小编Sel*_*vin的帖子

我正试图在我的应用程序中显示GoogleMap,但在此任务开始时我遇到了问题.这条线:

SupportMapFragment mapFrag = (SupportMapFragment) getActivity().getSupportFragmentManager().findFragmentById(R.id.map);

始终返回null.

我尝试了很多东西,但没有任何作用.你能帮我找到问题吗？

这是我的代码:

public class MapSectionFragment extends Fragment implements
    ConnectionCallbacks,
    OnConnectionFailedListener,
    LocationListener,
    OnMyLocationButtonClickListener,
    OnMapReadyCallback{

    private GoogleMap map;
    Location location;
    GoogleApiClient mGoogleApiClient;

    private static final LocationRequest REQUEST = LocationRequest.create()
        .setInterval(5000)         // 5 seconds
        .setFastestInterval(16)    // 16ms = 60fps
        .setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);

    private void createMapView(){
        try{
            //here it comes
            SupportMapFragment mapFrag = (SupportMapFragment) getActivity().getSupportFragmentManager().findFragmentById(R.id.map);

            map = mapFrag.getMap(); //throws NullPointerException
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        View rootView = inflater.inflate(R.layout.fragment_section_map,
            container, false);

        createMapView(); …

尝试startActivityForResult(intent, requestCode);使用final Intent intent = new Intent(Settings.ACTION_USAGE_ACCESS_SETTINGS);intent 时,我得到java.lang.SecurityException .有趣的是这次崩溃只发生在华为的Android 5.1 - 5.1.1上我没有华为设备.你能告诉我它的建议吗？

堆栈跟踪

Fatal Exception: java.lang.SecurityException: Permission Denial: starting Intent { act=android.settings.USAGE_ACCESS_SETTINGS cmp=com.android.settings/.Settings$UsageAccessSettingsActivity } from ProcessRecord{11b5f1a1 19764:com.myproject.my/u0a167} (pid=19764, uid=10167) not exported from uid 1000
       at android.os.Parcel.readException(Parcel.java:1546)
       at android.os.Parcel.readException(Parcel.java:1499)
       at android.app.ActivityManagerProxy.startActivity(ActivityManagerNative.java:2448)
       at android.app.Instrumentation.execStartActivity(Instrumentation.java:1496)
       at android.app.Activity.startActivityForResult(Activity.java:3794)
       at android.support.v4.app.BaseFragmentActivityJB.startActivityForResult(BaseFragmentActivityJB.java:48)
       at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:77)
       at android.app.Activity.startActivityForResult(Activity.java:3755)
       at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:859)
       at com.myproject.my.utils.PermissionsHelper$2.onClick(PermissionsHelper.java:134)
       at android.support.v7.app.AlertController$ButtonHandler.handleMessage(AlertController.java:157)
       at android.os.Handler.dispatchMessage(Handler.java:102)
       at android.os.Looper.loop(Looper.java:135)
       at android.app.ActivityThread.main(ActivityThread.java:5298)
       at java.lang.reflect.Method.invoke(Method.java)
       at java.lang.reflect.Method.invoke(Method.java:372)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:911)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:706)

我在解码json字符串时遇到了困难.下面是我的json字符串:

{
    "udeals":"[{\"vName\":\"bussinessname3\",\"vAddress\":\"address3\",\"vState\":\"Kerala\",\"vZip\":\"232\",\"vCountry\":\"Algeria\",\"id\":\"3\",\"dealCategoryID\":\"2\",\"dealCaption\":\"deal3\",\"dealurl\":\"http:\\/\\/192.168.0.8\\/ppppp\\/deals\\/deal3-3\\/\",\"dealImage\":\"http:\\/\\/192.168.0.8\\/ppppp\\/images\\/deals\\/thumb390x256\\/Duizl1.jpg\",\"dealPrice\":\"50.00\",\"dealCost\":\"100.00\",\"dealSave\":-50,\"dealOfferRate\":\"50.00\",\"jsDeadLine\":{\"seconds\":0,\"minutes\":0,\"hours\":0,\"mday\":5,\"wday\":3,\"mon\":1,\"year\":2011,\"yday\":4,\"weekday\":\"Wednesday\",\"month\":\"January\",\"0\":1294165800},\"unlockedStamp\":{\"seconds\":53,\"minutes\":56,\"hours\":18,\"mday\":5,\"wday\":3,\"mon\":1,\"year\":2011,\"yday\":4,\"weekday\":\"Wednesday\",\"month\":\"January\",\"0\":1294234013},\"description\":\"Google URL Shortener at goo.gl is used by Google products to create short URLs that can be easily shared, tweeted, or emailed to friends.\"},{\"vName\":\"bussinessname20010\",\"vAddress\":\"address20010\",\"vState\":\"Kerala\",\"vZip\":\"232\",\"vCountry\":\"Argentina\",\"id\":\"20010\",\"dealCategoryID\":\"2\",\"dealCaption\":\"deal20010\",\"dealurl\":\"http:\\/\\/192.168.0.8\\/ppppp\\/deals\\/deal20010-20010\\/\",\"dealImage\":\"http:\\/\\/192.168.0.8\\/ppppp\\/images\\/deals\\/thumb390x256\\/oCcfTj.jpg\",\"dealPrice\":\"50.00\",\"dealCost\":\"100.00\",\"dealSave\":-50,\"dealOfferRate\":\"50.00\",\"jsDeadLine\":{\"seconds\":0,\"minutes\":0,\"hours\":0,\"mday\":28,\"wday\":2,\"mon\":12,\"year\":2010,\"yday\":361,\"weekday\":\"Tuesday\",\"month\":\"December\",\"0\":1293474600},\"unlockedStamp\":{\"seconds\":53,\"minutes\":56,\"hours\":18,\"mday\":5,\"wday\":3,\"mon\":1,\"year\":2011,\"yday\":4,\"weekday\":\"Wednesday\",\"month\":\"January\",\"0\":1294234013},\"description\":\"this is\"}]"
}

任何人都可以给我一个解决方案,如何在Android中解析这个...

嗨,我正在尝试将数据发送到Web服务

String url =" https://www.myurl.com ";

    URL urlobj =  new URL(url);
    HttpsURLConnection con = (HttpsURLConnection) urlobj.openConnection();
    con.setRequestMethod("POST");
    con.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");

    String urlParameters = GenerateUrlParameters(data);

    con.setDoOutput(true);
    con.setDoInput(true);

    Log.i("test", "hit1");

    DataOutputStream  wr = new DataOutputStream(con.getOutputStream());

    Log.i("test", "hit2");

    wr.writeBytes(urlParameters);

    wr.flush();
    wr.close();

Hit1被击中,但它在下一行失败并且没有击中hit2.我究竟做错了什么 ？

我的logcat

10-18 09:17:33.302: D/gralloc_goldfish(2228): Emulator without GPU emulation detected.
10-18 09:17:33.322: W/TextLayoutCache(2228): computeValuesWithHarfbuzz -- need to force to single run
10-18 09:17:37.862: I/test(2228): hit1
10-18 09:17:37.872: D/AndroidRuntime(2228): Shutting down VM
10-18 09:17:37.872: W/dalvikvm(2228): threadid=1: thread exiting with uncaught exception (group=0x409961f8)
10-18 …

我试图显示6个图像,我保存在gridview中的res/drawable文件夹中.

但我得到以下错误

10-29 09:44:20.025: E/AndroidRuntime(1549): FATAL EXCEPTION: main
10-29 09:44:20.025: E/AndroidRuntime(1549): java.lang.OutOfMemoryError
10-29 09:44:20.025: E/AndroidRuntime(1549):     at android.graphics.BitmapFactory.nativeDecodeAsset(Native Method)
10-29 09:44:20.025: E/AndroidRuntime(1549):     at android.graphics.BitmapFactory.decodeStream(BitmapFactory.java:501)
10-29 09:44:20.025: E/AndroidRuntime(1549):     at android.graphics.BitmapFactory.decodeResourceStream(BitmapFactory.java:354)
10-29 09:44:20.025: E/AndroidRuntime(1549):     at android.graphics.drawable.Drawable.createFromResourceStream(Drawable.java:785)
10-29 09:44:20.025: E/AndroidRuntime(1549):     at android.content.res.Resources.loadDrawable(Resources.java:1965)
10-29 09:44:20.025: E/AndroidRuntime(1549):     at android.content.res.Resources.getDrawable(Resources.java:660)
10-29 09:44:20.025: E/AndroidRuntime(1549):     at android.widget.ImageView.resolveUri(ImageView.java:616)
10-29 09:44:20.025: E/AndroidRuntime(1549):     at android.widget.ImageView.setImageResource(ImageView.java:349)
10-29 09:44:20.025: E/AndroidRuntime(1549):     at com.shiva.bajarangi.ImageAdapter.getView(ImageAdapter.java:55)
10-29 09:44:20.025: E/AndroidRuntime(1549):     at android.widget.AbsListView.obtainView(AbsListView.java:2159)
10-29 09:44:20.025: E/AndroidRuntime(1549):     at android.widget.GridView.makeAndAddView(GridView.java:1341)
10-29 09:44:20.025: E/AndroidRuntime(1549):     at android.widget.GridView.makeRow(GridView.java:341)
10-29 09:44:20.025: E/AndroidRuntime(1549):     at android.widget.GridView.fillDown(GridView.java:283)
10-29 09:44:20.025: …

我有两个类，一个继承自另一个，我想覆盖子类中父类的默认值。

这是正确的做法吗？

public class Foo 
{
    public virtual string FooValue { get; set; } = "foo default value";
}

public class Bar : Foo 
{
    private string _fooValue = "bar default value";
    public override string FooValue 
    {
        get => _fooValue;
        set => _fooValue = value;
    }
}

我看到有人使用DefaultValue属性，但不确定正确的方法是什么。

我从XML解析得到日期字符串,如下所示:2012-04-05 07:55:29 +05.30

现在,我希望这个字符串为:2012年4月5日

我怎样才能做到这一点？

我是java新手,我还在处理基本主题.通过调用URL.openConnection()并将结果转换为HttpURLConnection,我无法理解以下行在获取新的HttpURLConnection时如何工作.

URL url = new URL("http://www.android.com/");
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();

如果URL类不从HttpURLConnection继承,如何使用URL对象实例化HttpURLConnection？

根据java API参考,这是两个类的层次结构:

Java.lang.Object⇒java.net.URLConnection⇒java.net.HttpURLConnection

java.lang.Object⇒java.net.URL

据我所知,铸件的使用方式如下:

在这种情况下,HttpURLConnection是URLConnection和Object的后代.因此,HttpURLConnection是一个URLConnection,也是一个Object.

反过来不一定正确:URLConnection可能是HttpURLConnection,但不一定如此.所以你必须使用铸造.

但URL类和HttpURLConnection不相关.只有通过OBJECT类.

这是我无法理解的.有人能帮我吗？

先感谢您.

我用它来生成5to 之间的值13

 int randomGeneratedLevelValue = ThreadLocalRandom.current().nextInt(5, 13);

如何减少相同的匹配？