我有一个名为calcDays（）的方法，它一遍又一遍地遍历数据库，直到满足某个条件。问题是Android工作室告诉我我的文件用完了。我意识到我打开数据库并没有关闭它们，这就是我有错误的原因。但是，我似乎无法解决此错误。
使用calcDays（）方法的类
package com.example.brandon.netflixcalculator;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.sql.SQLException;
import java.util.Calendar;
public class MainActivity extends Activity {
private Button b1;
private Button b2;
private Button b3;
private Button b4;
private TextView daysRemaining, showName;;
private int x;
private int[] dailyMin = new int[7];
private String[] dailyPercent = {"100%", "75%", "50%", "25%", "0%"};
private double[] percent = {1, .75, .5, .25, 0};
private DatabaseHelper db;
String[] stringDays = {"Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"};
private File viewingInfo;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setOnButton1ClickListener();
setOnButton2ClickListener();
setOnButton3ClickListener();
setOnButton4ClickListener();
daysRemaining = (TextView)findViewById(R.id.textViewRemainingDays);
showName = (TextView)findViewById(R.id.textViewCurrentShow);
if(!ifFileExists()){
createDBFirstTime();
}
else{
db = new DatabaseHelper(getApplicationContext());
daysRemaining.setText(String.valueOf(calcDays()));
showName.setText(db.getShowName());
}
}
public void createDBFirstTime(){
System.out.println("Database deleted? " + this.deleteDatabase("viewing_database"));
db = new DatabaseHelper(this.getApplicationContext());
for(int i = 0; i < stringDays.length; i++){
db.insertDataViewing(stringDays[i], 0, "100%");
}
db.insertDataShow("N/A", 0, 0, 0);
try {
FileOutputStream fos = openFileOutput("madeDB", MODE_PRIVATE);
try {
fos.write("true".getBytes());
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
public boolean ifFileExists(){
File file = getApplicationContext().getFileStreamPath("madeDB");
if(file.exists())
return true;
else return false;
}
public int calcDays() {
int seasons, episodes, epiLength;
int[] info = new int[3];
for(int i = 0; i < info.length; i++){
info[i] = db.extractShowInfo()[i];
}
seasons = info[0];
episodes = info[1];
epiLength = info[2];
int totalTime = (seasons * episodes * epiLength);
System.out.println(seasons);
int dayOfWeek = getDay();
int days = 0;
int y;
double z;
while (totalTime > 0) {
y = db.getMin(dayOfWeek);
z = db.getPercentage(dayOfWeek);
totalTime -= y*z;
dayOfWeek++;
if (dayOfWeek == 7) {
dayOfWeek = 0;
}
days++;
}
return days;
}
public int getDay() {
Calendar calendar = Calendar.getInstance();
int day = calendar.get(Calendar.DAY_OF_WEEK);
return day;
}
public void setOnButton1ClickListener() {
b1 = (Button) findViewById(R.id.button);
b1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent i = new Intent("com.example.brandon.netflixcalculator.RoughGuessActivity");
startActivity(i);
}
});
}
public void setOnButton2ClickListener() {
b2 = (Button) findViewById(R.id.button2);
b2.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent i = new Intent("com.example.brandon.netflixcalculator.Exact_Activity");
startActivity(i);
}
});
}
public void setOnButton3ClickListener() {
b3 = (Button) findViewById(R.id.button3);
b3.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent i = new Intent("com.example.brandon.netflixcalculator.ShowInfoActivity");
startActivity(i);
}
});
}
public void setOnButton4ClickListener() {
b4 = (Button) findViewById(R.id.btnUpdate);
b4.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
System.out.println("-----------------------------------------------------");
System.out.println(calcDays());
showMessage("Days remaining", String.valueOf(calcDays()));
daysRemaining.setText(String.valueOf(calcDays()));
}
});
}
public int getTotalMin(){
int x = 0;
Cursor res = db.getWritableDatabase().rawQuery("select MINUTES from VIEWING", null);
StringBuffer sb = new StringBuffer();
while(res.moveToNext()){
x += Integer.parseInt(res.getString(0));
}
return x;
}
public void readDB(){
Cursor res = db.getAllData("SHOW_INFO");
if (res.getCount() == 0) {
showMessage("Error", "No data found");
return;
}
StringBuffer sb = new StringBuffer();
while (res.moveToNext()) {
sb.append("\nName: " + res.getString(1) + "\nSeasons: "
+ res.getString(2) + "\nEpisodes: " + res.getString(3) + "\nEpisode Length: " +
res.getString(4));
}
showMessage("Test", sb.toString());
db.close();
}
public void showMessage(String title, String msg){
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setCancelable(true);
builder.setTitle(title);
builder.setMessage(msg);
builder.show();
}
}
DatabaseHelper Class
public class DatabaseHelper extends SQLiteOpenHelper{
private static final String dbName = "viewing_database";
private static final String tableViewing = "VIEWING";
private static final String tableShowInfo = "SHOW_INFO";
private static final String COL_1 = "ID";
private static final String COL_2 = "WEEKDAY";
private static final String COL_3 = "MINUTES";
private static final String COL_4 = "PERCENTAGE";
private static DatabaseHelper sInstance;
public DatabaseHelper(Context context) {
super(context, dbName, null, 1);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table " + tableViewing + " (ID INTEGER PRIMARY KEY AUTOINCREMENT, WEEKDAY TEXT, MINUTES INTEGER, PERCENTAGE TEXT)");
db.execSQL("create table " + tableShowInfo + " (ID INTEGER PRIMARY KEY AUTOINCREMENT, NAME TEXT, SEASONS INTEGER, EPISODES INTEGER," +
" EPISODE_LENGTH INTEGER)");
}
public static synchronized DatabaseHelper getInstance(Context context) {
// Use the application context, which will ensure that you
// don't accidentally leak an Activity's context.
if (sInstance == null) {
sInstance = new DatabaseHelper(context.getApplicationContext());
}
return sInstance;
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + tableViewing);
db.execSQL("DROP TABLE IF EXISTS " + tableShowInfo);
onCreate(db);
}
public boolean updateDataViewing(String id, String weekday, int minutes, String percentage){
SQLiteDatabase myDataBase = this.getWritableDatabase();
ContentValues cv = new ContentValues();
cv.put(COL_1, id);
cv.put(COL_2, weekday);
cv.put(COL_3, minutes);
cv.put(COL_4, percentage);
myDataBase.update(tableViewing, cv, "ID = ?", new String[]{id});
myDataBase.close();
return true;
}
public boolean updateDataShow(String id, String name, int seasons, int episodes, int episodeLength){
SQLiteDatabase myDataBase = this.getWritableDatabase();
ContentValues cv = new ContentValues();
cv.put(COL_1, id);
cv.put("NAME", name);
cv.put("SEASONS", seasons);
cv.put("EPISODES", episodes);
cv.put("EPISODE_LENGTH", episodeLength);
myDataBase.update(tableShowInfo, cv, "ID = ?", new String[]{id});
return true;
}
public double getPercentage(int id){
SQLiteDatabase myDataBase = this.getWritableDatabase();
Cursor res = myDataBase.rawQuery("select PERCENTAGE from " + tableViewing + " where ID =" + id, null);
if (res.getCount() == 0) {
return 0;
}
StringBuffer sb = new StringBuffer();
while (res.moveToNext()) {
sb.append(res.getString(0));
}
String msg = sb.toString();
myDataBase.close();
return Integer.parseInt(msg.substring(0, msg.length()-1)) / 100.0;
}
public int getMin(int id){
SQLiteDatabase myDataBase = this.getWritableDatabase();
Cursor res = myDataBase.rawQuery("select MINUTES from " + tableViewing + " where ID =" + id, null);
if (res.getCount() == 0) {
return 0;
}
StringBuffer sb = new StringBuffer();
while (res.moveToNext()) {
sb.append(res.getString(0));
}
myDataBase.close();
return Integer.parseInt(sb.toString());
}
public Cursor getAllData(String tableName){
SQLiteDatabase myDataBase = this.getWritableDatabase();
Cursor res = myDataBase.rawQuery("select * from " + tableName, null);
return res;
}
public boolean insertDataViewing(String dayOfWeek, int minutes, String percentage){
SQLiteDatabase myDataBase = getWritableDatabase();
ContentValues cv = new ContentValues();
cv.put(COL_2, dayOfWeek);
cv.put(COL_3, minutes);
cv.put(COL_4, percentage);
double result = myDataBase.insert(tableViewing, null, cv);
myDataBase.close();
return(result != -1);
}
public boolean insertDataShow(String name, int seasons, int episodes, int episodeLength){
SQLiteDatabase myDataBase = getWritableDatabase();
ContentValues cv = new ContentValues();
cv.put("NAME", name);
cv.put("SEASONS", seasons);
cv.put("EPISODES", episodes);
cv.put("EPISODE_LENGTH", episodeLength);
double result = myDataBase.insert(tableShowInfo, null, cv);
myDataBase.close();
return(result != -1);
}
public String getShowName(){
Cursor res = getAllData("SHOW_INFO");
if (res.getCount() == 0) {
System.out.println("No data found");
return "N/A";
}
StringBuffer sb = new StringBuffer();
while (res.moveToNext()) {
sb.append(res.getString(1));
}
return sb.toString();
}
public int[] extractShowInfo() {
int[] info = new int[3];
Cursor res = getAllData("SHOW_INFO");
if (res.getCount() == 0) {
System.out.println("No data found");
return new int[] {0, 0, 0};
}
while(res.moveToNext()){
info[0] = Integer.parseInt(res.getString(2)); //seasons
info[1] = Integer.parseInt(res.getString(3)); //episodes
info[2] = Integer.parseInt(res.getString(4)); //episode length
}
for(int x:info){
System.out.println(x);
}
return info;
}
}
最后是错误
04-06 13:59:22.081 1327-1327/com.example.brandon.netflixcalculator W/SQLiteLog: (28) failed to open "/data/user/0/com.example.brandon.netflixcalculator/databases/viewing_database-journal" with flag (131072) and mode_t (1b0) due to error (24)
04-06 13:59:22.081 1327-1327/com.example.brandon.netflixcalculator E/SQLiteLog: (14) cannot open file at line 31517 of [2ef4f3a5b1]
04-06 13:59:22.081 1327-1327/com.example.brandon.netflixcalculator E/SQLiteLog: (14) os_unix.c:31517: (24) open(/data/user/0/com.example.brandon.netflixcalculator/databases/viewing_database-journal) -
04-06 13:59:22.081 1327-1327/com.example.brandon.netflixcalculator W/SQLiteLog: (28) failed to open "/data/user/0/com.example.brandon.netflixcalculator/databases/viewing_database-journal" with flag (131074) and mode_t (1b0) due to error (24)
04-06 13:59:22.081 1327-1327/com.example.brandon.netflixcalculator W/SQLiteLog: (28) failed to open "/data/user/0/com.example.brandon.netflixcalculator/databases/viewing_database-journal" with flag (131072) and mode_t (1b0) due to error (24)
04-06 13:59:22.081 1327-1327/com.example.brandon.netflixcalculator E/SQLiteLog: (14) cannot open file at line 31517 of [2ef4f3a5b1]
04-06 13:59:22.081 1327-1327/com.example.brandon.netflixcalculator E/SQLiteLog: (14) os_unix.c:31517: (24) open(/data/user/0/com.example.brandon.netflixcalculator/databases/viewing_database-journal) -
04-06 13:59:22.081 1327-1327/com.example.brandon.netflixcalculator E/SQLiteLog: (2062) statement aborts at 9: [select PERCENTAGE from VIEWING where ID =4] unable to open database file
04-06 13:59:22.091 1327-1327/com.example.brandon.netflixcalculator E/SQLiteQuery: exception: unable to open database file (code 2062)
#################################################################
Error Code : 2062 (SQLITE_CANTOPEN_EMFILE)
Caused By : Application has opened two many files. Maximum of available file descriptors in one process is 1024 in default.
(unable to open database file (code 2062))
#################################################################; query: select PERCENTAGE from VIEWING where ID =4
04-06 13:59:22.091 1327-1327/com.example.brandon.netflixcalculator D/AndroidRuntime: Shutting down VM
04-06 13:59:22.091 1327-1327/com.example.brandon.netflixcalculator E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.brandon.netflixcalculator, PID: 1327
android.database.sqlite.SQLiteCantOpenDatabaseException: unable to open database file (code 2062)
#################################################################
Error Code : 2062 (SQLITE_CANTOPEN_EMFILE)
Caused By : Application has opened two many files. Maximum of available file descriptors in one process is 1024 in default.
(unable to open database file (code 2062))
#################################################################
at android.database.sqlite.SQLiteConnection.nativeExecuteForCursorWindow(Native Method)
at android.database.sqlite.SQLiteConnection.executeForCursorWindow(SQLiteConnection.java:980)
at android.database.sqlite.SQLiteSession.executeForCursorWindow(SQLiteSession.java:836)
at android.database.sqlite.SQLiteQuery.fillWindow(SQLiteQuery.java:62)
at android.database.sqlite.SQLiteCursor.fillWindow(SQLiteCursor.java:143)
at android.database.sqlite.SQLiteCursor.getCount(SQLiteCursor.java:132)
at com.example.brandon.netflixcalculator.DatabaseHelper.getPercentage(DatabaseHelper.java:83)
at com.example.brandon.netflixcalculator.MainActivity.calcDays(MainActivity.java:108)
at com.example.brandon.netflixcalculator.MainActivity$4.onClick(MainActivity.java:166)
at android.view.View.performClick(View.java:5697)
at android.widget.TextView.performClick(TextView.java:10815)
at android.view.View$PerformClick.run(View.java:22526)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7229)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
04-06 13:59:28.401 1327-1338/com.example.brandon.netflixcalculator W/SQLiteConnectionPool: A SQLiteConnection object for database '+data+user+0+com_example_brandon_netflixcalculator+databases+viewing_database' was leaked! Please fix your application to end transactions in progress properly and to close the database when it is no longer needed.
04-06 14:04:22.231 1327-1327/com.example.brandon.netflixcalculator I/Process: Sending signal. PID: 1327 SIG: 9
答案 0 :(得分：12)
您应该只为整个应用创建a single SqliteOpenHelper object，并在需要数据库访问权限的地方使用它。这将防止并发访问数据库时出现很多问题。
答案 1 :(得分：8)
我遇到了同样的问题，我设法解决了这个问题，方法是通过调用以下内容来关闭游标：
cursor.close（）;
我在循环中创建了一个Cursor类的新对象而没有关闭它。在小循环迭代中，它工作正常，在数据变大和循环迭代之后，我开始看到这个问题。