上一篇實現了葉子飄動功能，《Android自定義葉子飄動》 現在實現旋轉效果
要實現這個效果，要在之前的功能上添加2個功能
1、通過matrix.postTranslate(int x, int y)在添加在Y軸上滑動
2、通過matrix.postRotate(float degrees, float px, float py)實現葉子旋轉
代碼實現
1、獲取Y坐標
private float getMatrixY() { float w = (float) ((float) 2 * Math.PI / width); int y = (int) (18 * Math.sin(w * getMatrixX())) + (height-mLeafHeight)/2; return y; }math.sin(Math.PI....)的取值范圍貌似是-1~1之間。通過X坐標在整個width的比例，獲取到Y坐標的比例。
這里方法有很多，我這邊葉子Y坐標默認在Y軸中間，然后上下+-18px實現在Y軸的滑動，18滑動浮動比較大了
public LeafView(Context context, AttributeSet attrs) { super(context, attrs); mResources = getResources(); bgBitmap = ((BitmapDrawable) mResources.getDrawable(R.drawable.leaf_kuang, null)).getBitmap(); leafBitmap = ((BitmapDrawable) mResources.getDrawable(R.drawable.leaf, null))).getBitmap(); mLeafHeight = leafBitmap.getWidht(); bgPaint = new Paint(); bgPaint.setColor(mResources.getColor(R.color.bg_color)); } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); width = w; height = h; bgDestRect = new Rect(0, 0 , width, height); } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); bgRect = new RectF(0, 0 , width, height); //添加黃色背景 canvas.drawRect(bgRect, bgPaint); //添加背景圖片 canvas.drawBitmap(bgBitmap, null, bgDestRect, null); //添加葉子 Matrix matrix = new Matrix(); matrix.postTranslate(getMatriX(), getMatrixY); canvas.drawBitmap(leafBitmap, new Matrix(), new Paint()); //重復調用onDraw() postInvalidate(); } long cycleTime = 5000; //葉子滑動一周的時間5秒 long startTime = 0; //葉子滑動開始時間 private float getMatriX() { float betweenTime = startTime - System.currentTimeMillis(); //周期結束再加一個cycleTime if(betweenTime < 0) { startTime = System.currentTimeMillis() + cycleTime; betweenTime = cycleTime; } //通過時間差計算出葉子的坐標 float fraction = (float) betweenTime / cycleTime; float x = (int)(width * fraction); return x; } private float getMatrixY() { float w = (float) ((float) 2 * Math.PI / width); int y = (int) (18 * Math.sin(w * getMatrixX())) + (height-mLeafHeight)/2; return y; }看下效果就這樣，在Y軸上實現上下浮動，如果要浮動小點，可以把18改小
2、實現旋轉
主要通過matrix.postRotate(float degrees, float px, float py)
degrees就是角度（0~360），px，py就是圖片的中心點
private int getRotate() { float scale = ((startTime - System.currentTimeMillis())%cycleTime)/ (float)cycleTime; int rotate = (int)(scale * 360); return rotate; }同樣，通過當前葉子在X軸的比例，來計算出旋轉的角度(0~360)
完整代碼：
public class LeafView extends View { private Resources mResources; private Bitmap mLeafBitmap, bgBitmap; private int width, height; private int mLeafWidth,mLeafHeight; private Paint bgPaint; private RectF bgRect; private Rect bgDestRect; public LeafView(Context context, AttributeSet attrs) { super(context, attrs); mResources = getResources(); mLeafBitmap = ((BitmapDrawable) mResources.getDrawable(R.drawable.leaf, null)).getBitmap(); mLeafWidth = mLeafBitmap.getWidht(); mLeafHeight = mLeafBitmap.getHeight(); bgBitmap = ((BitmapDrawable) mResources.getDrawable(R.drawable.leaf_kuang, null)).getBitmap(); bgPaint = new Paint(); bgPaint.setColor(mResources.getColor(R.color.bg_color)); } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); width = w; height = h; bgDestRect = new Rect(0, 0 , width, height); } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); bgRect = new RectF(0, 0 , width, height); //添加黃色白金 canvas.drawRect(bgRect, bgPaint); //添加背景圖片 canvas.drawBitmap(bgBitmap, null, bgDestRect, null); canvas.save(); Matrix matrix = new Matrix(); //添加滑動 matrix.postTranslate(getMatrixX(), getMatrixY()); //添加旋轉 matrix.postRotate(getRotate(), getMatrixX() + mLeafWidth / 2, getMatrixY() + mLeafHeight / 2); canvas.drawBitmap(mLeafBitmap, matrix, new Paint()); canvas.restore(); postInvalidate(); } long cycleTime = 5000; //葉子滑動一周的時間5秒 long startTime = 0; private float getMatrixX() { float betweenTime = startTime - System.currentTimeMillis(); //周期結束再加一個cycleTime if(betweenTime < 0) { startTime = System.currentTimeMillis() + cycleTime; betweenTime = cycleTime; } //通過時間差計算出葉子的坐標 float fraction = (float) betweenTime / cycleTime; float x = (int)(width * fraction); return x; } private float getMatrixY() { float w = (float) ((float) 2 * Math.PI / width); int y = (int) (18 * Math.sin(w * getMatrixX())) + (height-mLeafHeight)/2; return y; } private int getRotate() { float scale = ((startTime - System.currentTimeMillis())%cycleTime)/ (float)cycleTime; int rotate = (int)(scale * 360); return rotate; }}以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持VEVB武林網。
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