上一篇對自定義View及一些方法有所了解，下面做一個簡單的葉子飄動的例子

主要技術點

1、添加背景圖片canvas.drawBitmap()

2、Matrix動畫類

3、Matrix添加到畫布上

步驟

1、添加黃色背景顏色

public LeafView(Context context, AttributeSet attrs) {

super(context, attrs);

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;

}

@Override

protected void onDraw(Canvas canvas) {

super.onDraw(canvas);

bgRect = new RectF(0, 0 , width, height);

canvas.drawRect(bgRect, bgPaint);

}

2、添加背景圖片

public LeafView(Context context, AttributeSet attrs) {

super(context, attrs);

mResources = getResources();

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);

canvas.drawRect(bgRect, bgPaint);

canvas.drawBitmap(bgBitmap, null, bgDestRect, null);

}

canvas.drawBitmap(Bitmap bitmap, Rect src, Rect dst, Paint paint) 添加圖片到畫布

Rect src：圖片剪裁,null圖片顯示全屏，? RectF dst：圖片在Canvas畫布區域

3、添加葉子

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();

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

canvas.drawBitmap(leafBitmap, new Matrix(), new Paint());

}

canvas.drawBitmap(Bitmap bitmap, Matrix matrix, Paint paint)添加一個帶動畫的bitmap到畫布

這里matrix什么都沒定義，所以默認如下顯示，左上角葉子

4、給葉子添加Matrix動畫

Matrix作用：

a、translate 平移

b、rotate 旋轉

c、scale 縮放

d、skew 傾斜

這里要用到matrix.postTranslate(float x, float y)，以畫布左上角為(0,0); xy為平移絕對值

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(), (height-mLeadHeight)/2);

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;

}

好了，看到的效果就是如下，由于Matrix沒有設置動畫時間長度概念，所以通過時間差來計算出位移值的方式，來設置滑動快慢

完整代碼不貼了，就把上面這段代碼復制到一個LeafView extends View中，然后在里面定義幾個全局變量就好了。

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找一找教程網。

總結

以上是生活随笔為你收集整理的android 屏幕飘动,Android自定义View实现飘动的叶子效果（三）的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。