Question

我遇到了以下问题，我的程序告诉我有一个NullPointerException，即使我想将内容插入我的数据库，我的变量也会填充内容。如果你们能帮助我，我将感激不尽。我知道我的编程风格有点脏，因为我在编程方面有点新鲜。

我的数据库插入功能：

 public void insertCar(String hersteller, String name, String farbe, String sonderausstattung, int abteilungID, String ausgeliefert, String barcode, int programmID) {
        ContentValues values = new ContentValues();

        values.put(Databasehandler.CAR_COLUMN_Hersteller, hersteller);
        values.put(Databasehandler.CAR_COLUMN_KFZTyp, name);
        values.put(Databasehandler.CAR_COLUMN_Farbe, farbe);
        values.put(Databasehandler.CAR_COLUMN_SONDERAUSSTATTUNG, sonderausstattung);
        values.put(Databasehandler.CAR_COLUMN_Ausgeliefert, ausgeliefert);
        values.put(Databasehandler.CAR_COLUMN_AbteilungID, abteilungID);
        values.put(Databasehandler.CAR_COLUMN_ID_BARCODE, barcode);
        values.put(Databasehandler.CAR_COLUMN_ProgrammID, programmID);

        try {
            openDatabase();
            database.insert(this.TABLE_CARS, null, values);
            closeDatabase();
        } catch (Exception ex) {
            System.out.println("Error  inserting entry!" + ex.toString());

        }
}

我的OpenDatabase：

/**
 * Opens the database
 * @return
 */
private Databasehandler openDatabase() {
    database = this.getWritableDatabase();
    return this;
}

我的Create_Table：

        String CREATE_CAR_TABLE = "CREATE TABLE " + TABLE_CARS + "(" +
            CAR_COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
            CAR_COLUMN_ID_BARCODE + " TEXT, " +
            CAR_COLUMN_Hersteller + " TEXT, " +
            CAR_COLUMN_KFZTyp + " TEXT, " +
            CAR_COLUMN_Farbe + " TEXT, " +
            CAR_COLUMN_AbteilungID + " INTEGER, " +
            CAR_COLUMN_Ausgeliefert + " TEXT, " +
            CAR_COLUMN_SONDERAUSSTATTUNG + " TEXT, " +
            CAR_COLUMN_ProgrammID + " INTEGER" +
            ")";

我的班级，我称之为：

package com.example.prog3;

import com.example.prog3.R.drawable;

import Database.Databasehandler;
import android.support.v7.app.ActionBarActivity;
import android.app.ActionBar.LayoutParams;
import android.content.Intent;
import android.graphics.Color;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.print.PrintAttributes.Margins;
import android.view.Gravity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup.MarginLayoutParams;
import android.widget.Button;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.RelativeLayout;
import android.widget.Toast;

public class AdminCar extends ActionBarActivity {

Databasehandler dbhandler = new Databasehandler(null);

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

        Button create = (Button) findViewById(R.id.admincreatecar);
        create.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {

                EditText herstelleredit = (EditText) findViewById(R.id.Herstelleredit);
                EditText modelledit = (EditText) findViewById(R.id.Modelledit);
                EditText farbeedit = (EditText) findViewById(R.id.Farbeedit);
                EditText sonderedit = (EditText) findViewById(R.id.Sonderedittext);
                EditText abteilungedit = (EditText) findViewById(R.id.Abteilungedittext);
                EditText Barcodeedit = (EditText) findViewById(R.id.Barcodeedittext);
                EditText programmedit = (EditText) findViewById(R.id.programmEdit);
                if(herstelleredit.getText().toString() == " " || modelledit.getText().toString() == " " || farbeedit.getText().toString() == "" || sonderedit.getText().toString() == "" || abteilungedit.getText().toString() == "" || Barcodeedit.getText().toString() == "" || programmedit.getText().toString() == ""){
                    Toast.makeText(getApplicationContext(), "Bitte alle Felder ausfüllen", Toast.LENGTH_LONG).show();
                }else{
                    createentry();
                    Intent Mainpage = new Intent(getApplicationContext(), LoginActivity.class);
                    startActivityForResult(Mainpage, 0);
                }


            }
        });



    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        switch(item.getItemId()){
        case R.id.close:
            System.exit(0);
        }
        return super.onOptionsItemSelected(item);
    }
    public void createentry(){

        EditText herstelleredit = (EditText) findViewById(R.id.Herstelleredit);
        EditText modelledit = (EditText) findViewById(R.id.Modelledit);
        EditText farbeedit = (EditText) findViewById(R.id.Farbeedit);
        EditText sonderedit = (EditText) findViewById(R.id.Sonderedittext);
        EditText abteilungedit = (EditText) findViewById(R.id.Abteilungedittext);
        EditText Barcodeedit = (EditText) findViewById(R.id.Barcodeedittext);
        EditText programmedit = (EditText) findViewById(R.id.programmEdit);
        System.out.println(herstelleredit.getText().toString() + modelledit.getText().toString() + farbeedit.getText().toString() + sonderedit.getText().toString() + Integer.parseInt(abteilungedit.getText().toString()) + "Nein" + Barcodeedit.getText().toString() +  Integer.parseInt(programmedit.getText().toString()));
        dbhandler.insertCar(herstelleredit.getText().toString(), modelledit.getText().toString(), farbeedit.getText().toString(), sonderedit.getText().toString(), Integer.parseInt(abteilungedit.getText().toString()), "Nein", Barcodeedit.getText().toString(), Integer.parseInt(programmedit.getText().toString()));

    }
}

这是我的错误日志文件：

02-23 13:33:52.400: I/System.out(4611): adgsfhnsdghwdgv2Neinwrzh2
02-23 13:33:52.400: I/System.out(4611): Error  inserting entry!java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.sqlite.SQLiteDatabase android.content.Context.openOrCreateDatabase(java.lang.String, int, android.database.sqlite.SQLiteDatabase$CursorFactory, android.database.DatabaseErrorHandler)' on a null object reference
02-23 13:33:52.400: I/Timeline(4611): Timeline: Activity_launch_request id:com.example.prog3 time:66776262
02-23 13:33:52.550: I/Timeline(4611): Timeline: Activity_idle id: android.os.BinderProxy@d159069 time:66776417

Answer 1

您传递给数据库处理程序构造函数的Context在此处为null：

Databasehandler dbhandler = new Databasehandler(null);

通常您需要将初始化推迟到onCreate()以使用Activity作为Context，但在这种情况下它可以，因为Context实际上不是在您调用getWritableDatabase()之前使用。

因此，请在此处将null替换为this。

使用sqlite数据库的Java.lang.nullpointerexception

1 个答案: