【移动应用开发技术】Android如何实现画板功能

【移动应用开发技术】Android如何实现画板功能

public

class

MySurfaceView

extends

SurfaceView

implements

SurfaceHolder.Callback,

Runnable

{

//

SurfaceHolder实例

private

SurfaceHolder

mSurfaceHolder;

//

Canvas对象

private

Canvas

mCanvas;

//

控制子线程是否运行

private

boolean

startDraw;

//

Path实例

private

Path

mPath

=

new

Path();

//

Paint实例

private

Paint

mpaint

=

new

Paint();

public

MySurfaceView(Context

context,

AttributeSet

attrs)

{

super(context,

attrs);

initView();

//

初始化

}

private

void

initView()

{

mSurfaceHolder

=

getHolder();

mSurfaceHolder.addCallback(this);

//

设置可获得焦点

setFocusable(true);

setFocusableInTouchMode(true);

//

设置常亮

this.setKeepScreenOn(true);

}

@Override

public

void

run()

{

//

如果不停止就一直绘制

while

(startDraw)

{

//

绘制

draw();

}

}

/*

*

创建

*/

@Override

public

void

surfaceCreated(SurfaceHolder

holder)

{

startDraw

=

true;

new

Thread(this).start();

}

/*

*

改变

*/

@Override

public

void

surfaceChanged(SurfaceHolder

holder,

int

format,

int

width,

int

height)

{

}

/*

*

销毁

*/

@Override

public

void

surfaceDestroyed(SurfaceHolder

holder)

{

startDraw

=

false;

}

private

void

draw()

{

try

{

mCanvas

=

mSurfaceHolder.lockCanvas();

mCanvas.drawColor(Color.WHITE);

mpaint.setStyle(Paint.Style.STROKE);

mpaint.setStrokeWidth(DensityUtil.px2dip(getContext(),

30));

mpaint.setColor(Color.BLACK);

mCanvas.drawPath(mPath,

mpaint);

}

catch

(Exception

e)

{

}

finally

{

//

对画布内容进行提交

if

(mCanvas

!=

null)

{

mSurfaceHolder.unlockCanvasAndPost(mCanvas);

}

}

}

@Override

public

boolean

onTouchEvent(MotionEvent

event)

{

int

x

=

(int)

event.getX();

//获取手指移动的x坐标

int

y

=

(int)

event.getY();

//获取手指移动的y坐标

switch

(event.getAction())

{

case

MotionEvent.ACTION_DOWN:

mPath.moveTo(x,

y);

break;

case

MotionEvent.ACTION_MOVE:

mPath.lineTo(x,

y);

break;

case

MotionEvent.ACTION_UP:

break;

}

return

true;

}

//

重置画布

public

void

reset()

{

mPath.reset();

}

}/upload/information/20200623/125/124154.pngprivate

Button

reset_btn;

private

MySurfaceView

mview;

@Override

protected

void

onCreate(Bundle

savedInstanceState)

{

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

context

=

this;

mview

=

(MySurfaceView)

findViewById(R.id.MySurfaceView);

reset_btn

=

(Button)

findViewById(R.id.reset_btn);

reset_btn.setOnClickListener(new

View.OnClickListener()

{

@Override

public

void

onClick(View

v)

{

//清除

mview.reset();

}

});public

class

SecondActivity

extends

Activity

{

private

ImageView

img;

private

Bitmap

mBitmap;

private

Canvas

canvas;

private

Paint

paint;

//

重置按钮

private

Button

reset_btn;

@Override

protected

void

onCreate(Bundle

savedInstanceState)

{

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_second);

img

=

(ImageView)

findViewById(R.id.img);

reset_btn

=

(Button)

findViewById(R.id.reset_btn);

reset_btn.setOnClickListener(new

View.OnClickListener()

{

@Override

public

void

onClick(View

v)

{

img.setImageBitmap(null);

showImage();

}

});

//

绘图

showImage();

}

private

void

showImage()

{

//

创建一张空白图片

mBitmap

=

Bitmap.createBitmap(720,

1280,

Bitmap.Config.ARGB_8888);

//

创建一张画布

canvas

=

new

Canvas(mBitmap);

//

画布背景为白色

canvas.drawColor(Color.WHITE);

//

创建画笔

paint

=

new

Paint();

//

画笔颜色为蓝色

paint.setColor(Color.BLUE);

//

宽度5个像素

paint.setStrokeWidth(5);

//

先将白色背景画上

canvas.drawBitmap(mBitmap,

new

Matrix(),

paint);

img.setImageBitmap(mBitmap);

img.setOnTouchListener(new

OnTouchListener()

{

int

startX;

int

startY;

@Override

public

boolean

onTouch(View

v,

MotionEvent

event)

{

switch

(event.getAction())

{

case

MotionEvent.ACTION_DOWN:

//

获取手按下时的坐标

startX

=

(int)

event.getX();

startY

=

(int)

event.getY();

break;

case

MotionEvent.ACTION_MOVE:

//

获取手移动后的坐标

int

endX

=

(int)

event.getX();

int

endY

=

(int)

event.getY();

//

在开始和结束坐标间画一条线

canvas.drawLine(startX,

startY,

endX,

endY,

paint);

//

刷新开始坐标

startX

=

(int)

event.getX();

startY

=

(int)

event.getY();

img.setImageBitmap(mBitmap);

break;

}

return

true;

}

});

}

}File

file

=

new

File(Environment.getExternalSto