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我在Android编程中是begginer，我试图使登录功能。这个系统将被两个用户admin和用户访问。管理员只需输入用户名和密码的“admin”即可访问系统。但是，用户在登录系统之前需要注册他们的账户。尝试登录系统时无法检索数据（Android Studio）
我试图找到错误但仍然不知道错误发生。请帮我解决错误。谢谢。
DatabaseOperations.java
public Cursor getInformation(DatabaseOperations dob)
{
SQLiteDatabase database=dob.getReadableDatabase();
String[] columns={TableInfo.USERNAME,TableInfo.USERPASS};
Cursor cr=database.query(TableInfo.TABLE_NAME,columns,null,null,null,null,null);
return cr;
}
MainActivity.java
public void onClick(View view)
Toast.makeText(getBaseContext(), "Please wait....", Toast.LENGTH_LONG).show();
txtusername = Username.getText().toString();
txtpassword = Password.getText().toString();
DatabaseOperations dop = new DatabaseOperations(this, null, null, 1);
Cursor CR = dop.getInformation(dop);
CR.moveToFirst();
boolean login_status = false;
String NAME = "";
if (txtusername.equals("Admin") && (txtpassword).equals("Admin")) {
Intent in = new Intent(MainActivity.this, AdminMenu.class);
startActivity(in);
} else {
do {
if (txtusername.equals(CR.getString(0)) && (txtpassword.equals(CR.getString(1)))) {
login_status = true;
NAME = CR.getString(0);
}
} while (CR.moveToNext());
if (login_status) {
Toast.makeText(getBaseContext(), "Login Success....\n Welcome " + NAME, Toast.LENGTH_LONG).show();
Intent i=new Intent(MainActivity.this,UserMenu.class);
Bundle bundle=new Bundle();
bundle.putString("username",NAME);
i.putExtras(bundle);
startActivity(i);
finish();
} else {
Toast.makeText(getBaseContext(), "Login Failed...", Toast.LENGTH_LONG).show();
Intent i = new Intent();
Bundle bundle=new Bundle();
bundle.putString("username",NAME);
i.putExtras(bundle);
startActivity(i);
finish();
}
}
}
这是错误...
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.google.mobile_flexi_parking, PID: 6777
java.lang.IllegalStateException: Could not execute method for android:onClick
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
at android.view.View.performClick(View.java:5198)
at android.view.View$PerformClick.run(View.java:21147)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
at android.view.View.performClick(View.java:5198)
at android.view.View$PerformClick.run(View.java:21147)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: android.content.ActivityNotFoundException: No Activity found to handle Intent { (has extras) }
at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:1798)
at android.app.Instrumentation.execStartActivity(Instrumentation.java:1512)
at android.app.Activity.startActivityForResult(Activity.java:3917)
at android.app.Activity.startActivityForResult(Activity.java:3877)
at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:842)
at android.app.Activity.startActivity(Activity.java:4200)
at android.app.Activity.startActivity(Activity.java:4168)
at com.google.mobile_flexi_parking.MainActivity.onclickLogin(MainActivity.java:67)
at java.lang.reflect.Method.invoke(Native Method)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
at android.view.View.performClick(View.java:5198)
at android.view.View$PerformClick.run(View.java:21147)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
检查您在menifest文件中的所有活动....... – sushildlh
'原因：android.content.ActivityNotFoundException：未找到处理Intent的活动。检查您的所有活动是否在Manifest中声明。 – Vikrant
'引起：android.content.ActivityNotFoundException：找不到处理意图的活动。在你登录失败的时候，你并没有定义要跳转到的类。 in Intent i = new Intent（）;'。它应该像'Intent i = new Intent（MainActivity.this，YOURCLASS.class）'; –