我有一个数据库，我想要执行SQL语句，即文件 但我在InputStream行上得到一个例外，我不知道为什么 请帮我解决这个问题。
package com.example.hasana.databases;
import android.content.Context;
import android.content.res.AssetManager;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.provider.BaseColumns;
import android.util.Log;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
/**
* Created by hasana on 1/14/2016.
*/
public class DatabaseHelper extends SQLiteOpenHelper implements BaseColumns {
private static final String DATABASE_NAME = "mydatabase.db";
private static final int DATABASE_VERSION = 1;
public static final String CAT_NAME_COLUMN = "gruppa";
public static final String PHONE_COLUMN = "name";
public static final String AGE_COLUMN = "age";
private static final String DATABASE_TABLE = "cats";
Context mycont;
String libraryPath;
String sql;
DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
mycont=context;
}
public DatabaseHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
Log.d("mytag", "readFile");
// try {
// insertFromFile(mycont,R.raw.sqlstat);
// } catch (IOException e) {
// e.printStackTrace();
// }
db.execSQL(sql);
}
/**
* This reads a file from the given Resource-Id and calls every line of it as a SQL-Statement
*
* @param context
*
* @param resourceId
* e.g. R.raw.food_db
*
* @return Number of SQL-Statements run
* @throws IOException
*/
public void insertFromFile(Context context, int resourceId) throws IOException {
// Open the resource
InputStream insertsStream = context.getResources().openRawResource(resourceId);
BufferedReader insertReader = new BufferedReader(new InputStreamReader(insertsStream));
// Iterate through lines (assuming each insert has its own line and theres no other stuff)
while (insertReader.ready()) {
sql += insertReader.readLine();
}
insertReader.close();
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// Запишем в журнал
Log.w("SQLite", "Обновляемся с версии " + oldVersion + " на версию " + newVersion);
// Удаляем старую таблицу и создаём новую
db.execSQL("DROP TABLE IF IT EXISTS " + DATABASE_TABLE);
// Создаём новую таблицу
onCreate(db);
}
}
但在InputStream insertsStream = context.getResources().openRawResource(resourceId);我得到了一个例外
FATAL EXCEPTION: main Process: com.example.hasana.databases, PID: 21716
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.hasana.databases/com.example.hasana.databases.MainActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2184)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
at android.app.ActivityThread.access$800(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at android.database.DatabaseUtils.getSqlStatementType(DatabaseUtils.java:1375)
at android.database.sqlite.SQLiteDatabase.executeSql(SQLiteDatabase.java:1659)
at android.database.sqlite.SQLiteDatabase.execSQL(SQLiteDatabase.java:1603)
at com.example.hasana.databases.DatabaseHelper.onCreate(DatabaseHelper.java:53)
at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:252)
at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:164)
at com.example.hasana.databases.MainActivity.onCreate(MainActivity.java:23)
at android.app.Activity.performCreate(Activity.java:5231)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2148)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
at android.app.ActivityThread.access$800(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：0)
我解决了这个问题。 问题是我有两个构造函数，我首先接收上下文但是调用第二个构造。我添加mycont = context;在第二个构造函数和它;它确定
image = Magick::Image.read(original_image_path).first
image.change_geometry!(@attributes['width']+"x"+
@attributes['height']) { |cols, rows, img|
newimg = img.resize(cols, rows)
newimg.write(new_filename)
}