Android自定义View实现体重表盘详解流程

效果视频

分析

起始角度

如下图所示，起点角度为150，终点角度为240

圆弧

白色圆弧为整个圆弧范围，蓝色圆弧为根据数据变动而覆盖白色圆弧，蓝色圆弧比白色圆弧大一点，突出显示

 innerarcpaint.setstrokewidth( width * (float)0.1 );
 outerarcpaint.setstrokewidth( width * (float)0.12 );

指针

中间的水滴指针是一个白色的水滴图片，下图蓝色为选择文件的背景颜色（截图），由于水滴指向-135度，将图像旋转-75度，水滴尖刚好指向150度的起点。

代码

初始化属性

 private void initpaint(){
        innerarcpaint = new paint(  );
        innerarcpaint.setcolor( color.white );
        innerarcpaint.setantialias( true );
        innerarcpaint.setstyle( paint.style.stroke );

        outerarcpaint = new paint(  );
        outerarcpaint.setcolor( color.blue );
        outerarcpaint.setantialias( true );
        outerarcpaint.setstyle( paint.style.stroke );
        outerarcpaint.setshadowlayer( (float)10,(float)10,(float)10,color.parsecolor( "#99000000" ) );

        textpaint = new paint(  );
        textpaint.setcolor( color.red );
        textpaint.setstyle( paint.style.stroke );
        textpaint.settextsize( 60 );
        textpaint.setstrokewidth( 2 );

        scalepaint = new paint(  );
        scalepaint.setcolor( color.white );
        scalepaint.settextsize( 25 );
        //硬件加速
        setlayertype( layer_type_software,null );
    }

画布

protected void onmeasure(int widthmeasurespec, int heightmeasurespec) {
        super.onmeasure( widthmeasurespec, heightmeasurespec );
        int width = measurespec.getsize( widthmeasurespec );
        innerarcpaint.setstrokewidth( width * (float)0.1 );
        outerarcpaint.setstrokewidth( width * (float)0.12 );

        oval = new rectf(  );
        oval.left = width * (float)0.2;
        oval.top = width * (float)0.2;
        oval.right = width * (float)0.8;
        oval.bottom = width * (float)0.8;
        //宽、高一致，使画布无论边长如何变化，都成为一个正方形
        setmeasureddimension( width,width );
    }

绘制内圆弧

 //绘制内圆弧
    private void drawinnerarc(canvas canvas){
        //保存之前的画布
        canvas.save();
        canvas.drawarc( oval, startangle,sweepangle,false,innerarcpaint);
    }

绘制外圆弧

//绘制外圆弧
    private void drawouterarc(canvas canvas){
        canvas.save();
        canvas.drawarc( oval, startangle,sweepangle * currentdata / 300,false,outerarcpaint);
    }

绘制中间指针

 //绘制中间指针
    private void drawarrow(canvas canvas){
       canvas.save();
        bitmap bitmap = bitmapfactory.decoderesource( getresources(),r.mipmap.waterdrop );
        int width = 75;
        int height = 75;
        int newwidth = (int)(getwidth() * 0.08);
        float scalewidth = (float) (newwidth / width);
        float scaleheight = (float) (newwidth / height);
        matrix matrix = new matrix(  );
        //顺序不能颠倒
        matrix.setrotate( -75 + (sweepangle * currentdata / 300),bitmap.getwidth()/2,bitmap.getheight()/2 );
        matrix.postscale( scalewidth,scaleheight );

        bitmap bitmap1 = bitmap.createbitmap( bitmap,0,0,width,height,matrix,true );
        canvas.drawbitmap( bitmap1,getwidth()/2 - bitmap1.getwidth()/2,getheight()/2 - bitmap1.getheight()/2,innerarcpaint );
        bitmap.recycle();
        bitmap1.recycle();
    }

绘制中间文字

private void drawcurrentdatatext(canvas canvas){
        canvas.save();
        rect rect = new rect(  );
        string str = string.valueof( currentdata ) + "kg";
        textpaint.setcolor( color.red );
        textpaint.gettextbounds( str,0,str.length(),rect );
        canvas.drawtext( str,getwidth()/2 - rect.width()/2,(int)(getheight() * (float)0.38),textpaint );
    }

绘制左右两边文字

 private void drawscalerighttext(canvas canvas){
        canvas.save();
        rect rect = new rect(  );
        string str =  "300kg";
        textpaint.settextsize( 45 );
        textpaint.gettextbounds( str,0,str.length(),rect );
        textpaint.setcolor( color.white );
        canvas.drawtext( str,getwidth()-getwidth()/6,(getheight()/2+getwidth()/5) ,textpaint );
    }
    private void drawscalelefttext(canvas canvas){
        canvas.save();
        rect rect = new rect(  );
        string str =  "0kg";
        textpaint.settextsize( 45 );
        textpaint.gettextbounds( str,0,str.length(),rect );
        textpaint.setcolor( color.white );
        canvas.drawtext( str,(getwidth()/2-(getwidth()/3 + 75)),(getheight()/2+getwidth()/5) ,textpaint );
    }

动画

 public void setcurrentdata(final float data, timeinterpolator interpolator){
        long time = ( (long)math.abs( data- currentdata ) *20);
        final valueanimator valueanimator = valueanimator.offloat( currentdata,data ).setduration( time );
        valueanimator.setinterpolator( interpolator );
        valueanimator.addupdatelistener( new valueanimator.animatorupdatelistener() {
            @override
            public void onanimationupdate(valueanimator animation) {
                customview_clockdial.this.currentdata = (float)valueanimator.getanimatedvalue();
                invalidate();
            }
        } );
        valueanimator.start();
    }

全部代码

public class customview_clockdial extends view {
    //内圆弧画笔
    private paint innerarcpaint;
    //外圆弧画笔
    private paint outerarcpaint;
    //文字画笔
    private paint textpaint;
    //刻度画笔
    private paint scalepaint;
    //圆弧范围
    private rectf oval;
    //当前数据
    private float currentdata = 0;
    //起点角度
    private float startangle = 150;
    //终点角度
    private float sweepangle = 240;
    public customview_clockdial(context context) {
        super( context );
        initpaint();
    }

    public customview_clockdial(context context, @nullable attributeset attrs) {
        super( context, attrs );
        initpaint();
    }

    public customview_clockdial(context context, @nullable attributeset attrs, int defstyleattr) {
        super( context, attrs, defstyleattr );
        initpaint();
    }
    private void initpaint(){
        innerarcpaint = new paint(  );
        innerarcpaint.setcolor( color.white );
        innerarcpaint.setantialias( true );
        innerarcpaint.setstyle( paint.style.stroke );

        outerarcpaint = new paint(  );
        outerarcpaint.setcolor( color.blue );
        outerarcpaint.setantialias( true );
        outerarcpaint.setstyle( paint.style.stroke );
        outerarcpaint.setshadowlayer( (float)10,(float)10,(float)10,color.parsecolor( "#99000000" ) );

        textpaint = new paint(  );
        textpaint.setcolor( color.red );
        textpaint.setstyle( paint.style.stroke );
        textpaint.settextsize( 60 );
        textpaint.setstrokewidth( 2 );

        scalepaint = new paint(  );
        scalepaint.setcolor( color.white );
        scalepaint.settextsize( 25 );
        //硬件加速
        setlayertype( layer_type_software,null );
    }

    @override
    protected void onmeasure(int widthmeasurespec, int heightmeasurespec) {
        super.onmeasure( widthmeasurespec, heightmeasurespec );
        int width = measurespec.getsize( widthmeasurespec );
        innerarcpaint.setstrokewidth( width * (float)0.1 );
        outerarcpaint.setstrokewidth( width * (float)0.12 );

        oval = new rectf(  );
        oval.left = width * (float)0.2;
        oval.top = width * (float)0.2;
        oval.right = width * (float)0.8;
        oval.bottom = width * (float)0.8;
        //宽、高一致，使画布无论边长如何变化，都成为一个正方形
        setmeasureddimension( width,width );
    }

    @override
    protected void ondraw(canvas canvas) {
        super.ondraw( canvas );
        drawinnerarc(canvas);
        drawouterarc(canvas);
        drawarrow(canvas);
        drawcurrentdatatext(canvas);
        drawscalerighttext(canvas);
        drawscalelefttext(canvas);
    }
    //绘制内圆弧
    private void drawinnerarc(canvas canvas){
        //保存之前的画布
        canvas.save();
        canvas.drawarc( oval, startangle,sweepangle,false,innerarcpaint);
    }
    //绘制外圆弧
    private void drawouterarc(canvas canvas){
        canvas.save();
        canvas.drawarc( oval, startangle,sweepangle * currentdata / 300,false,outerarcpaint);
    }
    //绘制中间指针
    private void drawarrow(canvas canvas){
       canvas.save();
        bitmap bitmap = bitmapfactory.decoderesource( getresources(),r.mipmap.waterdrop );
        int width = 75;
        int height = 75;
        int newwidth = (int)(getwidth() * 0.08);
        float scalewidth = (float) (newwidth / width);
        float scaleheight = (float) (newwidth / height);
        matrix matrix = new matrix(  );
        //顺序不能颠倒
        matrix.setrotate( -75 + (sweepangle * currentdata / 300),bitmap.getwidth()/2,bitmap.getheight()/2 );
        matrix.postscale( scalewidth,scaleheight );

        bitmap bitmap1 = bitmap.createbitmap( bitmap,0,0,width,height,matrix,true );
        canvas.drawbitmap( bitmap1,getwidth()/2 - bitmap1.getwidth()/2,getheight()/2 - bitmap1.getheight()/2,innerarcpaint );
        bitmap.recycle();
        bitmap1.recycle();
    }
    private void drawcurrentdatatext(canvas canvas){
        canvas.save();
        rect rect = new rect(  );
        string str = string.valueof( currentdata ) + "kg";
        textpaint.setcolor( color.red );
        textpaint.gettextbounds( str,0,str.length(),rect );
        canvas.drawtext( str,getwidth()/2 - rect.width()/2,(int)(getheight() * (float)0.38),textpaint );
    }
    private void drawscalerighttext(canvas canvas){
        canvas.save();
        rect rect = new rect(  );
        string str =  "300kg";
        textpaint.settextsize( 45 );
        textpaint.gettextbounds( str,0,str.length(),rect );
        textpaint.setcolor( color.white );
        canvas.drawtext( str,getwidth()-getwidth()/6,(getheight()/2+getwidth()/5) ,textpaint );
    }
    private void drawscalelefttext(canvas canvas){
        canvas.save();
        rect rect = new rect(  );
        string str =  "0kg";
        textpaint.settextsize( 45 );
        textpaint.gettextbounds( str,0,str.length(),rect );
        textpaint.setcolor( color.white );
        canvas.drawtext( str,(getwidth()/2-(getwidth()/3 + 75)),(getheight()/2+getwidth()/5) ,textpaint );
    }
    public void setcurrentdata(final float data, timeinterpolator interpolator){
        long time = ( (long)math.abs( data- currentdata ) *20);
        final valueanimator valueanimator = valueanimator.offloat( currentdata,data ).setduration( time );
        valueanimator.setinterpolator( interpolator );
        valueanimator.addupdatelistener( new valueanimator.animatorupdatelistener() {
            @override
            public void onanimationupdate(valueanimator animation) {
                customview_clockdial.this.currentdata = (float)valueanimator.getanimatedvalue();
                invalidate();
            }
        } );
        valueanimator.start();
    }
}

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