# 电量优化

## 获取电量 

1.导入文件 

2.设置监控为true

```
#import "IOPSKeys.h"
#import "IOPowerSources.h"

-(double) getBatteryLevel{
    // 返回电量信息
    CFTypeRef blob = IOPSCopyPowerSourcesInfo();
    // 返回电量句柄列表数据
    CFArrayRef sources = IOPSCopyPowerSourcesList(blob);
    CFDictionaryRef pSource = NULL;
    const void *psValue;
    // 返回数组大小
    int numOfSources = CFArrayGetCount(sources);
    // 计算大小出错处理
    if (numOfSources == 0) {
        NSLog(@"Error in CFArrayGetCount");
        return -1.0f;
    }

    // 计算所剩电量
    for (int i=0; i<numOfSources; i++) {
        // 返回电源可读信息的字典
        pSource = IOPSGetPowerSourceDescription(blob, CFArrayGetValueAtIndex(sources, i));
        if (!pSource) {
            NSLog(@"Error in IOPSGetPowerSourceDescription");
            return -1.0f;
        }
        psValue = (CFStringRef) CFDictionaryGetValue(pSource, CFSTR(kIOPSNameKey));

        int curCapacity = 0;
        int maxCapacity = 0;
        double percentage;

        psValue = CFDictionaryGetValue(pSource, CFSTR(kIOPSCurrentCapacityKey));
        CFNumberGetValue((CFNumberRef)psValue, kCFNumberSInt32Type, &curCapacity);

        psValue = CFDictionaryGetValue(pSource, CFSTR(kIOPSMaxCapacityKey));
        CFNumberGetValue((CFNumberRef)psValue, kCFNumberSInt32Type, &maxCapacity);

        percentage = ((double) curCapacity / (double) maxCapacity * 100.0f);
        NSLog(@"curCapacity : %d / maxCapacity: %d , percentage: %.1f ", curCapacity, maxCapacity, percentage);
        return percentage;
    }
    return -1.
```

## 查看哪个线程耗电高

查看线程中电量使用情况&#x20;

1.通过线程信息中的threads数组里的线程信息结构体的thread\_basic\_info里面有一个记录CPU使用百分比的字段cpu\_usage

```
struct thread_basic_info {
        time_value_t    user_time;      /* user 运行的时间 */
        time_value_t    system_time;    /* system 运行的时间 */
        integer_t       cpu_usage;      /* CPU 使用百分比 */
        policy_t        policy;         /* 有效的计划策略 */
        integer_t       run_state;      /* run state (see below) */
        integer_t       flags;          /* various flags (see below) */
        integer_t       suspend_count;  /* suspend count for thread */
        integer_t       sleep_time;     /* 休眠时间 */
};
```

有了这个cpu\_usage字段，就可以遍历所有线程，查看哪个线程cpu使用百分比过高

```
// 轮询检查多个线程 CPU 情况
+ (void)updateCPU {
    thread_act_array_t threads;
    mach_msg_type_number_t threadCount = 0;
    const task_t thisTask = mach_task_self();
    kern_return_t kr = task_threads(thisTask, &threads, &threadCount);
    if (kr != KERN_SUCCESS) {
        return;
    }
    for (int i = 0; i < threadCount; i++) {
        thread_info_data_t threadInfo;
        thread_basic_info_t threadBaseInfo;
        mach_msg_type_number_t threadInfoCount = THREAD_INFO_MAX;
        if (thread_info((thread_act_t)threads[i], THREAD_BASIC_INFO, (thread_info_t)threadInfo, &threadInfoCount) == KERN_SUCCESS) {
            threadBaseInfo = (thread_basic_info_t)threadInfo;
            if (!(threadBaseInfo->flags & TH_FLAGS_IDLE)) {
                integer_t cpuUsage = threadBaseInfo->cpu_usage / 10;
                if (cpuUsage > 90) {
                    //cup 消耗大于 90 时打印和记录堆栈
                    NSString *reStr = smStackOfThread(threads[i]);
                    // 记录数据库中
                    [[[SMLagDB shareInstance] increaseWithStackString:reStr] subscribeNext:^(id x) {}];
                    NSLog(@"CPU useage overload thread stack：\n%@",reStr);
                }
            }
        }
    }
}
```

## 优化cpu耗电问题

1.避免在app处理大量复杂的数据计算，把数据传到服务器去处理&#x20;

2.对一定要在app处理的复杂计算，通过gcd的dispatch\_block\_create\_with\_qos\_class方法指定队列的qos为QOS\_CLASS\_UTILITY,因为他对电量做了优化 -------------------优化cpu耗电问题

## 优化I/O操作耗电问题

1.使用NSCache方式延时对I/0进行操作&#x20;

2.类似SDWebImage，先缓存到内存中，后缓存到磁盘中

```
- (UIImage *)imageFromMemoryCacheForKey:(NSString *)key {
    return [self.memCache objectForKey:key];
}

- (UIImage *)imageFromDiskCacheForKey:(NSString *)key {
    // 检查 NSCache 里是否有
    UIImage *image = [self imageFromMemoryCacheForKey:key];
    if (image) {
        return image;
    }
    // 从磁盘里读
    UIImage *diskImage = [self diskImageForKey:key];
    if (diskImage && self.shouldCacheImagesInMemory) {
        NSUInteger cost = SDCacheCostForImage(diskImage);
        [self.memCache setObject:diskImage forKey:key cost:cost];
    }
    return diskImage;
}
```

## 苹果电量优化最佳实践

1.可以从cpu、设备唤醒、网络、图形、动画、视频、定位、加速度计、陀螺仪、磁力计、蓝牙等考虑

1、<https://developer.apple.com/library/archive/documentation/Performance/Conceptual/EnergyGuide-iOS/index.html>

2、<https://developer.apple.com/videos/play/wwdc2017/238/>

3、<https://www.jianshu.com/p/4555704f9696>


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