RuntimeError而从Android的SQLite数据库retriving数据 [英] RuntimeError while retriving data from sqlite database in android
问题描述
我试图插入和使用SQLite在Eclipse中检索数据库中的数据,但它显示了一个 RuntimeError
。我创建一个具有三个编辑文本和一个按钮的布局来创建,但在创建没有简单的信息。我创建Java数据库具有以下code:
包com.example.databasetest;
进口android.content.ContentValues;
进口android.content.Context;
进口android.database.SQLException;
进口android.database.sqlite.SQLiteDatabase;
进口android.database.sqlite.SQLiteOpenHelper;
进口android.util.Log;
公共类DBHelper扩展SQLiteOpenHelper {
私有静态最终诠释DATABASE_VERSION = 1;
私有静态最后弦乐DATABASE_NAME =老师;
私有静态最后弦乐TABLE_NAME =teacher_table;
私有静态最后字符串名称=teacher_name;
私有静态最后弦乐FATHER_NAME =father_name;
私有静态最后弦乐MOTHER_NAME =mother_name;
SQLiteDatabase数据= this.getWritableDatabase();
上下文CTX;
公共DBHelper(上下文的背景下){
超(背景下,DATABASE_NAME,空,DATABASE_VERSION);
CTX =背景;
Log.d(数据库操作,数据库中创建);
}
@覆盖
公共无效的onCreate(SQLiteDatabase DB){
数据= DB;
db.execSQL(CREATE TABLE+ TABLE_NAME +(
+姓名+TEXT
+ FATHER_NAME +TEXT
+ MOTHER_NAME +INTEGER
+););
Log.d(数据库操作,表创建);
}
公共无效的open()抛出的SQLException
{
DBHelper DB1 =新DBHelper(CTX);
数据= db1.getWritableDatabase();
}
公共无效的close()
{
data.close();
}
@覆盖
公共无效onUpgrade(SQLiteDatabase分贝,INT oldVersion,诠释静态网页){
db.execSQL(DROP TABLE IF EXISTS EXCEPTION);
的onCreate(DB);
}
公共无效onInsert(DBHelper分贝,字符串名称,字符串f_name,字符串m_name)
{
SQLiteDatabase SQL = db.getWritableDatabase();
ContentValues CV =新ContentValues();
cv.put(teacher_name,名);
cv.put(father_name,f_name);
cv.put(mother_name,m_name);
sql.insert(TABLE_NAME,空,CV);
Log.d(数据库操作,一排INSERTED ......);
}
}
和java文件...
包com.example.databasetest;
进口android.app.Activity;
进口android.content.Context;
进口android.os.Bundle;
进口android.view.View;
进口android.view.View.OnClickListener;
进口android.widget.Button;
进口android.widget.EditText;
进口android.widget.Toast;
公共类MainActivity延伸活动{
EditText上的名字,父亲,母亲,身份证;
字符串名称,爸爸,妈妈,身份证;
INT I = 1;
按钮保存;
语境ctxx;
@覆盖
保护无效的onCreate(包savedInstanceState){
super.onCreate(savedInstanceState);
的setContentView(R.layout.activity_main);
NAME =(EditText上)findViewById(R.id.name);
父亲=(EditText上)findViewById(R.id.father_name);
母亲=(EditText上)findViewById(R.id.mother_name);
ID =(EditText上)findViewById(R.id.emp_id);
节省=(按钮)findViewById(R.id.submit);
save.setOnClickListener(新OnClickListener(){
@覆盖
公共无效的onClick(视图v){
。ID = ID.getText()的toString();
。NAME = NAME.getText()的toString();
父亲= FATHER.getText()的toString()。
母亲= MOTHER.getText()的toString()。
如果(id.equals(i))的
{
Toast.makeText(getBaseContext(),而不是允许插入,Toast.LENGTH_LONG).show();
}
其他
{
DBHelper DB =新DBHelper(ctxx);
DB.open();
DB.onInsert(DB,名,父,母);
Toast.makeText(getBaseContext(),插入SUCESSFUL,Toast.LENGTH_LONG).show();
完();
}
}
});
}
}
和它的显示运行时错误,当我点击按钮,在日志的猫。
2月5号至8日:54:05.932:D / AndroidRuntime(922):关闭虚拟机
2月5号至8日:54:05.999:W / dalvikvm(922):主题ID = 1:螺纹退出与未捕获的异常(组= 0x41465700)
2月5号至8日:54:06.189:E / AndroidRuntime(922):致命异常:主要
2月5号至8日:54:06.189:E / AndroidRuntime(922):显示java.lang.NullPointerException
2月5号至8日:54:06.189:E / AndroidRuntime(922):在android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:224)
2月5号至8日:54:06.189:E / AndroidRuntime(922):在android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:164)
2月5号至8日:54:06.189:E / AndroidRuntime(922):在com.example.databasetest.DBHelper< INIT>(DBHelper.java:22)
2月5号至8日:54:06.189:E / AndroidRuntime(922):在com.example.databasetest.MainActivity $ 1.onClick(MainActivity.java:49)
2月5号至8日:54:06.189:E / AndroidRuntime(922):在android.view.View.performClick(View.java:4240)
2月5号至8日:54:06.189:E / AndroidRuntime(922):在android.view.View $ PerformClick.run(View.java:17721)
2月5号至8日:54:06.189:E / AndroidRuntime(922):在android.os.Handler.handleCallback(Handler.java:730)
2月5号至8日:54:06.189:E / AndroidRuntime(922):在android.os.Handler.dispatchMessage(Handler.java:92)
2月5号至8日:54:06.189:E / AndroidRuntime(922):在android.os.Looper.loop(Looper.java:137)
2月5号至8日:54:06.189:E / AndroidRuntime(922):在android.app.ActivityThread.main(ActivityThread.java:5103)
2月5号至8日:54:06.189:E / AndroidRuntime(922):在java.lang.reflect.Method.invokeNative(本机方法)
2月5号至8日:54:06.189:E / AndroidRuntime(922):在java.lang.reflect.Method.invoke(Method.java:525)
2月5号至8日:54:06.189:E / AndroidRuntime(922):在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:737)
2月5号至8日:54:06.189:E / AndroidRuntime(922):在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
2月5号至8日:54:06.189:E / AndroidRuntime(922):在dalvik.system.NativeStart.main(本机方法)
2月5号至8日:54:09.589:I /处理(922):发送信号。 PID:922 SIG:9
ctxx
从不initialzed和崩溃的这可能是原因。一般来说,当你处理活动和片段的子类,你几乎永远需要保持一个参考语境。活动是背景下的一个子类
,通常这
就足够了。在一个片段,您可以检索活动
托管与的片段的背景下getActivity()
CHANTE
DBHelper DB =新DBHelper(ctxx);
与
DBHelper DB =新DBHelper(MainActivity.this);
由于@DerGolem指出,正在使用的类型INTEGER的列 MOTHER_NAME
。也许你想使用文本
,相反,你还需要一个主键_ ID
db.execSQL(CREATE TABLE+ TABLE_NAME +(
+ BaseColumns._ID +INTEGER PRIMARY KEY AUTOINCREMENT,
+姓名+TEXT
+ FATHER_NAME +TEXT
+ MOTHER_NAME +TEXT
+););
I'm trying to insert and retrieve data from database in eclipse using sqlite, but it shows a RuntimeError
. I create a layout with three edit texts and one button to create simple information from but nothing is created. I create java database with the following code:
package com.example.databasetest;
import android.content.ContentValues;
import android.content.Context;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class DBHelper extends SQLiteOpenHelper{
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_NAME = "teacher";
private static final String TABLE_NAME = "teacher_table";
private static final String NAME = "teacher_name";
private static final String FATHER_NAME = "father_name";
private static final String MOTHER_NAME = "mother_name";
SQLiteDatabase data=this.getWritableDatabase();
Context ctx;
public DBHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
ctx=context;
Log.d("DATABASE OPERATION", "DATABASE CREATED");
}
@Override
public void onCreate(SQLiteDatabase db) {
data=db;
db.execSQL("CREATE TABLE " + TABLE_NAME + " ("
+ NAME + " TEXT,"
+ FATHER_NAME + " TEXT,"
+ MOTHER_NAME + " INTEGER,"
+ ");");
Log.d("DATABASE OPERATION", "TABLE CREATED");
}
public void open() throws SQLException
{
DBHelper db1 = new DBHelper(ctx);
data = db1.getWritableDatabase();
}
public void close()
{
data.close();
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXCEPTION EXISTS");
onCreate(db);
}
public void onInsert(DBHelper db,String name,String f_name, String m_name)
{
SQLiteDatabase sql= db.getWritableDatabase();
ContentValues cv=new ContentValues();
cv.put("teacher_name",name);
cv.put("father_name", f_name);
cv.put("mother_name", m_name);
sql.insert(TABLE_NAME, null, cv);
Log.d("DATABASE OPERATION", "ONE ROW INSERTED.....");
}
}
AND java file as...
package com.example.databasetest;
import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class MainActivity extends Activity {
EditText NAME,FATHER,MOTHER,ID;
String name,father,mother,id;
int i=1;
Button save;
Context ctxx;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
NAME=(EditText)findViewById(R.id.name);
FATHER=(EditText)findViewById(R.id.father_name);
MOTHER=(EditText)findViewById(R.id.mother_name);
ID=(EditText)findViewById(R.id.emp_id);
save=(Button)findViewById(R.id.submit);
save.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
id=ID.getText().toString();
name=NAME.getText().toString();
father=FATHER.getText().toString();
mother=MOTHER.getText().toString();
if(id.equals(i))
{
Toast.makeText(getBaseContext(), "not allow insertion", Toast.LENGTH_LONG).show();
}
else
{
DBHelper DB=new DBHelper(ctxx);
DB.open();
DB.onInsert(DB, name, father, mother);
Toast.makeText(getBaseContext(), "insertion sucessful", Toast.LENGTH_LONG).show();
finish();
}
}
});
}
}
and its show run time error when i click on button as in log cat..
05-08 02:54:05.932: D/AndroidRuntime(922): Shutting down VM
05-08 02:54:05.999: W/dalvikvm(922): threadid=1: thread exiting with uncaught exception (group=0x41465700)
05-08 02:54:06.189: E/AndroidRuntime(922): FATAL EXCEPTION: main
05-08 02:54:06.189: E/AndroidRuntime(922): java.lang.NullPointerException
05-08 02:54:06.189: E/AndroidRuntime(922): at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:224)
05-08 02:54:06.189: E/AndroidRuntime(922): at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:164)
05-08 02:54:06.189: E/AndroidRuntime(922): at com.example.databasetest.DBHelper.<init>(DBHelper.java:22)
05-08 02:54:06.189: E/AndroidRuntime(922): at com.example.databasetest.MainActivity$1.onClick(MainActivity.java:49)
05-08 02:54:06.189: E/AndroidRuntime(922): at android.view.View.performClick(View.java:4240)
05-08 02:54:06.189: E/AndroidRuntime(922): at android.view.View$PerformClick.run(View.java:17721)
05-08 02:54:06.189: E/AndroidRuntime(922): at android.os.Handler.handleCallback(Handler.java:730)
05-08 02:54:06.189: E/AndroidRuntime(922): at android.os.Handler.dispatchMessage(Handler.java:92)
05-08 02:54:06.189: E/AndroidRuntime(922): at android.os.Looper.loop(Looper.java:137)
05-08 02:54:06.189: E/AndroidRuntime(922): at android.app.ActivityThread.main(ActivityThread.java:5103)
05-08 02:54:06.189: E/AndroidRuntime(922): at java.lang.reflect.Method.invokeNative(Native Method)
05-08 02:54:06.189: E/AndroidRuntime(922): at java.lang.reflect.Method.invoke(Method.java:525)
05-08 02:54:06.189: E/AndroidRuntime(922): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
05-08 02:54:06.189: E/AndroidRuntime(922): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
05-08 02:54:06.189: E/AndroidRuntime(922): at dalvik.system.NativeStart.main(Native Method)
05-08 02:54:09.589: I/Process(922): Sending signal. PID: 922 SIG: 9
ctxx
is never initialzed, and this probably the cause of the crash. Generally speaking, when you deal with Activity and Fragment subclass, you almost never need to keep a reference to the Context. Activity is a subclass of Context
, and usually this
is enough. In a Fragment you can retrieve the context of the Activity
hosting the Fragment with getActivity()
Chante
DBHelper DB=new DBHelper(ctxx);
with
DBHelper DB=new DBHelper(MainActivity.this);
As @DerGolem pointed out, you are using the type INTEGER for the column MOTHER_NAME
. Probably you want to use TEXT
, instead, and you will also need a the primary key "_id"
db.execSQL("CREATE TABLE " + TABLE_NAME + " ("
+ BaseColumns._ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
+ NAME + " TEXT,"
+ FATHER_NAME + " TEXT,"
+ MOTHER_NAME + " TEXT"
+ ");");
这篇关于RuntimeError而从Android的SQLite数据库retriving数据的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!