4、释放内存缓冲区
下面的例子(一个画图板)将实现双缓冲画图
先自定义一个View(Bitmap将会绘制到这个View上)
[java] view plain copy print ? <span style="font-size:14px;">package Wangli.Graphics.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相同大小的缓存区 cacheBitmap = Bitmap.createBitmap(VIEW_WIDTH,VIEW_HEIGHT,Config.ARGB_8888); cacheCanvas = new Canvas(); path = new Path(); //设置cacheCanvas将会绘制到内存中的cacheBitmap上 cacheCanvas.setBitmap(cacheBitmap); //设置画笔的颜色 paint = new Paint(Paint.DITHER_FLAG); paint.setColor(Color.RED); //设置画笔的风格 paint.setStyle(Paint.Style.STROKE); paint.setStrokeWidth(1); //反锯齿 paint.setAntiAlias(true); paint.setDither(true); } public boolean onTouchEvent(MotionEvent event) { //获取拖动事件发生的位置 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; } public void onDraw(Canvas canvas) { Paint bmpPaint = new Paint(); //将cacheBitmap绘制到该View组件上 canvas.drawBitmap(cacheBitmap, 0, 0, bmpPaint); //沿着path绘制 canvas.drawPath(path, paint); } }</span><span style="font-size:12px;"> </span> 定义菜单资源文件my_menu
[html] view plain copy print ? <span style="font-size:14px;"><?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></span> strings.xml
[html] view plain copy print ? <?xml version="1.0" encoding="utf-8"?> <resources> <string name="hello">Hello World, HandDraw!</string> <string name="app_name">手绘</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> 主界面处理菜单事件
[java] view plain copy print ? package Wangli.Graphics.HandDraw; import android.app.Activity; import android.graphics.BlurMaskFilter; import android.graphics.Color; import android.graphics.EmbossMaskFilter; import android.os.Bundle; import android.view.Menu; import android.view.MenuInflater; import android.view.MenuItem; public class HandDraw extends Activity { /** Called when the activity is first created. */ 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,BlurMaskFilter.Blur.NORMAL); } //负责创建选项菜单 public boolean onCreateOptionsMenu(Menu menu) { MenuInflater inflator = new MenuInflater(this); //状态R.menu.context对应菜单,并添加到中 inflator.inflate(R.menu.my_menu,menu); return super.onCreateOptionsMenu(menu); } //菜单项被单击后的回调方法 public boolean onOptionsItemSelected(MenuItem mi) { 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(mi.getItemId()) { case R.id.red: dv.paint.setColor(Color.RED); mi.setChecked(true); break; case R.id.green: dv.paint.setColor(Color.GREEN); mi.setChecked(true); break; case R.id.blue: dv.paint.setColor(Color.BLUE); mi.setChecked(true); break; case R.id.width_1: dv.paint.setStrokeWidth(1); mi.setChecked(true); break; case R.id.width_3: dv.paint.setStrokeWidth(3); mi.setChecked(true); break; case R.id.width_5: dv.paint.setStrokeWidth(5); mi.setChecked(true); break; case R.id.blur: dv.paint.setMaskFilter(blur); mi.setChecked(true); break; case R.id.emboss: dv.paint.setMaskFilter(emboss); mi.setChecked(true); break; } return true; } } 下面是实现效果
更改画笔效果