Android 一个简单的绘图示例
这段代码应该是在画东西，但当我移动手指时，它不会画任何东西。请帮我调试一下Android 一个简单的绘图示例,android,Android,这段代码应该是在画东西，但当我移动手指时，它不会画任何东西。请帮我调试一下 @Override protected void onDraw(Canvas canvas) { canvas.drawPath(path, paint); } @Override public boolean onTouchEvent(MotionEvent event) { float eventX = event.getX(); float eventY = event
@Override
protected void onDraw(Canvas canvas) {
canvas.drawPath(path, paint);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
float eventX = event.getX();
float eventY = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
path.moveTo(eventX, eventY);
return true;
case MotionEvent.ACTION_MOVE:
path.lineTo(eventX, eventY);
break;
case MotionEvent.ACTION_UP:
// nothing to do
break;
default:
return false;
}
// Schedules a repaint.
invalidate();
return true;
}
}
@Override
protected void onDraw(Canvas canvas)
{
canvas.drawPath(path, paint);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
float eventX = event.getX();
float eventY = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
path.moveTo(eventX, eventY);
path.lineTo(eventX, eventY);
return true;
case MotionEvent.ACTION_MOVE:
path.quadTo(eventX, eventY, (x + eventX)/2, (y + eventY)/2);
break;
case MotionEvent.ACTION_UP:
canvas.drawPath(path, paint);
// kill this so we don't double draw
path.reset();
break;
default:
return false;
}
// Schedules a repaint.
invalidate();
return true;
}
}
@Override
protected void onDraw(Canvas canvas)
{
canvas.drawPath(path, paint);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
float eventX = event.getX();
float eventY = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
path.moveTo(eventX, eventY);
path.lineTo(eventX, eventY);
return true;
case MotionEvent.ACTION_MOVE:
path.quadTo(eventX, eventY, (x + eventX)/2, (y + eventY)/2);
break;
case MotionEvent.ACTION_UP:
canvas.drawPath(path, paint);
// kill this so we don't double draw
path.reset();
break;
default:
return false;
}
// Schedules a repaint.
invalidate();
return true;
}
}
这可能会对您有所帮助。这是我的工作示例，您可以徒手绘制
public class CanvasDrawingActivity extends Activity
{
private ArrayList<Path> _graphics = new ArrayList<Path>();
private Paint mPaint;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(new DrawingPanel(this));
mPaint = new Paint();
mPaint.setDither(true);
mPaint.setColor(0xFFFFFF00);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setStrokeWidth(3);
}
class DrawingPanel extends SurfaceView implements SurfaceHolder.Callback
{
private DrawingThread _thread;
private Path path;
public DrawingPanel(Context context)
{
super(context);
getHolder().addCallback(this);
_thread = new DrawingThread(getHolder(), this);
}
public boolean onTouchEvent(MotionEvent event)
{
synchronized (_thread.getSurfaceHolder()) {
if(event.getAction() == MotionEvent.ACTION_DOWN){
path = new Path();
path.moveTo(event.getX(), event.getY());
path.lineTo(event.getX(), event.getY());
}else if(event.getAction() == MotionEvent.ACTION_MOVE){
path.lineTo(event.getX(), event.getY());
}else if(event.getAction() == MotionEvent.ACTION_UP){
path.lineTo(event.getX(), event.getY());
_graphics.add(path);
}
return true;
}
}
@Override
public void onDraw(Canvas canvas) {
for (Path path : _graphics) {
//canvas.drawPoint(graphic.x, graphic.y, mPaint);
canvas.drawPath(path, mPaint);
}
}
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
// TODO Auto-generated method stub
}
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
_thread.setRunning(true);
_thread.start();
}
public void surfaceDestroyed(SurfaceHolder holder) {
// TODO Auto-generated method stub
boolean retry = true;
_thread.setRunning(false);
while (retry) {
try {
_thread.join();
retry = false;
} catch (InterruptedException e) {
// we will try it again and again...
}
}
}
}
class DrawingThread extends Thread {
private SurfaceHolder _surfaceHolder;
private DrawingPanel _panel;
private boolean _run = false;
public DrawingThread(SurfaceHolder surfaceHolder, DrawingPanel panel) {
_surfaceHolder = surfaceHolder;
_panel = panel;
}
public void setRunning(boolean run) {
_run = run;
}
public SurfaceHolder getSurfaceHolder() {
return _surfaceHolder;
}
@Override
public void run() {
Canvas c;
while (_run) {
c = null;
try {
c = _surfaceHolder.lockCanvas(null);
synchronized (_surfaceHolder) {
_panel.onDraw(c);
}
} finally {
// do this in a finally so that if an exception is thrown
// during the above, we don't leave the Surface in an
// inconsistent state
if (c != null) {
_surfaceHolder.unlockCanvasAndPost(c);
}
}
}
}
}
}
这是我的工作示例，你可以徒手画
public class CanvasDrawingActivity extends Activity
{
private ArrayList<Path> _graphics = new ArrayList<Path>();
private Paint mPaint;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(new DrawingPanel(this));
mPaint = new Paint();
mPaint.setDither(true);
mPaint.setColor(0xFFFFFF00);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setStrokeWidth(3);
}
class DrawingPanel extends SurfaceView implements SurfaceHolder.Callback
{
private DrawingThread _thread;
private Path path;
public DrawingPanel(Context context)
{
super(context);
getHolder().addCallback(this);
_thread = new DrawingThread(getHolder(), this);
}
public boolean onTouchEvent(MotionEvent event)
{
synchronized (_thread.getSurfaceHolder()) {
if(event.getAction() == MotionEvent.ACTION_DOWN){
path = new Path();
path.moveTo(event.getX(), event.getY());
path.lineTo(event.getX(), event.getY());
}else if(event.getAction() == MotionEvent.ACTION_MOVE){
path.lineTo(event.getX(), event.getY());
}else if(event.getAction() == MotionEvent.ACTION_UP){
path.lineTo(event.getX(), event.getY());
_graphics.add(path);
}
return true;
}
}
@Override
public void onDraw(Canvas canvas) {
for (Path path : _graphics) {
//canvas.drawPoint(graphic.x, graphic.y, mPaint);
canvas.drawPath(path, mPaint);
}
}
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
// TODO Auto-generated method stub
}
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
_thread.setRunning(true);
_thread.start();
}
public void surfaceDestroyed(SurfaceHolder holder) {
// TODO Auto-generated method stub
boolean retry = true;
_thread.setRunning(false);
while (retry) {
try {
_thread.join();
retry = false;
} catch (InterruptedException e) {
// we will try it again and again...
}
}
}
}
class DrawingThread extends Thread {
private SurfaceHolder _surfaceHolder;
private DrawingPanel _panel;
private boolean _run = false;
public DrawingThread(SurfaceHolder surfaceHolder, DrawingPanel panel) {
_surfaceHolder = surfaceHolder;
_panel = panel;
}
public void setRunning(boolean run) {
_run = run;
}
public SurfaceHolder getSurfaceHolder() {
return _surfaceHolder;
}
@Override
public void run() {
Canvas c;
while (_run) {
c = null;
try {
c = _surfaceHolder.lockCanvas(null);
synchronized (_surfaceHolder) {
_panel.onDraw(c);
}
} finally {
// do this in a finally so that if an exception is thrown
// during the above, we don't leave the Surface in an
// inconsistent state
if (c != null) {
_surfaceHolder.unlockCanvasAndPost(c);
}
}
}
}
}
}
你初始化了路径并用颜色对象绘制了吗，你能发布更多的代码吗..当然…我只是把它缩短了参考完整的教程。你初始化了路径并用颜色对象绘制了吗，你能发布更多的代码吗…当然…我只是把它简化成完整的教程。对于像我这样的初学者来说很好但是太重了：我怎么才能添加一个按钮来清除画布，我只需要清除线条的代码。为什么用曲面视图自由绘制时速度慢？为什么？对于像我这样的初学者来说，很好但是太重了：如何添加一个按钮来清除画布，我只需要清除线条的代码。为什么使用surface view徒手绘制时速度很慢？这幅画是在我们释放触摸之后绘制的为什么？我的paint.setColor在白色背景中被设置为白色，这很可笑，所以一切都正常，但我无法理解。顺便说一句，quadTo的作用是什么…我的代码没有这个就可以工作。我如何添加一个按钮来清除画布，我只需要代码来清除线条。我的paint.setColor在白色背景中被设置为白色是荒谬的，所以一切都可以工作，但我无法得到它。顺便说一句，quadTo的作用是什么…我的代码没有这个功能就可以工作。我如何添加一个按钮来清除画布，我只需要清除行的代码。。