public class TuyaView extends View {
private Bitmap mBitmap;
private Canvas mCanvas;
private Path mPath;
private Paint mBitmapPaint;// 画布的画笔
private Paint mPaint;// 真实的画笔
private float mX, mY;// 临时点坐标
private static final float TOUCH_TOLERANCE = 4;
// 保存Path路径的集合,用List集合来模拟栈
private static List<DrawPath> savePath;
// 记录Path路径的对象
private DrawPath dp;
private int screenWidth, screenHeight;// 屏幕長寬
private class DrawPath {
public Path path;// 路径
public Paint paint;// 画笔
}
public TuyaView(Context context, int w, int h) {
super(context);
screenWidth = w;
screenHeight = h;
mBitmap = Bitmap.createBitmap(screenWidth, screenHeight, Bitmap.Config.ARGB_8888);
// 保存一次一次绘制出来的图形
mCanvas = new Canvas(mBitmap);
mBitmapPaint = new Paint(Paint.DITHER_FLAG);
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);// 设置外边缘
mPaint.setStrokeCap(Paint.Cap.SQUARE);// 形状
mPaint.setStrokeWidth(5);// 画笔宽度
savePath = new ArrayList<DrawPath>();
}
@Override
public void onDraw(Canvas canvas) {
canvas.drawColor(0xFFAAAAAA);
// 将前面已经画过得显示出来
canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
if (mPath != null) {
// 实时的显示
canvas.drawPath(mPath, mPaint);
}
}
private void touch_start(float x, float y) {
mPath.moveTo(x, y);
mX = x;
mY = y;
}
private void touch_move(float x, float y) {
float dx = Math.abs(x - mX);
float dy = Math.abs(mY - y);
if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
// 从x1,y1到x2,y2画一条贝塞尔曲线，更平滑(直接用mPath.lineTo也是可以的)
mPath.quadTo(mX, mY, (x + mX) / 2, (y + mY) / 2);
mX = x;
mY = y;
}
}
private void touch_up() {
mPath.lineTo(mX, mY);
mCanvas.drawPath(mPath, mPaint);
//将一条完整的路径保存下来(相当于入栈操作)
savePath.add(dp);
mPath = null;// 重新置空
}
/**
* 撤销的核心思想就是将画布清空，
* 将保存下来的Path路径最后一个移除掉，
* 重新将路径画在画布上面。
*/
public void undo() {
mBitmap = Bitmap.createBitmap(screenWidth, screenHeight,
Bitmap.Config.ARGB_8888);
mCanvas.setBitmap(mBitmap);// 重新设置画布，相当于清空画布
// 清空画布，但是如果图片有背景的话，则使用上面的重新初始化的方法，用该方法会将背景清空掉...
if (savePath != null && savePath.size() > 0) {
// 移除最后一个path,相当于出栈操作
savePath.remove(savePath.size() - 1);
Iterator<DrawPath> iter = savePath.iterator();
while (iter.hasNext()) {
DrawPath drawPath = iter.next();
mCanvas.drawPath(drawPath.path, drawPath.paint);
}
invalidate();// 刷新
/*在这里保存图片纯粹是为了方便,保存图片进行验证*/
String fileUrl = Environment.getExternalStorageDirectory()
.toString() + "/android/data/test.png";
try {
FileOutputStream fos = new FileOutputStream(new File(fileUrl));
mBitmap.compress(CompressFormat.PNG, 100, fos);
fos.flush();
fos.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
/**
* 重做的核心思想就是将撤销的路径保存到另外一个集合里面(栈)，
* 然后从redo的集合里面取出最顶端对象，
* 画在画布上面即可。
*/
public void redo(){
//如果撤销你懂了的话，那就试试重做吧。
}
@Override
public boolean onTouchEvent(MotionEvent event) {
float x = event.getX();
float y = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
// 每次down下去重新new一个Path
mPath = new Path();
//每一次记录的路径对象是不一样的
dp = new DrawPath();
dp.path = mPath;
dp.paint = mPaint;
touch_start(x, y);
invalidate();
break;
case MotionEvent.ACTION_MOVE:
touch_move(x, y);
invalidate();
break;
case MotionEvent.ACTION_UP:
touch_up();
invalidate();
break;
}
return true;
}
}

public class TuyaActivity extends Activity {
private TuyaView tuyaView = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
DisplayMetrics dm = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(dm);
tuyaView = new TuyaView(this, dm.widthPixels, dm.heightPixels);
setContentView(tuyaView);
}
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) {// 返回键
tuyaView.undo();
return true;
}
return super.onKeyDown(keyCode, event);
}
}