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帮助我plzz ..在第一个应用程序版本中，我在DBHelper中写了错误的DB_PATH，安装apk后出现找不到数据库的异常。然后（下一个应用程序版本）我写了正确的DB_PATH，但安装后出现异常

    FATAL EXCEPTION: main
 java.lang.RuntimeException: Unable to start activity ComponentInfo: android.database.sqlite.SQLiteException: no such table: category: , while compiling: SELECT * FROM category
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1651)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
    at android.app.ActivityThread.access$1500(ActivityThread.java:117)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:130)
    at android.app.ActivityThread.main(ActivityThread.java:3691)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:507)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:907)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:665)
    at dalvik.system.NativeStart.main(Native Method)
 Caused by: android.database.sqlite.SQLiteException: no such table: category: , while compiling: SELECT * FROM category
    at android.database.sqlite.SQLiteCompiledSql.native_compile(Native Method)
    at android.database.sqlite.SQLiteCompiledSql.compile(SQLiteCompiledSql.java:92)
    at android.database.sqlite.SQLiteCompiledSql.<init>(SQLiteCompiledSql.java:65)
    at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:83)
    at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:49)
    at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:42)
    at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1497)
    at android.database.sqlite.SQLiteDatabase.queryWithFactory(SQLiteDatabase.java:1376)
    at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1330)
    at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1450)
    at package.name.MainPage.update(MainPage.java:125)
    at package.name.MainPage.onCreate(MainPage.java:88)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1615)
    ... 11 more

如果我重新安装 apk 并清除缓存，那么 apk 安装成功！如何在不清除缓存并重新安装的情况下成功安装？

主类

     ...
     public class MainPage extends MainHelper implements OnClickListener{
     ...
     public void onCreate(Bundle savedInstanceState) {
     ...
            DBHelper myDbHelper = new DBHelper(this);

            String oldpath = "/data/data/package.name1/databases/";
            String newpath = "/data/data/package.name/databases/";
            File dbFile = new File(newpath+"db.sqlite");

        if (!dbFile.exists()) {
        try {
            myDbHelper.copyDataBase(oldpath);
            myDbHelper.myContext.deleteDatabase(oldpath+bd_name);
        } catch (IOException e) {
            e.printStackTrace();
        }       
        }

        try {     
                myDbHelper.createDataBase();         
        } catch (IOException ioe) {      
            throw new Error("Unable to create database");        
        }  
    .... 
    }
    }

数据库助手

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import android.content.Context;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class DBHelper extends SQLiteOpenHelper{

    private static String DB_PATH = "/data/data/package.name/databases/"; 
    private static String DB_NAME = "db.sqlite"; 
    private SQLiteDatabase myDataBase;  
    public final Context myContext;

    public DBHelper(Context context) {
        super(context, DB_NAME, null, 1);
        this.myContext = context;
    }   

    public void createDataBase() throws IOException{

        boolean dbExist = checkDataBase();
        if(dbExist){
        }else{
            this.getReadableDatabase();         

            try {
                copyDataBase(DB_PATH);
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }

    }

    private boolean checkDataBase(){
        File dbFile = new File(DB_PATH + DB_NAME);
        return dbFile.exists();
    }

    public void copyDataBase(String bdpath) throws IOException{
        InputStream myInput = myContext.getAssets().open(DB_NAME);
        String outFileName = bdpath + DB_NAME;
        OutputStream myOutput = new FileOutputStream(outFileName);
        byte[] buffer = new byte[1024];
        int length;
        while ((length = myInput.read(buffer))>0){
            myOutput.write(buffer, 0, length);
        }

        myOutput.flush();
        myOutput.close();
        myInput.close();
    }

    public void openDataBase() throws SQLException{
        String myPath = DB_PATH + DB_NAME;
        myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);

    }

    @Override
    public synchronized void close() {

            if(myDataBase != null)
                myDataBase.close();

            super.close();

    }

    @Override
    public void onCreate(SQLiteDatabase db) {

    }

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

    }
}
4

1 回答 1

1

我想你知道解决方案

在进行数据库操作之前，请执行以下操作

您应在 NEW DB PATH 检查是否存在 db

如果它不存在

然后从您的 OLD DB PATH {其中预期的位置}复制它

如果它不在那个也

然后创建你的数据库

于 2013-09-22T09:03:53.300 回答