Question

我在Android中寻找一种解决方案，将远程图像（从webservices检索到的URL）存储到本地（SDcard或Sqlite数据库或缓存）中，这样图像也可以在离线模式下显示。因为我想在通话期间每次显示一张图片。

有没有解决方案？

Answer 1

请按照以下步骤操作（一次只能检索一次图像）：

从网址中将图片检索为位图。
将位图转换为字节数组。
将字节数组存储到SQLite数据库表的blob字段中。
从SQLite数据库表中获取blob。
将blob转换为字节数组。
将字节数组转换为位图。
最后，将Bitmap设置为Activity的ImageMap上的图像。

public class ImageStoreAndRetrievalActivity extends Activity {

private ImageView imageView;
private DatabaseHandler dbHandler;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_image_store);
    imageView = (ImageView)findViewById(R.id.imageView1);
    dbHandler = new DatabaseHandler(getApplicationContext());       
    new MyThread("http://www.fnordware.com/superpng/pnggrad8rgb.png");
    imageView.setImageBitmap(dbHandler.getBitmap(1));  // here 1 is id for the image into tbl_blob table in SQLite DB.
}

public class MyThread implements Runnable {
    private String url;
    private Bitmap bitmap = null;
    private Thread th;
    public MyThread(String url) {
        this.url = url;
        th = new Thread(this);
        th.start();
        try {
            th.join();
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    public void run() {
        URL fileUrl = null;  

        try {  
            fileUrl = new URL(url);  
            HttpURLConnection conn = (HttpURLConnection) fileUrl.openConnection();  
            conn.setConnectTimeout(0);  
            conn.setDoInput(true);  
            conn.connect();  
            InputStream is = conn.getInputStream();  
            bitmap = BitmapFactory.decodeStream(is);  
            is.close();  
        } catch (IOException e) {  
            e.printStackTrace();  
        }   
        dbHandler.insertBitmap(bitmap);
        Log.i("URL", url);
    }

}

}

    public static final String DATABASE_NAME = "blobdb";
    public static final int DATABASE_VERSION = 1;
    public static final String CREATE_BLOB_TABLE = "CREATE TABLE IF NOT EXISTS tbl_blob " + "(id INTEGER PRIMARY KEY AUTOINCREMENT, img BLOB NOT NULL, description TEXT NULL)";

公共类DatabaseHandler扩展了SQLiteOpenHelper { 私有上下文上下文;

public DatabaseHandler(Context context) 
{
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
    this.context = context;
}

// Creating Tables
@Override
public void onCreate(SQLiteDatabase db) 
{
    // create all tables in 'btlocdb'
    createTables(db);
}

/** create all tables in 'btlocdb'.
 * @param db
 */
public void createTables(SQLiteDatabase db) {       
    db.execSQL(CREATE_BLOB_TABLE);
}

// Upgrading database
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // Drop older table if existed
    //db.execSQL("DROP TABLE IF EXISTS " + Consts.Table.DATABASE_NAME);

    // Create tables again
    //onCreate(db);
}

public void insertBitmap(Bitmap bm) 
{

    ByteArrayOutputStream out = new ByteArrayOutputStream();
    bm.compress(Bitmap.CompressFormat.PNG, 100, out);
    byte[] buffer=out.toByteArray();

    SQLiteDatabase db = this.getWritableDatabase();


    // Starts the transaction.
    db.beginTransaction();
    ContentValues values;        
    try 
    {
        values = new ContentValues();
        values.put("img", buffer); 
        values.put("description", "This is a description"); 
        // Inserting Row
        long i = db.insert("tbl_blob", null, values);
        Log.i("Insert", i + "");
        // Insert or update data into database successfully.
        db.setTransactionSuccessful();                                    
    }       
    catch (SQLiteException e) 
    {
        e.printStackTrace();
    }                      
    finally
    {
        db.endTransaction(); // Ending the transaction.
        db.close(); // Closing database connection
    }
}

public Bitmap getBitmap(int id){
    Bitmap bm = null;
    SQLiteDatabase db = this.getWritableDatabase();
    // Starts the transaction.
    db.beginTransaction();
    try 
    {                       
        String selectQuery = "select * from tbl_blob where id = " + id;
        Cursor cursor = db.rawQuery(selectQuery, null);
        Log.i("Cursor", cursor.getCount() + "");        
        if(cursor.getCount() > 0)
        {

            if (cursor.moveToFirst()) {
                do {                        
                    byte[] blob = cursor.getBlob(cursor.getColumnIndex("img"));
                    ByteArrayInputStream imageStream = new ByteArrayInputStream(blob);
                    bm = BitmapFactory.decodeStream(imageStream);
                } while (cursor.moveToNext());
            }               
        }                   
        db.setTransactionSuccessful();  
    }       
    catch (SQLiteException e) 
    {
        e.printStackTrace();
    }                      
    finally
    {
        db.endTransaction(); // Ending the transaction.
        db.close(); // Closing database connection
    }
    return bm;      
}

}

希望这会对你有所帮助！如果您对此问题有任何疑问，请与我们联系。感谢..

如何在本地存储或保存和检索多个远程图像

1 个答案: