Java 仅为某些GSON方法调用返回JsonObject Null

编辑我的问题：

我一直在做我的第一个编程和Android项目

在以下代码中，我收到了一个：

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.google.gson.JsonElement.toString()' on a null object reference

用于尝试调用我的结果JSONOBJECT上的方法，该对象是使用网络库检索的，正在使用google GSON库进行解析

toast字符串消息和log.v表明JSON对象正在成功地传递，并且包含了所有必需的元素。（或者可能没有完全传递？log.v在某个点后被切断。）

我的困惑在于在result上调用toString（）GSON方法的能力，这会导致成功的toast消息，同时尝试调用任何其他GSON方法，如result.get（images\u count）。toString会导致我的错误。在执行代码之前，我尝试使用if（result.isJsonNull（））来确保结果不是null，但即使result.isJsonNull（）返回false，我的方法调用也会返回错误

我的两部分问题

是什么导致我返回的JsonObject结果成功执行某些GSON库方法（如toString（）），同时为其他方法返回空指针异常，就像我试图通过.get（字符串成员）访问json元素成员一样

将来，我如何放置/识别对象可能返回NullPointerException的检查点？到目前为止，我只使用日志记录或Toast来显示当前对象/变量值。谢谢布朗克斯的回答。我必须使用断点

导致NullPointer异常的代码：（我已将我的客户端ID替换为xxxxxxx，以便对internet保密）

好的，看看logCat，整个JSon对象似乎没有打印出来。这是Log.v可以打印的限制吗？还是因为网络调用没有返回完全完整的对象，所以我得到一个空对象引用

从Imgur的Api检索的Json对象的示例如下：

---

如果您可以发布一个json响应的示例，我们可以更好地帮助您。 但是，从我所看到的JsonElement“images_count”不存在，因此您得到了NullPointerException

据我所见，如果我尝试从浏览器调用，我会得到以下json响应：

{"data":{"error":"Authentication required","request":"\/3\/album\/gQxwy.json","method":"GET"},"success":false,"status":401}

您可能不从WebService添加一些查询参数请求

---

注意：要显示当前对象/变量值，您需要使用断点并在调试模式下运行应用程序

尝试在循环之前检查值：

boolean o=result.get（“images\u count”）.isNumber（）

。很可能，

images\u count

中的no

int

。我似乎无法解析该方法。isNumber（）；结果如何。我只有isJsonArray、isJsonNull、isJsonObject和isjsonprimitive选项。谢谢您的回复！我发布了包含JSON对象（显示为字符串）的日志。您无法从浏览器拨打电话的原因是您需要一个授权：标题中包含客户端ID“xxxxxxx”。但我的代码能够成功连接。我们还可以看到“images\u count”确实存在于JSon字符串输出中。我只是想知道为什么我能够对返回的JSonObject调用toString（），而不能调用任何其他方法。谢谢你的帮助！我想出来了。我调用了一个.get（string，member）到json对象，该对象只有外部参数“data”、“success”和“status”。我不得不改为使用以下内容：JsonObject album=result.getAsJsonObject（“数据”）；JsonArray images=album.getAsJsonArray（“图像”）；以便能够最终访问内部元素。谢谢你的帮助！

03-21 21:24:26.395    8035-8061/? D/ION_VERBOSE_LOGGING﹕ (353 ms) https://api.imgur.com/3/album/gQxwy.json: Connection successful
03-21 21:24:26.405    8035-8061/? D/ION_VERBOSE_LOGGING﹕ (363 ms) https://api.imgur.com/3/album/gQxwy.json: Recycling keep-alive socket
03-21 21:24:26.407    8035-8035/? V/JSONOBJECT_STRING﹕ {"data":{"id":"gQxwy","title":"playlist","description":null,"datetime":1425872636,"cover":"c7iJOmN","cover_width":160,"cover_height":120,"account_url":"JohnnyJem","account_id":18800283,"privacy":"public","layout":"blog","views":574,"link":"http://imgur.com/a/gQxwy","favorite":false,"nsfw":null,"section":null,"images_count":10,"images":[{"id":"c7iJOmN","title":"Title","description":"Description","datetime":1425872636,"type":"image/gif","animated":true,"width":160,"height":120,"size":65008,"views":1175,"bandwidth":76384400,"vote":null,"favorite":false,"nsfw":null,"section":null,"account_url":null,"account_id":null,"gifv":"http://i.imgur.com/c7iJOmN.gifv","webm":"http://i.imgur.com/c7iJOmN.webm","mp4":"http://i.imgur.com/c7iJOmN.mp4","link":"http://i.imgur.com/c7iJOmN.gif","looping":true},{"id":"SYRfZPy","title":"Title","description":"Description","datetime":1425872638,"type":"image/gif","animated":true,"width":160,"height":120,"size":139574,"views":1054,"bandwidth":147110996,"vote":null,"favorite":false,"nsfw":null,"section":null,"account_url":null,"account_id":null,"gifv":"http://i.imgur.com/SYRfZPy.gifv","webm":"http://i.imgur.com/SYRfZPy.webm","mp4":"http://i.imgur.com/SYRfZPy.mp4","link":"http://i.imgur.com/SYRfZPy.gif","looping":true},{"id":"1aD2tdR","title":"Title","description":"Description","datetime":1425872639,"type":"image/gif","animated":true,"width":160,"height":120,"size":117092,"views":882,"bandwidth":103275144,"vote":null,"favorite":false,"nsfw":null,"section":null,"account_url":null,"account_id":null,"gifv":"http://i.imgur.com/1aD2tdR.gifv","webm":"http://i.imgur.com/1aD2tdR.webm","mp4":"http://i.imgur.com/1aD2tdR.mp4","link":"http://i.imgur.com/1aD2tdR.gif","looping":true},{"id":"7UzUF79","title":"Title","description":"Description","datetime":1425872641,"type":"image/gif","animated":true,"width":160,"height":120,"size":146703,"views":785,"bandwidth":115161855,"vote":null,"favorite":false,"nsfw":null,"section":null,"account_url":null,"account_id":null,"gifv":"http://i.imgur.com/7UzUF79.gifv","webm":"http://i.imgur.com/7UzUF79.webm","mp4":"http://i.imgur.com/7UzUF79.mp4","link":"http://i.imgur.com/7UzUF79.gif","looping":true},{"id":"3PKeSiW","title":"Title","description":"Description","datetime":1425872642,"type":"image/gif","animated":true,"width":160,"height":120,"size":136914,"views":753,"bandwidth":103096242,"vote":null,"favorite":false,"nsfw":null,"section":null,"account_url":null,"account_id":null,"gifv":"http://i.imgur.com/3PKeSiW.gifv","webm":"http://i.imgur.com/3PKeSiW.webm","mp4":"http://i.imgur.com/3PKeSiW.mp4","link":"http://i.imgur.com/3PKeSiW.gif","looping":true},{"id":"o3UBVgR","title":"Title","description":"Description","datetime":1425872644,"type":"image/gif","animated":true,"width":160,"height":120,"size":129046,"views":483,"bandwidth":62329218,"vote":null,"favorite":false,"nsfw":null,"section":null,"account_url":null,"account_id":null,"gifv":"http://i.imgur.com/o3UBVgR.gifv","webm":"http://i.imgur.com/o3UBVgR.webm","mp4":"http://i.imgur.com/o3UBVgR.mp4","link":"http://i.imgur.com/o3UBVgR.gif","looping":true},{"id":"qraDqOQ","title":"Title","description":"Description","datetime":1425872645,"type":"image/gif","animated":true,"width":160,"height":120,"size":93116,"views":466,"bandwidth":43392056,"vote":null,"favorite":false,"nsfw":null,"section":null,"account_url":null,"account_id":null,"gifv":"http://i.imgur.com/qraDqOQ.gifv","webm":"http://i.imgur.com/qraDqOQ.webm","mp4":"http://i.imgur.com/qraDqOQ.mp4","link":"http://i.imgur.com/qraDqOQ.gif","looping":true},{"id":"K9PuB3S","title":"Title","description":"Description","datetime":1425872647,"type":"image/gif","animated":true,"width":160,"height":120,"size":84323,"views":481,"bandwidth":40559363,"vote":null,"favorite":false,"nsfw":null,"section":null,"account_url":null,"account_id":null,"gifv":"http://i.imgur.com/K9PuB3S.gifv","webm":"http://i.imgur.com/K9PuB3S.webm","mp4":"http://i.imgur.com/K9PuB3S.mp4","link":"http://i.imgur.com/K9PuB3S.gif","looping":true},{"id":"p3whCAz","title":"Title","descriptio

03-21 21:24:26.408    8035-8035/? D/AndroidRuntime﹕ Shutting down VM
03-21 21:24:26.408    8035-8035/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.johnnymolina.nextphase, PID: 8035
    java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.google.gson.JsonElement.toString()' on a null object reference
            at com.johnnymolina.nextphase.activities.Imgur$2.onCompleted(Imgur.java:116)
            at com.johnnymolina.nextphase.activities.Imgur$2.onCompleted(Imgur.java:98)
            at com.koushikdutta.async.future.SimpleFuture.handleCallbackUnlocked(SimpleFuture.java:107)
            at com.koushikdutta.async.future.SimpleFuture.setComplete(SimpleFuture.java:141)
            at com.koushikdutta.async.future.SimpleFuture.setComplete(SimpleFuture.java:128)
            at com.koushikdutta.ion.IonRequestBuilder$1.run(IonRequestBuilder.java:246)
            at com.koushikdutta.async.AsyncServer$RunnableWrapper.run(AsyncServer.java:57)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            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:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
03-21 21:24:26.411    6534-6864/? W/ActivityManager﹕ Force finishing activity com.johnnymolina.nextphase/.activities.Imgur
03-21 21:24:26.412    6534-6864/? W/ActivityManager﹕ Force finishing activity com.johnnymolina.nextphase/.activities.MainActivity

{
    "data": {
        "id": "lDRB2",
        "title": "Imgur Office",
        "description": null,
        "datetime": 1357856292,
        "cover": "24nLu",
        "account_url": "Alan",
        "account_id": 4,
        "privacy": "public",
        "layout": "blog",
        "views": 13780,
        "link": "http://alanbox.imgur.com/a/lDRB2",
        "images_count": 11,
        "images": [
            {
                "id": "24nLu",
                "title": null,
                "description": null,
                "datetime": 1357856352,
                "type": "image/jpeg",
                "animated": false,
                "width": 2592,
                "height": 1944,
                "size": 855658,
                "views": 135772,
                "bandwidth": 116174397976,
                "link": "http://i.imgur.com/24nLu.jpg"
            },
            {
                "id": "Ziz25",
                "title": null,
                "description": null,
                "datetime": 1357856394,
                "type": "image/jpeg",
                "animated": false,
                "width": 2592,
                "height": 1944,
                "size": 919391,
                "views": 135493,
                "bandwidth": 124571044763,
                "link": "http://i.imgur.com/Ziz25.jpg"
            },
            {
                "id": "9tzW6",
                "title": null,
                "description": null,
                "datetime": 1357856385,
                "type": "image/jpeg",
                "animated": false,
                "width": 2592,
                "height": 1944,
                "size": 655028,
                "views": 135063,
                "bandwidth": 88470046764,
                "link": "http://i.imgur.com/9tzW6.jpg"
            },
            {
                "id": "dFg5u",
                "title": null,
                "description": null,
                "datetime": 1357856378,
                "type": "image/jpeg",
                "animated": false,
                "width": 2592,
                "height": 1944,
                "size": 812738,
                "views": 134704,
                "bandwidth": 109479059552,
                "link": "http://i.imgur.com/dFg5u.jpg"
            },
            {
                "id": "oknLx",
                "title": null,
                "description": null,
                "datetime": 1357856338,
                "type": "image/jpeg",
                "animated": false,
                "width": 1749,
                "height": 2332,
                "size": 717324,
                "views": 32938,
                "bandwidth": 23627217912,
                "link": "http://i.imgur.com/oknLx.jpg"
            },
            {
                "id": "OL6tC",
                "title": null,
                "description": null,
                "datetime": 1357856321,
                "type": "image/jpeg",
                "animated": false,
                "width": 2592,
                "height": 1944,
                "size": 1443262,
                "views": 32346,
                "bandwidth": 46683752652,
                "link": "http://i.imgur.com/OL6tC.jpg"
            },
            {
                "id": "cJ9cm",
                "title": null,
                "description": null,
                "datetime": 1357856330,
                "type": "image/jpeg",
                "animated": false,
                "width": 2592,
                "height": 1944,
                "size": 544702,
                "views": 31829,
                "bandwidth": 17337319958,
                "link": "http://i.imgur.com/cJ9cm.jpg"
            },
            {
                "id": "7BtPN",
                "title": null,
                "description": null,
                "datetime": 1357856369,
                "type": "image/jpeg",
                "animated": false,
                "width": 2592,
                "height": 1944,
                "size": 844863,
                "views": 31257,
                "bandwidth": 26407882791,
                "link": "http://i.imgur.com/7BtPN.jpg"
            },
            {
                "id": "42ib8",
                "title": null,
                "description": null,
                "datetime": 1357856424,
                "type": "image/jpeg",
                "animated": false,
                "width": 2592,
                "height": 1944,
                "size": 905073,
                "views": 30945,
                "bandwidth": 28007483985,
                "link": "http://i.imgur.com/42ib8.jpg"
            },
            {
                "id": "BbwIx",
                "title": null,
                "description": null,
                "datetime": 1357856360,
                "type": "image/jpeg",
                "animated": false,
                "width": 1749,
                "height": 2332,
                "size": 662413,
                "views": 30107,
                "bandwidth": 19943268191,
                "link": "http://i.imgur.com/BbwIx.jpg"
            },
            {
                "id": "x7b91",
                "title": null,
                "description": null,
                "datetime": 1357856406,
                "type": "image/jpeg",
                "animated": false,
                "width": 1944,
                "height": 2592,
                "size": 618567,
                "views": 29259,
                "bandwidth": 18098651853,
                "link": "http://i.imgur.com/x7b91.jpg"
            }
        ]
    },
    "success": true,
    "status": 200
}

{"data":{"error":"Authentication required","request":"\/3\/album\/gQxwy.json","method":"GET"},"success":false,"status":401}