我是Android新手，并使用教程自学了应用程序中的SQLite数据库。
目前，我遇到了如何处理SQLite中的图像并使用TextView描述在ListView中显示它的问题......这些是我的类：
DatabaseHelper
public class DatabaseHelper extends SQLiteOpenHelper {
// Table Name
public static final String TABLE_NAME = "COUNTRIES";
// Table columns
public static final String _ID = "_id";
public static final String SUBJECT = "subject";
public static final String DESC = "description";
public static final String KEY_IMAGE = "image";
// Database Information
static final String DB_NAME = "JOURNALDEV_COUNTRIES.DB";
// database version
static final int DB_VERSION = 5;
// Creating table query
private static final String CREATE_TABLE = "create table " + TABLE_NAME + "(" + _ID
+ " INTEGER PRIMARY KEY AUTOINCREMENT, " + SUBJECT + " TEXT NOT NULL, " + DESC + " TEXT," +
KEY_IMAGE + " BLOB);";
public DatabaseHelper(Context context) {
super(context, DB_NAME, null, DB_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
onCreate(db);
}
public void insertBitmap(Bitmap bm) {
// Convert the image into byte array
ByteArrayOutputStream out = new ByteArrayOutputStream();
bm.compress(Bitmap.CompressFormat.JPEG, 100, out);
byte[] buffer=out.toByteArray();
// Open the database for writing
SQLiteDatabase db = this.getWritableDatabase();
// Start the transaction.
db.beginTransaction();
ContentValues values;
try
{
values = new ContentValues();
values.put("image", buffer);
// Insert Row
long i = db.insert(TABLE_NAME, null, values);
Log.i("Insert", i + "");
// Insert into database successfully.
db.setTransactionSuccessful();
}
catch (SQLiteException e)
{
e.printStackTrace();
}
finally
{
db.endTransaction();
// End the transaction.
db.close();
// Close database
}
}
public Bitmap getBitmap(int id){
Bitmap bitmap = null;
// Open the database for reading
SQLiteDatabase db = this.getReadableDatabase();
// Start the transaction.
db.beginTransaction();
try
{
String selectQuery = "SELECT * FROM "+ TABLE_NAME+" WHERE id = " + id;
Cursor cursor = db.rawQuery(selectQuery, null);
if(cursor.getCount() >0)
{
while (cursor.moveToNext()) {
// Convert blob data to byte array
byte[] blob = cursor.getBlob(cursor.getColumnIndex("image"));
// Convert the byte array to Bitmap
bitmap= BitmapFactory.decodeByteArray(blob, 0, blob.length);
}
}
db.setTransactionSuccessful();
}
catch (SQLiteException e)
{
e.printStackTrace();
}
finally
{
db.endTransaction();
// End the transaction.
db.close();
// Close database
}
return bitmap;
} }
的DatabaseManager
public class DBManager {
private DatabaseHelper dbHelper;
private Context context;
private SQLiteDatabase database;
public DBManager(Context c) {
context = c;
}
public DBManager open() throws SQLException {
dbHelper = new DatabaseHelper(context);
database = dbHelper.getWritableDatabase();
return this;
}
public void close() {
dbHelper.close();
}
public void insert(String name, String desc, String image) {
ContentValues contentValue = new ContentValues();
contentValue.put(DatabaseHelper.SUBJECT, name);
contentValue.put(DatabaseHelper.DESC, desc);
contentValue.put(DatabaseHelper.KEY_IMAGE, image);
database.insert(DatabaseHelper.TABLE_NAME, null, contentValue);
}
public Cursor fetch() {
String[] columns = new String[] { DatabaseHelper._ID, DatabaseHelper.SUBJECT, DatabaseHelper.DESC,
DatabaseHelper.KEY_IMAGE };
Cursor cursor = database.query(DatabaseHelper.TABLE_NAME, columns, null, null, null, null, null);
if (cursor != null) {
cursor.moveToFirst();
}
return cursor;
}
public int update(long _id, String name, String desc, String image) {
ContentValues contentValues = new ContentValues();
contentValues.put(DatabaseHelper.SUBJECT, name);
contentValues.put(DatabaseHelper.DESC, desc);
contentValues.put(DatabaseHelper.KEY_IMAGE, image);
int i = database.update(DatabaseHelper.TABLE_NAME, contentValues, DatabaseHelper._ID + " = " + _id, null);
return i;
}
public void delete(long _id) {
database.delete(DatabaseHelper.TABLE_NAME, DatabaseHelper._ID + "=" + _id, null);
}
}
CountryListActivity
public class CountryListActivity extends ActionBarActivity {
private DBManager dbManager;
private ListView listView;
private SimpleCursorAdapter adapter;
final String[] from = new String[] {
DatabaseHelper.SUBJECT, DatabaseHelper.DESC, DatabaseHelper.KEY_IMAGE };
final int[] to = new int[] { R.id.title, R.id.desc, R.id.ivSlika };
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.fragment_emp_list);
dbManager = new DBManager(this);
dbManager.open();
Cursor cursor = dbManager.fetch();
listView = (ListView) findViewById(R.id.list_view);
listView.setEmptyView(findViewById(R.id.empty));
adapter = new SimpleCursorAdapter(this, R.layout.activity_view_record, cursor, from, to, 0);
adapter.notifyDataSetChanged();
listView.setAdapter(adapter);
// OnCLickListiner For List Items
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long viewId) {
//TextView idTextView = (TextView) view.findViewById(R.id.id);
TextView titleTextView = (TextView) view.findViewById(R.id.title);
TextView descTextView = (TextView) view.findViewById(R.id.desc);
ImageView slikaImageView = (ImageView) findViewById(R.id.ivSlika);
//String id = idTextView.getText().toString();
String title = titleTextView.getText().toString();
String desc = descTextView.getText().toString();
String image = slikaImageView.toString();
//ByteArrayOutputStream blob = new ByteArrayOutputStream();
//byte[] bitmapdata = blob.toByteArray();
//Bitmap bm = BitmapFactory.decodeByteArray(bitmapdata, 0, bitmapdata.length);
Intent modify_intent = new Intent(getApplicationContext(), ModifyCountryActivity.class);
modify_intent.putExtra("title", title);
modify_intent.putExtra("desc", desc);
//modify_intent.putExtra("id", id);
modify_intent.putExtra("image", image);
startActivity(modify_intent);
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.add_record) {
Intent add_mem = new Intent(this, AddCountryActivity.class);
startActivity(add_mem);
}
return super.onOptionsItemSelected(item);
}
}
我已尝试将图片放入ListView，但由于ListView仅显示文字，因此它似乎无法正常工作。我尝试过使用上面的代码，但是没有用。
如何在ListView中显示图像并将其保存在SQLite中，以便在重新启动应用后重新显示？
谢谢！
答案 0 :(得分：0)
首先，您不应该将图像存储在数据库中。您应该将图像作为文件存储在应用程序的目录或缓存中，并将URI存储到数据库中的这些文件中。或者将它们作为资源包含在您的应用中。
其次，你的图像来自哪里？它们是由应用程序本身生成的，还是从服务器下载的？如果它是后者，那么你应该查看一个库来帮助你处理它，像Picasso这样的东西会做得很好。
最后，使用ListView不要让你的生活更加艰难。查看RecyclerView，因为它是更好的API。