A small summary of qbytearray usage

    Qbytearray Array;

    Array.resize (3);
    array[1]=0x7f;
    Qdebug ("I Array[1]=0x7f;array 1 is%d,%x", Qvariant (Array[1]). ToInt (), Qvariant (Array[1]). ToInt ());
    Qdebug ("I Array[1]=0x7f;__array 1 is%d,%x", array.at (1), array.at (1)); Qdebug ("I Array[1]=0x7f;___array 1 is%d,%x", Qvariant ((unsigned char) array[1]). ToInt (), Qvariant ((unsigned char) array [1]).

    ToInt ());
    Array[1]=0xff;
    Qdebug ("II Array[1]=0xff;array 1 is%d,%x", Qvariant (Array[1]). ToInt (), Qvariant (Array[1]). ToInt ());
    Qdebug ("II Array[1]=0xff;__array 1 is%d,%x", array.at (1), array.at (1)); Qdebug ("II Array[1]=0xff;___array 1 is%d,%x", Qvariant ((unsigned char) array[1]). ToInt (), Qvariant ((unsigned char)

    ARRAY[1]). ToInt ());
    ARRAY[1]=0X000000FF;
    Qdebug ("III Array[1]=0x000000ff;array 1 is%d,%x", Qvariant (Array[1]). ToInt (), Qvariant (Array[1]). ToInt ());
    Qdebug ("III Array[1]=0x000000ff;__array 1 is%d,%x", array.at (1), array.at (1)); Qdebug ("III Array[1]=0x000000ff;___array 1 is%d,%x", Qvariant ((UnsigneD char) array[1]. ToInt (), Qvariant ((unsigned char) array[1]). ToInt ());
    array[1]=-127;
    Qdebug ("IV Array[1]=-127;array 1 is%d,%x", Qvariant (Array[1]). ToInt (), Qvariant (Array[1]). ToInt ());
    Qdebug ("IV Array[1]=-127;__array 1 is%d,%x", array.at (1), array.at (1)); Qdebug ("IV Array[1]=-127;___array 1 is%d,%x", Qvariant ((unsigned char) array[1]). ToInt (), Qvariant ((unsigned char)

    ARRAY[1]). ToInt ());
    array[1]=0x7f01;
    Qdebug ("V Array[1]=0x7f01;array 1 is%d,%x", Qvariant (Array[1]). ToInt (), Qvariant (Array[1]). ToInt ());
    Qdebug ("V Array[1]=0x7f01;__array 1 is%d,%x", array.at (1), array.at (1)); Qdebug ("V Array[1]=0x7f01;___array 1 is%d,%x", Qvariant ((unsigned char) array[1]). ToInt (), Qvariant ((unsigned char)
     ARRAY[1]). ToInt ());

The output is:

I Array[1]=0x7f;array 1 is 127,7f
I Array[1]=0x7f;__array 1 is 127,7f
I Array[1]=0x7f;___array 1 is 127,7f
II Array[1]=0xff;array 1 is-1,ffffffff
II Array[1]=0xff;__array 1 is-1,ffffffff
II Array[1]=0xff;___array 1 is 255,ff
III Array[1]=0x000000ff;array 1 is-1,ffffffff
III Array[1]=0x000000ff;__array 1 is-1,ffffffff
III Array[1]=0x000000ff;___array 1 is 255,ff
IV Array[1]=-127;array 1 is-127,ffffff81
IV Array[1]=-127;__array 1 is-127,ffffff81
IV Array[1]=-127;___array 1 is 129,81
V Array[1]=0x7f01;array 1 is
V Array[1]=0x7f01;__array 1 is
V Array[1]=0x7f01;___array 1 is

As seen in the code and the results,

The elements in 1.QByteArray have 32 bits, but at the time of assignment array[] only the low 8 bits of the assigned value are stored, and the remaining high 24 bits in array[] are consolidated by 0 or 1 with the highest bit of the lower eight bits.

Elements in 2.QByteArray are signed

3.QByteArray can only use array[i]=value when assigning values, this form, array.at (i) is read-only, and forcing type conversions to array.at (i) does not work.

4. To read using its element value, if you want to get a signed number form, Qvariant (Array[i]). ToInt () is equivalent to array.at (i). If you get the unsigned number form of its element value, you need Qvariant ((unsigned char) array[i]). ToInt ()

5.array.data () points to its stored char*