小编use*_*443的帖子

我如何投射到派生类？以下方法都会出现以下错误:

无法从BaseType转换为DerivedType.没有构造函数可以采用源类型,或构造函数重载解析是不明确的.

BaseType m_baseType;

DerivedType m_derivedType = m_baseType; // gives same error

DerivedType m_derivedType = (DerivedType)m_baseType; // gives same error

DerivedType * m_derivedType = (DerivedType*) & m_baseType; // gives same error

我现在试图隐藏iOS 4.3中的状态栏,现在setStatusBarHidden:animated:已弃用:

[[UIApplication sharedApplication] setStatusBarHidden:YES animated:NO]; //deprecated

plist文件中唯一存在的选项是:状态栏最初是隐藏的.这只会隐藏应用程序开头的状态栏.

干杯

我正在尝试将一个库添加到Visual Studio C++项目中,但是,当我转到项目属性时,我只有选项,

Common Properties
    Startup Project
    Project Dependencies
    Debug Source File
Configuration Properites
    Configuration

为什么我看不到链接器选项？

我知道这个问题已经在网站上被问了很多,但是,我似乎无法找到解决方案.当应用程序未运行时,不会调用我的BOOT_COMPLETED接收器.

表现:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.startuptest"
    android:versionCode="1"
    android:versionName="1.0"
    android:installLocation="internalOnly">
    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
    <uses-sdk android:minSdkVersion="8" android:targetSdkVersion="17" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.startuptest.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <receiver android:name="com.example.startuptest.StartUpBootReceiver" >
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED" />
            </intent-filter>
        </receiver>
    </application>
</manifest>

StartUpBootReceiver:

public class StartUpBootReceiver  extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {

        Log.d("startuptest", "StartUpBootReceiver " + intent.getAction());

        if ("android.intent.action.BOOT_COMPLETED".equals(intent.getAction())) {
            Log.d("startuptest", "StartUpBootReceiver BOOT_COMPLETED");
        }
    }
}

如果应用程序正在运行,我用模拟呼叫

adb shell
am broadcast -a …

我需要能够同时拥有AVCaptureVideoDataOutput和AVCaptureMovieFileOutput工作.以下代码有效,但视频录制没有.在didFinishRecordingToOutputFileAtURL直接后调用委托startRecordingToOutputFileURL被调用.现在,如果我AVCaptureVideoDataOutput从 AVCaptureSession简单的评论中删除该行:

[captureSession addOutput:captureDataOutput];

视频录制工作,但然后不调用SampleBufferDelegate(我需要).

我怎样才能兼顾AVCaptureVideoDataOutput并AVCaptureMovieFileOutput同时工作.

- (void)initCapture {
 AVCaptureDeviceInput *captureInput = [AVCaptureDeviceInput deviceInputWithDevice:[AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo] error:NULL]; 

 captureDataOutput = [[AVCaptureVideoDataOutput alloc] init]; 
 [captureDataOutput setSampleBufferDelegate:self queue:dispatch_get_main_queue()]; 

 m_captureFileOutput = [[AVCaptureMovieFileOutput alloc] init];

 NSString* key = (NSString*)kCVPixelBufferPixelFormatTypeKey; 
 NSNumber* value = [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA]; 
 NSDictionary* videoSettings = [NSDictionary dictionaryWithObject:value forKey:key]; 

 [captureDataOutput setVideoSettings:videoSettings]; 

 captureSession = [[AVCaptureSession alloc] init]; 

 [captureSession addInput:captureInput];
 [captureSession addOutput:m_captureFileOutput]; 
 [captureSession addOutput:captureDataOutput]; 

 [captureSession beginConfiguration]; 
 [captureSession setSessionPreset:AVCaptureSessionPresetLow]; 
 [captureSession commitConfiguration]; 

 [self performSelector:@selector(startRecording) …

我想知道是否有一种简单的方法来访问IOS中的主窗口或视图.类似的东西:

[UIScreen mainScreen]

谢谢.

我使用rails 4.0.3并尝试在Active-Admin中设置多个复选框.复选框选项未保存.这就是我所拥有的

class Product < ActiveRecord::Base
  has_many :categorizations
  has_many :categories, :through => :categorizations
  accepts_nested_attributes_for :categorizations
end

class Category < ActiveRecord::Base
  has_many :categorizations
  has_many :products, :through => :categorizations
  accepts_nested_attributes_for :categorizations
end

class Categorization < ActiveRecord::Base
  belongs_to :category
  belongs_to :product
end

ActiveAdmin.register Product do

  permit_params :title, :price, category_ids:[:id]

  form do |f|
    f.semantic_errors *f.object.errors.keys
    f.inputs "Product" do
      f.input :title
      f.input :price
      f.input :categories, :as => :check_boxes
    end
    f.actions
  end
end

我也尝试过使用has_and_belongs_to_many,但仍然无法获得保存的选择.

任何指导都将受到高度赞赏.

干杯

嗨,我想弄清楚如何计算四元数的倒数.一个代码示例将是非常棒的.

干杯

我正在寻找有关如何在IOS上播放midi文件的一些信息.我不需要任何midi输入或输出消息.我只想阅读midi文件并将曲目播放给用户,将每个音符替换为钢琴声音样本.能够调节节奏将是另一个要求.

请注意,我没有兴趣将midi文件转换为wav或其他格式.我想直接读取midi文件.

任何人都可以向我指出一些可能有助于我理解所需过程的信息.

干杯

我似乎无法让nsdata写入文件.我有什么想法可能做错了.提前致谢.

NSString* filename = @"myfile.txt";

NSString *applicationDocumentsDir = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];

NSString *storePath = [applicationDocumentsDir stringByAppendingPathComponent:filename];    

if ([fileManager fileExistsAtPath:applicationDocumentsDir])
    NSLog(@"applicationDocumentsDir exists");   // verifies directory exist

NSData *data = [NSData dataWithContentsOfURL:URL];

if (data) {    
     NSString *content = [[NSString alloc]  initWithBytes:[data bytes]
                                                      length:[data length] encoding: NSUTF8StringEncoding];

    NSLog(@"%@", content); // verifies data was downloaded correctly

    NSError* error;
    [data writeToFile:storePath options:NSDataWritingAtomic error:&error];

    if(error != nil)
        NSLog(@"write error %@", error);
}

我一直在收到错误

"The operation couldn’t be completed. No such file or directory"