使用Canvas自定义图形 之 自定义加载动画效果

public class LoadAnimationView extends View {

    private int width;
    private int height;
    private int size;
    private int length;
    private Paint paint;
    private float strokeWidth;
    private int distanceBoundary;
    private int alpha;
    private int color;
    private final int DEFAULT_ROTATE_DEGREE = 45;
    private int degree = DEFAULT_ROTATE_DEGREE;
    private boolean isStopped;

    public LoadAnimationView(Context context) {
        this(context, null);
    }

    public LoadAnimationView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        if(attrs != null){
            TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.LoadAnimationView);
            strokeWidth = typedArray.getFloat(R.styleable.LoadAnimationView_stroke_width,5f);
            distanceBoundary = typedArray.getInt(R.styleable.LoadAnimationView_distance_padding,10);
            length = typedArray.getInt(R.styleable.LoadAnimationView_length,12);
            color = typedArray.getInt(R.styleable.LoadAnimationView_base_color,Color.DKGRAY);
            typedArray.recycle();
        }
        paint = new Paint();
        alpha = 150;
        paint.setStyle(Paint.Style.FILL_AND_STROKE);
        paint.setColor(color);
        paint.setAlpha(alpha);
        paint.setAntiAlias(true);
        paint.setStrokeWidth(strokeWidth);
        paint.setStrokeCap(Paint.Cap.ROUND);
        new Thread(new Runnable() {
            @Override
            public void run() {
                while (!isStopped) {
                    try {
                        Thread.sleep(90);
                        degree += DEFAULT_ROTATE_DEGREE;
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    LoadAnimationView.this.invalidate();
                }
            }
        }).start();
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        width = getMeasuredWidth();
        height = getMeasuredHeight();
        size = Math.min(width, height);
        setMeasuredDimension(size, size);
        distanceBoundary = size / 10;

    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        drawAnimation(canvas);
    }

    private void drawAnimation(Canvas canvas) {
        canvas.save();
        canvas.rotate(degree, size / 2, size / 2);
        drawOnce(canvas);
        canvas.restore();
    }

    private void drawOnce(Canvas canvas) {
        int startX = size / 2;
        int startY = distanceBoundary;
        int stopX = size / 2;
        int stopY = distanceBoundary + length;
        canvas.drawLine(startX, startY, stopX, stopY, paint);
        alpha = 150;
        for (int i = 0; i < 4; i++) {
            alpha -= 15;
            paint.setAlpha(alpha);
            canvas.rotate(DEFAULT_ROTATE_DEGREE, size / 2, size / 2);
            canvas.drawLine(startX, startY, stopX, stopY, paint);
        }
        alpha -= 15;
        for (int j = 0; j < 4; j++) {
            paint.setAlpha(alpha);
            canvas.rotate(DEFAULT_ROTATE_DEGREE, size / 2, size / 2);
            canvas.drawLine(startX, startY, stopX, stopY, paint);
        }
    }

    public void drawIsStopped(boolean isStopped){
        if(this.isStopped != isStopped)
            this.isStopped = isStopped;
    }
}

另外，canvas还有drawBitmap方法

private void drawBitmap(Canvas canvas) {
        Rect rect = new Rect((int) distanceBoundary, (int) distanceBoundary, (int) (size - distanceBoundary), (int) (size - distanceBoundary));
        if (state) {
            canvas.drawBitmap(bitmapPause, null, rect, paintButton);
        } else {
            canvas.drawBitmap(bitmapStart, null, rect, paintButton);
        }
    }

drawable转bitmap

public Bitmap decodeBitmapFromResource(Context context, int drawableId) {
        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP)
            return BitmapFactory.decodeResource(context.getResources(), drawableId);
        Drawable drawable = ContextCompat.getDrawable(context, drawableId);
        Bitmap bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight(), Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(bitmap);
        drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());
        drawable.draw(canvas);
        return bitmap;
    }