Android图形与图像处理-采用双缓冲实现画图板

package wwj.handdraw;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

public class DrawView extends View{
float preX;
float preY;
private Path path;
public Paint paint = null;
final int VIEW_WIDTH = 320;
final int VIEW_HEIGHT = 480;
//定义一个内存中的图片，该图片将作为缓冲区
Bitmap cacheBitmap = null;
//定义cacheBitmap上的Canvas对象
Canvas cacheCanvas = null;
public DrawView(Context context, AttributeSet attrs) {
super(context, attrs);
//创建一个与该View相同大小的缓冲区
cacheBitmap = Bitmap.createBitmap(VIEW_WIDTH, VIEW_HEIGHT, Config.ARGB_8888);
cacheCanvas = new Canvas();
path = new Path();
//设置cacheCanvas将会绘制到内存中cacheBitmap上
cacheCanvas.setBitmap(cacheBitmap);
//设置画笔的颜色
paint = new Paint(Paint.DITHER_FLAG);
paint.setColor(Color.RED);
//设置画笔风格
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeWidth(1);
//反锯齿
paint.setAntiAlias(true);
paint.setDither(true);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
// TODO Auto-generated method stub
//获取拖动事件的发生位置
float x = event.getX();
float y = event.getY();
switch(event.getAction()){
case MotionEvent.ACTION_DOWN:
path.moveTo(x, y);
preX = x;
preY = y;
break;
case MotionEvent.ACTION_MOVE:
path.quadTo(preX, preY, x, y);
preX = x;
preY = y;
break;
case MotionEvent.ACTION_UP:
cacheCanvas.drawPath(path, paint);
path.reset();
break;
}
invalidate();
//返回true表明处理方法已经处理该事件
return true;
}
@Override
protected void onDraw(Canvas canvas) {
// TODO Auto-generated method stub
Paint bmpPaint = new Paint();
//将cacheBitmap绘制到该View组件
canvas.drawBitmap(cacheBitmap, 0, 0, bmpPaint);
//沿着Path绘制
canvas.drawPath(path, bmpPaint);
}

}

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
<item android:title="@string/color">
<menu>
<!-- 定义一组单选菜单项 -->
<group android:checkableBehavior="single">
<!-- 定义多个菜单项 -->
<item
android:id="@+id/red" android:title="@string/color_red"/>
<item
android:id="@+id/green" android:title="@string/color_green"/>
<item
android:id="@+id/blue" android:title="@string/color_blue"/>
</group>
</menu>
</item>
<item android:title="@string/width">
<menu>
<!-- 定义一组菜单项 -->
<group>
<!-- 定义3个菜单项 -->
<item
android:id="@+id/width_1" android:title="@string/width_1"/>
<item
android:id="@+id/width_3" android:title="@string/width_3"/>
<item
android:id="@+id/width_5" android:title="@string/width_5"/>
</group>
</menu>
</item>
<item
android:id="@+id/blur" android:title="@string/blur"/>
<item
android:id="@+id/emboss" android:title="@string/emboss"/>
</menu>

package wwj.handdraw;

import android.os.Bundle;
import android.app.Activity;
import android.graphics.BlurMaskFilter;
import android.graphics.Color;
import android.graphics.BlurMaskFilter.Blur;
import android.graphics.EmbossMaskFilter;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.support.v4.app.NavUtils;

public class HandDraw extends Activity {

EmbossMaskFilter emboss;
BlurMaskFilter blur;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
emboss = new EmbossMaskFilter(new float[]{1.5f, 1.5f, 1.5f}, 0.6f, 6, 4.2f);
blur = new BlurMaskFilter(8, Blur.NORMAL);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflator = new MenuInflater(this);
//状态R.menu.context对应的菜单，并添加到menu中
inflator.inflate(R.menu.my_menu, menu);
return super.onCreateOptionsMenu(menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
// TODO Auto-generated method stub
DrawView dv = (DrawView)findViewById(R.id.draw);
//判断单击的是哪个菜单项，并有针对性地做出响应
switch(item.getItemId()){
case R.id.red:
dv.paint.setColor(Color.RED);
item.setChecked(true);
break;
case R.id.green:
dv.paint.setColor(Color.GREEN);
item.setChecked(true);
break;
case R.id.blue:
dv.paint.setColor(Color.BLUE);
item.setChecked(true);
break;
case R.id.width_1:
dv.paint.setStrokeWidth(1);
break;
case R.id.width_3:
dv.paint.setStrokeWidth(3);
break;
case R.id.width_5:
dv.paint.setStrokeWidth(5);
break;
case R.id.blur:
dv.paint.setMaskFilter(blur);
break;
case R.id.emboss:
dv.paint.setMaskFilter(emboss);
break;
}
return true;
}
}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/LinearLayout1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<wwj.handdraw.DrawView
android:id="@+id/draw"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:width="320px"
android:height="480px"
/>
</LinearLayout>

<resources>

<string name="app_name">手绘</string>
<string name="hello_world">Hello world!</string>
<string name="menu_settings">Settings</string>
<string name="title_activity_hand_draw">HandDraw</string>
<string name="width_1">1像素</string>
<string name="width_3">3像素</string>
<string name="width_5">5像素</string>
<string name="color_red">红色</string>
<string name="color_green">绿色</string>
<string name="color_blue">蓝色</string>
<string name="color">画笔颜色</string>
<string name="width">画笔宽度</string>
<string name="blur">模糊效果</string>
<string name="emboss">浮雕效果</string>
</resources>