Change the image transparency using a SeekBar

Question

I have to do an Android Studio project that it has to change the transparency of an ImageView using a SeekBar.

I have this program:

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ImageView;
import android.widget.SeekBar;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    private int seekTransparent;
    ImageView color;
    SeekBar seekBarTransparent;

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

        color = (ImageView)findViewById(R.id.changeColor);
        seekBarTransparent = (SeekBar) findViewById(R.id.seekBar);
        updateNow();


        seekBarTransparent.setOnSeekBarChangeListener(seekBarChangeListener);

    }

    private SeekBar.OnSeekBarChangeListener seekBarChangeListener = new 
SeekBar.OnSeekBarChangeListener() {


        @Override
        public void onProgressChanged(SeekBar seekBar, int progress, boolean 
fromUser) {
            updateNow();
        }

        @Override
        public void onStartTrackingTouch(SeekBar seekBar) {
             Toast.makeText(getApplicationContext(), "toast in uso", 
Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onStopTrackingTouch(SeekBar seekBar) {
            Toast.makeText(getApplicationContext(), "toast non in uso", 
Toast.LENGTH_SHORT).show();
        }
    };

        private void updateNow(){
            seekTransparent = seekBarTransparent.getProgress();
        color.getBackground().setAlpha(192 + seekTransparent * 0x10000);

    }
}

I run the application but on my smartphone it doesn't work anyone can help me?

Answer 1

This is the xml of the seekbar

<SeekBar
            android:id="@+id/opacitybar"
            android:layout_width="200dp"
            android:layout_height="wrap_content"
            android:max="10"
            android:progress="10"
            android:layout_alignTop="@+id/opacitylbl"
            android:layout_centerHorizontal="true" />

And this is the code of the Activity

 logoseekbar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
        int opacity = 100; // from 0 to 255
        @Override
        public void onProgressChanged(SeekBar seekBar, int progresValue, boolean fromUser) {
            im_move_zoom_rotate.setAlpha(progresValue * 25);

        }
        @Override
        public void onStartTrackingTouch(SeekBar seekBar) {

        }
        @Override
        public void onStopTrackingTouch(SeekBar seekBar) {

        }

    });

You can change the values if you want