看看效果

Demo效果圖

總體的實(shí)現(xiàn)思路

• 用一個(gè)View（ImageView）容器來呈現(xiàn)動(dòng)畫
• 給ImageView設(shè)置一個(gè)Drawable（在這個(gè)drawable里面實(shí)現(xiàn)所有的繪制邏輯）
• 實(shí)現(xiàn)動(dòng)畫的效果的核心就是，當(dāng)ImageView調(diào)用Drawable的draw（系統(tǒng)自動(dòng)調(diào)用）方法的時(shí)候再次調(diào)用ImageView的重繪方法就實(shí)現(xiàn)了動(dòng)畫效果了

看看這個(gè)demo的實(shí)現(xiàn)

• 重寫了一個(gè)ImageView僅僅就是為了設(shè)置一個(gè)Drawable，不用重寫也可以。

public class LoadingView extends ImageView{

    public LoadingView(Context context) {
        super(context);
        setImageDrawable(new LoadingDrawable(this));
    }

    public LoadingView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        setImageDrawable(new LoadingDrawable(this));
    }

    public LoadingView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        setImageDrawable(new LoadingDrawable(this));
    }

}

• 核心就是這個(gè)LoadingDrawable，直接看draw方法吧

    @Override
    public void draw(@NonNull Canvas canvas) {
        //默認(rèn)從左到右
        int width = canvas.getWidth();
        int height = canvas.getHeight();
        int centerX = width / 2;
        int centerY = height / 2;
        //canvas.drawCircle(centerX,centerY,width / 2 - 8,paint);
        for(int i=0;i < lineModels.size();i++){
            drawLine(canvas,lineModels.get(i));
        }
        //updatedata
        contannier.invalidate();
    }


    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    private void drawLine(Canvas canvas, LineModel lineModel){
        int width = canvas.getWidth() / 2;
        int height = canvas.getHeight() / 2;
        paint.setColor(lineModel.color);
        canvas.drawArc(
                width - lineModel.raudis - strokeWidth,height - lineModel.raudis - strokeWidth,
                width + lineModel.raudis + strokeWidth,height + lineModel.raudis + strokeWidth,
                lineModel.start,lineModel.end,
                false,paint
        );
        lineModel.updata();
    }

- 這里的**drawLine**就是具體的繪制過程，并且在繪制完成之后更新了下次需要繪制的各種信息
- 繪制完成之后調(diào)用了 **ImageView**的**invalidate**方法進(jìn)行循環(huán)繪制

實(shí)現(xiàn)思路來自

[==↓ ] https://github.com/81813780/AVLoadingIndicatorView

[== ↑] https://github.com/tyrantgit/ExplosionField

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