跨标签的Android数据库访问

时间：2010-07-22 20:27:28

标签： android database sqlite

我有四个标签（报告，评论报告，地图和设置）。我有一个填充了报告信息的sqlite数据库。我希望整个应用程序都可以访问数据库。 “报告”选项卡成功地将数据添加到数据库，但是使用相同的方法会使应用程序崩溃。 Android调试器指向再次调用数据库的行。

在“报告”标签中，以下代码用于启动数据库... 

this.reportDatabase = new ReportDatabase(this);
  this.reportDatabase.insert("(" + latitude + ", " + longitude + ", " + time + ", '" + spinnerState + "', " + lower + ", " + upper + ", " + agreed + ", " + getAlgorithmCount() + ", " + xAxis + ", " + yAxis + ", " + zAxis + ", " + altitude + ", "+ accuracy + ", 'photo');");

在Review选项卡的onCreate（）方法中 - 我希望查看报告 - 我尝试通过调用返回报告方法的访问来访问数据库

this.reportDatabase = new ReportDatabase（this）;

然而，这无效。在android调试器中突出显示问题属于提供给它的上下文。我意识到报告选项卡已经访问过报告数据库，并想知道这是否是导致问题的原因。我是编程android的新手，该应用程序旨在报告非洲的火烈鸟，任何帮助将不胜感激！

根据Seva Alekseyev的建议，我改编如下......

我已将ReportDatabase改编为...... 

 public ReportDatabase(Context context) {
  super(context, DATABASE_NAME, null, DATABASE_VERSION);
  ReportDatabase.context = context;
  OpenHelper openHelper = new OpenHelper(ReportDatabase.context);
  this.database = openHelper.getWritableDatabase();
 }

 static ReportDatabase open(Context c){
  if(reportDatabase == null){
   reportDatabase = new ReportDatabase(ReportDatabase.context);
   return reportDatabase;
  }
  return reportDatabase;
 }

...使用

 reportDatabase = ReportDatabase.open(this);

作为报告和审核标签中的通话。不幸的是，这似乎不起作用，调试器停止在相同的方法上。完整的ReportDatabase.java文件在这里...... 

package com.android.flamingo;

import java.util.Vector;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

public class ReportDatabase extends SQLiteOpenHelper {
private static Context context;
private SQLiteDatabase database;

static ReportDatabase reportDatabase;

private static final String DATABASE_NAME = "flamingo_reports";
private static final int DATABASE_VERSION = 1;
private static final String TABLE_NAME = "reports";

/**
 * Default (and only) constructor....
 * 
 * @param context
 */

public ReportDatabase(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
    ReportDatabase.context = context;
    OpenHelper openHelper = new OpenHelper(ReportDatabase.context);
    this.database = openHelper.getWritableDatabase();
}

static ReportDatabase open(Context c){
    if(reportDatabase == null){
        reportDatabase = new ReportDatabase(ReportDatabase.context);
        return reportDatabase;
    }
    return reportDatabase;
}

/**
 * 
 * @param name
 */

public void insert(String name){
    this.database.execSQL("INSERT INTO " + TABLE_NAME + "(latitude, longitude, time, lake, lower_estimate, higher_estimate, agreed_estimate, algorithm_count, xaxis, yaxis, zaxis, altitude, accuracy, photo_identifier) VALUES " + name);
}

/**
 * This method returns a double array and probably shouldn't be this hacky...
 * 
 * 
 * @return
 */

public Vector<ReportInstanceQuery> reportSelect(){
    Vector<ReportInstanceQuery> tempReports = new Vector<ReportInstanceQuery>();

    Cursor c = database.rawQuery("SELECT id,time,lake,lower_estimate,higher_estimate,agreed_estimate,algorithm_count FROM" + TABLE_NAME + ";",null);
    int indexTime = c.getColumnIndex("time");
    int indexLake = c.getColumnIndex("lake");
    int indexLowerEstimate = c.getColumnIndex("lower_estimate");
    int indexHigherEstimate = c.getColumnIndex("higher_estimate");
    int indexAgreedEstimate = c.getColumnIndex("agreed_estimate");
    int indexAlgorithmCount = c.getColumnIndex("algorithm_count");


    if (c != null){
        int i = 0;
        do {
            i++;
            int columnTime = c.getInt(indexTime);
            String columnLake = c.getString(indexLake);
            int columnLowerEstimate = c.getInt(indexLowerEstimate);
            int columnHigherEstimate = c.getInt(indexHigherEstimate);
            int columnAgreedEstimate = c.getInt(indexAgreedEstimate);
            int columnAlgorithmCount = c.getInt(indexAlgorithmCount);

            tempReports.add(new ReportInstanceQuery(columnTime, columnLake, columnLowerEstimate, columnHigherEstimate, columnAgreedEstimate, columnAlgorithmCount));
        } while (c.moveToNext());
    }
    reportDatabase.close();
    return tempReports;
}

/**
 * This method connects to the database  
 * 
 */

public void CSVReportSelect(){

}

public void delete(){
    this.database.delete(TABLE_NAME, null, null);
}

@Override
public void onCreate(SQLiteDatabase database) {        
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {      
}


private static class OpenHelper extends SQLiteOpenHelper {

    OpenHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE " + TABLE_NAME + "(id INTEGER PRIMARY KEY AUTOINCREMENT, latitude REAL, longitude REAL, time INTEGER, lake TEXT, lower_estimate INTEGER, higher_estimate INTEGER, agreed_estimate INTEGER, algorithm_count INTEGER, xaxis REAL, yaxis REAL, zaxis REAL, altitude REAL, accuracy REAL, photo_identifier TEXT)");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        Log.w("Example", "Upgrading database, this will drop tables and recreate.");
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
        onCreate(db);
    }
}

}

错误堆栈是...... 

ReportDatabase.<init>(Context) line: 29 
ReportDatabase.open(Context) line: 37   
ReviewTab.onCreate(Bundle) line: 26 
Instrumentation.callActivityOnCreate(Activity, Bundle) line: 1123   
ActivityThread.performLaunchActivity(ActivityThread$ActivityRecord) line: 2231  
ActivityThread.startActivityNow(Activity, String, Intent, ActivityInfo, IBinder, Bundle, Object) line: 2112 
LocalActivityManager.moveToState(LocalActivityManager$LocalActivityRecord, int) line: 130   
LocalActivityManager.startActivity(String, Intent) line: 342    
TabHost$IntentContentStrategy.getContentView() line: 600    
TabHost.setCurrentTab(int) line: 310    
TabHost$2.onTabSelectionChanged(int, boolean) line: 126 
TabWidget$TabClickListener.onClick(View) line: 268  
RelativeLayout(View).performClick() line: 2183  
RelativeLayout(View).onTouchEvent(MotionEvent) line: 3849   
RelativeLayout(View).dispatchTouchEvent(MotionEvent) line: 3389 
RelativeLayout(ViewGroup).dispatchTouchEvent(MotionEvent) line: 831 
TabWidget(ViewGroup).dispatchTouchEvent(MotionEvent) line: 863  
LinearLayout(ViewGroup).dispatchTouchEvent(MotionEvent) line: 863   
TabHost(ViewGroup).dispatchTouchEvent(MotionEvent) line: 863    
FrameLayout(ViewGroup).dispatchTouchEvent(MotionEvent) line: 863    
LinearLayout(ViewGroup).dispatchTouchEvent(MotionEvent) line: 863   
PhoneWindow$DecorView(ViewGroup).dispatchTouchEvent(MotionEvent) line: 863  
PhoneWindow$DecorView.superDispatchTouchEvent(MotionEvent) line: 1707   
PhoneWindow.superDispatchTouchEvent(MotionEvent) line: 1197 
HelloFlamingos(Activity).dispatchTouchEvent(MotionEvent) line: 1993 
PhoneWindow$DecorView.dispatchTouchEvent(MotionEvent) line: 1691    
ViewRoot.handleMessage(Message) line: 1525  
ViewRoot(Handler).dispatchMessage(Message) line: 99 
Looper.loop() line: 123 
ActivityThread.main(String[]) line: 3948    
Method.invokeNative(Object, Object[], Class, Class[], Class, int, boolean) line: not available [native method]  
Method.invoke(Object, Object...) line: 521  
ZygoteInit$MethodAndArgsCaller.run() line: 782  
ZygoteInit.main(String[]) line: 540 
NativeStart.main(String[]) line: not available [native method]

想法？

1 个答案:

答案 0 :(得分：1)

您正尝试多次打开数据库。使用单个ReportDatabase对象，可通过静态方法ReportDatabase获得。像这样：

class ReportDatabase
{
    static ReportDatabase TheDatabase = null;

    static ReportDatabase Open(Context c)
    {
        if(TheDatabase == null)
            TheDatabase = new ReportDatabase(c);
        return TheDatabase;
    }
}

这通常被称为单身人士。或全球：）

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