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      1 package com.android.launcher3.util;
      2 
      3 import android.content.ContentValues;
      4 import android.content.Context;
      5 import android.database.Cursor;
      6 import android.database.sqlite.SQLiteDatabase;
      7 import android.database.sqlite.SQLiteException;
      8 import android.database.sqlite.SQLiteFullException;
      9 import android.database.sqlite.SQLiteOpenHelper;
     10 import android.util.Log;
     11 
     12 /**
     13  * An extension of {@link SQLiteOpenHelper} with utility methods for a single table cache DB.
     14  * Any exception during write operations are ignored, and any version change causes a DB reset.
     15  */
     16 public abstract class SQLiteCacheHelper {
     17     private static final String TAG = "SQLiteCacheHelper";
     18 
     19     private final String mTableName;
     20     private final MySQLiteOpenHelper mOpenHelper;
     21 
     22     private boolean mIgnoreWrites;
     23 
     24     public SQLiteCacheHelper(Context context, String name, int version, String tableName) {
     25         mTableName = tableName;
     26         mOpenHelper = new MySQLiteOpenHelper(context, name, version);
     27 
     28         mIgnoreWrites = false;
     29     }
     30 
     31     /**
     32      * @see SQLiteDatabase#update(String, ContentValues, String, String[])
     33      */
     34     public void update(ContentValues values, String whereClause, String[] whereArgs) {
     35         if (mIgnoreWrites) {
     36             return;
     37         }
     38         try {
     39             mOpenHelper.getWritableDatabase().update(mTableName, values, whereClause, whereArgs);
     40         } catch (SQLiteFullException e) {
     41             onDiskFull(e);
     42         } catch (SQLiteException e) {
     43             Log.d(TAG, "Ignoring sqlite exception", e);
     44         }
     45     }
     46 
     47     /**
     48      * @see SQLiteDatabase#delete(String, String, String[])
     49      */
     50     public void delete(String whereClause, String[] whereArgs) {
     51         if (mIgnoreWrites) {
     52             return;
     53         }
     54         try {
     55             mOpenHelper.getWritableDatabase().delete(mTableName, whereClause, whereArgs);
     56         } catch (SQLiteFullException e) {
     57             onDiskFull(e);
     58         } catch (SQLiteException e) {
     59             Log.d(TAG, "Ignoring sqlite exception", e);
     60         }
     61     }
     62 
     63     /**
     64      * @see SQLiteDatabase#insertWithOnConflict(String, String, ContentValues, int)
     65      */
     66     public void insertOrReplace(ContentValues values) {
     67         if (mIgnoreWrites) {
     68             return;
     69         }
     70         try {
     71             mOpenHelper.getWritableDatabase().insertWithOnConflict(
     72                     mTableName, null, values, SQLiteDatabase.CONFLICT_REPLACE);
     73         } catch (SQLiteFullException e) {
     74             onDiskFull(e);
     75         } catch (SQLiteException e) {
     76             Log.d(TAG, "Ignoring sqlite exception", e);
     77         }
     78     }
     79 
     80     private void onDiskFull(SQLiteFullException e) {
     81         Log.e(TAG, "Disk full, all write operations will be ignored", e);
     82         mIgnoreWrites = true;
     83     }
     84 
     85     /**
     86      * @see SQLiteDatabase#query(String, String[], String, String[], String, String, String)
     87      */
     88     public Cursor query(String[] columns, String selection, String[] selectionArgs) {
     89         return mOpenHelper.getReadableDatabase().query(
     90                 mTableName, columns, selection, selectionArgs, null, null, null);
     91     }
     92 
     93     protected abstract void onCreateTable(SQLiteDatabase db);
     94 
     95     /**
     96      * A private inner class to prevent direct DB access.
     97      */
     98     private class MySQLiteOpenHelper extends SQLiteOpenHelper {
     99 
    100         public MySQLiteOpenHelper(Context context, String name, int version) {
    101             super(context, name, null, version);
    102         }
    103 
    104         @Override
    105         public void onCreate(SQLiteDatabase db) {
    106             onCreateTable(db);
    107         }
    108 
    109         @Override
    110         public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    111             if (oldVersion != newVersion) {
    112                 clearDB(db);
    113             }
    114         }
    115 
    116         @Override
    117         public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    118             if (oldVersion != newVersion) {
    119                 clearDB(db);
    120             }
    121         }
    122 
    123         private void clearDB(SQLiteDatabase db) {
    124             db.execSQL("DROP TABLE IF EXISTS " + mTableName);
    125             onCreate(db);
    126         }
    127     }
    128 }
    129