java - 即使应用成功地从 Assets 文件夹打开数据库，也没有找到这样的表

Question

我是 Android 开发的新手。我正在尝试使用存储在我的 Assets 文件夹中的预填充数据库。日志显示数据库已打开，但显示“NO SUCH TABLE ERROR”。我找不到解决此错误的任何方法。请帮忙。

我的数据库.java :

package com.example.android.atlas;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteQueryBuilder;

import com.readystatesoftware.sqliteasset.SQLiteAssetHelper;

/**
 * Created by Deep on 22-06-2015.
 */
public class MyDatabase extends SQLiteAssetHelper {

private static final String DATABASE_NAME = "appver-1.db";
private static final int DATABASE_VERSION = 1;

public MyDatabase(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);

    // you can use an alternate constructor to specify a database location
    // (such as a folder on the sd card)
    // you must ensure that this folder is available and you have permission
    // to write to it
    //super(context, DATABASE_NAME, context.getExternalFilesDir(null).getAbsolutePath(), null, DATABASE_VERSION);

}

public SQLiteDatabase getData() {

    SQLiteDatabase db = getReadableDatabase();

    return db;

     }
}

PlayActivity.java

public class PlayActivity extends Activity {
private MyDatabase db;
private SQLiteDatabase dbh;
private Cursor togo;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    db = new MyDatabase(this);
    dbh = db.getData();
    setContentView(R.layout.activity_play);
}

public void onClickGo(View view){


    String nm1;
    String nm2;
    String nm3;
    String sendsql,send;
    char last;
    int l;
    TextView tv2_text, tv4_text;
    EditText et1_input;
    tv2_text = (TextView)findViewById(R.id.tv2_text);
    tv4_text = (TextView)findViewById(R.id.tv4_text);
    et1_input = (EditText)findViewById(R.id.et1_input);
    nm1 = et1_input.getText().toString();
    l = nm1.length();
    last = nm1.charAt(l - 1);
    nm2 = "Africa";
    nm3 = "A";
    sendsql = "Select PLACES from countries where PLACES like " + "'" + nm3 + "%'" + " LIMIT 1" ;
    togo = dbh.rawQuery(sendsql,null);
    togo.moveToFirst();
    send = togo.getString(0);
    tv2_text.setText(send);
    tv4_text.setText("A");
}

LOGCAT 结果:

06-23 11:57:57.193    2330-2330/? I/SQLiteAssetHelper﹕ successfully opened     database appver-1.db
06-23 11:57:57.294    2330-2345/? W/EGL_emulation﹕ eglSurfaceAttrib not implemented
06-23 11:57:57.294    2330-2345/? W/OpenGLRenderer﹕ Failed to set   EGL_SWAP_BEHAVIOR on surface 0xa5d8a300, error=EGL_SUCCESS
06-23 11:57:57.497    1234-1257/? I/ActivityManager﹕ Displayed com.example.android.atlas/.PlayActivity: +346ms
06-23 11:57:57.623    2330-2345/? D/OpenGLRenderer﹕ endAllStagingAnimators on 0xa6d6e400 (RippleDrawable) with handle 0xae1bb990
06-23 11:57:58.842    2330-2330/? E/SQLiteLog﹕ (1) no such table: COUNTRIES
06-23 11:57:58.843    2330-2330/? D/AndroidRuntime﹕ Shutting down VM
06-23 11:57:58.843    2330-2330/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.android.atlas, PID: 2330
java.lang.IllegalStateException: Could not execute method of the activity
        at android.view.View$1.onClick(View.java:4007)
        at android.view.View.performClick(View.java:4756)
        at android.view.View$PerformClick.run(View.java:19749)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5221)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at   com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
 Caused by: java.lang.reflect.InvocationTargetException
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at android.view.View$1.onClick(View.java:4002)
at android.view.View.performClick(View.java:4756)
        at android.view.View$PerformClick.run(View.java:19749)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5221)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
 Caused by: android.database.sqlite.SQLiteException: no such table: COUNTRIES (code 1): , while compiling: SELECT * FROM COUNTRIES
        at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
        at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:889)
        at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:500)
        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:44)
        at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1316)
        at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1255)
        at com.example.android.atlas.PlayActivity.onClickGo(PlayActivity.java:53)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at android.view.View$1.onClick(View.java:4002)
        at android.view.View.performClick(View.java:4756)
        at android.view.View$PerformClick.run(View.java:19749)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5221)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
06-23 11:57:58.851    1234-1508/? W/ActivityManager﹕ Force finishing activity com.example.android.atlas/.PlayActivity

Answer 1

您应该将 .db 文件从 Assets 文件夹复制到内部/外部存储。您可以使用以下代码，

private static String DB_PATH = "/data/data/your package/database/";  
private static String DB_NAME ="final.db";// Database name 

要创建一个数据库，

public void createDataBase() throws IOException 
{ 
  //If database not exists copy it from the assets 

   boolean mDataBaseExist = checkDataBase(); 
   if(!mDataBaseExist) 
   { 
      try  
      { 
        //Copy the database from assests 
        copyDataBase(); 
        Log.e(TAG, "createDatabase database created"); 
      }  
      catch (IOException mIOException)  
      { 
         throw new Error("ErrorCopyingDataBase"); 
     } 
  } 
} 

检查数据库是否存在:/data/data/your package/database/DB Name

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

从 Assets 中复制数据库

  private void copyDataBase() throws IOException 
  { 
    InputStream mInput = getApplicationContext().getAssets().open(DB_NAME); 
    String outFileName = DB_PATH + DB_NAME; 
    OutputStream mOutput = new FileOutputStream(outFileName); 
    byte[] mBuffer = new byte[1024]; 
    int mLength; 
    while ((mLength = mInput.read(mBuffer))>0) 
    { 
        mOutput.write(mBuffer, 0, mLength); 
    } 
    mOutput.flush(); 
    mOutput.close(); 
    mInput.close(); 
}

希望对您有所帮助。

这link也可以帮助你...