android - 应用程序打开的文件太多 - Android

Question

我有一个名为 calcDays() 的方法，它一遍又一遍地循环遍历数据库，直到满足特定条件。问题是 Android Studio 告诉我文件用完了。我意识到我正在打开数据库而不是关闭它们，这就是我出现错误的原因。但是，我似乎无法修复此错误。

用 calcDays() 方法类

    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();
    }
}

数据库助手类

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

Answer 1

您应该只创建 a single SqliteOpenHelper object适用于您的整个应用程序，并在需要访问数据库的任何地方使用它。这将防止并发访问数据库时出现很多问题。