Android自定义SurfaceView实现画板功能

接触了这么久的View，总不能一直停留在View里，现在开始呢，就要学习一个新的知识点：SurfaceView，实际上SurfaceView与View的原理都差不多，只是效率和渲染方式上，SurfaceView要优于View，这也是我们写这个的原因。今天就看看这个SurfaceView，好了，下面就是今天要说的效果。

界面很简单，就是一个按钮以及一个画板，先看看界面的代码吧

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
  android:orientation="vertical"
 tools:context="com.example.xinxindemo.MainActivity" >
 <com.example.xinxindemo.view.SecondSurfaceView
  android:id="@+id/surfaceview"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:layout_weight="20"
   />
 <LinearLayout
  android:layout_width="match_parent"
  android:layout_height="55dip"
  android:orientation="horizontal"
  android:padding="5dip" >
  <Button
   android:onClick="onClick"
   android:layout_width="wrap_content"
   android:layout_height="match_parent"
   android:text="clean" />
</LinearLayout>
</LinearLayout>

对吧，界面不是很复杂，下面再看看这个SecondSurfaceView是怎么实现的;

public class SecondSurfaceView extends SurfaceView implements SurfaceHolder.Callback,Runnable{
 
 private boolean mIsDrawing;
 
 private SurfaceHolder mHolder;
 
 private Canvas mCanvas;
 
 private Path mPath;
 
 private Paint mPaint;
 public SecondSurfaceView(Context context, AttributeSet attrs, int defStyle) {
  super(context, attrs, defStyle);
  initView();
 }
 public SecondSurfaceView(Context context, AttributeSet attrs) {
  super(context, attrs);
  initView();
 }
 public SecondSurfaceView(Context context) {
  super(context);
  initView();
 }
 @Override
 public boolean onTouchEvent(MotionEvent event) {
  int x=(int) event.getX();
  int y=(int) event.getY();
  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;
  default:
   break;
  }
  return true;
 }
 private void initView() {
  mHolder=getHolder();
  mHolder.addCallback(this);
  setFocusable(true);
  setFocusableInTouchMode(true);
  this.setKeepScreenOn(true);
  mPath=new Path();
  mPaint=new Paint();
  mPaint.setAntiAlias(true);
  mPaint.setColor(Color.BLACK);
  mPaint.setStyle(Style.STROKE);
  mPaint.setStrokeWidth(15);
 }
 @Override
 public void run() {
  long start =System.currentTimeMillis();
  while(mIsDrawing){
   draw();
  }
  long end =System.currentTimeMillis();
  if (end-start<100) {
   try {
    Thread.sleep(100-(end-start));
   } catch (Exception e) {
    e.printStackTrace();
   }
  }
 }
 @Override
 public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) {
 }
 @Override
 public void surfaceCreated(SurfaceHolder arg0) {
  mIsDrawing=true;
  new Thread(this).start();
 }
 @Override
 public void surfaceDestroyed(SurfaceHolder arg0) {
  mIsDrawing=false;
 }
 private void draw(){
  try {
   mCanvas=mHolder.lockCanvas();
   mCanvas.drawColor(Color.WHITE);
   mCanvas.drawPath(mPath, mPaint);
  } catch (Exception e) {
   e.printStackTrace();
  }finally{
   if (mCanvas!=null) {
    mHolder.unlockCanvasAndPost(mCanvas);
   }
  }
 }
 
 public void clean(){
  initView();
 }
}

然后就是MainActivity.java

public class MainActivity extends Activity{
 SecondSurfaceView surfaceView;
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  surfaceView=(SecondSurfaceView)findViewById(R.id.surfaceview);
 }
 public void onClick(View v){
  surfaceView.clean();
 }
}

源码下载：http://xiazai.jb51.net/201607/yuanma/SurfaceView(jb51.net).rar

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