本人菜鳥，往大神們出招相助：
本人寫了一個鏈接mysql資料庫的DButils類，在Activity中可以順利鏈接，但在Fragment中就無法連接，除錯顯示連接為空。且顯示((MySQLNonTransientConnectionException)e).SQLState=Cannot find local variable 'e'。代碼如下，請幫忙呀！
DButils類：
package com.example.asus.wechat;
import android.util.Log;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
/**
* 資料庫工具類：連接資料庫用、獲取資料庫資料用
* 相關操作資料庫的方法均可寫在該類
*/
public class DBUtils {
public static Connection connection=null;
private static String driver = "com.mysql.jdbc.Driver";// MySql驅動
private static PreparedStatement pds;
private static String user = "root";// 用戶名
private static String password = "888888";// 密碼
/**
* 連接資料庫
* */
public static Connection getConn(String dbName){
connection = null;
try{
Class.forName(driver);// 動態加載類
String ip = "10.0.2.2";// 寫成10.0.2.2，不能寫成localhost，因為手機的IP是loaclhost
// 嘗試建立到給定資料庫URL的連接
connection = DriverManager.getConnection("jdbc:mysql://" + ip + ":3306/" + dbName+"?useUnicode=true&characterEncoding=UTF-8&useSSL=false&autoReconnect=true&failOverReadOnly=false",
user, password);
}catch (Exception e){
e.printStackTrace();
}
return connection;
}
/**
* 查詢
* */
public static HashMap<String, Object> getInfoByName(String name){
HashMap<String, Object> map = new HashMap<>();
// 根據資料庫名稱，建立連接
Connection connection = getConn("dblearner");
try {
// mysql簡單的查詢陳述句。這里是根據MD_CHARGER表的NAME欄位來查詢某條記錄
String sql = "select * from uase where name = ?";
// String sql = "select * from MD_CHARGER";
if (connection != null){// connection不為null表示與資料庫建立了連接
PreparedStatement ps = connection.prepareStatement(sql);
if (ps != null){
// 設定上面的sql陳述句中的？的值為name
ps.setString(1, name);
// 執行sql查詢陳述句并回傳結果集
ResultSet rs = ps.executeQuery();
if (rs != null){
int count = rs.getMetaData().getColumnCount();
Log.e("DBUtils","列總數：" + count);
while (rs.next()){
// 注意：下標是從1開始的
for (int i = 1;i <= count;i++){
String field = rs.getMetaData().getColumnName(i);
map.put(field, rs.getString(field));
}
}
connection.close();
ps.close();
return map;
}else {
return null;
}
}else {
return null;
}
}else {
return null;
}
}catch (Exception e){
e.printStackTrace();
Log.e("DBUtils","例外：" + e.getMessage());
return null;
}
}
}
fragment_11.java
package com.example.asus.wechat;
import android.annotation.SuppressLint;
import android.app.Person;
import android.content.Context;
import android.net.Uri;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class fragment_11 extends Fragment {
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
private SimpleAdapter mAdpater;
private Button btn_get_data;
private TextView tv_data;
private EditText editText;
private Button ButAdd;
private Button ButSelect;
private EditText editid;
private EditText editname;
private EditText editpassword;
private EditText editsex;
private EditText editphote;
private Button ButDel;
private ListView lv;
private Button ButQue;
private Button ButNext;
private List<Person> lists;
private List<Map<String, Object>> data = new ArrayList<Map<String, Object>>();
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private OnFragmentInteractionListener mListener;
@SuppressLint("HandlerLeak")
private Handler handler = new Handler(){
@Override
public void handleMessage(Message msg) {
switch (msg.what){
case 0x11:
String s = (String) msg.obj;
tv_data.setText(s);
break;
case 0x12:
String ss = (String) msg.obj;
tv_data.setText(ss);
break;
}
}
};
public fragment_11() {
// Required empty public constructor
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* @param param1 Parameter 1.
* @param param2 Parameter 2.
* @return A new instance of fragment fragment_11.
*/
// TODO: Rename and change types and number of parameters
public static fragment_11 newInstance(String param1, String param2) {
fragment_11 fragment = new fragment_11();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_11, container, false);
btn_get_data = view.findViewById(R.id.btn_get_data);
tv_data =view. findViewById(R.id.tv_data);
editText=view.findViewById(R.id.editText);
return view;
//return inflater.inflate(R.layout.fragment_11, container, false);
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
@Override
public void onDetach() {
super.onDetach();
mListener = null;
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p>
* See the Android Training lesson <a href=https://bbs.csdn.net/topics/
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
public void onActivityCreated(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onActivityCreated(savedInstanceState);
btn_get_data.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
new Thread(new Runnable() {
@Override
public void run() {
HashMap<String, Object> map = DBUtils.getInfoByName(editText.getText().toString());
Message message = handler.obtainMessage();
if (map != null) {
String s = "";
for (String key : map.keySet()) {
s += key + ":" + map.get(key) + "\n";
}
message.what = 0x12;
message.obj = s;
} else {
message.what = 0x11;
message.obj = "查詢結果為空";
}
// 發訊息通知主執行緒更新UI
handler.sendMessage(message);
}
}).start();
}
});
}
}
uj5u.com熱心網友回復：
自己頂，別沉底；uj5u.com熱心網友回復：
大神們，趕緊來施救呀！uj5u.com熱心網友回復：
不是已經提示找不到“e”這個變數了么uj5u.com熱心網友回復：
你說的那個錯誤是代碼沒有運行上去或者開混淆了。還有Fragment這樣寫不會崩潰嗎？
uj5u.com熱心網友回復：
還有沒有高手幫著解決一下轉載請註明出處，本文鏈接：https://www.uj5u.com/yidong/130712.html
標籤：Android
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