Question

）我是Android编程的初学者，我没有什么问题。我写了简单的DataBase应用程序（我已准备好数据库），我需要将其复制到手机上的app文件夹。我有方法。当我在模拟器上运行应用程序时，一切正常，但当我将此应用程序复制到手机时，应用程序崩溃了。你能帮助我吗？这是dbAdapter：

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import android.app.Application;
import android.content.ContentValues;
import android.content.Context;
import android.content.ContextWrapper;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;

public class dbAdapter {
private static final String DB_NAME = "names2.db";
private static final int DB_VERSION = 1;
private static final String DB_TABLE = "names";
String DB_PATH;
public static final String KEY_ID = "_id";
public static final String KEY_NAME = "name";
public static final int NAME_COLUMN = 1;
public static final String KEY_SEX = "sex";
public static final int SEX_COLUMN = 2;
public static final String KEY_RACE = "race";
public static final int RACE_COLUMN = 3;
private SQLiteDatabase db;
private final Context context;
private DatabaseHelper myDatabaseHelper;

public dbAdapter(Context _context){
    context = _context;
    //DB_PATH = context.getApplicationContext().getFilesDir().getPath();

    DB_PATH = context.getFilesDir().getPath()+"/databases/";
    myDatabaseHelper = new DatabaseHelper(_context,DB_NAME,null,DB_VERSION);
}

public dbAdapter open(){
    db = myDatabaseHelper.getReadableDatabase();
    return this;
}

public void close(){
    db.close();
}

public long insert(rekord _rekord){
    ContentValues newRekord = new ContentValues();
    newRekord.put(KEY_NAME, _rekord.getName());
    newRekord.put(KEY_SEX, _rekord.getSex());
    newRekord.put(KEY_RACE, _rekord.getRace());
    return db.insert(DB_TABLE, null, newRekord);
}
public String getData(String sex, String race) {
    Cursor mycursor = db.rawQuery("SELECT name FROM names WHERE sex ="+sex+" AND race="+race+" ORDER BY RANDOM() LIMIT 1", null);
      if(mycursor.moveToFirst()){ //Edited based on suggestion from SAM
          String strCatName = mycursor.getString(mycursor.getColumnIndex(KEY_NAME));
                  return strCatName;
        } else {
        return null;
         }
      // return db.rawQuery("SELECT name FROM names WHERE sex =1 ORDER BY RANDOM() LIMIT 1", new String[]{"name"});
    }
public void copyDatabase() throws IOException{ //niby kopiowanie bazy danych. Nie wiem czy dobre bo nie chce działać

    //Open your local db as the input stream
    InputStream myInput = context.getAssets().open(DB_NAME);

    // Path to the just created empty db
    String outFileName = DB_PATH + DB_NAME;

    //Open the empty db as the output stream
    OutputStream myOutput = new FileOutputStream(outFileName);

    //transfer bytes from the inputfile to the outputfile
    byte[] buffer = new byte[1024];
    int length;
    while ((length = myInput.read(buffer))>0){
        myOutput.write(buffer, 0, length);
    }

    //Close the streams
    myOutput.flush();
    myOutput.close();
    myInput.close();
}
public void del(){
    File file = new File(DB_PATH+DB_NAME);
    if(file.exists())
        file.delete();
}



public SQLiteDatabase assetOpenDatabase() {
    File dbFile = context.getDatabasePath(DB_NAME);
    if (!dbFile.exists()) {
        try {
            assetCopyDatabase(dbFile);
        } catch (IOException e) {
            throw new RuntimeException("Error creating source database", e);
        }
    }

    return SQLiteDatabase.openDatabase(dbFile.getPath(), null, SQLiteDatabase.OPEN_READONLY);
}

private void assetCopyDatabase(File dbFile) throws IOException {
    InputStream is = context.getAssets().open(DB_NAME);
    OutputStream os = new FileOutputStream(dbFile);

    byte[] buffer = new byte[1024];
    while (is.read(buffer) > 0) {
        os.write(buffer);
    }

    os.flush();
    os.close();
    is.close();
}
//--------------------------------------------------------
class DatabaseHelper extends SQLiteOpenHelper{
    public DatabaseHelper(Context context, String name, CursorFactory factory, int version){
        super(context,name,factory,version);
    }
    @Override
    public void onCreate(SQLiteDatabase _db){
        //_db.execSQL("CREATE TABLE names(_id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT NOT NULL, sex NUMERIC NOT NULL, race NUMERIC NOT NULL)");
    }
    @Override
    public void onUpgrade(SQLiteDatabase _db, int oldVer, int newVer){
        _db.execSQL("DROP TABLE IF EXISTS "+DB_TABLE);
        onCreate(_db);
    }
}
}

这就是我复制文件的方式：

dbAdapter baza = new dbAdapter(this);
baza.copyDatabase();

或 baza.assetOpenDatabase（）; 同样的效果。

Ehh, now I have error on emulator too...
06-11 21:31:20.510: E/AndroidRuntime(537): FATAL EXCEPTION: main
06-11 21:31:20.510: E/AndroidRuntime(537): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.namesgenerator/com.example.namesgenerator.sex}: java.lang.RuntimeException: Error creating source database
06-11 21:31:20.510: E/AndroidRuntime(537):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
06-11 21:31:20.510: E/AndroidRuntime(537):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
06-11 21:31:20.510: E/AndroidRuntime(537):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)
06-11 21:31:20.510: E/AndroidRuntime(537):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
06-11 21:31:20.510: E/AndroidRuntime(537):  at android.os.Handler.dispatchMessage(Handler.java:99)
06-11 21:31:20.510: E/AndroidRuntime(537):  at android.os.Looper.loop(Looper.java:123)
06-11 21:31:20.510: E/AndroidRuntime(537):  at android.app.ActivityThread.main(ActivityThread.java:3683)
06-11 21:31:20.510: E/AndroidRuntime(537):  at java.lang.reflect.Method.invokeNative(Native Method)
06-11 21:31:20.510: E/AndroidRuntime(537):  at java.lang.reflect.Method.invoke(Method.java:507)
06-11 21:31:20.510: E/AndroidRuntime(537):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
06-11 21:31:20.510: E/AndroidRuntime(537):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
06-11 21:31:20.510: E/AndroidRuntime(537):  at dalvik.system.NativeStart.main(Native Method)
06-11 21:31:20.510: E/AndroidRuntime(537): Caused by: java.lang.RuntimeException: Error creating source database
06-11 21:31:20.510: E/AndroidRuntime(537):  at com.example.namesgenerator.dbAdapter.assetOpenDatabase(dbAdapter.java:108)
06-11 21:31:20.510: E/AndroidRuntime(537):  at com.example.namesgenerator.sex.onCreate(sex.java:39)
06-11 21:31:20.510: E/AndroidRuntime(537):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
06-11 21:31:20.510: E/AndroidRuntime(537):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
06-11 21:31:20.510: E/AndroidRuntime(537):  ... 11 more
06-11 21:31:20.510: E/AndroidRuntime(537): Caused by: java.io.FileNotFoundException: /data/data/com.example.namesgenerator/databases/names2.db (No such file or directory)
06-11 21:31:20.510: E/AndroidRuntime(537):  at org.apache.harmony.luni.platform.OSFileSystem.open(Native Method)
06-11 21:31:20.510: E/AndroidRuntime(537):  at dalvik.system.BlockGuard$WrappedFileSystem.open(BlockGuard.java:232)
06-11 21:31:20.510: E/AndroidRuntime(537):  at java.io.FileOutputStream.<init>(FileOutputStream.java:94)
06-11 21:31:20.510: E/AndroidRuntime(537):  at java.io.FileOutputStream.<init>(FileOutputStream.java:66)
06-11 21:31:20.510: E/AndroidRuntime(537):  at com.example.namesgenerator.dbAdapter.assetCopyDatabase(dbAdapter.java:117)
06-11 21:31:20.510: E/AndroidRuntime(537):  at com.example.namesgenerator.dbAdapter.assetOpenDatabase(dbAdapter.java:106)
06-11 21:31:20.510: E/AndroidRuntime(537):  ... 14 more

Answer 1

找不到用于为数据库设定种子的文件，它必须位于您计算机上的文件系统上（模拟器可以找到它）。

以下是Logcat的相关错误：

Caused by: java.io.FileNotFoundException: /data/data/com.example.namesgenerator/databases/names2.db

Answer 2

目录/data/data/com.example.namesgenerator/databases不存在或访问权限存在问题（您不允许在目录中创建文件，或者您不允许读取或修改现有文件）< / p>

Answer 3

在手机上转到

Settings->Storage

并验证是否未选择Mass storage only的标记。选择此选项后，您的设备无法访问SD卡以进行调试（一般情况下也不会出于其他目的）。这很可能是您的文件创建失败的原因。

手机上的应用程序错误，但模拟器上没有

3 个答案: