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最近的一个项目,需要用到很多数据,所以想的是用数据库的形式进行存储, 虽然安卓中自带的有创建数据库,表的操作,但是因为要插入的数据太多, 太麻烦,所以还是希望用可视化的软件进行制作,然后再导入到项目中. 因此我就用了SQliteStudio进行操作的.接下来我就讲讲如何解决我在这之中遇到的坑.
首先用SQliteStudio写好数据库之后,直接去你创建的文件夹去拷贝你创建的数据库,切记千万不要用软件导出来(因为导出来会选择一个格式,但是并没有发现db,所以导出来后就不是数据库了), 因为我就是导出来发现再用软件打开时打开不了,最好就直接拷贝出来. 这是我遇到的第一个坑.
接下来我拷贝的数据库,拷贝到资源目录(assets)下,然后就把数据库写到文件中(这里我写到了sd卡中,也可以写到/data/data/包名/databases/),我在网上搜了很多,但发现有很多都用不了,最后就自己取他们的有用的代码拼接加上自己写了一些.接下来我来贴下我自己的代码：
首先是SQLiteOpenHelper类
public class BookSqliteOpenHelper extends SQLiteOpenHelper {
public BookSqliteOpenHelper(Context context) {
super(context, "book.db", null, 1);
this.myContext = context;
}
private Context myContext;
//The Android's default system path of your application database.
private String DB_PATH = android.os.Environment.getExternalStorageDirectory().getAbsolutePath() + "/booksql/";
private static String DB_NAME = "book.db";
private static String ASSETS_NAME = "book.db";
private SQLiteDatabase myDataBase = null;
public void createDataBase() throws IOException {
boolean dbExist = checkDataBase();
if (!dbExist) {
try {
File dir = new File(DB_PATH);
if (!dir.exists()) {
dir.mkdir();
}
File dbf = new File(DB_PATH + DB_NAME);
if (dbf.exists()) {
dbf.delete();
}
SQLiteDatabase.openOrCreateDatabase(dbf, null);
copyDataBase();
} catch (IOException e) {
throw new Error("数据库创建失败");
}
}
}
private void copyDataBase() throws IOException {
InputStream myInput = null;
// try {
myInput = myContext.getAssets().open(ASSETS_NAME);
String outFileName = DB_PATH + DB_NAME;
OutputStream myOutput = new FileOutputStream(outFileName);
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer)) > 0) {
myOutput.write(buffer, 0, length);
}
myOutput.flush();
myOutput.close();
myInput.close();
// } catch (IOException e) {
// e.printStackTrace();
// }
}
private boolean checkDataBase() {
SQLiteDatabase checkDB = null;
String myPath = DB_PATH + DB_NAME;
try {
checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
} catch (SQLiteException e) { //database does't exist yet.
}
if (checkDB != null) {
checkDB.close();
}
return checkDB != null ? true : false;
}
@Override
public synchronized void close() {
if (myDataBase != null) {
myDataBase.close();
}
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}然后是Activity中的代码,因为这只是一个demo所以没有放在子线程中进行,希望大家注意. 这里第二个坑就是在获取SQLiteDatabase 的对象时必须要用SQLiteDatabase.openDatabase()或者SQLiteDatabase中其它几个方法,这样才可以对自己写出的文件进行查询.
public class MainActivity extends AppCompatActivity {
private String DB_PATH = android.os.Environment.getExternalStorageDirectory().getAbsolutePath() + "/booksql/";
private static String DB_NAME = "book.db";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
BookSqliteOpenHelper helper = new BookSqliteOpenHelper(this);
try {
helper.createDataBase();
} catch (IOException e) {
e.printStackTrace();
}
SQLiteDatabase database = SQLiteDatabase.openDatabase(DB_PATH+DB_NAME,null,SQLiteDatabase.OPEN_READWRITE);
Cursor cursor = database.query("book", null, null, null, null, null, null, null);
while (cursor.moveToNext()){
String bookname = cursor.getString(cursor.getColumnIndex("bookname"));
Log.i("11111111111111111",bookname);
}
}
}最后一个就是权限问题了
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/> <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/> <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>
根据下面网友提供的建议 在进行检查数据库存在时还可以用下面方法进行检测
private boolean checkDataBase() {
String myPath = DB_PATH + DB_NAME;
File file=new File(myPath);
return file.exists();
}