Android中SurfaceView和view画出触摸轨迹
短信预约 -IT技能 免费直播动态提醒
一、引言
想实现一个空白的画板，上面可以画出手滑动的轨迹，就这么一个小需求。一般就来讲就两种实现方式，view或者surfaceview。下面看看两种是如何实现的。
二、实现原理
先简单说一下实现原理：
（1）用一张白色的Bitmap作为画板
（2）用canvas在bitmap上画线
（3）为了画出平滑的曲线，要用canvas的drawPath（Path，Paint）方法。
（4）同时使用贝塞尔曲线来使曲线更加平滑
三、View实现
直接贴代码了：
package picturegame.view;
import android.annotation.SuppressLint;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.graphics.Path;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import com.winton.picturegame.R;
public class GameView extends View{
private Paint paint = null; //
private Bitmap originalBitmap = null;//原始图
private Bitmap new1Bitmap = null;
private Bitmap new2Bitmap = null;
private float clickX =0;
private float clickY=0;
private float startX=0;
private float startY=0;
private boolean isMove = true;
private boolean isClear = false;
private int color =Color.RED;//默认画笔颜色
private float strokeWidth =20f;//默认画笔宽度
Path mPath;
public GameView(Context context) {
this(context,null);
// TODO Auto-generated constructor stub
}
public GameView(Context context,AttributeSet atts) {
this(context,atts,0);
// TODO Auto-generated constructor stub
}
@SuppressWarnings("static-access")
public GameView(Context context,AttributeSet atts,int defStyle) {
super(context,atts,defStyle);
// TODO Auto-generated constructor stub
originalBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.default_pic).copy(Bitmap.Config.ARGB_8888, true);//白色的画板
new1Bitmap=originalBitmap.createBitmap(originalBitmap);
mPath=new Path();
}
//清楚
@SuppressWarnings("static-access")
public void clear(){
isClear =true;
new2Bitmap=originalBitmap.createBitmap(originalBitmap);
invalidate();//重置
}
public void setStrokeWidth(float width){
this.strokeWidth=width;
initPaint();
}
@Override
protected void onDraw(Canvas canvas) {
// TODO Auto-generated method stub
super.onDraw(canvas);
canvas.drawBitmap(writer(new1Bitmap),0,0, null);
}
@SuppressLint("ClickableViewAccessibility")
@Override
public boolean onTouchEvent(MotionEvent event) {
// TODO Auto-generated method stub
clickX =event.getX();
clickY=event.getY();
if(event.getAction()==MotionEvent.ACTION_DOWN){
//手指点下屏幕时触发
startX=clickX;
startY=clickY;
mPath.reset();
mPath.moveTo(clickX, clickY);
// isMove =false;
// invalidate();
// return true;
}
else if(event.getAction()==MotionEvent.ACTION_MOVE){
//手指移动时触发
float dx=Math.abs(clickX-startX);
float dy=Math.abs(clickY-startY);
// if(dx>=3||dy>=3){
//设置贝塞尔曲线的操作点为起点和终点的一半
float cX = (clickX + startX) / 2;
float cY = (clickY + startY) / 2;
mPath.quadTo(startX,startY, cX, cY);
startX=clickX;
startY=clickY;
// }
// isMove =true;
// invalidate();
// return true;
}
invalidate();
return true;
}
public Bitmap writer(Bitmap pic){
initPaint();
Canvas canvas =null;
if(isClear){
canvas=new Canvas(new2Bitmap);
}else{
canvas=new Canvas(pic);
}
//canvas.drawLine(startX, startY, clickX, clickY, paint);//画线
canvas.drawPath(mPath, paint);
if(isClear){
return new2Bitmap;
}
return pic;
}
private void initPaint(){
paint = new Paint();//初始化画笔
paint.setStyle(Style.STROKE);//设置为画线
paint.setAntiAlias(true);//设置画笔抗锯齿
paint.setColor(color);//设置画笔颜色
paint.setStrokeWidth(strokeWidth);//设置画笔宽度
}
public void setColor(int color){
this.color=color;
initPaint();
}
public Bitmap getPaint(){
return new1Bitmap;
}
}
看一下效果：
基本满足需求
三、surfaceView实现
package picturegame.view;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.graphics.Path;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceHolder.Callback;
import android.view.SurfaceView;
import com.winton.picturegame.R;
public class GameViewSurface extends SurfaceView implements Callback,Runnable{
boolean mRunning = false;
boolean mIsRunning = false;
public static final int TIME_IN_FRAME = 50;
private int paintColor=android.graphics.Color.WHITE;//默认画笔颜色为黑色
private float paintWidth=2f;//默认画笔宽度
private Style paintStyle=Style.STROKE;//默认画笔风格
private int paintAlph=255;//默认不透明
private Path mPath;//轨迹
private Paint mPaint;//画笔
private float startX=0.0f;//初始x
private float startY=0.0f;//初始Y
private SurfaceHolder surfaceHolder;
public Canvas mCanvas;
public boolean first=true;
Bitmap bg;
public GameViewSurface(Context context){
this(context,null);
}
public GameViewSurface(Context context,AttributeSet attrs){
this(context,attrs,0);
}
public GameViewSurface(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
// TODO Auto-generated constructor stub
this.setFocusable(true);//设置当前view拥有触摸事件
surfaceHolder=getHolder();
surfaceHolder.addCallback(this);
mPath=new Path();
initPaint();
bg = BitmapFactory.decodeResource(getResources(), R.drawable.default_pic).copy(Bitmap.Config.ARGB_8888, true);//白色的画板
}
private void initPaint(){
mPaint=new Paint();
mPaint.setAntiAlias(true);//消除锯齿
mPaint.setColor(paintColor);//画笔颜色
mPaint.setAlpha(paintAlph);//画笔透明度
mPaint.setStyle(paintStyle);//设置画笔风格
mPaint.setStrokeWidth(paintWidth);//设置画笔宽度
}
public void doDraw(){
mCanvas=surfaceHolder.lockCanvas();
mCanvas.drawPath(mPath, mPaint);//绘制
surfaceHolder.unlockCanvasAndPost(mCanvas);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
// TODO Auto-generated method stub
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
//手接触屏幕时触发
doTouchDown(event);
break;
case MotionEvent.ACTION_MOVE:
//手滑动时触发
doTouchMove(event);
break;
case MotionEvent.ACTION_UP:
//手抬起时触发
break;
default:
break;
}
return true;
}
private void doTouchDown(MotionEvent event){
float touchX=event.getX();
float touchY=event.getY();
startX=touchX;
startY=touchY;
mPath.reset();
mPath.moveTo(touchX, touchY);
}
private void doTouchMove(MotionEvent event){
float touchX=event.getX();
float touchY=event.getY();
float dx=Math.abs(touchX-startX);//移动的距离
float dy =Math.abs(touchY-startX);//移动的距离
if(dx>3||dy>3){
float cX=(touchX+startX)/2;
float cY=(touchY+startY)/2;
mPath.quadTo(startX, startY, cX, cY);
startX=touchX;
startY=touchY;
}
}
public void setPaintColor(int paintColor) {
this.paintColor = paintColor;
initPaint();
}
public void setPaintWidth(float paintWidth) {
this.paintWidth = paintWidth;
initPaint();
}
public void setPaintStyle(Style paintStyle) {
this.paintStyle = paintStyle;
initPaint();
}
public void setPaintAlph(int paintAlph) {
this.paintAlph = paintAlph;
initPaint();
}
@Override
public void run() {
// TODO Auto-generated method stub
while (mIsRunning) {
long startTime = System.currentTimeMillis();
synchronized(surfaceHolder){
doDraw();
}
long endTime = System.currentTimeMillis();
int diffTime = (int) (endTime - startTime);
while (diffTime <= TIME_IN_FRAME) {
diffTime = (int) (System.currentTimeMillis() - startTime);
Thread.yield();
}
}
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
mCanvas =surfaceHolder.lockCanvas();
mCanvas.drawBitmap(bg, 0,0, null);
surfaceHolder.unlockCanvasAndPost(mCanvas);
mIsRunning=true;
new Thread(this).start();
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
// TODO Auto-generated method stub
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
// TODO Auto-generated method stub
mIsRunning = false;
}
}
看看运行效果：
当我不设置背景时是没问题的，但使用了背景就不停的闪烁了，不知道有没同学知道的，可以说一下。
大家可以阅读本文《解决Android SurfaceView绘制触摸轨迹闪烁问题的方法》，或许对大家的学习有所帮助。
五、总结
两种方式都是可以实现的，而且仔细对比发现surfaceview响应的速度比view快很多，view想必与surfaceview更容易实现。
view用于显示被动更新的动画，即需要操作才会更新的动画，而surfaceview则用于主动更新的动画，如在界面上显示一个奔跑的小狗。
view更新界面是在UI主线程。surfaceview是自己起一个线程更新界面。
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