英文:
I am facing this error while connecting with the mysql database in Android Studio
问题
这是我修改后的代码:
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
username = findViewById(R.id.username);
password = findViewById(R.id.pass);
buttonLogin = findViewById(R.id.button);
buttonLogin.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
System.out.println("IN ONCLICK");
new CheckLogin().execute();
}
});
}
public class CheckLogin extends AsyncTask<Void, Void, Void> {
@Override
protected Void doInBackground(Void... voids) {
System.out.println("DOING BACKGROUND");
try {
System.out.println("IN TRY");
Class.forName("com.mysql.jdbc.Driver");
String dbName = "db_app";
String dbUserName = "root";
String dbPassword = "/*ajdsikijliaj*$lklk%n^T!#@";
String connectionString = "jdbc:mysql://localhost/" + dbName + "?user=" + dbUserName + "&password=" + dbPassword + "&useUnicode=true&characterEncoding=UTF-8";
Connection con = DriverManager.getConnection(connectionString);
String str = "Select * from users";
Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery(str);
rs.next();
if (rs.getString("Username").equals(username.getText().toString()) &&
rs.getString("Password").equals(password.getText().toString())) {
System.out.println("EQUAL");
Intent loginIntent = new Intent(MainActivity.this, login.class);
startActivity(loginIntent);
} else {
System.out.println("WRONG");
}
stmt.close();
} catch (ClassNotFoundException | SQLException e) {
System.out.println("In catch");
e.printStackTrace();
}
return null;
}
}
请注意，我将代码中的一些问题进行了修正。在比较用户名和密码时，我使用 .toString() 来获取 EditText 中的文本。另外，我还删除了注释中的非法字符，以便代码能够正常编译和执行。如果您继续遇到问题，请确保您的数据库连接配置正确，并且您的设备可以访问数据库。
英文:
I am using the below code. It is giving error in Android Studio. I have seen and other relevant posts and I understand that the error may be in doInBackground method, but I can't understand which place of code I must change.
Here is the Java code:
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
username = (EditText) findViewById(R.id.username);
password = (EditText) findViewById(R.id.pass);
buttonLogin = (Button) findViewById(R.id.button);
buttonLogin.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick (View v) {
System.out.println("IN ONCLICK");
new CheckLogin().execute();
}
});
}
public class CheckLogin extends AsyncTask<Void, Void ,Void>
{
@Override
protected Void doInBackground(Void... voids) {
System.out.println("DOING BACKGROUND");
try {
System.out.println("IN TRY");
Class.forName("com.mysql.jdbc.Driver");
//Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/db_app?characterEncoding=latin1","root","/*ajdsikijliaj*$lklk%n^T!#@");
String dbName = "db_app";
String dbUserName = "root";
String dbPassword = "/*ajdsikijliaj*$lklk%n^T!#@";
String connectionString = "jdbc:mysql://localhost/" + dbName + "?user=" + dbUserName + "&password=" + dbPassword + "&useUnicode=true&characterEncoding=UTF-8";
Connection con = DriverManager.getConnection(connectionString);
String str = "Select * from users";
Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery(str);
rs.next();
if(rs.getString("Username").equals(username.getText()) && rs.getString("Password").equals(password.getText()))
{ System.out.println("EQUAL");
Intent loginIntent = new Intent(MainActivity.this,login.class);
startActivity(loginIntent);
}
else {
System.out.println("WRONG");
}
stmt.close();
}
catch (ClassNotFoundException | SQLException e)
{
System.out.println("In catch");
e.printStackTrace();
}
return null;
}
}
}
Errors that I am facing
E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #1
Process: com.example.login10, PID: 17730
java.lang.RuntimeException: An error occurred while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:353)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:383)
at java.util.concurrent.FutureTask.setException(FutureTask.java:252)
at java.util.concurrent.FutureTask.run(FutureTask.java:271)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636)
at java.lang.Thread.run(Thread.java:764)
Caused by: java.lang.IllegalArgumentException: URLDecoder: Illegal hex characters in escape (%) pattern : %n^
at java.net.URLDecoder.decode(URLDecoder.java:177)
at com.mysql.jdbc.NonRegisteringDriver.parseURL(NonRegisteringDriver.java:605)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:277)
at java.sql.DriverManager.getConnection(DriverManager.java:569)
at java.sql.DriverManager.getConnection(DriverManager.java:237)
at com.example.login10.MainActivity$CheckLogin.doInBackground(MainActivity.java:75)
at com.example.login10.MainActivity$CheckLogin.doInBackground(MainActivity.java:56)
at android.os.AsyncTask$2.call(AsyncTask.java:333)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245) 
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162) 
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636) 
at java.lang.Thread.run(Thread.java:764) 
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