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我有 2 个活动，我想登录，而在另一个活动中，我想从我的数据库中获取一些数据。

一切正常，除非我想显示数据时出现错误。

我不知道这将如何工作，有错误日志

06-01 17:33:03.644: E/JSON Parser(555): Error parsing data org.json.JSONException: End of input at character 0 of 
06-01 17:33:03.644: D/AndroidRuntime(555): Shutting down VM
06-01 17:33:03.644: W/dalvikvm(555): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
06-01 17:33:03.654: E/AndroidRuntime(555): FATAL EXCEPTION: main
06-01 17:33:03.654: E/AndroidRuntime(555): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.androidhive/com.example.androidhive.DashboardActivity}: java.lang.NullPointerException
06-01 17:33:03.654: E/AndroidRuntime(555):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
06-01 17:33:03.654: E/AndroidRuntime(555):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
06-01 17:33:03.654: E/AndroidRuntime(555):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
06-01 17:33:03.654: E/AndroidRuntime(555):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
06-01 17:33:03.654: E/AndroidRuntime(555):  at android.os.Handler.dispatchMessage(Handler.java:99)
06-01 17:33:03.654: E/AndroidRuntime(555):  at android.os.Looper.loop(Looper.java:123)
06-01 17:33:03.654: E/AndroidRuntime(555):  at android.app.ActivityThread.main(ActivityThread.java:4627)
06-01 17:33:03.654: E/AndroidRuntime(555):  at java.lang.reflect.Method.invokeNative(Native Method)
06-01 17:33:03.654: E/AndroidRuntime(555):  at java.lang.reflect.Method.invoke(Method.java:521)
06-01 17:33:03.654: E/AndroidRuntime(555):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
06-01 17:33:03.654: E/AndroidRuntime(555):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
06-01 17:33:03.654: E/AndroidRuntime(555):  at dalvik.system.NativeStart.main(Native Method)
06-01 17:33:03.654: E/AndroidRuntime(555): Caused by: java.lang.NullPointerException
06-01 17:33:03.654: E/AndroidRuntime(555):  at com.example.androidhive.DashboardActivity.onCreate(DashboardActivity.java:60)
06-01 17:33:03.654: E/AndroidRuntime(555):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
06-01 17:33:03.654: E/AndroidRuntime(555):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
06-01 17:33:03.654: E/AndroidRuntime(555):  ... 11 more

我的 UserFunctions.java 中有一个函数 strijk()

public JSONObject strijk(String email){
    // Building Parameters
    List<NameValuePair> params = new ArrayList<NameValuePair>();
    params.add(new BasicNameValuePair("tag", strijk_tag));
    params.add(new BasicNameValuePair("email", email));

    JSONObject json = jsonParser.getJSONFromUrl(loginURL, params);
    // return json
    // Log.e("JSON", json.toString());
    return json;
}

在我的第二个活动中，我想显示从我的 json 获得的数据。

UserFunctions userFunction = new UserFunctions();

        JSONObject strijk = userFunction.strijk(name);

        //check for strijk

        try {
            if (strijk.getString(KEY_SUCCESS) != null) {
                error.setText("");
                String res =strijk.getString(KEY_SUCCESS);  
                if (Integer.parseInt(res)==1){
                    String strijkid = strijk.getString(KEY_STRIJK);
                    String klaar = strijk.getString(KEY_KLAAR);
                    kla =(TextView) findViewById(R.id.klaar);
                    strijkd = (TextView) findViewById(R.id.strijkid);
                    kla.setText(klaar);
                    strijkd.setText(strijkid);
                }

            }


        } catch (JSONException e) {
            Log.e("log_tag","Error in Display!" + e.toString());;
        }

这是我的 JSON 解析器

public class JSONParser {
static InputStream is = null;
static JSONObject jObj = null;
static String json = "";

// constructor
public JSONParser() {

}

public JSONObject getJSONFromUrl(String url, List<NameValuePair> params) {

    // Making HTTP request
    try {
        // defaultHttpClient
        DefaultHttpClient httpClient = new DefaultHttpClient();
        HttpPost httpPost = new HttpPost(url);
        httpPost.setEntity(new UrlEncodedFormEntity(params));

        HttpResponse httpResponse = httpClient.execute(httpPost);
        HttpEntity httpEntity = httpResponse.getEntity();
        is = httpEntity.getContent();

    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    } catch (ClientProtocolException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    try {
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "iso-8859-1"), 8);
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");
        }
        is.close();
        json = sb.toString();
        Log.e("JSON", json);
    } catch (Exception e) {
        Log.e("Buffer Error", "Error converting result " + e.toString());
    }

    // try parse the string to a JSON object
    try {
        jObj = new JSONObject(json);            
    } catch (JSONException e) {
        Log.e("JSON Parser", "Error parsing data " + e.toString());
    }

    // return JSON String
    return jObj;

}

}

这是给我的学校的，我还不太擅长android。

4

0 回答 0