db4o on Honeycomb Db4oException：文件格式不兼容

Question

我在一个小项目中使用 db4o，该项目在 Android 2.2、2.3 等上运行良好。然而，在 Honeycomb 上，数据库初始化会导致以下错误：

com.db4o.ext.Db4oException: File format incompatible: '/data/data/com.myapp/app_data/my_app.db4o'

此强制关闭并且错误发生在运行 Honeycomb 的 Xoom 和运行 Honeycomb 的 Galaxy Tab 上。

相关代码为：

public ObjectContainer db() {
    // Create, open, and close the database
    try {
        if (oc == null || oc.ext().isClosed()) {
            oc = Db4oEmbedded
                    .openFile(dbConfig(), db4oDBFullPath(mContext));
        }
        return oc;
    } catch (Exception e) {
        Log.e(CFAApplication.TAG, e.toString());
        return null;
    }
}

private String db4oDBFullPath(Context ctx) {
    // Returns the path for the database location
    return ctx.getDir("data", 2) + "/" + "myapp.db4o";
}

public List<MyItem> getListItem(final String passedItemTitle) {
    List<MyItem> result = db().query(new Predicate<MyItem>() { // Error occurs here
        public boolean match(MyItem listItem) {
            if (passedItemTitle.equals(listItem.getTitle())) {
                return true;
            }
            return false;
        }
    });
    return result;
}

Honeycomb 处理其外部文件系统的方式有什么不同吗？我可以在 db4oDBFullPath() 方法中进行任何更改以使两者兼容吗？我真的不知道发生了什么不同的事情。也许我需要启用一些 Honeycomb 特定的权限？

Answer 1

已在最新版本中修复：

http://community.versant.com/Blogs/db4o/tabid/197/entryid/1057/Default.aspx

Answer 2

我在 Xoom 上看到了类似的东西。结果证明文件创建出错了，因为 Xoom 在严格模式下运行，而严格模式阻止了 DB4o 打电话回家。留下损坏的存根数据库。尝试在 AsyncTask 中执行初始 Db4oEmbedded.openFile。

当然是在删除损坏的文件之后。

Answer 3

com.db4o.ext.Db4oException: File format incompatible

当我在 AndroidManifest.xml 中包含下一行时消失：

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />;

值得一提的是，我另外编写了用于在单独线程中处理 db4o 的代码...

所以代码看起来像：

package com.inbytebg;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import com.db4o.Db4oEmbedded;
import com.db4o.ObjectContainer;
import com.db4o.ObjectSet;
import com.inbytebg.entities.Customer;

public class MainActivity8 extends Activity {

    Button savetodb4o;
    Button readfromdb4o;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        savetodb4o = (Button) findViewById(R.id.save_to_db4o);
        savetodb4o.setOnClickListener(new View.OnClickListener() {

            public void onClick(View arg0) {

                new Thread() {

                    @Override
                    public void run() {
                        String dbPath = getApplicationContext().getDir("data", 0) + "/" + "customer.db4o";
                        ObjectContainer db = Db4oEmbedded.openFile(Db4oEmbedded.newConfiguration(), dbPath);

                        Customer cust = new Customer();
                        cust.setId(1);
                        cust.setName("stancho stanchev");
                        cust.setAddress("razgrad");

                        try {
                            db.store(cust);
                            Log.i("db4o...", "customer stored...");
                        } finally {
                            db.close();
                        }
                    }
                }.start();
            }
        });


        readfromdb4o = (Button) findViewById(R.id.read_from_db4o);
        readfromdb4o.setOnClickListener(new View.OnClickListener() {

            public void onClick(View arg0) {

                String dbPath = getApplicationContext().getDir("data", 0) + "/" + "customer.db4o";
                ObjectContainer db = Db4oEmbedded.openFile(Db4oEmbedded.newConfiguration(), dbPath);

                ObjectSet result;

                try {

                    result = db.queryByExample(Customer.class);

                    while (result.hasNext()) {
                        Customer customer = (Customer) result.next();
                        Log.i("db4o retrieve:...",
                                "Name: " + customer.getName()
                                + " id: " + customer.getId()
                                + " address: " + customer.getAddress());
                    }
                } finally {
                    db.close();
                }


            }
        });
    }
}

AndroidManifest.xml 是：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.inbytebg"
      android:versionCode="1"
      android:versionName="1.0">

    <uses-sdk android:minSdkVersion="11" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

    <application android:label="@string/app_name" android:icon="@drawable/icon">
        <activity android:name="MainActivity8"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>

调试输出是：

D/dalvikvm( 2231): GC_CONCURRENT freed 538K, 9% free 6705K/7367K, paused 7ms+14ms

I/db4o... ( 2231): customer stored...

I/db4o retrieve:...( 2231): Name: stancho stanchev id: 1 address: razgrad

I/db4o retrieve:...( 2231): Name: stancho stanchev id: 1 address: razgrad

I/db4o retrieve:...( 2231): Name: stancho stanchev id: 1 address: razgrad

I/db4o retrieve:...( 2231): Name: stancho stanchev id: 1 address: razgrad

I/db4o retrieve:...( 2231): Name: stancho stanchev id: 1 address: razgrad