我创建了一个带有数据库的应用程序，该数据库位于资产文件夹中。我编写了一段代码来将数据库复制到SD卡上，并且当然需要在Android 6+上运行时权限。我的问题是：在授予权限后第一次运行时，数据库不会加载，但第二次运行没有问题。请帮助我解决这个问题。
更新：问题已经解决！现在我的问题在于“最爱”部分。当我添加某些内容到最爱时，它无法更新，并且我必须重新启动应用程序，而且每次运行时数据都会显示多次。
以下是我的代码：
更新：问题已经解决！现在我的问题在于“最爱”部分。当我添加某些内容到最爱时，它无法更新，并且我必须重新启动应用程序，而且每次运行时数据都会显示多次。
以下是我的代码：
package farmani.com.essentialwordsforielts.mainPage;
import android.Manifest;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Build;
import android.os.Environment;
import android.support.annotation.NonNull;
import android.support.design.widget.NavigationView;
import android.support.design.widget.TabLayout;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v4.view.ViewPager;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Gravity;
import android.view.MenuItem;
import android.view.View;
import android.widget.ImageView;
import android.widget.Toast;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import farmani.com.essentialwordsforielts.R;
import farmani.com.essentialwordsforielts.search.ActivitySearch;
public class MainActivity extends AppCompatActivity {
public static Context context;
public static ArrayList<Structure> list = new ArrayList<>();
public static ArrayList<Structure> favorite = new ArrayList<>();
DrawerLayout drawerLayout;
NavigationView navigationView;
ImageView hamburger;
SQLiteDatabase database;
String destPath;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.navigation_activity_main);
if (Build.VERSION.SDK_INT >= 23) {
if (ContextCompat.checkSelfPermission(MainActivity.this,
Manifest.permission.READ_EXTERNAL_STORAGE) !=
PackageManager.PERMISSION_GRANTED) {
ActivityCompat.requestPermissions(MainActivity.this
, new String[]{Manifest.permission.READ_EXTERNAL_STORAGE
, Manifest.permission.WRITE_EXTERNAL_STORAGE}
, 1);
} else if (ContextCompat.checkSelfPermission(MainActivity.this,
Manifest.permission.WRITE_EXTERNAL_STORAGE) !=
PackageManager.PERMISSION_GRANTED) {
ActivityCompat.requestPermissions(MainActivity.this
, new String[]{Manifest.permission.READ_EXTERNAL_STORAGE
, Manifest.permission.WRITE_EXTERNAL_STORAGE}
, 1);
} else {
setupDB();
selectList();
selectFavorite();
Toast.makeText(MainActivity.this, "You grandet earlier",
Toast.LENGTH_LONG).show();
}
}
if (!favorite.isEmpty()){
favorite.clear();
selectFavorite();
} else if (!list.isEmpty()){
list.clear();
selectList();
}
context = getApplicationContext();
setTabOption();
drawerLayout = findViewById(R.id.navigation_drawer);
navigationView = findViewById(R.id.navigation_view);
hamburger = findViewById(R.id.hamburger);
hamburger.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
drawerLayout.openDrawer(Gravity.START);
}
});
navigationView.setNavigationItemSelectedListener(new
NavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
int id = item.getItemId();
if (id == R.id.exit) {
AlertDialog.Builder alertDialog = new AlertDialog.Builder(
MainActivity.this);
alertDialog.setTitle(R.string.exit);
alertDialog.setMessage(R.string.exit_ask);
alertDialog.setCancelable(false);
alertDialog.setPositiveButton(R.string.yes,
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int
which) {
finish();
}
});
alertDialog.setNegativeButton(R.string.no,
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int
which) {
dialog.cancel();
}
});
alertDialog.show();
}
if (id == R.id.search) {
Intent intent = new Intent(MainActivity.this,
ActivitySearch.class);
MainActivity.this.startActivity(intent);
}
return true;
}
});
}
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[]
permissions, @NonNull int[] grantResults) {
switch (requestCode) {
case 1: {
if (grantResults.length >= 2 && grantResults[0] ==
PackageManager.PERMISSION_GRANTED && grantResults[1] ==
PackageManager.PERMISSION_GRANTED) {
Toast.makeText(MainActivity.this, "Access granted",
Toast.LENGTH_LONG).show();
}
}
}
}
@Override
public void onBackPressed() {
if (drawerLayout.isDrawerOpen(Gravity.START)) {
drawerLayout.closeDrawer(Gravity.START);
} else {
AlertDialog.Builder alertDialog = new AlertDialog.Builder(
MainActivity.this);
alertDialog.setTitle(R.string.exit);
alertDialog.setMessage(R.string.exit_ask);
alertDialog.setCancelable(false);
alertDialog.setPositiveButton(R.string.yes,
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
finish();
}
});
alertDialog.setNegativeButton(R.string.no,
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
alertDialog.show();
}
}
private void setTabOption() {
ViewPager viewPager = findViewById(R.id.viewpager);
viewPager.setAdapter(new AdapterFragment(getSupportFragmentManager(),
context));
TabLayout tabStrip = findViewById(R.id.tabs);
tabStrip.setupWithViewPager(viewPager);
}
private void setupDB() {
try {
destPath =
Environment.getExternalStorageDirectory().getAbsolutePath()
+ "/ielts/";
File file = new File(destPath);
if (!file.exists()) {
file.mkdirs();
file.createNewFile();
CopyDB(getBaseContext().getAssets().open("md_book.db"),
new FileOutputStream(destPath + "/md_book.db"));
}
} catch (IOException e1) {
e1.printStackTrace();
}
}
@Override
protected void onResume() {
super.onResume();
if (!favorite.isEmpty()){
favorite.clear();
selectFavorite();
} else if (!list.isEmpty()){
list.clear();
selectList();
}
}
private void CopyDB(InputStream inputStream, OutputStream outputStream)
throws IOException {
byte[] buffer = new byte[1024];
int length;
while ((length = inputStream.read(buffer)) > 0) {
outputStream.write(buffer, 0, length);
}
inputStream.close();
outputStream.close();
}
private void selectFavorite() {
database = SQLiteDatabase.openOrCreateDatabase(destPath + "/md_book.db",
null);
Cursor cursor = database.rawQuery("SELECT * FROM main WHERE fav = 1",
null);
while (cursor.moveToNext()) {
String word = cursor.getString(cursor.getColumnIndex("word"));
String definition =
cursor.getString(cursor.getColumnIndex("definition"));
String trans = cursor.getString(cursor.getColumnIndex("trans"));
String img = cursor.getString(cursor.getColumnIndex("img"));
int id = cursor.getInt(cursor.getColumnIndex("id"));
Structure struct = new Structure(word, definition, trans, img, id);
struct.setWord(word);
struct.setDefinition(definition);
struct.setTrans(trans);
struct.setImg(img);
struct.setId(id);
favorite.add(struct);
}
}
private void selectList() {
database = SQLiteDatabase.openOrCreateDatabase(destPath + "/md_book.db",
null);
Cursor cursor = database.rawQuery("SELECT * FROM main", null);
while (cursor.moveToNext()) {
String word = cursor.getString(cursor.getColumnIndex("word"));
String definition =
cursor.getString(cursor.getColumnIndex("definition"));
String trans = cursor.getString(cursor.getColumnIndex("trans"));
String img = cursor.getString(cursor.getColumnIndex("img"));
int id = cursor.getInt(cursor.getColumnIndex("id"));
Structure struct = new Structure(word, definition, trans, img, id);
struct.setWord(word);
struct.setDefinition(definition);
struct.setTrans(trans);
struct.setImg(img);
struct.setId(id);
list.add(struct);
}
}
}