Android 开发实例简单涂鸦板

<?xml version="1.0" encoding="utf-8"?>  <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" >  <SurfaceView android:id="@+id/surfaceview"android:layout_width="fill_parent"android:layout_height="wrap_content"android:layout_above="@+id/line"android:layout_alignParentTop="true"/> <LinearLayoutandroid:id="@+id/line"android:layout_width="fill_parent"android:layout_height="wrap_content"android:layout_alignParentBottom="true"> <Buttonandroid:id="@+id/flushbutton"android:layout_width="fill_parent"android:layout_height="wrap_content"android:layout_weight="1"android:text="清屏"/> <Buttonandroid:id="@+id/colorbutton"android:layout_width="fill_parent"android:layout_height="wrap_content"android:layout_weight="1" android:text="颜色"/></LinearLayout></RelativeLayout> 

package com.nan.wall;      import android.app.Activity;   import android.app.AlertDialog;   import android.app.Dialog;   import android.content.DialogInterface;   import android.graphics.Canvas;   import android.graphics.Color;   import android.graphics.Paint;   import android.graphics.Rect;   import android.os.Bundle;   import android.view.MotionEvent;   import android.view.SurfaceHolder;    import android.view.SurfaceView;   import android.view.View;    import android.widget.Button;       public class MyWallActivity extends Activity    {    private SurfaceView mSurfaceView = null;    private SurfaceHolder mSurfaceHolder = null;    private Button cleanButton = null;    private Button colorButton = null;       private float oldX = 0f;    private float oldY = 0f;       private boolean canDraw = false;   private Paint mPaint = null;   //用来记录当前是哪一种颜色    private int whichColor = 0;       /** Called when the activity is first created. */     @Override    public void onCreate(Bundle savedInstanceState)    {    super.onCreate(savedInstanceState);   setContentView(R.layout.main);         mSurfaceView = (SurfaceView)this.findViewById(R.id.surfaceview);   mSurfaceHolder = mSurfaceView.getHolder();      mPaint = new Paint();    //画笔的颜色    mPaint.setColor(Color.RED);    //画笔的粗细    mPaint.setStrokeWidth(2.0f);   cleanButton = (Button)this.findViewById(R.id.flushbutton);    //按钮监听    cleanButton.setOnClickListener(new View.OnClickListener()    {       @Override    public void onClick(View v)    {    // TODO Auto-generated method stub    //锁定整个SurfaceView    Canvas mCanvas = mSurfaceHolder.lockCanvas();    mCanvas.drawColor(Color.BLACK);    //绘制完成，提交修改   mSurfaceHolder.unlockCanvasAndPost(mCanvas);    //重新锁一次    mSurfaceHolder.lockCanvas(new Rect(0, 0, 0, 0));    mSurfaceHolder.unlockCanvasAndPost(mCanvas);    }   });        colorButton = (Button)this.findViewById(R.id.colorbutton);   //按钮监听    colorButton.setOnClickListener(new View.OnClickListener()    {       @Override    public void onClick(View v)    {     // TODO Auto-generated method stub      Dialog mDialog = new AlertDialog.Builder(MyWallActivity.this)    .setTitle("颜色设置")    .setSingleChoiceItems(new String[]{"红色","绿色","蓝色"}, whichColor, new DialogInterface.OnClickListener()    {    @Override   public void onClick(DialogInterface dialog, int which)    {     // TODO Auto-generated method stub    switch(which)    {    case 0:    {    //画笔的颜色    mPaint.setColor(Color.RED);    whichColor = 0;    break;    }    case 1:    {    //画笔的颜色   mPaint.setColor(Color.GREEN);   whichColor = 1;   break;   }   case 2:   {   //画笔的颜色106                 mPaint.setColor(Color.BLUE);   whichColor = 2;                 break;                 }   }   }   })   .setPositiveButton("确定", new DialogInterface.OnClickListener()   {   @Override   public void onClick(DialogInterface dialog, int which)    {   // TODO Auto-generated method stub   dialog.dismiss();   }   })   .create();   mDialog.show();   }   });         @Override   public boolean onTouchEvent(MotionEvent event)   {      //获取x坐标   float x = event.getX();   //获取y坐标（不知道为什么要减去一个偏移值才对得准屏幕）   float y = event.getY()-50;   //第一次进来先不管   if(canDraw)   {      //获取触屏事件   switch(event.getAction())   {   //如果是拖动事件   case MotionEvent.ACTION_MOVE:   {   //锁定整个SurfaceView   Canvas mCanvas = mSurfaceHolder.lockCanvas();     mCanvas.drawLine(x, y, oldX, oldY, mPaint);   mSurfaceHolder.unlockCanvasAndPost(mCanvas);   //重新锁一次   mSurfaceHolder.lockCanvas(new Rect(0, 0, 0, 0));   mSurfaceHolder.unlockCanvasAndPost(mCanvas);   break;   }   }   }   //保存目前的x坐标值   oldX = x;   //保存目前的y坐标值   oldY = y;      canDraw = true;      return true;   }      }