无法将数据从数据库检索到android应用程序

我无法将数据从

MySQL

数据库检索到应用程序。当我点击按钮显示数据时，活动会自动关闭并转到主活动

公共阶层群体扩大了活动范围{

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

    String result = null;
    InputStream is = null;
    try {
        HttpClient httpclient = new DefaultHttpClient();
        HttpPost httppost = new HttpPost("http://website/new/db_connect.php");
        HttpResponse response = httpclient.execute(httppost);
        HttpEntity entity = response.getEntity();
        is = entity.getContent();

        Log.e("log_tag", "connection success");
        //   Toast.makeText(getApplicationContext(), “pass”, Toast.LENGTH_SHORT).show();
    } catch (Exception e) {
        Log.e("log_tag", "Error in http connection" + e.toString());
        Toast.makeText(getApplicationContext(), "Connection fail", Toast.LENGTH_SHORT).show();

    }
    //convert response to string
    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");
            //  Toast.makeText(getApplicationContext(), “Input Reading pass”, Toast.LENGTH_SHORT).show();
        }
        is.close();

        result = sb.toString();
    } catch (Exception e) {
        Log.e("log_tag", "Error converting result" + e.toString());
        Toast.makeText(getApplicationContext(), "Input reading fail", Toast.LENGTH_SHORT).show();

    }

    //parse json data
    try {
        JSONArray jArray = new JSONArray(result);
        TableLayout tv = (TableLayout) findViewById(R.id.table);
        tv.removeAllViewsInLayout();
        int flag = 1;
        for (int i = -1; i < jArray.length() - 1; i++) {
            TableRow tr = new TableRow(Cohorts.this);
            tr.setLayoutParams(new LayoutParams(
                    LayoutParams.FILL_PARENT,
                    LayoutParams.WRAP_CONTENT));
            if (flag == 1) {
                TextView b6 = new TextView(Cohorts.this);
                b6.setText("Cohort Id");
                b6.setTextColor(Color.BLUE);
                b6.setTextSize(15);
                tr.addView(b6);
                TextView b19 = new TextView(Cohorts.this);
                b19.setPadding(10, 0, 0, 0);
                b19.setTextSize(15);
                b19.setText("Cohort Name");
                b19.setTextColor(Color.BLUE);
                tr.addView(b19);
                TextView b29 = new TextView(Cohorts.this);
                b29.setPadding(10, 0, 0, 0);
                b29.setText("Cohort Leader");
                b29.setTextColor(Color.BLUE);
                b29.setTextSize(15);
                tr.addView(b29);
                TextView b30 = new TextView(Cohorts.this);
                b30.setText("Certified Leader");
                b30.setTextColor(Color.BLUE);
                b30.setTextSize(15);
                tr.addView(b30);
                TextView b35 = new TextView(Cohorts.this);
                b35.setText("Associate Faculty");
                b35.setTextColor(Color.BLUE);
                b35.setTextSize(15);
                tr.addView(b35);
                TextView b39 = new TextView(Cohorts.this);
                b39.setText("Cohort Location");
                b39.setTextColor(Color.BLUE);
                b39.setTextSize(15);
                tr.addView(b39);
                tv.addView(tr);
                final View vline = new View(Cohorts.this);
                vline.setLayoutParams(new TableRow.LayoutParams(TableRow.LayoutParams.FILL_PARENT, 2));
                vline.setBackgroundColor(Color.BLUE);
                tv.addView(vline);
                flag = 0;
            } else {
                JSONObject json_data = jArray.getJSONObject(i);
                Log.i("log_tag", "Cohort ID: " + json_data.getInt("Cohort_ID") + ", Cohort Name: " + json_data.getString("Cohort_Name") + ", Cohort Leader" + json_data.getString("Cohort_Leader") + ", Certified Leader: " + json_data.getString("Certified_Leader") + ", Associate Faculty" + json_data.getString("Associate_Faculty") + ", Cohort Location" + json_data.getString("Cohort_Location"));
                TextView b = new TextView(Cohorts.this);
                String stime = String.valueOf(json_data.getInt("Cohort_ID"));
                b.setText(stime);
                b.setTextColor(Color.RED);
                b.setTextSize(15);
                tr.addView(b);
                TextView b1 = new TextView(Cohorts.this);
                b1.setPadding(10, 0, 0, 0);
                b1.setTextSize(15);
                String stime1 = json_data.getString("Cohort_Name");
                b1.setText(stime1);
                b1.setTextColor(Color.BLACK);
                tr.addView(b1);
                TextView b2 = new TextView(Cohorts.this);
                b2.setPadding(10, 0, 0, 0);
                String stime2 = json_data.getString("Cohort_Leader");
                b2.setText(stime2);
                b2.setTextColor(Color.BLACK);
                b2.setTextSize(15);
                tr.addView(b2);
                TextView b3 = new TextView(Cohorts.this);
                String stime3 = String.valueOf(json_data.getInt("Certified_Leader"));
                b3.setText(stime3);
                b3.setTextColor(Color.BLACK);
                b3.setTextSize(15);
                tr.addView(b3);
                TextView b4 = new TextView(Cohorts.this);
                b4.setPadding(10, 0, 0, 0);
                b4.setTextSize(15);
                String stime4 = json_data.getString("Associate_Faculty");
                b4.setText(stime4);
                b4.setTextColor(Color.BLACK);
                tr.addView(b4);
                TextView b5 = new TextView(Cohorts.this);
                b5.setPadding(10, 0, 0, 0);
                String stime5 = json_data.getString("Cohort_Location");
                b5.setText(stime5);
                b5.setTextColor(Color.BLACK);
                b5.setTextSize(15);
                tr.addView(b5);
                tv.addView(tr);
                final View vline1 = new View(Cohorts.this);
                vline1.setLayoutParams(new TableRow.LayoutParams(TableRow.LayoutParams.FILL_PARENT, 1));
                vline1.setBackgroundColor(Color.WHITE);
                tv.addView(vline1);
            }
        }
    } catch (JSONException e) {
        Log.e("log_tag", "Error parsing data" + e.toString());
        Toast.makeText(getApplicationContext(), "JsonArray fail", Toast.LENGTH_SHORT).show();
    }
}

@覆盖
创建时的公共void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity_队列）；
字符串结果=null；
InputStream=null；
试一试{
HttpClient HttpClient=新的DefaultHttpClient（）；
HttpPost HttpPost=新的HttpPost（“http://website/new/db_connect.php");
HttpResponse response=httpclient.execute（httppost）；
HttpEntity=response.getEntity（）；
is=entity.getContent（）；
Log.e（“Log_标签”，“连接成功”）；
//Toast.makeText（getApplicationContext（），“pass”，Toast.LENGTH\u SHORT.show（）；
}捕获（例外e）{
e（“Log_标记”，“http连接错误”+e.toString（））；
Toast.makeText（getApplicationContext（），“连接失败”，Toast.LENGTH\u SHORT.show（）；
}
//将响应转换为字符串
试一试{
BufferedReader reader=新的BufferedReader（新的InputStreamReader（is，“iso-8859-1”），8；
StringBuilder sb=新的StringBuilder（）；
字符串行=null；
而（（line=reader.readLine（））！=null）{
sb.追加（第+行“\n”）；
//Toast.makeText（getApplicationContext（），“输入读取过程”，Toast.LENGTH\u SHORT.show（）；
}
is.close（）；
结果=sb.toString（）；
}捕获（例外e）{
Log.e（“Log_标记”，“错误转换结果”+e.toString（））；
Toast.makeText（getApplicationContext（），“输入读取失败”，Toast.LENGTH\u SHORT.show（）；
}
//解析json数据
试一试{
JSONArray jArray=新JSONArray（结果）；
TableLayout tv=（TableLayout）findViewById（R.id.table）；
tv.removeAllViewsInLayout（）；
int标志=1；
for（int i=-1；iprivate class back_up extends AsyncTask<Void, Void, Void>
{

    ProgressDialog pd = null;


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

        pd = new ProgressDialog(your_activity.this);
        pd.setTitle("Creating Backup");
        pd.setMessage("processing.....");
        pd.show();
    }

    @Override
    protected Void doInBackground(Void... arg0) {
        // TODO Auto-generated method stub

        // execute operation here

        return null;
    }

    @Override
    protected void onPostExecute(Void result) {
        // TODO Auto-generated method stub
        super.onPostExecute(result);
    if(pd != null){
                pd.dismiss();
    }
    // update UI
}

class TestAsync extends AsyncTask<Void, Integer, String>
{
    protected void onPreExecute (){
        Log.d("PreExceute","On pre Exceute......");
    }

    protected String doInBackground(Void...arg0) {
        Log.d("DoINBackGround","On doInBackground...");
        // Do your HTTP network request code here
        return "You are at PostExecute";
    }

    protected void onPostExecute(String result) {
        // Update all UI widgets values here
        Log.d(""+result);
    }
}

new TestAsync().execute();