Unable to convert BLOB to String using Loadermanager in android

问题

I have a table with following structure.

    public static final String TABLE_NAME = "contact";
    public static final String ID = "_id";
    public static final String DEVICE_ID = "device_id";
    public static final String NAME = "name";
    public static final String CONTACT = "contact";
    public static final String IMAGE = "image";

    private static final int VERSION = 1;

    private static final String CREATE_TABLE_QUERY = "CREATE TABLE "
            + TABLE_NAME + "( " + ID + " INTEGER PRIMARY KEY , " + DEVICE_ID
            + " TEXT NOT NULL ,  " + NAME + "  TEXT NOT NULL , " + CONTACT
            + " TEXT NOT NULL ," 
            + IMAGE + "  BLOB " + 
            " ) ";

I have stored images in contact table in BLOB form . Now i have to retrieve device_id,name , image from table and attach the result to view .

I have used Loadermanager for this .

    public class FriendList extends Activity implements OnItemClickListener,
            LoaderManager.LoaderCallbacks {
        ListView friendList;
        SimpleCursorAdapter simpleCursorAdapter;
        CursorLoader cursorLoader;
        LoaderManager.LoaderCallbacks loaderCallback;
        static final int CONTACT_LOADER_ID = 77;

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.friend_list);
            friendList = (ListView) findViewById(R.id.lvFriendList);
            String[] uiBindFrom = new String[] { MyContacts.NAME,
                    MyContacts.DEVICE_ID ,MyContacts.IMAGE};
            int[] idBindTo = { R.id.tvFriendName, R.id.tvDeviceID ,R.id.ivContactProfile};
            loaderCallback = this;
            simpleCursorAdapter = new SimpleCursorAdapter(FriendList.this,
                    R.layout.custom_friend_list, null, uiBindFrom, idBindTo, 0);
            friendList.setAdapter(simpleCursorAdapter);
            friendList.setOnItemClickListener(this);
            getLoaderManager().initLoader(CONTACT_LOADER_ID, new Bundle(),
                    loaderCallback);
        }

Here R.id.ivContactProfile is id of ImageView .

    @Override
    public Loader onCreateLoader(int id, Bundle args) {
        String[] projectionFields = new String[] { MyContacts.ID,
                MyContacts.NAME, MyContacts.DEVICE_ID,MyContacts.IMAGE };
        cursorLoader = new CursorLoader(FriendList.this,
                MyContacts.CONTENT_URI, projectionFields, null, null, null);
        return cursorLoader;
    }

    @Override
    public void onLoadFinished(Loader loader, Cursor cursor) {
        switch (loader.getId()) {
        case CONTACT_LOADER_ID:
            simpleCursorAdapter.swapCursor(cursor);
            break;
        }

    }

Basically i have images save in table in byte[] form , and i have to attach data to the view , but it's returning me an exception like this .

05-21 19:30:05.169: E/AndroidRuntime(22609): android.database.sqlite.SQLiteException: unknown error: Unable to convert BLOB to string

Here is the complete log for this .

05-21 19:30:05.169: E/AndroidRuntime(22609): FATAL EXCEPTION: main
05-21 19:30:05.169: E/AndroidRuntime(22609): android.database.sqlite.SQLiteException: unknown error: Unable to convert BLOB to string
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.database.CursorWindow.nativeGetString(Native Method)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.database.CursorWindow.getString(CursorWindow.java:450)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:51)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.database.CursorWrapper.getString(CursorWrapper.java:114)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.support.v4.widget.SimpleCursorAdapter.bindView(SimpleCursorAdapter.java:135)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.support.v4.widget.CursorAdapter.getView(CursorAdapter.java:256)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.widget.AbsListView.obtainView(AbsListView.java:2452)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.widget.ListView.measureHeightOfChildren(ListView.java:1250)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.widget.ListView.onMeasure(ListView.java:1161)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.view.View.measure(View.java:12865)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4712)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1385)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.widget.LinearLayout.measureVertical(LinearLayout.java:670)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.widget.LinearLayout.onMeasure(LinearLayout.java:563)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.view.View.measure(View.java:12865)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4712)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.view.View.measure(View.java:12865)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.widget.LinearLayout.measureVertical(LinearLayout.java:822)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.widget.LinearLayout.onMeasure(LinearLayout.java:563)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.view.View.measure(View.java:12865)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4712)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2242)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.view.View.measure(View.java:12865)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1240)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2628)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.os.Handler.dispatchMessage(Handler.java:99)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.os.Looper.loop(Looper.java:137)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at android.app.ActivityThread.main(ActivityThread.java:4517)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at java.lang.reflect.Method.invokeNative(Native Method)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at java.lang.reflect.Method.invoke(Method.java:511)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:993)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:760)
05-21 19:30:05.169: E/AndroidRuntime(22609):    at dalvik.system.NativeStart.main(Native Method)

Can anyone tell me why am i getting this exception and how can i resolve this problem ?

Thanks!

回答1:

I have found solution of my problem . As suggested by @pskink in his comment above , i used ViewBinder . I created a ViewBinder like this .

public class MyViewBinder implements ViewBinder{
    @Override
    public boolean setViewValue(View view, Cursor cursor, int columnIndex) {
        int viewID = view.getId();
        switch(viewID){

        case R.id.tvFriendName :
            TextView friendName = (TextView) view;
            String friend_name;
            friend_name = cursor.getString(cursor.getColumnIndex(MyContacts.NAME));
            friendName.setText(friend_name);
            break;

        case R.id.tvDeviceID :
            TextView deviceID = (TextView) view;
            String device_id = cursor.getString(cursor.getColumnIndex(MyContacts.DEVICE_ID));
            deviceID.setText(device_id);
            break;

        case R.id.ivContactProfile :
            ImageView contactProfile = (ImageView) view;
            byte[] imageBytes = cursor.getBlob(cursor.getColumnIndex(MyContacts.IMAGE));
            if(imageBytes != null ){
                // Pic image from database
                contactProfile.setImageBitmap(BitmapFactory.decodeByteArray(imageBytes, 0, imageBytes.length));
            }else {
                // If image not found in database , assign a default image
                contactProfile.setBackgroundResource(R.drawable.bubble_a);
            }
            break;
        }
        return true;
    }


}

And i set ViewBinder for my SimpleCursorAdapter .

simpleCursorAdapter.setViewBinder( new MyViewBinder());

It worked for me properly . Here is the output.

来源：https://stackoverflow.com/questions/30388843/unable-to-convert-blob-to-string-using-loadermanager-in-android