小编Rob*_*urt的帖子

我正在我的应用程序上尝试新的MultiDex支持,到目前为止我已经设法正确编译我的应用程序,但在运行它时,我得到以下异常:

java.lang.RuntimeException: Unable to instantiate application android.support.multidex.MultiDexApplication: java.lang.ClassNotFoundException: Didn't find class "android.support.multidex.MultiDexApplication" on path: DexPathList[[zip file "/data/app/me.myapp.main-2.apk"],nativeLibraryDirectories=[/data/app-lib/me..main-2, /vendor/lib, /system/lib]]
    at android.app.LoadedApk.makeApplication(LoadedApk.java:507)
    at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4382)
    at android.app.ActivityThread.access$1500(ActivityThread.java:139)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1270)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:136)
    at android.app.ActivityThread.main(ActivityThread.java:5086)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:515)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
    at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.ClassNotFoundException: Didn't find class "android.support.multidex.MultiDexApplication" on path: DexPathList[[zip file "/data/app/me.myapp.main-2.apk"],nativeLibraryDirectories=[/data/app-lib/me.myapp.main-2, /vendor/lib, /system/lib]]
    at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:497)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:457)
    at android.app.Instrumentation.newApplication(Instrumentation.java:998)
    at android.app.LoadedApk.makeApplication(LoadedApk.java:502)

这是我的gradle文件:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 21
    buildToolsVersion …

我想为我的调试/发布构建变体保留不同的配置,但显然,google-services.json文件只允许一个.还有其他选择吗？有没有办法保存几个文件？

我绝对是SQL的菜鸟,我一直在用Postgresql中的以下表结构编写一个复杂的查询:

CREATE TABLE reports
(
  reportid character varying(20) NOT NULL,
  userid integer NOT NULL,
  reporttype character varying(40) NOT NULL,  
)

CREATE TABLE users
(
  userid serial NOT NULL,
  username character varying(20) NOT NULL,
)

查询的目标是获取每个用户的报告类型数量并将其显示在一列中.有三种不同类型的报告.

使用group-by的简单查询将解决问题,但将其显示在不同的行中:

select count(*) as Amount,
       u.username,
       r.reporttype 
from reports r,
     users u 
where r.userid=u.userid 
group by u.username,r.reporttype 
order by u.username

是否可以执行运行时检查以查看设备是否正在运行Android-Things？

我正试图从这样的远程蓝牙设备中取出UUIDS:

        device.fetchUuidsWithSdp();

这将在所有设备上静默工作,无需用户交互,除了那些使用Android 6.0的设备明显要求配对对话框连接远程设备以获取UUID.这是预期的行为吗？这记录在哪里？有没有办法触发UUID发现而不必明确地从另一端允许它？

我的应用程序在使用Android 6.0或Android 7.0的设备时正在构建并运行正常,但在运行任何带有Android 5.1的设备(未测试较低)时,它会失败并出现以下异常:

09-06 11:50:46.100 29601-29601/? E/AndroidRuntime: FATAL EXCEPTION: main
                                               Process: me.myapp.main, PID: 29601
                                               java.lang.NoClassDefFoundError: Failed resolution of: Lcom/google/android/gms/common/internal/zzab;
                                                   at com.google.firebase.provider.FirebaseInitProvider.zza(Unknown Source)
                                                   at com.google.firebase.provider.FirebaseInitProvider.attachInfo(Unknown Source)
                                                   at android.app.ActivityThread.installProvider(ActivityThread.java:5084)
                                                   at android.app.ActivityThread.installContentProviders(ActivityThread.java:4679)
                                                   at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4619)
                                                   at android.app.ActivityThread.access$1500(ActivityThread.java:155)
                                                   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1378)
                                                   at android.os.Handler.dispatchMessage(Handler.java:102)
                                                   at android.os.Looper.loop(Looper.java:135)
                                                   at android.app.ActivityThread.main(ActivityThread.java:5343)
                                                   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:905)
                                                   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:700)
                                                Caused by: java.lang.ClassNotFoundException: Didn't find class "com.google.android.gms.common.internal.zzab" on path: DexPathList[[zip file "/data/app/me.myapp.main-1/base.apk"],nativeLibraryDirectories=[/data/app/me.myapp.main-1/lib/arm, /vendor/lib, /system/lib]]
                                                   at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
                                                   at java.lang.ClassLoader.loadClass(ClassLoader.java:511)
                                                   at java.lang.ClassLoader.loadClass(ClassLoader.java:469)
                                                   at com.google.firebase.provider.FirebaseInitProvider.zza(Unknown Source) 
                                                   at com.google.firebase.provider.FirebaseInitProvider.attachInfo(Unknown Source) 
                                                   at android.app.ActivityThread.installProvider(ActivityThread.java:5084) 
                                                   at …

我需要找到一种在生成文件下载后执行页面导航的方法.到目前为止,我已经准备好了文件下载和工作:

FileInputStream stream = new FileInputStream(file);
        FacesContext fc = FacesContext.getCurrentInstance();
        ExternalContext ec = fc.getExternalContext();
        ec.responseReset();
        ec.setResponseContentType("application/octet-stream");
        ec.setResponseHeader("Content-Disposition", "attachment; filename=\"" + fileName + "\"");

        OutputStream out = ec.getResponseOutputStream();

        byte[] outputByte = new byte[4096];

        while(stream.read(outputByte, 0, 4096) != -1)
        {
                out.write(outputByte, 0, 4096);
        }
        stream.close();
        out.flush();
        out.close();
        fc.responseComplete();

到目前为止,我尝试从ExternalContext重定向,但我得到一个IllegalStateException.

ec.redirect(url)

我还尝试将所有以前的代码包装在一个字符串方法中,该方法返回最后要导航的页面.那也行不通.

有什么建议？

我正在尝试使用Kotlin对Architecture Component的实时数据进行基本实现,如下所示:

class MarketFragment : LifecycleFragment(){
......
 override fun onActivityCreated(savedInstanceState: Bundle?) {
        super.onActivityCreated(savedInstanceState)
        viewModel=ViewModelProviders.of(this).get(MarketViewModel::class.java)
        viewModel.book?.observe(this, Observer { book-> //updateUI })
....

我的ViewModel类是这样创建的:

class MarketViewModel : ViewModel()
{
    var book: MutableLiveData<Book>? =MutableLiveData()
    var repository: Repository?= Repository()

    init {
        update("parameter")
    }

    fun update(s: String)
    {
         book=repository?.getBook(s)

    }

}

和我的存储库:

fun getBook(bookSymbol:String):MutableLiveData<Book>
{
    val book=MutableLiveData<Book>()
    ......

            call . enqueue (object : Callback<Book> {
        override fun onResponse(call: Call<Book>?, response: Response<Book>?) {

            book.value=response?.body()

        }
     .....
    })
            return book
}

}

所有这些都很有效,UI应该更新,但只是第一次.如果我尝试进行手动调用以从UI操作更新viewModel,则改装调用仍然按预期工作,但新数据不会发送到片段中的Observer:

//this doesn't work:
viewModel.update("string") …