小编pun*_*sta的帖子

在java中,我们可以使用双重Checked Locking&volatile编写thead-safe单例:

    public class Singleton {
        private static volatile Singleton instance;

        public static Singleton getInstance(String arg) {
        Singleton localInstance = instance;
        if (localInstance == null) {
            synchronized (Singleton.class) {
                localInstance = instance;
                if (localInstance == null) {
                    instance = localInstance = new Singleton(arg);
                }
            }
        }
        return localInstance;
    }
}

我们怎么能用kotlin写呢？

关于对象

object A {
    object B {}
    object C {}
    init {
        C.hashCode()
    }
}

我使用kotlin反编译器来实现

public final class A {
   public static final A INSTANCE;

   private A() { …

我在不同的布局中有两个视图,我想将它们移动到另一个.我的代码出了什么问题？Y动画播放错误.第一个视图位于片段的布局中,第二个视图位于状态栏中

    ...
    int p1[] = new int[2];
    int p2[] = new int[2];
    viewOne.getLocationInWindow(p1);
    viewTwo.getLocationInWindow(p2);


    AnimatorSet animatorSet = new AnimatorSet();
    animatorSet
            .play(ObjectAnimator.ofFloat(expandedImageView, "X", p1[0], p2[0] - p1[0]))
            .with(ObjectAnimator.ofFloat(expandedImageView, "Y", p1[1], p2[1] - p1[1]))
            .with(ObjectAnimator.ofFloat(expandedImageView, View.SCALE_X, startScale))
            .with(ObjectAnimator.ofFloat(expandedImageView, View.SCALE_Y, startScale));

gradle同步时出现此错误。我在android defaultConfig块中调用该方法。我使用com.android.tools.build:gradle:1.3.0 com.neenbedankt.gradle.plugins：android-apt：1.4

build.gradle

    // Top-level build file where you can add configuration options common to all sub-projects/modules.
apply from: 'config.gradle'

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:1.3.0'
        classpath 'com.neenbedankt.gradle.plugins:android-apt:1.4'

    }
}

allprojects {
    repositories {
        jcenter()
    }
}

build.gradle

 buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:1.3.0'
    }
}


plugins {
    id "me.tatarka.retrolambda" version "3.2.2"
}


apply plugin: 'com.android.application'
apply plugin: 'com.neenbedankt.android-apt'


repositories {
    jcenter()
    mavenCentral()
}

def googlePlayServiceVersion = "8.1.0"
def supportVersion = …

我需要清晰的 QT 控制台。什么是命令？

主.cpp：

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    cout<<"How delete this?";
    //system("CLS")?
    return a.exec();
}

我尝试制作静态qt,并在mingw-make期间出错.这是错误的文本.

static\qhttpnetworkreply.o access\qhttpnetworkreply.cpp
In file included from ..\..\mkspecs\win32-g++/qplatformdefs.h:56:0,
             from access\qhttpnetworkreply_p.h:55,
             from access\qhttpnetworkreply.cpp:42:
c:\mingw\include\io.h:301:14: error: 'off64_t' does not name a type
__CRT_INLINE off64_t lseek64 (int, off64_t, int);
           ^
c:\mingw\include\io.h:302:14: error: 'off64_t' does not name a type
__CRT_INLINE off64_t lseek64 (int fd, off64_t offset, int whence) {
          ^
Makefile.Debug:8214: recipe for target '.obj/debug_static/qhttpnetworkreply.o' f   ailed
mingw32-make[3]: *** [.obj/debug_static/qhttpnetworkreply.o] Error 1
mingw32-make[3]: Leaving directory 'C:/Qt/Qt5.1.1/5.1.1/Src/qtbase/src/network'
Makefile:38: recipe for target 'debug-all' failed
mingw32-make[2]: *** [debug-all] Error 2
mingw32-make[2]: Leaving directory 'C:/Qt/Qt5.1.1/5.1.1/Src/qtbase/src/network'
Makefile:182: recipe for …

在研究lambda期间,我希望list按第二个元素(int)排序.这个使用的代码.

#include <iostream>
#include <algorithm>
#include <list>

using namespace std;
int main()
{
list<pair <string, int>> s = {{"two", 2}, {"one", 1}, {"three", 3}};
sort(s.begin(), s.end(), [](pair<string,int> a, pair<string,int> b) -> bool
                            {
                            return (a.second) > (b.second);
                            }
);

for_each(s.begin(),s.end(),[](pair<string,int> a)
{
    cout << a.first << " " << a.second << endl;
});
}

我收到错误:

c:\qt\qt5.2.0\tools\mingw48_32\lib\gcc\i686-w64-mingw32\4.8.0\include\c++\bits\stl_algo.h:5513: error: no match for 'operator-' (operand types are 'std::_List_iterator<std::pair<std::basic_string<char>, int> >' and 'std::_List_iterator<std::pair<std::basic_string<char>, int> >')
     std::__lg(__last - __first) * 2, __comp);
                  ^ …

在我的测试中

@LargeTest
@RunWith(AndroidJUnit4.class)
public class SimpleActicityTest {


@Rule
public ActivityTestRule<MainActivity> activityActivityTestRule =
        new ActivityTestRule<>(MainActivity.class);

@Test
public void testActivity() throws Exception {
    Activity a = activityActivityTestRule.getActivity();
    Screenshot.snapActivity(activity).setName("s1").record();
}

我有

ava.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.app.Instrumentation.getContext()' on a null object reference
at com.facebook.testing.screenshot.internal.ScreenshotImpl.getInstance(ScreenshotImpl.java:338)
at com.facebook.testing.screenshot.Screenshot.snapActivity(Screenshot.java:45)
at com.mobium.reference.activity.Util.takeScreenshot(Util.java:32)
at com.mobium.reference.activity.SimpleActicityTest.lambda$testLeftMenuTest$1(SimpleActicityTest.java:52)
at com.mobium.reference.activity.SimpleActicityTest.access$lambda$0(SimpleActicityTest.java)
at com.mobium.reference.activity.SimpleActicityTest$$Lambda$1.run(Unknown Source)
at android.os.Handler.handleCallback(Handler.java:815)
at android.os.Handler.dispatchMessage(Handler.java:104)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5549)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:964)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:759)

faceebook的lib getInstance()的来源:

public static ScreenshotImpl getInstance() {
        if(sInstance != …

我有一个3000字符串的文件(1个字符串 - 几个字).我需要把字符串读成一个QList.我怎样才能做到这一点？我尝试过以下方法:

1.txt
string
string2

function()<=> MyList<<"string"<<"string2";

我想在抽象类构造函数中注入接口实现并在子类中使用它.

我有编译时错误:

Error:Gradle: Dagger does not support injection into private fields
Error:Gradle: Example.A cannot be provided without an @Provides-annotated method.
Error:Gradle: Example.B cannot be provided without an @Inject constructor or from an @Provides-annotated method.
Error:Gradle: Execution failed for task ':app:compileDemoDebugJavaWithJavac'.
> Compilation failed; see the compiler error output for details.

kotlin中的例子.

   object Example {
    interface IData {

        fun foo() {
        }
    }

    class Data : IData {

    }

    @Module
    class DataModel {
        @Provides
        fun data(): IData = Data()
    }

    @Singleton …

我该如何更改此代码？

QString s="123";
QStringList *myList=new QStringList;

myList<<s;

错误:

'operator <<'不匹配(操作数类型是'QStringList*'和'QString')

*myList<<s;

也不起作用:myList为空,此后.