Question

我创建了一个简单的应用程序，用于存储人员的紧急联系方式，如姓名，血型，联系电话号码，并在文本视图中显示。所有这一切都应该发生在我点击调用saveMe（）方法的保存按钮时，但当我这样做时，应用程序只是崩溃，请帮助代码并记录下面发布的猫

数据库代码

package com.example.androidsimpledbapp1;

import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.Cursor;
import android.content.Context;
import android.content.ContentValues;


public class MyDBHandler extends SQLiteOpenHelper {

/*
 * Class for Working with DB 
 */

//Update each time DB structure changes e.g. adding new property
private static final int DATABASE_VERSION =1;
//DB Name
private static final String DATABASE_NAME = "deets.db";
//Table name
public static final String  TABLE_PRODUCTS = "products";
//DB Columns 
public static final String  COLUMN_ID = "_Id";
public static final String  COLUMN_PERSONNAME  = "firstName";
public static final String  COLUMN_PERSONBLOOD  = "bloodType";
public static final String  COLUMN_PERSONCONTACT  = "contactName";
public static final String  COLUMN_PERSONNUMBER  = "phoneNumber";
public static final String  COLUMN_PERSONRELATION = "relationship";

//Constructor
/*
 * Passing information to super class in SQL
 * Context is background information 
 * name of db 
 * Database version
 */
public MyDBHandler(Context context, String name, SQLiteDatabase.CursorFactory factory, int version){
    super(context, DATABASE_NAME, factory, DATABASE_VERSION);
}


/*
 * What to do first time when you create DB
 * Creates the table the very first time
 * (non-Javadoc)
 * @see android.database.sqlite.SQLiteOpenHelper#onCreate(android.database.sqlite.SQLiteDatabase)
 */
@Override
public void onCreate(SQLiteDatabase db){
    String query = "CREATE TABLE "+ TABLE_PRODUCTS + "(" +
            COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT "+
            COLUMN_PERSONNAME + " TEXT "+
            COLUMN_PERSONBLOOD + " TEXT "+
            COLUMN_PERSONCONTACT + " TEXT "+
            COLUMN_PERSONNUMBER + " TEXT " +
            COLUMN_PERSONRELATION + " TEXT " +
            ");";
    //Execute the query
    db.execSQL(query);
}

/*
 * If ever upgrading DB call this method
 * (non-Javadoc)
 * @see android.database.sqlite.SQLiteOpenHelper#onUpgrade(android.database.sqlite.SQLiteDatabase, int, int)
 */
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){
    //Delete the current table
    db.execSQL("DROP TABLE IF EXISTS" + TABLE_PRODUCTS);
    //create new table 
    onCreate(db);
}


//Add new row to the database
public void addProduct(Details details){
    //Built in class - set values for different columns 
    //Makes inserting rows quick and easy
    ContentValues values = new ContentValues();
    values.put(COLUMN_PERSONNAME, details.get_firstName());
    values.put(COLUMN_PERSONBLOOD, details.get_bloodType());
    values.put(COLUMN_PERSONCONTACT, details.get_contactName());
    values.put(COLUMN_PERSONNUMBER, details.get_phoneNumber());
    values.put(COLUMN_PERSONRELATION, details.get_relationship());
    SQLiteDatabase db = getWritableDatabase();
    db.insert(TABLE_PRODUCTS, null, values);
    db.close();
}

/*
public void deleteProducts(){
    SQLiteDatabase = getWritableDatabase();
    db.execSQL("DROP TABLE");

    How to delete the database...
}
*/


//Take DB and Convert to String 
public String databaseToString(){
    String dbString = "";
    SQLiteDatabase db = getWritableDatabase();
    //Every Column and row
    String query = "SELECT * FROM " + TABLE_PRODUCTS + " WHERE 1";

    //Cursor points to a location in your results
    //First row point here, second row point here

    Cursor c = db.rawQuery(query, null);
    c.moveToFirst();

    while(!c.isAfterLast()){
        //Extracts first name and adds to string
        if(c.getString(c.getColumnIndex("firstName"))!=null){
            dbString += c.getString(c.getColumnIndex("firstName"));
            /*
             * Displaying all other columns 
             */
        }
    }
    db.close();
    return dbString;
}
 }

详细信息类

package com.example.androidsimpledbapp1;

public class Details {

//primary key
private int _id;
//Properties 
private String _firstName;
private String _bloodType;
private String _contactName;
private String _phoneNumber;
private String _relationship;

//Dont Have to Enter Everything each time
public Details(){

}

public Details(String firstName){
    this.set_firstName(firstName);
}

//Passing in details 
//Setting values from the user 
public Details(String firstName, String bloodType,
        String contactName, String phoneNumber,
        String relationship){
    this.set_firstName(firstName);
    this.set_bloodType(bloodType);
    this.set_contactName(contactName);
    this.set_phoneNumber(phoneNumber);
    this.set_relationship(relationship);

}

//Retrieve the data 
public int get_id() {
    return _id;
}

//Setter allows to give property
public void set_id(int _id) {
    this._id = _id;
}

public String get_firstName() {
    return _firstName;
}

public void set_firstName(String _firstName) {
    this._firstName = _firstName;
}

public String get_bloodType() {
    return _bloodType;
}

public void set_bloodType(String _bloodType) {
    this._bloodType = _bloodType;
}

public String get_contactName() {
    return _contactName;
}

public void set_contactName(String _contactName) {
    this._contactName = _contactName;
}

public String get_phoneNumber() {
    return _phoneNumber;
}

public void set_phoneNumber(String _phoneNumber) {
    this._phoneNumber = _phoneNumber;
}

public String get_relationship() {
    return _relationship;
}

public void set_relationship(String _relationship) {
    this._relationship = _relationship;
}

}

主要活动（此处将显示所有数据）

package com.example.androidsimpledbapp1;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

}

//Changing Activity
public void editBtnPressed(View v){
    Intent intent = new Intent(MainActivity.this, EditScreen.class);
    startActivity(intent);
}
}

编辑屏幕 - 所有编辑文本的屏幕，带有保存按钮的屏幕

package com.example.androidsimpledbapp1;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class EditScreen extends Activity {

EditText firstNameInput;
EditText bloodTypeInput;
EditText contacNameInput;
EditText phoneNumberInput;
EditText relationshipInput;

TextView displayName;
MyDBHandler dbHandler;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_edit_screen);
    firstNameInput = (EditText) findViewById(R.id.inputname);
    displayName = (TextView) findViewById(R.id.dbname);
    dbHandler = new MyDBHandler(this, null, null, 1);

}

/*
 * Causing error fix the error
 */
public void saveMe(View v){
    Details detail = new Details(firstNameInput.getText().toString(),
            bloodTypeInput.getText().toString(),
            contacNameInput.getText().toString(),
            phoneNumberInput.getText().toString(),
            relationshipInput.getText().toString()

            );
    dbHandler.addProduct(detail);
    printDatabase();
}

private void printDatabase() {
    //Taking the string
    String dbString = dbHandler.databaseToString();
    //Display in the textview
    displayName.setText(dbString);
}

 }

Log Cat - 错误

08-08 21：58：33.896：E / AndroidRuntime（368）：致命异乎寻常：主要 08-08 21：58：33.896：E / AndroidRuntime（368）：java.lang.IllegalStateException：无法执行活动的方法 08-08 21：58：33.896：E / AndroidRuntime（368）：在android.view.View $ 1.onClick（View.java:2144） 08-08 21：58：33.896：E / AndroidRuntime（368）：在android.view.View.performClick（View.java:2485） 08-08 21：58：33.896：E / AndroidRuntime（368）：在android.view.View $ PerformClick.run（View.java:9080） 08-08 21：58：33.896：E / AndroidRuntime（368）：在android.os.Handler.handleCallback（Handler.java:587） 08-08 21：58：33.896：E / AndroidRuntime（368）：在android.os.Handler.dispatchMessage（Handler.java:92） 08-08 21：58：33.896：E / AndroidRuntime（368）：在android.os.Looper.loop（Looper.java:130） 08-08 21：58：33.896：E / AndroidRuntime（368）：在android.app.ActivityThread.main（ActivityThread.java:3683） 08-08 21：58：33.896：E / AndroidRuntime（368）：at java.lang.reflect.Method.invokeNative（Native Method） 08-08 21：58：33.896：E / AndroidRuntime（368）：at java.lang.reflect.Method.invoke（Method.java:507） 08-08 21：58：33.896：E / AndroidRuntime（368）：at com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:839） 08-08 21：58：33.896：E / AndroidRuntime（368）：at com.android.internal.os.ZygoteInit.main（ZygoteInit.java:597） 08-08 21：58：33.896：E / AndroidRuntime（368）：at dalvik.system.NativeStart.main（Native Method） 08-08 21：58：33.896：E / AndroidRuntime（368）：引起：java.lang.reflect.InvocationTargetException 08-08 21：58：33.896：E / AndroidRuntime（368）：at java.lang.reflect.Method.invokeNative（Native Method） 08-08 21：58：33.896：E / AndroidRuntime（368）：at java.lang.reflect.Method.invoke（Method.java:507） 08-08 21：58：33.896：E / AndroidRuntime（368）：在android.view.View $ 1.onClick（View.java:2139） 08-08 21：58：33.896：E / AndroidRuntime（368）：... 11更多 08-08 21：58：33.896：E / AndroidRuntime（368）：引起：java.lang.NullPointerException 08-08 21：58：33.896：E / AndroidRuntime（368）：at com.example.androidsimpledbapp1.EditScreen.saveMe（EditScreen.java:38） 08-08 21：58：33.896：E / AndroidRuntime（368）：... 14更多

Answer 1

字符串查询的语法缺少逗号。它应该是

@Override
public void onCreate(SQLiteDatabase db){
    String query = "CREATE TABLE "+ TABLE_PRODUCTS + "(" +
            COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "+
            COLUMN_PERSONNAME + " TEXT, "+
            COLUMN_PERSONBLOOD + " TEXT, "+
            COLUMN_PERSONCONTACT + " TEXT, "+
            COLUMN_PERSONNUMBER + " TEXT, " +
            COLUMN_PERSONRELATION + " TEXT " +
            ");";
    //Execute the query
    db.execSQL(query);
}

Android Simple Database App收到错误

1 个答案: