How to get pixel color played on screen on Android? (Without using images)

Question

I’m developing an application for calligraphy and what I’m looking for is the following:

I intend to, using a TextView, put the letters on the screen and want to detect if the user is touching the screen inside or outside the letter/character area (black letter, white background).

All ways found to do this involve the use of images and I need another alternative!

How can I do that?

Answer 1

If you know how to do it with an image(Bitmap) then you only need a Bitmap that plays Textview.

The following method returns an image(bitmap) that represents the contents of view past tense.

public static Bitmap getViewBitmap(View view){

    //Cria um bitmap com as dimensões da view
    Bitmap bitmap = Bitmap.createBitmap(view.getWidth(),
            view.getHeight(),
            Bitmap.Config.ARGB_8888);

    //Cria um canvas para escrever no bitmap
    Canvas canvas = new Canvas(bitmap);

    //Pede à view que escreva o seu conteúdo no bitmap, usando o canvas
    //anteriormente criado.
    view.draw(canvas);

    return bitmap;
}

Note that the method can only be used after "Tree of views" has been created, for example in the method onWindowFocusChanged().

Example of use for your case: black letters, white background:

Mainactivity.java

public class MainActivity extends AppCompatActivity {

    TextView textView;
    Bitmap textViewBitmap;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        textView = (TextView) findViewById(R.id.text1);
        textView.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                handleTouch(event.getX(), event.getY());
                return true;
            }
        });
    }

    private void handleTouch(float x, float y) {
        int pixel = textViewBitmap.getPixel((int)x, (int)y);
        if(pixel == Color.WHITE){
            Toast.makeText(this, "Branco", Toast.LENGTH_SHORT).show();
        }else{
            Toast.makeText(this, "Preto", Toast.LENGTH_SHORT).show();
        }
    }

    private static Bitmap getViewBitmap(View view){
        Bitmap bitmap = Bitmap.createBitmap(view.getWidth(),
                view.getHeight(),
                Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(bitmap);
        view.draw(canvas);
        return bitmap;
    }

    @Override
    public void onWindowFocusChanged(boolean hasFocus) {
        super.onWindowFocusChanged(hasFocus);
        if(textViewBitmap == null){
            textViewBitmap = getViewBitmap(textView);
        }
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app = "http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:orientation="vertical">

    <TextView
        android:id="@+id/text1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@android:color/white"
        android:textColor="@android:color/black"
        android:text="TextView"
        android:textSize="40sp"/>

</LinearLayout>