鹅厂系列五--仿微信底部导航菜单

Posted 2023-02-15 z8z87878

海纳百川
上篇学习了一下遮罩Xfermode的使用，简单的运用了下，详见http://blog.csdn.net/z8z87878/article/details/52841320，先来看看Xfermode来做微信底部导航菜单吧

其中底部的四个菜单控件GradientView(实现详见上篇Xfermode的学习)

public class GradientView extends View
    public GradientView(Context context) 
        this(context,null);
    

    public GradientView(Context context, AttributeSet attrs) 
        this(context, attrs,0);
    


    public GradientView(Context context, AttributeSet attrs, int defStyleAttr) 
        super(context, attrs, defStyleAttr);
    

    public Bitmap icon;

    public  void setBitmap(Bitmap bitmap)
        icon = bitmap;  //外部传图标
        postInvalidate();//主动调draw方法刷新视图
    

    private String txt;
    public  void setText(String text)
        txt = text;    //外部传文字
        postInvalidate();//主动调draw方法刷新视图
    

    private int alpha = 255;
    public void  setMyAlpha(int alpha)

        this.alpha = alpha;
        postInvalidate();
    ;


    @Override
    public void draw(Canvas canvas)   //与上面的实现圆形头像一样，只是换了个遮罩模式

        Bitmap bitmap = Bitmap.createBitmap(getWidth(),getHeight(), Bitmap.Config.ARGB_8888);
        Canvas canvas1 = new Canvas(bitmap);
        super.draw(canvas1);   //背景色画在bitmap上

        Bitmap bitmap1 = Bitmap.createBitmap(bitmap.getWidth(),bitmap.getHeight(), Bitmap.Config.ARGB_8888);
        Canvas canvas2 = new Canvas(bitmap1);

        canvas2.drawARGB(0,0,0,0);
        Paint paint = new Paint();
        paint.setAntiAlias(true);
        paint.setTextAlign(Paint.Align.CENTER);
        paint.setTextSize(13);
        paint.setColor(Color.BLACK);

        if(txt != null) //画文字
            canvas2.drawText(txt,getWidth()/2,getHeight()-dp2px(9),paint);
        


        if(icon != null) //画图片

            Matrix matrix = new Matrix(); //帮助实现bitmap缩放

            matrix.postScale(getWidth()/3.0f/icon.getWidth(),getWidth()/3.0f/icon.getHeight());
            canvas2.drawBitmap(Bitmap.createBitmap(icon,0,0,icon.getWidth(),icon.getHeight(),matrix,true),getWidth()/3,dp2px(7),null);
        


        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_ATOP));

        paint.setAlpha(alpha); //透明度变化
        canvas2.drawBitmap(bitmap,0,0,paint);  //将背景色画在图标和文字上面，相交的部分才显示

        canvas.drawBitmap(bitmap1,0,0,null);  //最后画在画板上，不理解回去看圆形图片实现

    


    private int dp2px(float dp)

        float density = getResources().getDisplayMetrics().density;

        return (int) (dp * density + .5f);
    

activity的实现,主要是监听viewpager的滑动事件

mViewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() 

            @Override  //positionOffset得到当前position向左滑动的比例 ,以最左边第一个可见视图为position的取值，
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) 

                mViews.get(position).setMyAlpha((int) (255 * (1 -positionOffset)));

                if(position < 3)
                    mViews.get(position + 1).setMyAlpha((int) (255 * positionOffset));
                

            

            @Override
            public void onPageSelected(int position) 

                if (position == 2)  //到第三个菜单换背景图片

                    mFx.setBitmap(BitmapFactory.decodeResource(getResources(),R.mipmap.fxw));
                    flag = true;
                else 
                    if (flag)
                        mFx.setBitmap(BitmapFactory.decodeResource(getResources(),R.mipmap.fx));
                        flag = false;
                    
                

                curPosition = position;
            

            @Override
            public void onPageScrollStateChanged(int state) 

            
        );

底菜单点击事件

@Override
    public void onClick(View view) 

        mViews.get(curPosition).setMyAlpha(0);//清除上次的选中
        switch (view.getId())
            case R.id.gv1:
                mViewPager.setCurrentItem(0,false); //禁止滑动到相应条目，直接跳转到
                break;

            case R.id.gv2:
                mViewPager.setCurrentItem(1,false);
                break;

            case R.id.gv3:
                mViewPager.setCurrentItem(2,false);
                break;

            case R.id.gv4:
                mViewPager.setCurrentItem(3,false);
                break;
        
    

主要是底部菜单控件的问题。不清楚的看我上偏的介绍吧，这整部份源码下载地址我会在评论区贴出