Question

我是Android编程新手。我正在尝试从MYSQL数据库中检索数据。但我无法检索我的数据。我的代码是

public class News_Updates extends Activity implements View.OnClickListener {
EditText ettitle, etdescription, etdate; // et is edit text
String title;
String description;
String date;
InputStream is = null;
String result = null;
String line = null;
int code;
JSONArray json_data;
String custtitle[]; // cus means custom
String custdescrption[];
String custdate[];

// ListView Declaration
ListView lvcust;
Context c;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_news__updates);

    lvcust = (ListView) findViewById(R.id.mylistview);

    MyAsyncSearch asr = new MyAsyncSearch();
    asr.execute();
}

// Insert AsyncTask
class MyAsync extends AsyncTask<Void, Void, Void> {

    @Override
    protected Void doInBackground(Void... params) {
        // TODO Auto-generated method stub
        // insert();
        return null;
    }

}

// Search Async Task for Search query
class MyAsyncSearch extends AsyncTask<Void, Void, Void> {

    @Override
    protected Void doInBackground(Void... params) {
        // TODO Auto-generated method stub
        search();
        return null;
    }

    @Override
    protected void onPostExecute(Void result) {
        // TODO Auto-generated method stub
        super.onPostExecute(result);

        // Fill listview with records through MyAdapter
        MyAdapter aa = new MyAdapter(c, custtitle, custdescrption, custdate);
        lvcust.setAdapter(aa);
    }

}

// Search method for extracting records
public void search() {
    ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();

    try {
        HttpClient httpclient = new DefaultHttpClient();
        HttpPost httppost = new HttpPost(
                "http://10.0.0.1/FYP/admin/search_android.php");
        httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
        HttpResponse response = httpclient.execute(httppost);
        HttpEntity entity = response.getEntity();
        is = entity.getContent();
        Log.e("pass 1", "connection success ");
    } catch (Exception e) {
        Log.e("Fail 1", e.toString());

    }

    try {
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "iso-8859-1"), 8);
        StringBuilder sb = new StringBuilder();
        while ((line = reader.readLine()) != null) {

            result = line;
            json_data = new JSONArray(result);

        }

        custtitle = new String[json_data.length()];
        custdate = new String[json_data.length()];
        custdescrption = new String[json_data.length()];

        // Processing the result row by row and storing it in arrays called
        // custnamelist and custphonelist
        for (int i = 0; i < json_data.length(); i++) {

            JSONObject jsonobject = json_data.getJSONObject(i);
            title = jsonobject.getString("news_title");
            date = jsonobject.getString("news_date");
            description = jsonobject.getString("news_desc");

            custtitle[i] = jsonobject.getString("news_title"); // (news_title
                                                                // database
                                                                // field
                                                                // name
            custdate[i] = jsonobject.getString("news_date");
            custdescrption[i] = jsonobject.getString("news_desc");
        }
        is.close();

    } catch (Exception e) {
        Log.e("Fail 2", e.toString());
    }

}

@Override
public void onClick(View v) {
    // TODO Auto-generated method stub

}
}

我的logcat是

11-07 09:59:34.296: E/AndroidRuntime(1263): java.lang.NullPointerException: storage == null
11-07 09:59:34.296: E/AndroidRuntime(1263):     at java.util.Arrays$ArrayList.<init>(Arrays.java:38)
11-07 09:59:34.296: E/AndroidRuntime(1263):     at java.util.Arrays.asList(Arrays.java:154)
11-07 09:59:34.296: E/AndroidRuntime(1263):     at android.widget.ArrayAdapter.<init>(ArrayAdapter.java:141)
11-07 09:59:34.296: E/AndroidRuntime(1263):     at com.example.bcs_final_project.MyAdapter.<init>(MyAdapter.java:17)
11-07 09:59:34.296: E/AndroidRuntime(1263):     at com.example.bcs_final_project.News_Updates$MyAsyncSearch.onPostExecute(News_Updates.java:89)
11-07 09:59:34.296: E/AndroidRuntime(1263):     at com.example.bcs_final_project.News_Updates$MyAsyncSearch.onPostExecute(News_Updates.java:1)
11-07 09:59:34.296: E/AndroidRuntime(1263):     at android.os.AsyncTask.finish(AsyncTask.java:631)
11-07 09:59:34.296: E/AndroidRuntime(1263):     at android.os.AsyncTask.access$600(AsyncTask.java:177)
11-07 09:59:34.296: E/AndroidRuntime(1263):     at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
11-07 09:59:34.296: E/AndroidRuntime(1263):     at android.os.Handler.dispatchMessage(Handler.java:99)
11-07 09:59:34.296: E/AndroidRuntime(1263):     at android.os.Looper.loop(Looper.java:137)
11-07 09:59:34.296: E/AndroidRuntime(1263):     at android.app.ActivityThread.main(ActivityThread.java:5103)
11-07 09:59:34.296: E/AndroidRuntime(1263):     at java.lang.reflect.Method.invokeNative(Native Method)
11-07 09:59:34.296: E/AndroidRuntime(1263):     at java.lang.reflect.Method.invoke(Method.java:525)
11-07 09:59:34.296: E/AndroidRuntime(1263):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
11-07 09:59:34.296: E/AndroidRuntime(1263):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)

适配器代码公共类MyAdapter扩展ArrayAdapter { 字符串标题[]，日期[]，描述[]; 活动c;

@SuppressWarnings("unchecked")
public MyAdapter(Context context, String ti[], String dt[], String des[]) {
    super(context, R.layout.custom_rows, R.id.title, ti);
    c = (Activity) context;
    title = ti;
    date = dt;
    description = des;

}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    // TODO Auto-generated method stub
    super.getView(position, convertView, parent);

    LayoutInflater l = c.getLayoutInflater();
    View v = l.inflate(R.layout.custom_rows, null);
    TextView tv1 = (TextView) v.findViewById(R.id.news_title);
    TextView tv2 = (TextView) v.findViewById(R.id.news_description);
    TextView tv3 = (TextView) v.findViewById(R.id.news_date);
    tv1.setText(title[position]);
    tv2.setText(description[position]);
    tv1.setText(date[position]);
    return v;
}
}

Answer 1

在我看来，你永远不会实例化你的'c'变量，导致NPE。

Android：无法检索日期

1 个答案: