我正在尝试使用本教程作为基础，使用 GSON解析由Redmine API生成的一些 JSON。不幸的是，我不能给你我的 JSON 的 URL，因为它只在内部工作，但它看起来像这样：
{
"limit": 25,
"total_count": 653,
"offset": 0,
"time_entries": [
{
"spent_on": "2013-02-14",
"activity": {
"name": "Blah1",
"id": 10
},
"project": {
"name": "TEST",
"id": 10
},
"id": 661,
"hours": 1,
"updated_on": "2013-02-14T14:32:19Z",
"user": {
"name": "USER1",
"id": 7
},
"issue": {
"id": 467
},
"comments": "COMMENT 1",
"created_on": "2013-02-14T14:32:19Z"
},
{
"spent_on": "2013-02-14",
"activity": {
"name": "Bla2",
"id": 10
},
"project": {
"name": "TEST TEST",
"id": 10
},
"id": 660,
"hours": 1,
"updated_on": "2013-02-14T11:52:13Z",
"user": {
"name": "USER2",
"id": 4
},
"issue": {
"id": 466
},
"comments": "COMMENT 2.",
"created_on": "2013-02-14T11:52:13Z"
}
]
}
我得到了一个NullPointerException，但我不确定是因为未能获取 JSON 还是建模错误。我担心我缺少与内部类有关的东西。如果它像错误地获取 JSON 一样简单，我会非常生气。
我的设备都是通过连接到内部网络的 WIFI 运行的，当我使用浏览器时可以看到 JSON，所以我认为这不是网络问题。
这是我的 LogCat：
02-20 21:11:11.175: E/AndroidRuntime(14450): FATAL EXCEPTION: main
02-20 21:11:11.175: E/AndroidRuntime(14450): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.javacodegeeks.android.json/com.javacodegeeks.android.json.JsonParsingActivity}: java.lang.NullPointerException
02-20 21:11:11.175: E/AndroidRuntime(14450): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
02-20 21:11:11.175: E/AndroidRuntime(14450): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
02-20 21:11:11.175: E/AndroidRuntime(14450): at android.app.ActivityThread.access$600(ActivityThread.java:141)
02-20 21:11:11.175: E/AndroidRuntime(14450): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
02-20 21:11:11.175: E/AndroidRuntime(14450): at android.os.Handler.dispatchMessage(Handler.java:99)
02-20 21:11:11.175: E/AndroidRuntime(14450): at android.os.Looper.loop(Looper.java:137)
02-20 21:11:11.175: E/AndroidRuntime(14450): at android.app.ActivityThread.main(ActivityThread.java:5041)
02-20 21:11:11.175: E/AndroidRuntime(14450): at java.lang.reflect.Method.invokeNative(Native Method)
02-20 21:11:11.175: E/AndroidRuntime(14450): at java.lang.reflect.Method.invoke(Method.java:511)
02-20 21:11:11.175: E/AndroidRuntime(14450): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
02-20 21:11:11.175: E/AndroidRuntime(14450): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
02-20 21:11:11.175: E/AndroidRuntime(14450): at dalvik.system.NativeStart.main(Native Method)
02-20 21:11:11.175: E/AndroidRuntime(14450): Caused by: java.lang.NullPointerException
02-20 21:11:11.175: E/AndroidRuntime(14450): at com.javacodegeeks.android.json.JsonParsingActivity.onCreate(JsonParsingActivity.java:46)
02-20 21:11:11.175: E/AndroidRuntime(14450): at android.app.Activity.performCreate(Activity.java:5104)
02-20 21:11:11.175: E/AndroidRuntime(14450): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
02-20 21:11:11.175: E/AndroidRuntime(14450): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
我的JsonParsingActivity：
public class JsonParsingActivity extends Activity {
String url = "URL";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
InputStream source = retrieveStream(url);
Gson gson = new Gson();
Reader reader = new InputStreamReader(source);
RedmineResponse response = gson.fromJson(reader, RedmineResponse.class);
Toast.makeText(this, response.query, Toast.LENGTH_SHORT).show();
List<Result> results = response.results;
for (Result result : results) {
if (result.comments != null) {
Toast.makeText(this, result.comments, Toast.LENGTH_SHORT).show();
} else {
Toast.makeText(this, "EMPTY", Toast.LENGTH_SHORT).show();
}
}
}
private InputStream retrieveStream(String url) {
DefaultHttpClient client = new DefaultHttpClient();
HttpGet getRequest = new HttpGet(url);
try {
HttpResponse getResponse = client.execute(getRequest);
final int statusCode = getResponse.getStatusLine().getStatusCode();
if (statusCode != HttpStatus.SC_OK) {
Log.w(getClass().getSimpleName(), "Error " + statusCode + " for URL " + url);
return null;
}
HttpEntity getResponseEntity = getResponse.getEntity();
return getResponseEntity.getContent();
} catch (IOException e) {
getRequest.abort();
Log.w(getClass().getSimpleName(), "Error for URL " + url, e);
}
return null;
}
}
我的Result班级：
public class Result {
@SerializedName("id")
public String time_entry_ID;
@SerializedName("spent_on")
public String spent_on;
@SerializedName("created_on")
public String created_on;
public Project project;
@SerializedName("hours")
public String hours;
@SerializedName("comments")
public String comments;
@SerializedName("iso_language_code")
public String isoLanguageCode;
@SerializedName("to_user_id_str")
public String toUserIdStr;
public String source;
}
我的RedmineResponse班级：
public class RedmineResponse {
public List<Result> results;
@SerializedName("limit")
public int limit;
@SerializedName("offset")
public int offset;
public String query;
}
我的Activity班级：
public class Activity {
@SerializedName("id")
public String activity_ID;
@SerializedName("name")
public String activity_name;
}
我的Issue班级：
public class Issue {
@SerializedName("id")
public String issue_ID;
}
我的Project班级：
public class Issue {
@SerializedName("id")
public String issue_ID;
}
我的User班级：
public class User {
@SerializedName("id")
public String user_ID;
@SerializedName("name")
public String user_name;
}