Android中的SQLite数据库连接

时间：2014-03-01 10:44:32

标签： android

我创建了一个app reg数据库连接。存储和检索data.name（应输入名字和姓氏）和电子邮件ID用于布局。三个按钮用于显示表格，创建表格并关闭布局。

但是在运行我的应用程序时，它显示“不幸的是应用程序已被停止”。我在logcat中遇到错误。

我发布了我的logcat错误和我的所有代码。我不知道在哪里存放桌子？

logcat错误

02-28 22:13:01.430: D/AndroidRuntime(785): Shutting down VM
02-28 22:13:01.430: W/dalvikvm(785): threadid=1: thread exiting with uncaught exception (group=0xb4aa8b90)
02-28 22:13:01.440: E/AndroidRuntime(785): FATAL EXCEPTION: main
02-28 22:13:01.440: E/AndroidRuntime(785): Process: com.example.studentdatabase, PID: 785
02-28 22:13:01.440: E/AndroidRuntime(785): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.studentdatabase/com.example.studentdatabase.MainActivity}: java.lang.NullPointerException
02-28 22:13:01.440: E/AndroidRuntime(785):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2176)
02-28 22:13:01.440: E/AndroidRuntime(785):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226)
02-28 22:13:01.440: E/AndroidRuntime(785):  at android.app.ActivityThread.access$700(ActivityThread.java:135)
02-28 22:13:01.440: E/AndroidRuntime(785):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1397)
02-28 22:13:01.440: E/AndroidRuntime(785):  at android.os.Handler.dispatchMessage(Handler.java:102)
02-28 22:13:01.440: E/AndroidRuntime(785):  at android.os.Looper.loop(Looper.java:137)
02-28 22:13:01.440: E/AndroidRuntime(785):  at android.app.ActivityThread.main(ActivityThread.java:4998)
02-28 22:13:01.440: E/AndroidRuntime(785):  at java.lang.reflect.Method.invokeNative(Native Method)
02-28 22:13:01.440: E/AndroidRuntime(785):  at java.lang.reflect.Method.invoke(Method.java:515)
02-28 22:13:01.440: E/AndroidRuntime(785):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
02-28 22:13:01.440: E/AndroidRuntime(785):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
02-28 22:13:01.440: E/AndroidRuntime(785):  at dalvik.system.NativeStart.main(Native Method)
02-28 22:13:01.440: E/AndroidRuntime(785): Caused by: java.lang.NullPointerException
02-28 22:13:01.440: E/AndroidRuntime(785):  at com.example.studentdatabase.MainActivity.onCreate(MainActivity.java:27)
02-28 22:13:01.440: E/AndroidRuntime(785):  at android.app.Activity.performCreate(Activity.java:5243)
02-28 22:13:01.440: E/AndroidRuntime(785):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
02-28 22:13:01.440: E/AndroidRuntime(785):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2140)
02-28 22:13:01.440: E/AndroidRuntime(785):  ... 11 more

activity_main.xml中

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="22dp"
        android:layout_marginTop="54dp"
        android:text="FirstName" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignRight="@+id/textView1"
        android:layout_below="@+id/textView1"
        android:layout_marginTop="48dp"
        android:text="LastName" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignRight="@+id/textView2"
        android:layout_below="@+id/textView2"
        android:layout_marginTop="55dp"
        android:text="Email" />

    <EditText
        android:id="@+id/firstname"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/textView2"
        android:layout_alignParentRight="true"
        android:ems="10" />

    <EditText
        android:id="@+id/lastname"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/textView3"
        android:layout_alignParentRight="true"
        android:ems="10" />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignRight="@+id/textView3"
        android:layout_below="@+id/textView3"
        android:layout_marginTop="69dp"
        android:onClick = "Adddata"
        android:text="Create" />

    <Button
        android:id="@+id/button3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_marginBottom="31dp"
        android:layout_toLeftOf="@+id/button2"
        android:onClick="Showdata"
        android:text="Show" />

    <EditText
        android:id="@+id/email"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/textView3"
        android:layout_alignParentRight="true"
        android:ems="10" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/button1"
        android:layout_alignBottom="@+id/button1"
        android:layout_alignRight="@+id/email"
        android:layout_marginRight="24dp"
        android:onClick="close"
        android:text="Close" />

</RelativeLayout>

MainActivity.java 

package com.example.studentdatabase;

import android.R.color;
import android.R.integer;
import android.os.Bundle;
import android.provider.Settings.System;
import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.graphics.Typeface;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
import android.widget.TableLayout;
import android.widget.TableRow;
import android.widget.TextView;

public class MainActivity extends Activity {
    private static final String[] Student = null;
    String fname,lname,email;
    SQLiteDatabase db;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        db= openOnCreateDatabase("MYDB1 MODE_PRIVATE",null);
        db.execSQL("CREATE TABLE IF NOT EXITS student(fname  VARCHAR,lname VARCHAR,email VARCHAR);");
    }
    private SQLiteDatabase openOnCreateDatabase(String string, Object object) {
        // TODO Auto-generated method stub
        return null;
    }
    private void Adddata(View view)
    {
    EditText editText1 = (EditText)findViewById(R.id.firstname);
    EditText editText2 = (EditText)findViewById(R.id.lastname);
    EditText editText3 = (EditText)findViewById(R.id.email);
    fname = editText1.getText().toString();
    lname = editText2.getText().toString();
    email = editText3.getText().toString();
    db.execSQL("INSERT INTO Student VALUES('"+fname+"','"+lname+"','"+email+"');");
    }

    private void Showdata(View view)
    {
Cursor c = db.rawQuery("SELECT from Student",null);
int count = c.getCount();
c.moveToFirst();
TableLayout tableLayout = new TableLayout(getApplicationContext());
tableLayout.setVerticalScrollBarEnabled(true);
TableRow tableRow;
TextView textview,textview1,textview2,textview3,textview4,textview5;
tableRow = new TableRow(getApplicationContext());
textview = new TextView(getApplicationContext());
textview.setText("firstname");
textview.setTypeface(null,Typeface.BOLD);
textview.setPadding(20,20,20,20);
tableRow.addView(textview);

textview4 = new TextView(getApplicationContext());
textview4.setText("lastname");
textview4.setTypeface(null,Typeface.BOLD);
textview4.setPadding(20,20,20,20);
tableRow.addView(textview4);

textview5 = new TextView(getApplicationContext());
textview5.setText("email");
textview5.setTypeface(null,Typeface.BOLD);
textview5.setPadding(20,20,20,20);
tableRow.addView(textview5);

tableLayout.addView(tableRow);
for(int j=0;j<count;j++)
{
    tableRow = new TableRow(getApplicationContext());
    textview1 = new TextView(getApplicationContext());
    textview1.setText(c.getString(c.getColumnIndex("fname")));
    textview2 = new TextView(getApplicationContext());
    textview2.setText(c.getString(c.getColumnIndex("lname")));
    textview3 = new TextView(getApplicationContext());
    textview3.setText(c.getString(c.getColumnIndex("email")));

    textview1.setPadding(20, 20, 20, 20);
    textview2.setPadding(20, 20, 20, 20);
    textview3.setPadding(20, 20, 20, 20);

    tableRow.addView(textview1);
    tableRow.addView(textview2);
    tableRow.addView(textview3);
    tableLayout.addView(tableRow);
    c.moveToNext();

}
setContentView(tableLayout);
db.close();
    }
public void close(View view)
{
    java.lang.System.exit(0);
}

1 个答案:

答案 0 :(得分：0)

尝试使用

db= openOnCreateDatabase("MYDB1 MODE_PRIVATE",Context.MODE_PRIVATE,null);
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