优势
SurfaceView 继承于View
自定义view是在主线程进行绘制的
SurfaceView的绘制是在一个子线程中对自己进行绘制，所以可以避免UI线程阻塞
绘制
SurfaceView中包含一个专门用于绘制的surface，Surface中包含一个canvas
如何获取canvas呢
getHolder -> SurfaceHolder
holder -> Canvas
这样我们就可以获取Canvas 对象了，其实Holder不仅可以获取canvas对象，同时也管理着SurfaceView的生命周期，通过holder.addCallback实现SurfaceHolder.Callback:
- surfaceCreated
- surfaceChanged
- surfaceDestoryed
编写SurfaceView模版
具体看如下代码
/**
* @author: robert
* @date: 2017-10-21
* @time: 11:57
* @说明: SurfaceView 编写模板
*/
public class SurfaceViewTemplate extends SurfaceView implements SurfaceHolder.Callback, Runnable {
private SurfaceHolder mHolder;
private Canvas mCanvas;
/**
* 用于绘制的线程
*/
private Thread mThread;
/**
* 是否绘制
*/
private boolean isRunning;
public SurfaceViewTemplate(Context context) {
this(context, null);
}
public SurfaceViewTemplate(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
mHolder = getHolder();
mHolder.addCallback(this);
//设置焦点
setFocusable(true);
setFocusableInTouchMode(true);
//屏幕常亮
setKeepScreenOn(true);
}
@Override
public void surfaceCreated(SurfaceHolder surfaceHolder) {
isRunning = true;
mThread = new Thread(this);
mThread.start();
}
@Override
public void surfaceChanged(SurfaceHolder surfaceHolder, int i, int i1, int i2) {
}
@Override
public void surfaceDestroyed(SurfaceHolder surfaceHolder) {
isRunning = false;
}
private void draw() {
try {
mCanvas = mHolder.lockCanvas();
if (mCanvas != null) {
//drawSomeThing
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (mCanvas != null) {//释放canvas
mHolder.unlockCanvasAndPost(mCanvas);
}
}
}
@Override
public void run() {
//不断进行绘制
while (isRunning) {
draw();
}
}
}
示例：
/**
* @author: robert
* @date: 2017-10-21
* @time: 11:57
* @说明: 旋转转盘，可设置选中项
*/
public class LuckyPanView extends SurfaceView implements SurfaceHolder.Callback, Runnable {
private static final String TAG = "LuckyPanView";
private SurfaceHolder mHolder;
private Canvas mCanvas;
/* 用于绘制的线程*/
private Thread mThread;
/* 是否绘制*/
private boolean isRunning;
/* 转盘文字 */
private String[] mStrings = new String[]{"单反相机", "IPad", "恭喜发财",
"IPhone", "服装一套", "恭喜发财"};
/* 转盘图标 */
private int[] mImages = new int[]{R.drawable.danfan, R.drawable.ipad, R.drawable.f040,
R.drawable.iphone, R.drawable.meizi, R.drawable.f015};
/* 转盘背景颜色 */
private int[] mColors = new int[]{0xFFFFC300, 0xFFF17E01, 0xFFFFC300, 0xFFF17E01, 0xFFFFC300, 0xFFF17E01};
/* 图片对应的Bitmap对象 */
private Bitmap[] mImageBmp;
/* 背景bitmap */
private Bitmap mBgBmp = decodeResource(getResources(), R.drawable.bg2);
/* 绘制文字大小 */
private float mTextSize = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, 20, getResources().getDisplayMetrics());
/* 条目个数 */
private int mItemSize = 6;
/* 盘块中心 */
private int mCenter;
/* 整个盘块的范围 */
private RectF mRectF = new RectF();
/* 盘块的半径*/
private int mRadius;
/* 盘块画笔 */
private Paint mArcPaint;
/* 文本的画笔 */
private Paint mTextPaint;
/* 转盘内边距,取转盘最小值,因为圆的 */
private int mPadding;
/* 键盘速度 */
private double mSpeed = 0;
/* 转盘起始角度 */
private volatile double mStartAngle;
/* 判断是否点击了停止按钮 */
private boolean isShouldEnd;
public LuckyPanView(Context context) {
this(context, null);
}
public LuckyPanView(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
mHolder = getHolder();
mHolder.addCallback(this);
//设置焦点
setFocusable(true);
setFocusableInTouchMode(true);
//屏幕常亮
setKeepScreenOn(true);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
int radius = Math.min(getMeasuredHeight(), getMeasuredWidth());
mPadding = getPaddingLeft();
//直径
mRadius = radius - mPadding * 2;
//中心点
mCenter = radius / 2;
setMeasuredDimension(radius, radius);
}
@Override
public void surfaceCreated(SurfaceHolder surfaceHolder) {
//初始化转盘画笔
Paint paint = new Paint();
paint.setDither(true);
paint.setAntiAlias(true);
mArcPaint = paint;
//初始化文字画笔
paint = new Paint();
paint.setAntiAlias(true);
paint.setDither(true);
paint.setColor(0xffffffff);
paint.setTextSize(mTextSize);
mTextPaint = paint;
//转盘矩阵范围
mRectF = new RectF(mPadding, mPadding, mRadius + mPadding, mRadius + mPadding);
//初始化图片
mImageBmp = new Bitmap[mItemSize];
for (int i = 0; i < mImages.length; i++) {
mImageBmp[i] = BitmapFactory.decodeResource(getResources(), mImages[i]);
}
isRunning = true;
mThread = new Thread(this);
mThread.start();
}
@Override
public void surfaceChanged(SurfaceHolder surfaceHolder, int format, int width, int height) {
}
@Override
public void surfaceDestroyed(SurfaceHolder surfaceHolder) {
isRunning = false;
}
@Override
public void run() {
//不断进行绘制
while (isRunning) {//维持50ms绘制一次
long start = System.currentTimeMillis();
draw();
long end = System.currentTimeMillis();
if (end - start < 50) {
SystemClock.sleep(50 - (end - start));
}
}
}
private void draw() {
try {
mCanvas = mHolder.lockCanvas();
if (mCanvas != null) {
//画背景
drawBg();
//绘制盘块
float tempAngle = (float) mStartAngle;
float sweepAngle = 360 / mItemSize;
for (int i = 0; i < mItemSize; i++) {
mArcPaint.setColor(mColors[i]);
//绘制盘块
mCanvas.drawArc(mRectF, tempAngle, sweepAngle, true, mArcPaint);
//绘制文本
drawText(tempAngle, sweepAngle, mStrings[i]);
//绘制图标
drawIcon(tempAngle, sweepAngle, mImageBmp[i]);
tempAngle = tempAngle + sweepAngle;
}
if (isShouldEnd) {
KLog.e(TAG, "draw: " + mStartAngle);
mSpeed--;
}
if (mSpeed < 0) {
mSpeed = 0;
isShouldEnd = false;
}
mStartAngle += mSpeed;
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (mCanvas != null) {//释放canvas
mHolder.unlockCanvasAndPost(mCanvas);
}
}
}
public void luckyStart(int index) {
float avAgngle = 360 / mItemSize;
//随机的一个角度
float randomAngle = (float) (avAgngle * Math.random());
//总共的角度，让他转4圈加上转的角度再加上一个随机的角度
float angle = 360 * 4 + avAgngle * index + randomAngle;
KLog.e(TAG, "luckyStart: " + angle);
//计算初始速度 s = 平均速度*时间 匀加速运动所以平均速度为(起始速度+结束速度)/2 时间 t = v/a 速度的变化除以加速度
mSpeed = Math.sqrt(2 * angle) + 0.5d;
KLog.e(TAG, "luckyStart: " + mSpeed);
isShouldEnd = false;
}
public void luckyStop() {
mStartAngle = 0;
isShouldEnd = true;
}
//是否在结束中，还在转，但是已经点击过停止即isShouldEnd为TRUE
public boolean isEnding() {
return isShouldEnd && isTurning();
}
/**
* 是否停止旋转
*
* @return
*/
public boolean isTurning() {
return mSpeed != 0;
}
/**
* 画图表
*
* @param tempAngle 弧度开始角度
* @param sweepAngle 弧度大小
* @param imageBmp icon
*/
private void drawIcon(float tempAngle, float sweepAngle, Bitmap imageBmp) {
int imgWidth = mRadius / 8;
double angle = Math.toRadians(tempAngle + sweepAngle / 2);
int x = mCenter + (int) ((mRadius / 2 / 2) * Math.cos(angle));
int y = mCenter + (int) ((mRadius / 2 / 2) * Math.sin(angle));
mCanvas.drawBitmap(imageBmp, null,
new RectF(x - imgWidth / 2, y - imgWidth / 2, x + imgWidth / 2, y + imgWidth / 2),
null);
}
/**
* 绘制每个盘块的文本
*
* @param startAngle 弧度开始角度
* @param sweepAngle 弧度大小
* @param string 文本
*/
private void drawText(float startAngle, float sweepAngle, String string) {
Path path = new Path();
path.addArc(mRectF, startAngle, sweepAngle);
//水平和垂直 偏移量
//利用水平偏移量让文字居中
float textWidth = mTextPaint.measureText(string);
//弧度的一半减去文字宽度的一半，则是文字的水平偏移量
int hOffset = (int) (mRadius * Math.PI / mItemSize / 2 - textWidth / 2);
//垂直偏移量设置为当前半径的六分之一
int vOffset = mRadius / 2 / 6;
mCanvas.drawTextOnPath(string, path, hOffset, vOffset, mTextPaint);
}
/**
* 绘制背景
*/
private void drawBg() {
if (mCanvas != null) {
mCanvas.drawColor(Color.WHITE);
mCanvas.drawBitmap(mBgBmp, null,
new RectF(mPadding / 2, mPadding / 2, getMeasuredWidth() - mPadding / 2, getMeasuredHeight() - mPadding / 2),
null);
}
}
}
整体demo已上传github https://github.com/IdioticMadman/SurfaceViewLean
