尝试从sqLite检索数据并在Alert Dialog Builder中显示它。 但根本没有显示数据。当我点击View Button时没有任何反应。
MainActivity.java
package com.example.database;
import android.support.v7.app.ActionBarActivity;
import android.text.Editable;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.AlertDialog.Builder;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class MainActivity extends Activity{
EditText first,last,age,classc;
Button add,view;
String FirstName;
String LastName;
String Class;
Integer Age;
sqLit myDB;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
myDB = new sqLit(this);
Link();
addButtonClicked();
viewButtonClicked();
}
public void addButtonClicked()
{
add.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
xmlToVar();
Integer flag=myDB.insertValue(FirstName, LastName, Class, Age);
if (flag==1)
{
Context context=MainActivity.this;
Toast toast = Toast.makeText(context, "Record Added" , Toast.LENGTH_LONG);
toast.show();
}
else
{
Context context=MainActivity.this;
Toast toast = Toast.makeText(context, "Error Occured" , Toast.LENGTH_LONG);
toast.show();
}
}
});
}
public void viewButtonClicked()
{
view.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Cursor res = myDB.getData();
if (res.getCount()==0)
{
showMessage("Error" , "No Data Found");
return;
}
StringBuffer buffer = new StringBuffer();
while (res.moveToNext())
{
buffer.append("ID : " + res.getString(0) + "\n");
buffer.append("FirstName : " + res.getString(1) + "\n");
buffer.append("LastName : " + res.getString(2) + "\n");
buffer.append("Class : " + res.getString(3) + "\n");
buffer.append("Age : " + res.getString(4) + "\n");
showMessage("Here is your Data",buffer.toString() );
}
}
});
}
public void showMessage(String title, String message)
{
AlertDialog.Builder Builder = new AlertDialog.Builder(this);
Builder.setCancelable(true);
Builder.setTitle(title);
Builder.setMessage(message);
}
public void Link()
{
first=(EditText) findViewById(R.id.editFirst);
last=(EditText) findViewById(R.id.editLast);
classc=(EditText) findViewById(R.id.editClass);
age=(EditText) findViewById(R.id.editAge);
add=(Button) findViewById(R.id.Add);
view=(Button) findViewById(R.id.ViewAll);
}
public void xmlToVar()
{
FirstName = first.getText().toString();
LastName = last.getText().toString();
Class = classc.getText().toString();
Age = Integer.parseInt(age.getText().toString());
}
}
sqLit.java
package com.example.database;
import org.w3c.dom.Text;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.text.Editable;
public class sqLit extends SQLiteOpenHelper
{
public static final String DB_NAME="student12.db";
public static final String TABLE_NAME="class1";
public static final String COL_1="ROLLNO";
public static final String COL_2="FirstName";
public static final String COL_3="LastName";
public static final String COL_4="Class";
public static final String COL_5="Age";
public sqLit(Context context) {
super(context, DB_NAME, null, 1);
// TODO Auto-generated constructor stub
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
db.execSQL("CREATE TABLE " + TABLE_NAME + "(" +COL_1 + " INTEGER PRIMARY KEY AUTOINCREMENT,"+COL_2 + " TEXT,"+COL_3 + " TEXT,"+COL_4 + " TEXT,"+COL_5 + " INTEGER)");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
db.execSQL("Drop Table If Exist" + TABLE_NAME );
onCreate(db);
}
public Integer insertValue(String firstName, String lastName, String Class, Integer Age)
{
SQLiteDatabase db = this.getWritableDatabase();
ContentValues contentV = new ContentValues();
contentV.put(COL_2, firstName);
contentV.put(COL_3, lastName);
contentV.put(COL_4, Class);
contentV.put(COL_5, Age);
long isInserted = db.insert(TABLE_NAME, null, contentV);
if (isInserted == -1){
return 0;
}
else
{
return 1;
}
}
public Cursor getData()
{
SQLiteDatabase db = this.getWritableDatabase();
Cursor res = db.rawQuery("Select * From "+TABLE_NAME, null);
return res;
}
}
logcat的
06-11 22:02:40.728: D/dalvikvm(1576): Not late-enabling CheckJNI (already on)
06-11 22:02:40.737: E/Trace(1576): error opening trace file: No such file or directory (2)
06-11 22:02:40.817: D/gralloc_goldfish(1576): Emulator without GPU emulation detected.
06-11 22:05:14.779: D/dalvikvm(1576): GC_CONCURRENT freed 197K, 5% free 6176K/6471K, paused 15ms+0ms, total 19ms
06-11 22:08:27.242: E/Trace(2066): error opening trace file: No such file or directory (2)
06-11 22:08:27.322: D/gralloc_goldfish(2066): Emulator without GPU emulation detected.
06-11 22:08:31.472: D/dalvikvm(2066): GC_CONCURRENT freed 225K, 5% free 6148K/6471K, paused 17ms+1ms, total 19ms
06-11 22:10:36.644: D/dalvikvm(2290): GC_CONCURRENT freed 225K, 5% free 6148K/6471K, paused 16ms+0ms, total 19ms
06-11 22:10:52.355: D/AndroidRuntime(2290): Shutting down VM
06-11 22:10:52.355: W/dalvikvm(2290): threadid=1: thread exiting with uncaught exception (group=0xb3f1c288)
06-11 22:10:52.355: E/AndroidRuntime(2290): FATAL EXCEPTION: main
06-11 22:10:52.355: E/AndroidRuntime(2290): java.lang.NumberFormatException: Invalid int: ""
06-11 22:10:52.355: E/AndroidRuntime(2290): at java.lang.Integer.invalidInt(Integer.java:138)
06-11 22:10:52.355: E/AndroidRuntime(2290): at java.lang.Integer.parseInt(Integer.java:359)
06-11 22:10:52.355: E/AndroidRuntime(2290): at java.lang.Integer.parseInt(Integer.java:332)
06-11 22:10:52.355: E/AndroidRuntime(2290): at com.example.database.MainActivity.xmlToVar(MainActivity.java:115)
06-11 22:10:52.355: E/AndroidRuntime(2290): at com.example.database.MainActivity$1.onClick(MainActivity.java:46)
06-11 22:10:52.355: E/AndroidRuntime(2290): at android.view.View.performClick(View.java:4084)
06-11 22:10:52.355: E/AndroidRuntime(2290): at android.view.View$PerformClick.run(View.java:16966)
06-11 22:10:52.355: E/AndroidRuntime(2290): at android.os.Handler.handleCallback(Handler.java:615)
06-11 22:10:52.355: E/AndroidRuntime(2290): at android.os.Handler.dispatchMessage(Handler.java:92)
06-11 22:10:52.355: E/AndroidRuntime(2290): at android.os.Looper.loop(Looper.java:137)
06-11 22:10:52.355: E/AndroidRuntime(2290): at android.app.ActivityThread.main(ActivityThread.java:4745)
06-11 22:10:52.355: E/AndroidRuntime(2290): at java.lang.reflect.Method.invokeNative(Native Method)
06-11 22:10:52.355: E/AndroidRuntime(2290): at java.lang.reflect.Method.invoke(Method.java:511)
06-11 22:10:52.355: E/AndroidRuntime(2290): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
06-11 22:10:52.355: E/AndroidRuntime(2290): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
06-11 22:10:52.355: E/AndroidRuntime(2290): at dalvik.system.NativeStart.main(Native Method)
06-11 22:12:22.676: D/dalvikvm(2455): GC_CONCURRENT freed 201K, 5% free 6172K/6471K, paused 17ms+0ms, total 19ms
06-11 22:14:01.238: D/dalvikvm(2652): Not late-enabling CheckJNI (already on)
06-11 22:14:01.248: E/Trace(2652): error opening trace file: No such file or directory (2)
06-11 22:14:01.338: D/gralloc_goldfish(2652): Emulator without GPU emulation detected.
按钮根本不起作用。
答案 0 :(得分：0)
xmlToVar方法的以下异常是问题，你在addButtonClicked方法中调用它
java.lang.NumberFormatException：无效的int：＆＃34;＆＃34;
如果未输入Age字段中的值，则在调用
之前进行空检查时会发生此错误Age = Integer.parseInt（age.getText（）。toString（））;
应解决问题
答案 1 :(得分：0)
在xmlToVar（）中使用parseInt之前验证输入：
String ageStr = age.getText().toString();
if (ageStr != "")
r.age = Integer.parseInt(ageStr);
如果可以有默认值，您也可以初始化Integer age。
答案 2 :(得分：0)
您需要提供以下信息：
i）您是否尝试过调试？ ii）如果是，光标是否获得任何数据？
现在采用不同的方法解决问题：
创建数据类[使其更易于处理，即存储和从数据库中获取]
示例：
班级：
public class NoticeInformation {
private String NoticeType, NoticeHeader, NoticeLink;
private int Important, NoticeId, Read;
public NoticeInformation(int NoticeId,
String NoticeType,
String NoticeHeader,
String NoticeLink,
int Important,
int Read){
this.NoticeId = NoticeId;
this.NoticeType = NoticeType;
this.NoticeHeader = NoticeHeader;
this.NoticeLink = NoticeLink;
this.Important = Important;
this.Read = Read;
}
public int getNoticeId() {
return NoticeId;
}
public void setNoticeId(int noticeId) {
NoticeId = noticeId;
}
public String getNoticeType() {
return NoticeType;
}
public void setNoticeType(String noticeType) {
NoticeType = noticeType;
}
public String getNoticeHeader() {
return NoticeHeader;
}
public void setNoticeHeader(String noticeHeader) {
NoticeHeader = noticeHeader;
}
public String getNoticeLink() {
return NoticeLink;
}
public void setNoticeLink(String noticeLink) {
NoticeLink = noticeLink;
}
public int getImportant() {
return Important;
}
public void setImportant(int important) {
Important = important;
}
public int getRead() {
return Read;
}
public void setRead(int read) {
Read = read;
}
}
数据库阅读：
public List<NoticeInformation> getScheduleNotice(){
SQLiteDatabase db = this.getReadableDatabase();
List<NoticeInformation> res = new ArrayList<>();
String Query = "SELECT * FROM " + TABLE_NAME1 + " WHERE NoticeType = 'Schedule';";
Cursor cursor = db.rawQuery(Query, null);
if (cursor.moveToFirst()){
cursor.moveToFirst();
do
{
NoticeInformation obj = new NoticeInformation(cursor.getInt(0), cursor.getString(1),
cursor.getString(2), cursor.getString(3), cursor.getInt(5),
cursor.getInt(4));
res.add(obj);
}while(cursor.moveToNext());
return res;
}
return null;
}
不是在应用程序端处理游标，而是将数据放在列表中。 [以我的拙见]更容易处理。
尝试这种方法，让我知道结果。