为什么我写的android调色板小程序只能调单一颜色深浅，无法混合调色？

package com.example.palettebyandroid;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.ColorMatrix;
import android.graphics.ColorMatrixColorFilter;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.os.Bundle;
import android.widget.ImageView;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;

public class MainActivity extends Activity {

private SeekBar  sb_red;
private SeekBar  sb_green;
private SeekBar  sb_blue;
private Bitmap bitmap;
private Bitmap newBitmap;
private Canvas canvas;
private ColorMatrix cm;
private Paint paint;
private SeekBar sb_transparent;
private ImageView iv_image;



@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    iv_image = (ImageView) findViewById(R.id.iv_image);
    sb_red = (SeekBar) findViewById(R.id.sb_red);
    sb_green = (SeekBar) findViewById(R.id.sb_green);
    sb_blue = (SeekBar) findViewById(R.id.sb_blue);
    sb_transparent = (SeekBar) findViewById(R.id.sb_transparent);

    bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.after8);

    newBitmap = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), bitmap.getConfig());

    canvas = new Canvas(newBitmap);

    paint =new Paint(); 

    cm = new ColorMatrix();

    cm.set(new float[] {
            1, 0, 0, 0, 0,
            0, 1, 0, 0, 0,
            0, 0, 1, 0, 0,
            0, 0, 0, 1, 0 
            });
    paint.setColorFilter(new ColorMatrixColorFilter(cm));

    canvas.drawBitmap(bitmap, new Matrix(), paint);

    sb_red.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {

        @Override
        public void onStopTrackingTouch(SeekBar seekBar) {
            int progress = seekBar.getProgress();

            float fred = progress/128.0f;

            cm.set(new float[] {
                    fred, 0, 0, 0, 0,
                    0, 1, 0, 0, 0,
                    0, 0, 1, 0, 0,
                    0, 0, 0, 1, 0 });

            paint.setColorFilter(new ColorMatrixColorFilter(cm));

            canvas.drawBitmap(bitmap, new Matrix(), paint);

            iv_image.setImageBitmap(newBitmap);
        }

        @Override
        public void onStartTrackingTouch(SeekBar seekBar) {

        }

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

        }
    });
    sb_green.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {

        @Override
        public void onStopTrackingTouch(SeekBar seekBar) {
            int progress = seekBar.getProgress();

            float fgreen = progress/128.0f;

            cm.set(new float[] {
                    1, 0, 0, 0, 0,
                    0, fgreen, 0, 0, 0,
                    0, 0, 1, 0, 0,
                    0, 0, 0, 1, 0 });

            paint.setColorFilter(new ColorMatrixColorFilter(cm));

            canvas.drawBitmap(bitmap, new Matrix(), paint);

            iv_image.setImageBitmap(newBitmap);
        }

        @Override
        public void onStartTrackingTouch(SeekBar seekBar) {


        }

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

        }
    });
    sb_blue.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {

        @Override
        public void onStopTrackingTouch(SeekBar seekBar) {
            int progress = seekBar.getProgress();

            float fblue = progress/128.0f;

            cm.set(new float[] {
                    1, 0, 0, 0, 0,
                    0, 1, 0, 0, 0,
                    0, 0, fblue, 0, 0,
                    0, 0, 0, 1, 0 });

            paint.setColorFilter(new ColorMatrixColorFilter(cm));

            canvas.drawBitmap(bitmap, new Matrix(), paint);

            iv_image.setImageBitmap(newBitmap);
        }

        @Override
        public void onStartTrackingTouch(SeekBar seekBar) {

        }

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

        }
    });
    sb_transparent.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {

        @Override
        public void onStopTrackingTouch(SeekBar seekBar) {
            int progress = seekBar.getProgress();

            float ftran = progress/128.0f;

            cm.set(new float[] {
                    1, 0, 0, 0, 0,
                    0, 1, 0, 0, 0,
                    0, 0, 1, 0, 0,
                    0, 0, 0, ftran, 0 });

            paint.setColorFilter(new ColorMatrixColorFilter(cm));

            canvas.drawBitmap(bitmap, new Matrix(), paint);

            iv_image.setImageBitmap(newBitmap);
        }

        @Override
        public void onStartTrackingTouch(SeekBar seekBar) {

        }

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

        }
    });

    }
}

说实话，你的代码写得挺乱的。建议你参考这篇文章整理一下代码
http://www.devstore.cn/essay/essayInfo/1570.html

说实话，你的代码写得挺乱的。建议你参考这篇文章整理一下代码
http://www.devstore.cn/essay/essayInfo/1570.html