我想要做的是我有一个我在我的应用程序中创建的数据库。我正在从我的手机复制相同的数据库（我的手机已植根，因此我很容易将其复制并粘贴到我的手机上）。在我的Mac上通过SQLite Manager我插入数据（这样做是因为我有需要将csv文件导入到db中）以后我将相同的db文件复制到我的app数据库文件夹中。
问题是每当我尝试插入或读取db文件时，我的应用程序都会崩溃。
这是我的清单档案：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.uttara.dbpull">
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
这是我的DBhelper课程。
public class DHelper extends SQLiteOpenHelper {
private static final String DATABASE_NAME = "sampledata1";
private static final String TABLE_NAME="sampledata1";
private static final int DATABASE_VERSION = 1;
private static final String NUMBER="NUMBER";
private static final String NAME = "NAME";
private static final String SURNAME = "SURNAME";
private static final String MARKS = "MARKS";
private static final String SQL_CREATE_TABLE_SAMPLE = "CREATE TABLE sampledata1 (NUMBER INTEGER PRIMARY KEY, NAME TEXT, SURNAME TEXT, MARKS INTEGER)";
public DHelper(Context applicationcontext ) {
super(applicationcontext, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(SQL_CREATE_TABLE_SAMPLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS sampledata1");
onCreate(db);
}
public boolean insertData(String name,String surname,String marks){
SQLiteDatabase db=this.getWritableDatabase();
ContentValues contentValues=new ContentValues();
contentValues.put(NAME,name);
contentValues.put(SURNAME,surname);
contentValues.put(MARKS,marks);
long result = db.insert(TABLE_NAME,null,contentValues);
if (result == -1)
return false;
else
return true;
}
public Cursor getAllData(){
SQLiteDatabase db=this.getWritableDatabase();
Cursor res=db.rawQuery("SELECT * FROM " +TABLE_NAME,null);
return res;
}
}
我的MainActivity.class
public class MainActivity extends AppCompatActivity {
DHelper myDb;
EditText editname,editsurname,editmarks;
Button btnadd,btnview;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
myDb=new DHelper(this);
editname= (EditText) findViewById(R.id.editText_name);
editsurname= (EditText) findViewById(R.id.editText_surname);
editmarks= (EditText) findViewById(R.id.editText_marks);
btnadd= (Button) findViewById(R.id.button_add);
btnview= (Button) findViewById(R.id.button_view);
viewAll();
addData();
}
public void addData(){
btnadd.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
boolean isInserted= myDb.insertData(editname.getText().toString(),editsurname.getText().toString(),editmarks.getText().toString());
if (isInserted==true)
Toast.makeText(MainActivity.this,"Data inserted",Toast.LENGTH_SHORT).show();
else
Toast.makeText(MainActivity.this,"Data not inserted",Toast.LENGTH_SHORT).show();
}
});
}
public void viewAll(){
btnview.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Cursor res= myDb.getAllData();
if (res.getCount()==0){
showMessage("Error","NO DATA FOUND");
return;
}
StringBuffer buffer=new StringBuffer();
while (res.moveToNext()){
buffer.append("NUMBER :"+ res.getString(0)+"\n");
buffer.append("NAME :"+ res.getString(1)+"\n");
buffer.append("SURNAME :"+ res.getString(2)+"\n");
buffer.append("MARKS :"+ res.getString(3)+"\n\n");
}
showMessage("Alert",buffer.toString());
}
});
}
public void showMessage(String title,String Message){
AlertDialog.Builder builder=new AlertDialog.Builder(this);
builder.setCancelable(true);
builder.setTitle(title);
builder.setMessage(Message);
builder.show();
}
}
logcat的：
E/SQLiteDatabase: Failed to open database '/data/user/0/com.uttara.dbpull/databases/sampledata1'.
android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database
at android.database.sqlite.SQLiteConnection.nativeOpen(Native Method)
at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:237)
at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:221)
at android.database.sqlite.SQLiteConnectionPool.openConnectionLocked(SQLiteConnectionPool.java:468)
at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:190)
at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:182)
at android.database.sqlite.SQLiteDatabase.openInner(SQLiteDatabase.java:876)
at android.database.sqlite.SQLiteDatabase.open(SQLiteDatabase.java:856)
at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:754)
at android.app.ContextImpl.openOrCreateDatabase(ContextImpl.java:579)
at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:269)
at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:223)
at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:163)
at com.uttara.dbpull.DHelper.getAllData(DHelper.java:55)
at com.uttara.dbpull.MainActivity$2.onClick(MainActivity.java:50)
at android.view.View.performClick(View.java:5226)
at android.view.View$PerformClick.run(View.java:21266)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:168)
at android.app.ActivityThread.main(ActivityThread.java:5845)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:797)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:687)
--------- beginning of crash
07-05 11:29:06.732 16734-16734/com.uttara.dbpull E/AndroidRuntime: FATAL EXCEPTION: main Process: com.uttara.dbpull, PID: 16734
android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database
at android.database.sqlite.SQLiteConnection.nativeOpen(Native Method)
at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:237)
at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:221)
at android.database.sqlite.SQLiteConnectionPool.openConnectionLocked(SQLiteConnectionPool.java:468)
at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:190)
at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:182)
at android.database.sqlite.SQLiteDatabase.open(SQLiteDatabase.java:856)
at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:754)
at android.app.ContextImpl.openOrCreateDatabase(ContextImpl.java:579)
at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:269)
at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:223)
at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:163)
at com.uttara.dbpull.DHelper.getAllData(DHelper.java:55)
at com.uttara.dbpull.MainActivity$2.onClick(MainActivity.java:50)
at android.view.View.performClick(View.java:5226)
at android.view.View$PerformClick.run(View.java:21266)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:168)
at android.app.ActivityThread.main(ActivityThread.java:5845)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:797)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:687)
答案 0 :(得分：0)
首先，我将解释如何复制Android应用中的现有数据库架构以及处理SQLite DB的良好实践，以便它对其他人也有帮助。当您具有静态数据库模式时，这种方法很有用。
在Android应用程序中使用数据库对象的推荐方法是，在应用程序级别创建它并在整个应用程序中使用它。
public class MyApplication extends Application{
public DBHelper dbHelper;
@Override
public void onCreate() {
super.onCreate();
dbHelper = new DBHelper(getApplicationContext());
try {
dbHelper.createDataBase();
} catch (IOException e) {
e.printStackTrace();
}
}
}
不要忘记在application标记的AndroidManifest文件中提及您的应用程序名称。假设您的应用程序类名称是MyApplication，它位于com.app包中，然后应该是： -
机器人：名称= “com.app.MyApplication”
下面是DBHelper类，它作为我们的应用程序和本地数据库之间的桥梁。
public class DBHelper extends SQLiteOpenHelper{
public static final String DATABASE_NAME = "Your database name";
public static final int DATABASE_VERSION = 1;
private static String DB_PATH = "";
private SQLiteDatabase mDataBase;
private final Context mContext;
/**
* Called when the database is created for the first time. This is where the
* creation of tables and the initial population of the tables should happen.
*
* @param db The database.
*/
@Override
public void onCreate(SQLiteDatabase db) {
}
/**
* Called when the database needs to be upgraded. The implementation
* should use this method to drop tables, add tables, or do anything else it
* needs to upgrade to the new schema version.
* <p/>
* <p>
* The SQLite ALTER TABLE documentation can be found
* <a href="http://sqlite.org/lang_altertable.html">here</a>. If you add new columns
* you can use ALTER TABLE to insert them into a live table. If you rename or remove columns
* you can use ALTER TABLE to rename the old table, then create the new table and then
* populate the new table with the contents of the old table.
* </p><p>
* This method executes within a transaction. If an exception is thrown, all changes
* will automatically be rolled back.
* </p>
*
* @param db The database.
* @param oldVersion The old database version.
* @param newVersion The new database version.
*/
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
/**
* Create a helper object to create, open, and/or manage a database.
* This method always returns very quickly. The database is not actually
* created or opened until one of {@link #getWritableDatabase} or
* {@link #getReadableDatabase} is called.
*
* @param context to use to open or create the database
*/
public DBHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
if(android.os.Build.VERSION.SDK_INT >= 17){
DB_PATH = context.getApplicationInfo().dataDir + "/databases/";
}
else
{
DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
}
this.mContext = context;
}
/**
Check if the database already exist to avoid re-copying the file each time you open the application.
* @return true if it exists, false if it doesn't
*/
public boolean checkDataBase(){
SQLiteDatabase checkDB = null;
try{
String myPath = DB_PATH + DATABASE_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}catch(SQLiteException e){
//database does't exist yet.
}
if(checkDB != null){
checkDB.close();
}
return checkDB != null ? true : false;
}
/**
* Creates a empty database on the system and rewrites it with your own database.
* */
public void createDataBase() throws IOException {
boolean dbExist = checkDataBase();
if(dbExist){
//do nothing - database already exist
}else{
//By calling this method and empty database will be created into the default system path
//of your application so we are gonna be able to overwrite that database with our database.
this.getReadableDatabase();
try {
copyDataBase();
} catch (IOException e) {
throw new Error("Error copying database");
}
}
}
/**
* Copies your database from your local assets-folder to the just created empty database in the
* system folder, from where it can be accessed and handled.
* This is done by transfering bytestream.
* */
private void copyDataBase() throws IOException{
//Open your local db as the input stream
InputStream myInput = mContext.getAssets().open(DATABASE_NAME+".sqlite");
// Path to the just created empty db
String outFileName = DB_PATH + DATABASE_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 openDataBase() throws SQLException {
//Open the database
String myPath = DB_PATH + DATABASE_NAME;
mDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}
@Override
public synchronized void close() {
if(mDataBase != null)
mDataBase.close();
super.close();
}
}
现在这可能是解决您问题的方法。您只需要从您的活动中打开数据库，执行数据库操作，完成后再关闭它。以下是代码段： -
MyApplication application = (MyApplication) getApplicationContext();
application.dbHelper.openDataBase();
boolean isInserted=application.dbHelper.insertData(editname.getText().toString(),editsurname.getText().toString(),editmarks.getText().toString());
application.dbHelper.close();
我希望这会对你有所帮助。