如何在Android Studio中从Sqlite数据库插入和检索图像

Question

我正在尝试从用户那里获取一些数据，包括相机拍摄的照片，然后将其插入到数据库（缩略图）中，然后检索它以便以后查看。 1- I used this and this

但是我仍然遇到错误

此错误中提到的第45行在这里：

，这是响应用户输入的OnclickListener。

sginUpButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            String Fname = fn.getText().toString();
            String Lname = ln.getText().toString();
            String Email = em.getText().toString();
            String Pass = pass.getText().toString();
            String mobile = mob.getText().toString();
            if(fn.length()!=0 && ln.length()!=0  && em.length()!=0 && pass.length()!=0&& mob.length()!=0)
            {
                AddData(Fname,Lname,Email,Pass,mobile,byteArray);
                fn.setText("");
                ln.setText("");
                em.setText("");
                pass.setText("");
                mob.setText("");
                Intent fromLoginToSignup = new Intent(SignUpScreen.this, Profile.class);
                notification();
            }
            else
            {
                toastmessage("lazem temla kol al fara3'at");
            }

        }
    });

最后，这是它插入数据库内部的部分，我认为这与要插入的图像有关，实际上存在错误。

 public void onCreate(SQLiteDatabase db) {
    String createTable="CREATE TABLE "+ TABLE_NAME + "(ID INTEGER PRIMARY KEY AUTOINCREMENT , "
            + FN + " TEXT , "
            + LN + " TEXT ,"
            + E_M + " TEXT ,"
            + PASS + " TEXT ,"
            + Mobnum + " INTEGER, "
            + image + " BLOB)";
    db.execSQL(createTable);

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS "+TABLE_NAME);
    onCreate(db);

}
public boolean addData(String FirstName,String LastName,String Email,String Password,String MobileNumber, byte[] Profileimg) //to write into the datbase
{
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues cv =new ContentValues();
    cv.put(FN,FirstName);
    cv.put(LN,LastName);
    cv.put(E_M,Email);
    cv.put(PASS,Password);
    cv.put(Mobnum,MobileNumber);
    cv.put(image, Profileimg);

    Log.d(DATABASE_NAME,"adding : " + FirstName + " TO " + TABLE_NAME );
    long result=db.insert(TABLE_NAME,null,cv);
    //if  the result inserted correctly or not
    if(result==-1)
    {
        return false;
    }
    else
    {
        return true;
    }
}

我已经在线获得了这两个函数，所以我认为将它们放在此处很重要，但是我认为它们与错误有关，但是我不确定

    private void dispatchTakePictureIntent() {
    Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
    if (takePictureIntent.resolveActivity(getPackageManager()) != null) {
        startActivityForResult(takePictureIntent, REQUEST_IMAGE_CAPTURE);
    }
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == REQUEST_IMAGE_CAPTURE && resultCode == RESULT_OK) {
        Bitmap photo = (Bitmap) data.getExtras().get("data");
        img.setImageBitmap(photo);
        ByteArrayOutputStream stream = new ByteArrayOutputStream();
        photo.compress(Bitmap.CompressFormat.PNG, 100, stream);
        byteArray = stream.toByteArray();
    }
}

Answer 1

该消息表明字节为空。 getBlob的文档指出：-

  

结果以及该方法在列时是否引发异常   值是null或列类型不是blob类型是   实现定义的。

因此，我相信getBlob返回的是null，因此，最有可能的是插入了null。

根据您的DatabaseHelper考虑以下内容：-

    mDB = new DatabaseHelper(this);
    mDB.addData("Test001", "Test001", "email", "password", "xxc", null);
    mDB.addData("Test002", "Test002", "email", "password", "xxc", new byte[]{0});
    Cursor csr = mDB.getData();
    DatabaseUtils.dumpCursor(csr);

    while (csr.moveToNext()) {
        bytes = csr.getBlob(6);
        if (bytes == null) {
            Log.d("OUCH", "Row " + String.valueOf(csr.getPosition()) + " is null");
        } else {
            Log.d("OK", "Row " + String.valueOf(csr.getPosition()) + " has byte array of length " + bytes.length);
        }
        Log.d("REPLICATE"," byte array length is " + bytes.length);
    }

这将两行相加，第一行以null作为byte []（图像），第二行具有有效值，尽管它是短byte []。

插入的行没有问题。

数据提取没有问题。

但是该日志将包含以下内容：-

2019-01-09 14:15:31.622 2783-2783/ptfc.populatetablefromcursor D/mydb: adding : Test001 TO mytable
2019-01-09 14:15:31.623 2783-2783/ptfc.populatetablefromcursor D/mydb: adding : Test002 TO mytable
2019-01-09 14:15:31.624 2783-2783/ptfc.populatetablefromcursor I/System.out: >>>>> Dumping cursor android.database.sqlite.SQLiteCursor@453edcd
2019-01-09 14:15:31.626 2783-2783/ptfc.populatetablefromcursor I/System.out: 0 {
2019-01-09 14:15:31.626 2783-2783/ptfc.populatetablefromcursor I/System.out:    ID=1
2019-01-09 14:15:31.626 2783-2783/ptfc.populatetablefromcursor I/System.out:    fn=Test001
2019-01-09 14:15:31.626 2783-2783/ptfc.populatetablefromcursor I/System.out:    ln=Test001
2019-01-09 14:15:31.626 2783-2783/ptfc.populatetablefromcursor I/System.out:    e_m=email
2019-01-09 14:15:31.626 2783-2783/ptfc.populatetablefromcursor I/System.out:    pass=password
2019-01-09 14:15:31.626 2783-2783/ptfc.populatetablefromcursor I/System.out:    mobnum=xxc
2019-01-09 14:15:31.626 2783-2783/ptfc.populatetablefromcursor I/System.out:    image=null
2019-01-09 14:15:31.626 2783-2783/ptfc.populatetablefromcursor I/System.out: }
2019-01-09 14:15:31.626 2783-2783/ptfc.populatetablefromcursor I/System.out: 1 {
2019-01-09 14:15:31.626 2783-2783/ptfc.populatetablefromcursor I/System.out:    ID=2
2019-01-09 14:15:31.626 2783-2783/ptfc.populatetablefromcursor I/System.out:    fn=Test002
2019-01-09 14:15:31.626 2783-2783/ptfc.populatetablefromcursor I/System.out:    ln=Test002
2019-01-09 14:15:31.626 2783-2783/ptfc.populatetablefromcursor I/System.out:    e_m=email
2019-01-09 14:15:31.626 2783-2783/ptfc.populatetablefromcursor I/System.out:    pass=password
2019-01-09 14:15:31.626 2783-2783/ptfc.populatetablefromcursor I/System.out:    mobnum=xxc
2019-01-09 14:15:31.626 2783-2783/ptfc.populatetablefromcursor I/System.out:    image=<unprintable>
2019-01-09 14:15:31.626 2783-2783/ptfc.populatetablefromcursor I/System.out: }
2019-01-09 14:15:31.626 2783-2783/ptfc.populatetablefromcursor I/System.out: 2 {
2019-01-09 14:15:31.626 2783-2783/ptfc.populatetablefromcursor I/System.out:    ID=3
2019-01-09 14:15:31.626 2783-2783/ptfc.populatetablefromcursor I/System.out:    fn=Test001
2019-01-09 14:15:31.627 2783-2783/ptfc.populatetablefromcursor I/System.out:    ln=Test001
2019-01-09 14:15:31.627 2783-2783/ptfc.populatetablefromcursor I/System.out:    e_m=email
2019-01-09 14:15:31.627 2783-2783/ptfc.populatetablefromcursor I/System.out:    pass=password
2019-01-09 14:15:31.627 2783-2783/ptfc.populatetablefromcursor I/System.out:    mobnum=xxc
2019-01-09 14:15:31.627 2783-2783/ptfc.populatetablefromcursor I/System.out:    image=null
2019-01-09 14:15:31.627 2783-2783/ptfc.populatetablefromcursor I/System.out: }
2019-01-09 14:15:31.629 2783-2783/ptfc.populatetablefromcursor I/System.out: <<<<<
2019-01-09 14:15:31.629 2783-2783/ptfc.populatetablefromcursor D/OUCH: Row 0 is null
2019-01-09 14:15:31.630 2783-2783/ptfc.populatetablefromcursor D/AndroidRuntime: Shutting down VM
2019-01-09 14:15:31.632 2783-2783/ptfc.populatetablefromcursor E/AndroidRuntime: FATAL EXCEPTION: main
    Process: ptfc.populatetablefromcursor, PID: 2783
    java.lang.RuntimeException: Unable to start activity ComponentInfo{ptfc.populatetablefromcursor/ptfc.populatetablefromcursor.MainActivity}: java.lang.NullPointerException: Attempt to get length of null array
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2914)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3049)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1809)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:6680)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
     Caused by: java.lang.NullPointerException: Attempt to get length of null array
        at ptfc.populatetablefromcursor.MainActivity.onCreate(MainActivity.java:40)
        at android.app.Activity.performCreate(Activity.java:7136)
        at android.app.Activity.performCreate(Activity.java:7127)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2894)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3049) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1809) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:193) 
        at android.app.ActivityThread.main(ActivityThread.java:6680) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858) 

stackTrace类似。显示如果插入空值，则 bytes.length 会导致失败。

有很多方法可以解决此问题，例如，如果传递给addData方法的ProfileImage为null，则可以将image列设置为具有DEFAULT值，并跳过cv.put。

在数据库助手中将+ image + " BLOB ')";更改为+ image + " BLOB DEFAULT X'00')";

在addData方法中进行以下更改：-

    if (Profileimg != null) {
        cv.put(image, Profileimg);
    }

• 尽管我认为它可以处理，但我不记得这会如何影响列表视图中的图像。

---

但是，根本原因是拍照将返回空值。

  

此外，如果图像可能还会遇到其他问题   由于存在限制，它们本身就很大（100万最近为200万）   具有CursorWindow（由Cursor使用）可以达到的数据大小   使用1张图片处理超过或接近2M，并且例外   保证。对于1M图像，如果出现以下情况，则CursorWindow最多可容纳1个   根本没有，所以您会期望显示问题。

     

如果图像平均大约100k，则可以将其存储在数据库中，并且   搜索可能会揭示SQlite如何变得更好的背后原因   比文件系统更有效。

Answer 2

如果您不想使用blob，这是另一种解决方案。您可以实现如下，

• 将图像位图转换为base64，并将其另存为sqlite中的文本。
• 检索时，将base64转换为位图并在ImageView中显示。

有关转换代码，请参考here