修复1

Question

我有一个词典应用程序，可以使用我提供的数据库完全脱机工作。为了能够使用数据库，我在开发人员的博客上应用了一种解决方案。您可以从this链接中引用它。解决方案基本上是从资产文件夹复制数据库并使用它。它在大多数设备上都可以正常工作，但是某些用户在尝试查询数据库时遇到崩溃。我已经附加了从华硕ZenFone 5（ZE620KL）（ASUS_X00QD）发送的崩溃报告中收到的堆栈跟踪。我的问题是：我正在应用的做法是否存在问题（使用位于Assets文件夹中的现有数据库）？我该如何避免这种例外情况？

  at android.database.sqlite.SQLiteConnection.nativePrepareStatement (Native Method)
  at android.database.sqlite.SQLiteConnection.acquirePreparedStatement (SQLiteConnection.java:903)
  at android.database.sqlite.SQLiteConnection.prepare (SQLiteConnection.java:514)
  at android.database.sqlite.SQLiteSession.prepare (SQLiteSession.java:588)
  at android.database.sqlite.SQLiteProgram.<init> (SQLiteProgram.java:58)
  at android.database.sqlite.SQLiteQuery.<init> (SQLiteQuery.java:37)
  at android.database.sqlite.SQLiteDirectCursorDriver.query (SQLiteDirectCursorDriver.java:46)
  at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory (SQLiteDatabase.java:1408)
  at android.database.sqlite.SQLiteDatabase.queryWithFactory (SQLiteDatabase.java:1255)
  at android.database.sqlite.SQLiteDatabase.query (SQLiteDatabase.java:1126)
  at android.database.sqlite.SQLiteDatabase.query (SQLiteDatabase.java:1294)
  at com.tur_cirdictionary.turkish_circassiandictionary.data.WordProvider.query (WordProvider.java:52)
  at android.content.ContentProvider.query (ContentProvider.java:1064)
  at android.content.ContentProvider.query (ContentProvider.java:1156)
  at android.content.ContentProvider$Transport.query (ContentProvider.java:241)
  at android.content.ContentResolver.query (ContentResolver.java:809)
  at android.content.ContentResolver.query (ContentResolver.java:758)
  at com.tur_cirdictionary.turkish_circassiandictionary.MainActivity.showSuggestionsForQuery (MainActivity.java:245)
  at com.tur_cirdictionary.turkish_circassiandictionary.MainActivity.access$000 (MainActivity.java:37)
  at com.tur_cirdictionary.turkish_circassiandictionary.MainActivity$2.onQueryTextChange (MainActivity.java:178)
  at android.widget.SearchView.onTextChanged (SearchView.java:1250)
  at android.widget.SearchView.access$2100 (SearchView.java:98)
  at android.widget.SearchView$10.onTextChanged (SearchView.java:1776)
  at android.widget.TextView.sendOnTextChanged (TextView.java:9784)
  at android.widget.TextView.handleTextChanged (TextView.java:9881)
  at android.widget.TextView$ChangeWatcher.onTextChanged (TextView.java:12539)
  at android.text.SpannableStringBuilder.sendTextChanged (SpannableStringBuilder.java:1263)
  at android.text.SpannableStringBuilder.replace (SpannableStringBuilder.java:575)
  at android.text.SpannableStringBuilder.replace (SpannableStringBuilder.java:506)
  at android.text.SpannableStringBuilder.replace (SpannableStringBuilder.java:36)
  at android.view.inputmethod.BaseInputConnection.replaceText (BaseInputConnection.java:843)
  at android.view.inputmethod.BaseInputConnection.commitText (BaseInputConnection.java:197)
  at com.android.internal.widget.EditableInputConnection.commitText (EditableInputConnection.java:183)
  at com.android.internal.view.IInputConnectionWrapper.executeMessage (IInputConnectionWrapper.java:341)
  at com.android.internal.view.IInputConnectionWrapper$MyHandler.handleMessage (IInputConnectionWrapper.java:85)
  at android.os.Handler.dispatchMessage (Handler.java:106)
  at android.os.Looper.loop (Looper.java:198)
  at android.app.ActivityThread.main (ActivityThread.java:6732)
  at java.lang.reflect.Method.invoke (Native Method)
  at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run (RuntimeInit.java:493)
  at com.android.internal.os.ZygoteInit.main (ZygoteInit.java:858)

WordContract.java

package com.tur_cirdictionary.turkish_circassiandictionary.data;

import android.content.ContentResolver;
import android.net.Uri;
import android.provider.BaseColumns;

public final class WordContract {

    public static final String CONTENT_AUTHORITY =
            "com.tur_cirdictionary.turkish_circassiandictionary";

    public static final Uri BASE_CONTENT_URI = Uri.parse("content://" + CONTENT_AUTHORITY);

    public static final String PATH_WORDS = "words";

    private WordContract() {}

    public static class WordEntry implements BaseColumns {

        public static final Uri CONTENT_URI = Uri.withAppendedPath(BASE_CONTENT_URI, PATH_WORDS);

        public static final String CONTENT_LIST_TYPE = ContentResolver.CURSOR_DIR_BASE_TYPE + "/" +
                CONTENT_AUTHORITY + PATH_WORDS;

        public static final String CONTENT_ITEM_TYPE = ContentResolver.CURSOR_ITEM_BASE_TYPE + "/" +
                CONTENT_AUTHORITY + "/" + PATH_WORDS;

        public static final String TABLE_NAME = "words";
        public static final String _ID = BaseColumns._ID;
        public static final String COLUMN_NAME_CIRCASSIAN = "circassian";
        public static final String COLUMN_NAME_TURKISH = "turkish";
    }
}

WordDbHelper.java

package com.tur_cirdictionary.turkish_circassiandictionary.data;

import android.content.Context;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import com.tur_cirdictionary.turkish_circassiandictionary.data.WordContract.WordEntry;

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

public class WordDbHelper extends SQLiteOpenHelper {

    private static final int DATABASE_VERSION = 1;
    private static String DATABASE_PATH
            = "/data/data/com.tur_cirdictionary.turkish_circassiandictionary/databases/";
    private static final String DATABASE_NAME = "Cir_Tur.sqlite";
    private SQLiteDatabase database;
    private final Context context;

    public WordDbHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
        this.context = context;
    }

    public void createDatabase() {
        boolean dbExist = checkDataBase();
        if (dbExist) {
            //Cool. Don't do anything.
        } else {
            try {
                this.getReadableDatabase();
                copyDataBase();
            } catch (IOException e) {
                throw new Error("Error copying database");
            }
        }
    }

    private boolean checkDataBase() {
        SQLiteDatabase checkDB = null;
        try {
            String path = DATABASE_PATH + DATABASE_NAME;
            checkDB = SQLiteDatabase.openDatabase(path, null, SQLiteDatabase.OPEN_READONLY);
        } catch (SQLException e) {
            //Database does not exist
        }
        if (checkDB != null) {
            checkDB.close();
        }
        return checkDB != null;
    }

    private void copyDataBase() throws IOException {
        InputStream inputStream = context.getAssets().open(DATABASE_NAME);
        String outFileName = DATABASE_PATH + DATABASE_NAME;
        OutputStream outputStream = new FileOutputStream(outFileName);
        byte[] buffer = new byte[1024];
        int length;
        while ((length = inputStream.read(buffer)) > 0) {
            outputStream.write(buffer, 0, length);
        }
        outputStream.flush();
        outputStream.close();
        inputStream.close();
    }

    public SQLiteDatabase openDatabase() {
        String path = DATABASE_PATH + DATABASE_NAME;
        database = SQLiteDatabase.openDatabase(path, null, SQLiteDatabase.OPEN_READONLY);
        return database;
    }

    @Override
    public synchronized void close() {
        if (database != null) {
            database.close();
        }
        super.close();
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

    }

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

    }

    private static final String SQL_CREATE_WORDS =
            "CREATE TABLE  " + WordEntry.TABLE_NAME + " ("
                    + WordEntry._ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
                    + WordEntry.COLUMN_NAME_CIRCASSIAN + " TEXT, "
                    + WordEntry.COLUMN_NAME_TURKISH + " TEXT)";

    private static final String SQL_DELETE_WORDS =
            "DROP TABLE IF EXISTS " + WordContract.WordEntry.TABLE_NAME;
}

WordProvider.java

package com.tur_cirdictionary.turkish_circassiandictionary.data;

import android.content.Context;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import com.tur_cirdictionary.turkish_circassiandictionary.data.WordContract.WordEntry;

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

public class WordDbHelper extends SQLiteOpenHelper {

    private static final int DATABASE_VERSION = 1;
    private static String DATABASE_PATH
            = "/data/data/com.tur_cirdictionary.turkish_circassiandictionary/databases/";
    private static final String DATABASE_NAME = "Cir_Tur.sqlite";
    private SQLiteDatabase database;
    private final Context context;

    public WordDbHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
        this.context = context;
    }

    public void createDatabase() {
        boolean dbExist = checkDataBase();
        if (dbExist) {
            //Cool. Don't do anything.
        } else {
            try {
                this.getReadableDatabase();
                copyDataBase();
            } catch (IOException e) {
                throw new Error("Error copying database");
            }
        }
    }

    private boolean checkDataBase() {
        SQLiteDatabase checkDB = null;
        try {
            String path = DATABASE_PATH + DATABASE_NAME;
            checkDB = SQLiteDatabase.openDatabase(path, null, SQLiteDatabase.OPEN_READONLY);
        } catch (SQLException e) {
            //Database does not exist
        }
        if (checkDB != null) {
            checkDB.close();
        }
        return checkDB != null;
    }

    private void copyDataBase() throws IOException {
        InputStream inputStream = context.getAssets().open(DATABASE_NAME);
        String outFileName = DATABASE_PATH + DATABASE_NAME;
        OutputStream outputStream = new FileOutputStream(outFileName);
        byte[] buffer = new byte[1024];
        int length;
        while ((length = inputStream.read(buffer)) > 0) {
            outputStream.write(buffer, 0, length);
        }
        outputStream.flush();
        outputStream.close();
        inputStream.close();
    }

    public SQLiteDatabase openDatabase() {
        String path = DATABASE_PATH + DATABASE_NAME;
        database = SQLiteDatabase.openDatabase(path, null, SQLiteDatabase.OPEN_READONLY);
        return database;
    }

    @Override
    public synchronized void close() {
        if (database != null) {
            database.close();
        }
        super.close();
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

    }

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

    }

    private static final String SQL_CREATE_WORDS =
            "CREATE TABLE  " + WordEntry.TABLE_NAME + " ("
                    + WordEntry._ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
                    + WordEntry.COLUMN_NAME_CIRCASSIAN + " TEXT, "
                    + WordEntry.COLUMN_NAME_TURKISH + " TEXT)";

    private static final String SQL_DELETE_WORDS =
            "DROP TABLE IF EXISTS " + WordContract.WordEntry.TABLE_NAME;

}

MainActivity.java

package com.tur_cirdictionary.turkish_circassiandictionary.data;

import android.content.Context;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import com.tur_cirdictionary.turkish_circassiandictionary.data.WordContract.WordEntry;

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

public class WordDbHelper extends SQLiteOpenHelper {

    private static final int DATABASE_VERSION = 1;
    private static String DATABASE_PATH
            = "/data/data/com.tur_cirdictionary.turkish_circassiandictionary/databases/";
    private static final String DATABASE_NAME = "Cir_Tur.sqlite";
    private SQLiteDatabase database;
    private final Context context;

    public WordDbHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
        this.context = context;
    }

    public void createDatabase() {
        boolean dbExist = checkDataBase();
        if (dbExist) {
            //Cool. Don't do anything.
        } else {
            try {
                this.getReadableDatabase();
                copyDataBase();
            } catch (IOException e) {
                throw new Error("Error copying database");
            }
        }
    }

    private boolean checkDataBase() {
        SQLiteDatabase checkDB = null;
        try {
            String path = DATABASE_PATH + DATABASE_NAME;
            checkDB = SQLiteDatabase.openDatabase(path, null, SQLiteDatabase.OPEN_READONLY);
        } catch (SQLException e) {
            //Database does not exist
        }
        if (checkDB != null) {
            checkDB.close();
        }
        return checkDB != null;
    }

    private void copyDataBase() throws IOException {
        InputStream inputStream = context.getAssets().open(DATABASE_NAME);
        String outFileName = DATABASE_PATH + DATABASE_NAME;
        OutputStream outputStream = new FileOutputStream(outFileName);
        byte[] buffer = new byte[1024];
        int length;
        while ((length = inputStream.read(buffer)) > 0) {
            outputStream.write(buffer, 0, length);
        }
        outputStream.flush();
        outputStream.close();
        inputStream.close();
    }

    public SQLiteDatabase openDatabase() {
        String path = DATABASE_PATH + DATABASE_NAME;
        database = SQLiteDatabase.openDatabase(path, null, SQLiteDatabase.OPEN_READONLY);
        return database;
    }

    @Override
    public synchronized void close() {
        if (database != null) {
            database.close();
        }
        super.close();
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

    }

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

    }

    private static final String SQL_CREATE_WORDS =
            "CREATE TABLE  " + WordEntry.TABLE_NAME + " ("
                    + WordEntry._ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
                    + WordEntry.COLUMN_NAME_CIRCASSIAN + " TEXT, "
                    + WordEntry.COLUMN_NAME_TURKISH + " TEXT)";

    private static final String SQL_DELETE_WORDS =
            "DROP TABLE IF EXISTS " + WordContract.WordEntry.TABLE_NAME;
}

如有必要，她是整个项目的link。

Answer 1

我正在应用的练习是否存在问题（使用资产文件夹中的现有数据库）？

并非如此，因为这是一种推荐且经常使用的技术。但是，如果实施不当，可能会出现问题，尤其是现在。

根据快速搜索，设备的操作系统为 Android 8.0（Oreo），可升级至Android 9.0（Pie）； ZenUI 5

使用Android Pie时肯定会发现1个问题，这很可能是您遇到的问题。

原因是在调用 copyDatabase 方法之前使用了 this.getReadableDatabase(); 。

默认情况下，随着Android Pie打开WAL（预写日志记录）两个文件，将创建 -wal 和 -shm 文件。这些剩余部分导致冲突，因为它们与刚复制的数据库不匹配。我相信最终结果是删除了复制的数据库，并创建了一个全新的数据库，以便提供可用的数据库。因此，不存在表或基础数据。这通常会导致未找到表错误/异常，通常是当尝试访问该表不存在的数据时。

如何避免这种例外情况？

修复1

简单的解决方法（但不是建议的解决方法）是重写WordDbHelper.java中 SQLiteOpenhelper 的 onConfigure 方法，以调用disableWriteAheadLogging方法。 / p>

但是，应用此修复程序意味着您放弃了Write-Ahead Logging的优势。

修复2

正确的解决方法是在复制之前不要使用 getReadableDatabase 。这似乎是一个简单问题的历史修复。也就是说，对于新安装的App，包的data / data / the_package /目录没有 databases 目录。因此，getWritableDatabase（或getReabableDatabase，如果可以的话，它会获取一个可写数据库）创建目录以及随后被覆盖的数据库。

应用程序应该做的是检查目录是否存在，然后创建目录，这一切都可以在checkDataBase方法中使用：-

private boolean checkDataBase() {

    File db = new File(DATABASE_PATH + DATABASE_NAME);
    if(db.exists()) return true;
    File dir = new File(db.getParent());
    if (!dir.exists()) {
        dir.mkdirs();
    }
    return false;
}

请注意，您还应该从 createDatabase 方法中删除行this.getReadableDatabase();。

尽管可能不是问题，但不要对数据库路径进行硬编码，而要使用Context类的 getDatabasePath 方法（如果对数据库使用标准/推荐位置）则更明智。例如

private boolean checkDataBase() {

    File db = new File(context.getDatabasePath(DBNAME)); //<<<<<<<<<< CHANGED
    if(db.exists()) return true;
    File dir = new File(db.getParent());
    if (!dir.exists()) {
        dir.mkdirs();
    }
    return false;
}

注意

从提供的堆栈跟踪中，以及 MainActivity.java ， WordProvidr.java 和 WordDBHelper 都具有相同的代码，无法确定确切原因。因此，以上是可能的原因或可能发生的原因。

Answer 2

我不知道这是否是导致您出现问题的原因，但是当我遇到类似的间歇性SQLite问题时，事实证明是Android（或Eclipse）在使用Assets进行编译时正在压缩数据库文件夹。解决方案是为文件提供Android不会压缩的文件类型的扩展名，例如带有.jpg扩展名的图像文件。听起来很奇怪，但是我将数据库文件作为mydb.jpg放在Assets中，然后在CopyDatabase方法中，它将扩展名更改为mydb.db并将其存储在/ data / data / databases应用程序文件夹中。

如何修复尝试进行查询时抛出的SQLiteException？

2 个答案:

修复1

修复2

注意