【发布时间】：2017-08-09 21:37:33
【问题描述】：
我开发了一个应用程序，我们可以在其中更改 IP 地址以连接到运行在 xampp 服务器上的数据库..
这是我的 MainActivity.java
我在其中声明了一个名为“ip”的公共静态字符串变量并为其设置了默认值。我使用警报框使用菜单选项更改了此 IP。当使用快餐栏显示更改的 ip 时，它会显示更改。但试图在 Mainactivity.ip 名为“doctor_login.java”的另一个活动中访问该“ip”。它不需要更改 ip，而是使用默认 ip 本身。下面我展示了截图和代码。请帮助我解决这个问题。
public class MainActivity extends AppCompatActivity { public static String ip="192.168.43.97";// This is default ip
public static final String dbuser = "root";
public static final String dbpass = "kughan";
private SectionsPagerAdapter mSectionsPagerAdapter;
private ViewPager mViewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "App by KUGHAN EV", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.action_settings) {
AlertDialog.Builder ipalert = new AlertDialog.Builder(MainActivity.this);
ipalert.setCancelable(false);
ipalert.setTitle("Change IP");
ipalert.setMessage("Enter your server ip below:");
final EditText input = new EditText(MainActivity.this);
input.setInputType(InputType.TYPE_NUMBER_FLAG_DECIMAL);
RelativeLayout.LayoutParams lp=new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT,RelativeLayout.LayoutParams.WRAP_CONTENT);
input.setLayoutParams(lp);
ipalert.setView(input);
ipalert.setPositiveButton("CHANGE", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
String cip=input.getText().toString();
ip=cip; // Trying to change ip address from edittext
Snackbar.make(getCurrentFocus(),"Ip changed to "+ip,Snackbar.LENGTH_LONG).setAction(null,null).show();
}
});
ipalert.setNegativeButton("CANCEL",null);
ipalert.show();
}
if(id== R.id.showip){
Snackbar.make(getCurrentFocus(),"Your IP is "+ip,Snackbar.LENGTH_LONG).setAction(null,null).show();
}
return super.onOptionsItemSelected(item);
}
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
switch (position){
case 0:
doctor_login tab1 = new doctor_login();
return tab1;
case 1:
patient_login tab2 = new patient_login();
return tab2;
default:
return null;
}
}
@Override
public int getCount() {
// Show 3 total pages.
return 2;
}
@Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "DOCTOR";
case 1:
return "PATIENT";
}
return null;
}
}
//This is my doctor_login activity
public class doctor_login extends Fragment {
public static String logged;
public static String loggedid;
private String url;
private static final String user = MainActivity.dbuser;
private static final String pass = MainActivity.dbpass;
EditText usertxt,passtxt;
Button login,reg;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState)
{
final View rootView = inflater.inflate(R.layout.activity_doctor_login, container, false);
url ="jdbc:mysql://"+MainActivity.ip+":3306/mediapp"; //getting value from mainactivity ip value
usertxt=(EditText) rootView.findViewById(R.id.editText);
passtxt=(EditText)rootView.findViewById(R.id.editText2);
login=(Button)rootView.findViewById(R.id.button);
reg=(Button)rootView.findViewById(R.id.button2);
login.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if(usertxt.getText().toString().length()==0 || passtxt.getText().toString().length()==0){
Snackbar.make(getView(),"Fill all credential details",Snackbar.LENGTH_LONG).setAction("Action",null).show();
}else{
testDB();
}
}
});
reg.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent1 = new Intent(doctor_login.this.getActivity(),doctor_signup.class);
startActivity(intent1);
}
});
return rootView;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Snackbar.make(getView(),"Welcome to DigiMedApp",Snackbar.LENGTH_LONG).setAction("Action",null).show();
}
public void testDB(){
Toast.makeText(getContext(),url,Toast.LENGTH_LONG).show();
try
{
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection(url,user,pass);
Statement st = con.createStatement();
ResultSet rs = st.executeQuery("select name,id from doctorlogin where username='"+usertxt.getText().toString()+"' and password='"+passtxt.getText().toString()+"';");
if(rs.next()){
logged=rs.getString(1);
loggedid=rs.getString(2);
Toast.makeText(getContext(),"Welcome "+rs.getString(1),Toast.LENGTH_LONG).show();
Intent intent = new Intent(doctor_login.this.getActivity(),doctor_home.class);
startActivity(intent);
} else
{
Snackbar.make(getView(),"Wrong Username or password",Snackbar.LENGTH_LONG).setAction("Action",null).show();
}
}
catch (Exception e)
{
e.printStackTrace();
Toast.makeText(getContext(),e.toString(),Toast.LENGTH_LONG).show();
}
}
}
使用 alertdialog 更改 ip See the editetxt__Screenshot
当尝试从医生登录页面登录时，它会显示连接异常，因为即使更改了 ip，您也可以看到它正在尝试连接的 ip
【问题讨论】：
-
尝试存储在共享首选项而不是静态。
标签： java android mysql exception connection