如何修复Assets文件夹中json文件的NullPointerException

Question

我正在尝试使用我的Assets文件夹中json中的字段填充Android应用中的RecyclerView。 json文件在我的res的资产文件夹中。但是getClass（）。getResourseAsStream（）和getAssets（）。open（）都无法在资产文件夹中找到json文件。 它提供FileNotFoundException或NullPointerException

我尝试使用

InputStream is = getAssets().open("activities.json");
InputStream is = getClass().getResourceAsStream("/activities.json");

还尝试使用org.json.simple.parser.JSONParser;

这是我的活动文件

try {
     URL url = getClass().getResource("activities.json");
     File f = new File(url.toURI());

     Object object = parser.parse(new FileReader(f));


    JSONObject obj = new JSONObject(json);
    JSONArray m_jArray = obj.getJSONArray("Activities");

    for (int i = 0; i < m_jArray.length(); i++) {
        JSONObject jo_inside = m_jArray.getJSONObject(i);
        myDataset.add(new Activity(
                jo_inside.getString("title"),
                jo_inside.getString("desc")
        ));
    }

} catch (JSONException e) {
    e.printStackTrace();
} catch (FileNotFoundException e) {
    e.printStackTrace();
} catch (IOException e) {
    e.printStackTrace();
} 

这是我的活动。json

{
  "Activities" : [ {
    "desc" : "Activity 0 desc",
    "title" : "Activity 0"
  }, {
    "desc" : "Activity 1 desc",
    "title" : "Activity 1"
  }, {
    "desc" : "Activity 2 desc",
    "title" : "Activity 2"
  }, {
    "desc" : "Activity 3 desc",
    "title" : "Activity 3"
  }, {
    "desc" : "Activity 4 desc",
    "title" : "Activity 4"
  }, {
    "desc" : "Activity 5 desc",
    "title" : "Activity 5"
  } ]
}

出现以下错误

    E/AndroidRuntime: FATAL EXCEPTION: main
        Process: com.example.ams_1, PID: 21647
        java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.ams_1/com.example.ams_1.Activities}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.net.URI java.net.URL.toURI()' on a null object reference
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
            at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
            at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
            at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
            at android.os.Handler.dispatchMessage(Handler.java:106)
            at android.os.Looper.loop(Looper.java:193)
            at android.app.ActivityThread.main(ActivityThread.java:6669)
            at java.lang.reflect.Method.invoke(Native Method)
            at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
         Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.net.URI java.net.URL.toURI()' on a null object reference
            at com.example.ams_1.Activities.onCreate(Activities.java:110)
            at android.app.Activity.performCreate(Activity.java:7136)
            at android.app.Activity.performCreate(Activity.java:7127)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048) 
            at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) 
            at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) 
            at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) 
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808) 
            at android.os.Handler.dispatchMessage(Handler.java:106) 
            at android.os.Looper.loop(Looper.java:193) 
            at android.app.ActivityThread.main(ActivityThread.java:6669) 
            at java.lang.reflect.Method.invoke(Native Method) 
            at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)