我正在制作一个应用程序以扩展我的知识，我遇到了这个问题，当我点击login按钮登录应用程序时，我有一个用户名登录，它给出了错误。我尝试了几件事但到目前为止都没有。这是错误代码我相信数据库查询或onclick方法有问题，任何帮助将不胜感激，谢谢。
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.bulkbuys.bulkbuysapp, PID: 23940
android.content.ActivityNotFoundException: No Activity found to handle Intent { act=com.bulkbuys.bulkbuysapp.Menu launchParam=MultiScreenLaunchParams { mDisplayId=0 mBaseDisplayId=0 mFlags=0 } }
at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:1844)
at android.app.Instrumentation.execStartActivity(Instrumentation.java:1531)
at android.app.Activity.startActivityForResult(Activity.java:4403)
at android.support.v4.app.BaseFragmentActivityApi16.startActivityForResult(BaseFragmentActivityApi16.java:54)
at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:67)
at android.app.Activity.startActivityForResult(Activity.java:4362)
at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:720)
at android.app.Activity.startActivity(Activity.java:4686)
at android.app.Activity.startActivity(Activity.java:4654)
at com.bulkbuys.bulkbuysapp.MainActivity$1.onClick(MainActivity.java:52)
at android.view.View.performClick(View.java:6261)
at android.widget.TextView.performClick(TextView.java:11180)
at android.view.View$PerformClick.run(View.java:23748)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6776)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1520)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1410)
MainActivity.java
package com.bulkbuys.bulkbuysapp;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
EditText editTextUsername;
Button buttonLogin;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
editTextUsername = (EditText) findViewById(R.id.editText_Username);
buttonLogin = (Button) findViewById(R.id.Button_Login);
//create preferences - used to store currently logged in user
}
public void login(View view) {
String username = editTextUsername.getText().toString(); //get Username from editText box
DBHandler dbHandler = new DBHandler(this, null, null, 7);
Admin a = dbHandler.findAdmin(username);
Log.i("Login: ","Trying to login with " + username);
if (username.equals("rick"))
{
Intent intent = new Intent(this, Menu.class);
startActivity(intent);
}
else
{
if (a == null) //if T is null no match came back, therefore incorrect username or password.
{
Toast.makeText(this, "Login failed - Username Wrong", Toast.LENGTH_SHORT).show();
}
else
{
Toast.makeText(this, "Login Successful", Toast.LENGTH_SHORT).show();
}
}
}
public void clear(View view) {
editTextUsername.setText("");
}
}
activity_main.xml文件
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
tools:context=".MainActivity"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="828dp"
android:layout_height="match_parent"
android:weightSum="1"
android:orientation="vertical"
android:baselineAligned="false"
android:divider="#262626">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:layout_marginBottom="0dp"
android:layout_marginLeft="0dp"
android:layout_marginRight="200dp"
android:layout_marginTop="250dp"
android:orientation="vertical">
<EditText
android:id="@+id/editText_Username"
android:layout_width="300dp"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:layout_marginLeft="0dp"
android:hint="Username" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginRight="400dp"
android:layout_weight="0.01"
android:orientation="vertical">
<Button
android:id="@+id/Button_Login"
android:layout_width="250dp"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:layout_marginBottom="5dp"
android:layout_marginLeft="20dp"
android:layout_marginRight="20dp"
android:layout_marginTop="20dp"
android:background="@drawable/roundbutton"
android:onClick="login"
android:text="Login"
android:textColor="#ffffff"
android:textSize="20sp"
android:textStyle="normal|bold" />
<Button
android:id="@+id/button2"
android:layout_width="250dp"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:layout_marginLeft="20dp"
android:layout_marginRight="20dp"
android:layout_marginTop="5dp"
android:background="@drawable/roundbutton"
android:onClick="clear"
android:text="clear"
android:textColor="#ffffff"
android:textSize="20sp"
android:textStyle="bold" />
</LinearLayout>
</LinearLayout>
</android.support.constraint.ConstraintLayout>
DBHandler
package com.bulkbuys.bulkbuysapp;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.provider.BaseColumns;
import java.util.ArrayList;
public class DBHandler extends SQLiteOpenHelper implements BaseColumns {
private static final int DATABASE_VERSION = 19;
private static final String DATABASE_NAME = "GradeDB.db";
//Declare Tables in Database
private static final String TABLE_CUSTOMERS = "customers";
private static final String Admin = "admin";
public static final String COLUMN_ID = "ID";
public static final String COLUMN_COMPANYNAME = "Company Name";
public static final String COLUMN_ADRESS = "Adress";
public static final String COLUMN_EMAIL = "Email";
public static final String COLUMN_ABN = "Abn";
public static final String COLUMN_MOBILENO = "Mobile Number";
public static final String COLUMN_COMPANYNO = "Company Number";
public static final String COLUMN_USERNAME = "User Name";
public DBHandler(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
String CREATE_ADMIN_TABLE = "CREATE TABLE " + Admin + "(" +
COLUMN_USERNAME + " TEXT) ";
db.execSQL(CREATE_ADMIN_TABLE);
String CREATE_CUSTOMERS_TABLE = "CREATE TABLE " + TABLE_CUSTOMERS + "(" +
COLUMN_ID + " INTEGER PRIMARY KEY, " +
COLUMN_COMPANYNAME + " TEXT, " +
COLUMN_ADRESS + " TEXT, " +
COLUMN_EMAIL + " TEXT, " +
COLUMN_ABN + " TEXT. " +
COLUMN_MOBILENO + " TEXT, " +
COLUMN_COMPANYNO + " TEXT) ";
db.execSQL(CREATE_CUSTOMERS_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + DBHandler.Admin);
db.execSQL("DROP TABLE IF EXISTS " + DBHandler.TABLE_CUSTOMERS);
onCreate(db);
}
//search for product
public Admin findAdmin(String username) {
String query = "SELECT * FROM " + Admin + " WHERE username = '" +
username + "'";
SQLiteDatabase db = this.getWritableDatabase();
//run query with cursor
Cursor cursor = db.rawQuery(query, null);
Admin a = new Admin();
//move to first existing object
if (cursor.moveToFirst()) {
do { //****** This IF loop may be pointless need to mess with...
if (username.equals(cursor.getString(3))) { //If a username matches one in the DB add info into Teacher object
a.setUsername(cursor.getString(0));
}
} while (cursor.moveToNext());
cursor.close();
}
else //no match found return a null object
{
a = null;
db.close();
}
return a;
}
public void addCustomers(Customers customers) {
ContentValues values = new ContentValues(); // simpler way of inserting into DB
//ID isn't added as the ID will automatically be assigned
values.put(COLUMN_ID, customers.getId());
values.put(COLUMN_COMPANYNAME, customers.getCompanyname());
values.put(COLUMN_ADRESS, customers.getAdress());
values.put(COLUMN_EMAIL, customers.getEmail());
values.put(COLUMN_ABN, customers.getAbn());
values.put(COLUMN_MOBILENO, customers.getMobileno());
values.put(COLUMN_COMPANYNO, customers.getCompanyno());
SQLiteDatabase db = this.getWritableDatabase();
db.insert(TABLE_CUSTOMERS, null, values);
db.close();
}
public ArrayList<Customers> listCustomers() {
String query = "SELECT * FROM " + TABLE_CUSTOMERS + " ORDER BY " + COLUMN_ID;
SQLiteDatabase db = this.getWritableDatabase();
ArrayList<Customers> list = new ArrayList<>(); //Array to store customer
Cursor cursor = db.rawQuery(query, null);
if (cursor.moveToFirst()) {
do { //run loop through all results and store each customer into arraylist
Customers p = new Customers();
p.setId(Integer.parseInt(cursor.getString(0)));
p.setCompanyname(cursor.getString(1));
p.setAdress(cursor.getString(2));
p.setEmail(cursor.getString(3));
p.setAbn(cursor.getString(4));
p.setMobileno(cursor.getString(5));
p.setCompanyno(cursor.getString(6));
list.add(p);
} while (cursor.moveToNext());
}
cursor.close();
db.close();
return list;
}
public boolean deleteCustomert(int id) {
boolean success = false;
//create query
String query = "SELECT * FROM " + TABLE_CUSTOMERS + " WHERE " + COLUMN_ID + " = '" + id + "'";
SQLiteDatabase db = this.getWritableDatabase();
//run query
Cursor cursor = db.rawQuery(query, null);
Customers Customers = new Customers(); //temp
//move to first object
if (cursor.moveToFirst()) //if exists delete object
{
cursor.moveToFirst();
Customers.setId(Integer.parseInt(cursor.getString(0)));
db.delete(TABLE_CUSTOMERS, COLUMN_ID + " = ?", new String[]{String.valueOf(Customers.getId())});
success = true;
cursor.close();
}
db.close();
return success;
}
public Customers findCustomers(String id) {
String query = "SELECT * FROM " + TABLE_CUSTOMERS + " WHERE " + COLUMN_ID + " = '" +
id + "'";
SQLiteDatabase db = this.getWritableDatabase();
//run query with cursor
Cursor cursor = db.rawQuery(query, null);
Customers p = new Customers();
return p;
}
}
Android清单
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.bulkbuys.bulkbuysapp">
<supports-screens
android:largeScreens="true"
android:normalScreens="true"
android:smallScreens="true"
android:xlargeScreens="true" />
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".CustomerListPage"></activity>
<activity android:name=".Menu"></activity>
</application>
</manifest>
我有这个额外的课程，我已经尝试了一些但它没有工作
package com.bulkbuys.bulkbuysapp;
import java.io.Serializable;
public class Admin implements Serializable {
private String username;
public Admin() {
}
public Admin(String username) {
this.username = username;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
@Override
public String toString() {
return " / Username: " + username;
}
}
Menu.class
package com.bulkbuys.bulkbuysapp;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
public class Menu extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main_menu);
Button buttonclick = (Button)findViewById(R.id.button_customer);
buttonclick.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// use Intent
Intent intent1= new Intent(Menu.this,CustomerListPage.class);
startActivity(intent1);
}
});
}
}
答案 0 :(得分：0)
调用startActivity（Intent）或者一个时抛出此异常 其变体失败，因为无法找到Activity执行 给定的意图。
<强> FYI
Intent intent = new Intent(this, Menu.class);
startActivity(intent);
确保菜单 Activity存在与否。
整改声明。使用 , 代替 .
<强>唐＆＃39;吨
String CREATE_CUSTOMERS_TABLE = "CREATE TABLE " + TABLE_CUSTOMERS + "(" +
COLUMN_ID + " INTEGER PRIMARY KEY, " +
COLUMN_COMPANYNAME + " TEXT , " +
COLUMN_ADRESS + " TEXT , " +
COLUMN_EMAIL + " TEXT , " +
COLUMN_ABN + " TEXT. " +
COLUMN_MOBILENO + " TEXT, " +
COLUMN_COMPANYNO + " TEXT) ";
<强>不要
String CREATE_CUSTOMERS_TABLE = "CREATE TABLE " + TABLE_CUSTOMERS + "(" +
COLUMN_ID + " INTEGER PRIMARY KEY , " +
COLUMN_COMPANYNAME + " TEXT , " +
COLUMN_ADRESS + " TEXT , " +
COLUMN_EMAIL + " TEXT , " +
COLUMN_ABN + " TEXT , " +
COLUMN_MOBILENO + " TEXT , " +
COLUMN_COMPANYNO + " TEXT) ";
修改
MainActivity $ 1.onClick（MainActivity.java:52）
public void clear(View view) {
// editTextUsername.setText(""); comment setText method
}