Android自学之图形图像之使用双缓冲画

来源：互联网发布：网络贷款条件编辑：程序博客网时间：2024/05/16 14:52

参考文章：http://blog.csdn.net/lee576/article/details/7870160

在他的基础上稍微补充了一点：

当数据量很大时，绘图可能需要几秒钟甚至更长的时间，而且有时还会出现闪烁现象，为了解决这些问题，可采用双缓冲技术来绘图。
　双缓冲即在内存中创建一个与屏幕绘图区域一致的对象，先将图形绘制到内存中的这个对象上，再一次性将这个对象上的图形拷贝到屏幕上，这样能大大加快绘图的速度。双缓冲实现过程如下：
　　1、在内存中创建与画布一致的缓冲区
　　2、在缓冲区画图
　　3、将缓冲区位图拷贝到当前画布上

　　4、释放内存缓冲区

代码已经传到网上，下载地址为：

http://download.csdn.net/download/qizheguang/9434947

下面贴代码：

MainActivity.java

package com.example.doublebuffer;import android.os.Bundle;import android.app.Activity;import android.graphics.BlurMaskFilter;import android.graphics.EmbossMaskFilter;import android.graphics.Color;  import android.view.Menu;import android.view.MenuInflater;import android.view.MenuItem;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;public class MainActivity extends Activity{ EmbossMaskFilter emboss;   BlurMaskFilter blur; DrawViewdrawview;//调用另一个类 @Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);emboss = new EmbossMaskFilter(new float[]{1.5f,1.5f,1.5f},0.6f,6,4.2f);          blur = new BlurMaskFilter(8,BlurMaskFilter.Blur.NORMAL);                 Button button = (Button)findViewById(R.id.Erase_Everything);                drawview = (DrawView)findViewById(R.id.draw);                button.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {// TODO Auto-generated method stubdrawview.ReleaseDraw();}});}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {// Inflate the menu; this adds items to the action bar if it is present.MenuInflater inflator = new MenuInflater(this);          //状态R.menu.context对应菜单,并添加到中          inflator.inflate(R.menu.main, menu);          return super.onCreateOptionsMenu(menu);                  //getMenuInflater().inflate(R.menu.main, menu);//return true;}//菜单项被单击后的回调方法  @Override    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;      }      }

DrawView.java

package com.example.doublebuffer;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;import android.view.WindowManager;import android.view.ViewGroup.LayoutParams;import android.widget.Button;public class DrawView extends View {//public Button btnEraseAll;//  public LayoutParams params;    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;      int width;//手机屏幕宽度    int height;//手机屏幕高度        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);           WindowManager wm = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);       width = wm.getDefaultDisplay().getWidth();//--表示函数很老       height = wm.getDefaultDisplay().getHeight();        //      btnEraseAll = new Button(context);//      btnEraseAll.setText("Erase Everything!!");//      params = new LayoutParams(LayoutParams.MATCH_PARENT,LayoutParams.WRAP_CONTENT);//动态构建布局//      btnEraseAll.setLayoutParams(params);               }         //释放    public void ReleaseDraw(){    cacheBitmap = null;    cacheCanvas = null;    path.reset();postInvalidate();  }        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:  //按下                 path.moveTo(x, y);                   preX = x;                   preY = y;                   break;              case MotionEvent.ACTION_MOVE:  //移动                 path.quadTo(preX, preY, x, y);                   preX = x;                   preY = y;                   break;              case MotionEvent.ACTION_UP:  //抬起                 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)      {      if (cacheBitmap == null) {    cacheBitmap = Bitmap.createBitmap(width, 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(5);                          //设置结合处的样子，MITER:结合处为锐角， ROUND:结合处为圆弧：BEVEL：结合处为直线。            paint.setStrokeJoin(Paint.Join.ROUND);                        //反锯齿              paint.setAntiAlias(true);              paint.setDither(true);  }            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);      } }

布局文件：

activity_main.xml

<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"    tools:context=".MainActivity" >    <LinearLayout    android:layout_width="fill_parent"    android:layout_height="fill_parent"    android:orientation="vertical" >             <com.example.doublebuffer.DrawView        android:id="@+id/draw"        android:layout_width="match_parent"        android:layout_height="0dp"        android:layout_weight="9"      />        <Buttonandroid:id="@+id/Erase_Everything"android:layout_width="match_parent"android:layout_height="0dp"android:layout_weight="1"android:text="Erase Everything"/>        <!-- View         android:layout_width="match_parent"        android:layout_height="0dp"        android:layout_weight="1"        android:background="#000000"/-->    </LinearLayout>        </LinearLayout>

menu菜单文件：

main.xml

<menu xmlns:android="http://schemas.android.com/apk/res/android" >    <!-- item        android:id="@+id/action_settings"        android:orderInCategory="100"        android:showAsAction="never"        android:title="@string/action_settings"/-->        <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>

strings.xml

    <string name="hello">Hello World, 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>

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