应用程序在更高版本的Android上崩溃

Question

I have been creating an app, built on target sdk version 15 and with minimum sdk version of 8. Every thing is running perfect when I run it on a devices running version 8. But when I try it on anything higher than version 10 it crashes with a NullPointerException.

The logcat gives me this:

10-06 19:23:12.927: E/AndroidRuntime(589): FATAL EXCEPTION: main
10-06 19:23:12.927: E/AndroidRuntime(589): java.lang.RuntimeException: Unable to start                 activity        ComponentInfo{com.fansheroid.facts.chicks/com.fansheroid.facts.chicks.MainActivity}:   java.lang.NullPointerException
10-06 19:23:12.927: E/AndroidRuntime(589):  at     android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1955)
10-06 19:23:12.927: E/AndroidRuntime(589):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980)
10-06 19:23:12.927: E/AndroidRuntime(589):  at android.app.ActivityThread.access$600(ActivityThread.java:122)
10-06 19:23:12.927: E/AndroidRuntime(589):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146)
10-06 19:23:12.927: E/AndroidRuntime(589):  at android.os.Handler.dispatchMessage(Handler.java:99)
10-06 19:23:12.927: E/AndroidRuntime(589):  at android.os.Looper.loop(Looper.java:137)
10-06 19:23:12.927: E/AndroidRuntime(589):  at android.app.ActivityThread.main(ActivityThread.java:4340)
10-06 19:23:12.927: E/AndroidRuntime(589):  at java.lang.reflect.Method.invokeNative(Native Method)
10-06 19:23:12.927: E/AndroidRuntime(589):  at java.lang.reflect.Method.invoke(Method.java:511)
10-06 19:23:12.927: E/AndroidRuntime(589):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
10-06 19:23:12.927: E/AndroidRuntime(589):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
10-06 19:23:12.927: E/AndroidRuntime(589):  at dalvik.system.NativeStart.main(Native Method)
10-06 19:23:12.927: E/AndroidRuntime(589): Caused by: java.lang.NullPointerException
10-06 19:23:12.927: E/AndroidRuntime(589):  at org.json.JSONTokener.nextCleanInternal(JSONTokener.java:116)
10-06 19:23:12.927: E/AndroidRuntime(589):  at org.json.JSONTokener.nextValue(JSONTokener.java:94)
10-06 19:23:12.927: E/AndroidRuntime(589):  at org.json.JSONObject.<init>(JSONObject.java:154)
10-06 19:23:12.927: E/AndroidRuntime(589):  at org.json.JSONObject.<init>(JSONObject.java:171)
10-06 19:23:12.927: E/AndroidRuntime(589):  at com.fansheroid.facts.chicks.MainActivity.getTumblrs(MainActivity.java:156)
10-06 19:23:12.927: E/AndroidRuntime(589):  at com.fansheroid.facts.chicks.MainActivity.onCreate(MainActivity.java:62)
10-06 19:23:12.927: E/AndroidRuntime(589):  at android.app.Activity.performCreate(Activity.java:4465)
10-06 19:23:12.927: E/AndroidRuntime(589):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
10-06 19:23:12.927: E/AndroidRuntime(589):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919)
10-06 19:23:12.927: E/AndroidRuntime(589):  ... 11 more

I have been trying to figure out the problem for the past two days, but it just doesn't make sense for me.

EDIT ADDED CODE

public ArrayList<Tumblr> getTumblrs() throws ClientProtocolException,
        IOException, JSONException {
    String searchUrl = "http://api.tumblr.com/v2/blog/factsandchicks.com/posts?api_key=API_KEY";

    ArrayList<Tumblr> tumblrs = new ArrayList<Tumblr>();

    HttpClient client = new DefaultHttpClient();
    HttpGet get = new HttpGet(searchUrl);

    ResponseHandler<String> responseHandler = new BasicResponseHandler();

    String responseBody = null;
    try {
        responseBody = client.execute(get, responseHandler);
    } catch (Exception ex) {
        ex.printStackTrace();
    }

    JSONObject jsonObject = new JSONObject(responseBody);

    JSONArray posts = jsonObject.getJSONObject("response").getJSONArray(
            "posts");
    for (int i = 0; i < posts.length(); i++) {
        JSONArray photos = posts.getJSONObject(i).getJSONArray("photos");
        for (int j = 0; j < photos.length(); j++) {
            JSONObject photo = photos.getJSONObject(j);
            String url = photo.getJSONArray("alt_sizes").getJSONObject(0)
                    .getString("url");

            Tumblr tumblr = new Tumblr(url);
            tumblrs.add(tumblr);
        }
    }
    return tumblrs;
}

Line 156:

JSONObject jsonObject = new JSONObject(responseBody);

Answer 1

Ah, look at this:

E/AndroidRuntime(589): Caused by: java.lang.NullPointerException 10-06 19:23:12.927: 
E/AndroidRuntime(589): at org.json.JSONTokener.nextCleanInternal(JSONTokener.java:116) 10-06 19:23:12.927:
E/AndroidRuntime(589): at org.json.JSONTokener.nextValue(JSONTokener.java:94) 10-06 19:23:12.927:
E/AndroidRuntime(589): at org.json.JSONObject.(JSONObject.java:154) 10-06 19:23:12.927: 
E/AndroidRuntime(589): at org.json.JSONObject.(JSONObject.java:171) 10-06 19:23:12.927: 
E/AndroidRuntime(589): at com.fansheroid.facts.chicks.MainActivity.getTumblrs(MainActivity.java:156) 10-06 19:23:12.927: 
E/AndroidRuntime(589): at com.fansheroid.facts.chicks.MainActivity.onCreate(MainActivity.java:62) 

It basically says the JSON parser fails: you're probably passing NULL on line 156 of MainActivity.java. You should check the value at that line and see if your device upgrade hasn't somehow wiped out a value or failed to retrieve a value correctly.

Answer 2

try {
    responseBody = client.execute(get, responseHandler);
} catch (Exception ex) {
    ex.printStackTrace();
}

That section of code is where your response is failing. You assign null to responsebody, chances are that your call there is failing so that responsebody is still null when it hits line 156.

Try looking in your debug output for the ex.printStackTrace(); output to see what is going on.

Answer 3

通过使用HttpResponse和HttpEntity而不是ResponseHandler来解决问题，这解决了这个问题。