 duration = 0;504 }505 }506 }507 mWakeLock.release();508 }509 synchronized (mVibrations) {510 if (mThread == this) {511 mThread = null;512 }513 if (!mDone) {514 // If this vibration finished naturally, start the next515 // vibration.516 mVibrations.remove(mVibration);517 unlinkVibration(mVibration);518 startNextVibrationLocked();519 }520 }521 }522 };523 524 BroadcastReceiver mIntentReceiver = new BroadcastReceiver() {525 public void onReceive(Context context, Intent intent) {526 if (intent.getAction().equals(Intent.ACTION_SCREEN_OFF)) {527 synchronized (mVibrations) {528 doCancelVibrateLocked();529 530 int size = mVibrations.size();531 for(int i = 0; i < size; i++) {532 unlinkVibration(mVibrations.get(i));533 }534 535 mVibrations.clear();536 }537 }538 }539 };540 }View Code
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：
1 package android.os; 2 3 import android.content.Context; 4 5 public abstract class Vibrator { 6 7 public Vibrator() { 8 } 9 10 public abstract boolean hasVibrator();11 12 public abstract void vibrate(long milliseconds);13 14 public abstract void vibrate(long[] pattern, int repeat);15 16 public abstract void cancel();17 }
5 SystemVibrator.java
frameworks/base/core/java/android/os/SystemVibrator.java源码如下：
1 /* 2 * Copyright (C) 2012 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 *10 * Unless required by applicable law or agreed to in writing, software11 * distributed under the License is distributed on an "AS IS" BASIS,12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.13 * See the License for the specific language governing permissions and14 * limitations under the License.15 */16 17 package android.os;18 19 import android.util.Log;20 21 /**22 * Vibrator implementation that controls the main system vibrator.23 *24 * @hide25 */26 public class SystemVibrator extends Vibrator {27 private static final String TAG = "Vibrator";28 29 private final IVibratorService mService;30 private final Binder mToken = new Binder();31 32 public SystemVibrator() {33 mService = IVibratorService.Stub.asInterface(34 ServiceManager.getService("vibrator"));35 }36 37 @Override38 public boolean hasVibrator() {39 if (mService == null) {40 Log.w(TAG, "Failed to vibrate; no vibrator service.");41 return false;42 }43 try {44 return mService.hasVibrator();45 } catch (RemoteException e) {46 }47 return false;48 }49 50 @Override51 public void vibrate(long milliseconds) {52 if (mService == null) {53 Log.w(TAG, "Failed to vibrate; no vibrator service.");54 return;55 }56 try {57 mService.vibrate(milliseconds, mToken);58 } catch (RemoteException e) {59 Log.w(TAG, "Failed to vibrate.", e);60 }61 }62 63 @Override64 public void vibrate(long[] pattern, int repeat) {65 if (mService == null) {66 Log.w(TAG, "Failed to vibrate; no vibrator service.");67 return;68 }69 // catch this here because the server will do nothing. pattern may70 // not be null, let that be checked, because the server will drop it71 // anyway72 if (repeat < pattern.length) {73 try {74 mService.vibratePattern(pattern, repeat, mToken);75 } catch (RemoteException e) {76 Log.w(TAG, "Failed to vibrate.", e);77 }78 } else {79 throw new ArrayIndexOutOfBoundsException();80 }81 }82 83 @Override84 public void cancel() {85 if (mService == null) {86 return;87 }88 try {89 mService.cancelVibrate(mToken);90 } catch (RemoteException e) {91 Log.w(TAG, "Failed to cancel vibration.", e);92 }93 }94 }View Code
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：
1 package com.test; 2 3 import android.app.Activity; 4 import android.os.Bundle; 5 import android.os.Vibrator; 6 import android.view.View; 7 import android.view.View.OnClickListener; 8 import android.widget.Button; 9 import android.widget.ToggleButton;10 import android.util.Log;11 12 public class VibratorTest extends Activity {13 private static final String TAG = "skywang-->VibratorTest";14 15 private Vibrator mVibrator;16 private Button mOnce = null;17 private ToggleButton mEndless = null;18 19 @Override20 protected void onCreate(Bundle savedInstanceState) {21 super.onCreate(savedInstanceState);22 setContentView(R.layout.main);23 24 // 获取震动马达服务25 mVibrator= (Vibrator) getSystemService(VIBRATOR_SERVICE);26 27 mOnce = (Button) findViewById(R.id.vib_once);28 mOnce.setOnClickListener(new View.OnClickListener() {29 30 @Override31 public void onClick(View view) {32 //震动指定时间33 mVibrator.vibrate(100);34 }35 });36 37 mEndless = (ToggleButton) findViewById(R.id.vib_endless);38 mEndless.setOnClickListener(new OnClickListener() {39 @Override40 public void onClick(View v) {41 if (mEndless.isChecked()) {42 //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43 mVibrator.vibrate(new long[]{100,20,100,40,100,60}, 0);44 } else {45 // 取消震动 46 mVibrator.cancel();47 }48 }49 });50 51 }52 53 @Override54 protected void onStop() {55 super.onStop();56 if (mVibrator != null)57 mVibrator= null;58 }59 }
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：
1 @Override2 public Object getSystemService(String name) {3 ServiceFetcher fetcher = SYSTEM_SERVICE_MAP.get(name);4 return fetcher == null ? null : fetcher.getService(this);5 }
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：
1 private static final HashMap<String, ServiceFetcher> SYSTEM_SERVICE_MAP = 2 new HashMap<String, ServiceFetcher>(); 3 4 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： 5 static { 6 7 ... 8 9 // 注册“传感器服务”10 registerService(SENSOR_SERVICE, new ServiceFetcher() {11 public Object createService(ContextImpl ctx) {12 return new SystemSensorManager(ctx.mMainThread.getHandler().getLooper());13 }});14 15 // 注册其它服务 ...16 17 // 注册马达服务18 registerService(VIBRATOR_SERVICE, new ServiceFetcher() {19 public Object createService(ContextImpl ctx) {20 return new SystemVibrator();21 }});22 23 ...24 }
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。
1 private static int sNextPerContextServiceCacheIndex = 0;2 private static void registerService(String serviceName, ServiceFetcher fetcher) {3 if (!(fetcher instanceof StaticServiceFetcher)) {4 fetcher.mContextCacheIndex = sNextPerContextServiceCacheIndex++;5 }6 SYSTEM_SERVICE_MAP.put(serviceName, fetcher);7 }
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)
1 public Object getSystemService(String name) {2 ServiceFetcher fetcher = SYSTEM_SERVICE_MAP.get(name);3 return fetcher == null ? null : fetcher.getService(this);4 }
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：
1 static class ServiceFetcher { 2 int mContextCacheIndex = -1; 3 4 public Object getService(ContextImpl ctx) { 5 ArrayList<Object> cache = ctx.mServiceCache; 6 Object service; 7 synchronized (cache) { 8 if (cache.size() == 0) { 9 10 // “服务对象”缓冲11 for (int i = 0; i < sNextPerContextServiceCacheIndex; i++) {12 cache.add(null);13 }14 } else {15 service = cache.get(mContextCacheIndex);16 if (service != null) {17 return service;18 }19 }20 service = createService(ctx);21 cache.set(mContextCacheIndex, service);22 return service;23 }24 }25 26 public Object createService(ContextImpl ctx) {27 throw new RuntimeException("Not implemented");28 }29 }
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。
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