安卓自定义View，实时绘图保存为图片

采用单缓冲与双缓冲机制分别实现。 

一、单缓冲机制

1.1自定义View，重写ondraw函数

public class Brush extends View
{

	private Paint	brush	= new Paint();
	private Path	path	= new Path();
	int	        j	= 0, n = 0;

	// xml创建view时调用的构造函数
	public Brush(Context context,AttributeSet attrs)
	{
		super(context,attrs);
		brush.setAntiAlias(true);
		brush.setColor(Color.BLACK);
		brush.setStyle(Paint.Style.STROKE);// stroke轮廓，fill填充
		brush.setStrokeJoin(Paint.Join.ROUND);// 设置绘制时各图形的结合方式，如平滑效果等
		// brush.setStrokeCap(Cap.ROUND);//当style不是fill时，图形样式
		brush.setStrokeWidth(2f);
	}
	
	@Override
	public boolean onTouchEvent(MotionEvent event)
	{
		float pointX = event.getX();
		float pointY = event.getY();
<span style="white-space:pre">		</span><pre name="code" class="java"> <span style="white-space:pre">		</span>setDrawingCacheEnabled(true);//开启该View的缓冲机制,将此操作放在1.1中

<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=".MainActivity" >

    <Button
        android:id="@+id/save"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="save" />

     <com.example.move.Brush
                android:id="@+id/picture"
                android:layout_width="match_parent"
                android:layout_height="match_parent"/> 

</LinearLayout>

public class MainActivity extends Activity
{

	@Override
	protected void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
	        Brush picture = (Brush) findViewById(R.id.picture);
		Button btnSave = (Button) findViewById(R.id.save);
		
		btnSave.setOnClickListener(new OnClickListener()
		{

			public void onClick(View v)
			{
				Bitmap bm=Bitmap.createBitmap(picture.getDrawingCache());
				picture.setDrawingCacheEnabled(false);
				try
				{
					FileOutputStream stream=new FileOutputStream(new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),"hello.png"));<span style="white-space: pre;"> </span><pre name="code" class="java"><span style="white-space:pre">					</span>bm.compress(CompressFormat.PNG, 80, stream);//将bm数据压缩为png图片格式stream.close();<pre name="code" class="java"><span style="white-space:pre">					</span> } catch (Exception e1){e1.printStackTrace();}	<pre name="code" class="java"><span style="font-family: Arial, Helvetica, sans-serif;"><span style="white-space:pre">						</span>}</span>

<span style="font-family: Arial, Helvetica, sans-serif;"><span style="white-space:pre">					</span>}）;</span><pre name="code" class="java"><span style="font-family: Arial, Helvetica, sans-serif;"><span style="white-space:pre">		</span>}</span><pre name="code" class="java"><span style="font-family: Arial, Helvetica, sans-serif;">}</span>

2.1自定义View，重载ondraw函数

public class Brush extends View
{

	private Paint	brush	= new Paint();
	private Path	path	= new Path();

	private Canvas	cacheCanvas;
	private Bitmap	cachebBitmap;

	// C1是代码创建view时，C2是xml创建view时
	public Brush(Context context,AttributeSet attrs)
	{
		super(context,attrs);

		brush.setAntiAlias(true);
		brush.setColor(Color.BLACK);
		brush.setStyle(Paint.Style.STROKE);// stroke轮廓，fill填充
		brush.setStrokeJoin(Paint.Join.ROUND);// 设置绘制时各图形的结合方式，如平滑效果等
		// brush.setStrokeCap(Cap.ROUND);//当style不是fill时，图形样式
		brush.setStrokeWidth(2f);
<span style="white-space:pre">		</span>//注意下面，用来存图像
		cachebBitmap = Bitmap.createBitmap(1000, 1600, Config.ARGB_8888);
		cacheCanvas = new Canvas(cachebBitmap);
		cacheCanvas.drawColor(Color.WHITE);
	}
	
	@Override
	public boolean onTouchEvent(MotionEvent event)
	{
		float pointX = event.getX();
		float pointY = event.getY();

		switch (event.getAction())
		{
			case MotionEvent.ACTION_DOWN:
				path.moveTo(pointX, pointY);
				break;
			case MotionEvent.ACTION_MOVE:
				path.lineTo(pointX, pointY);
				break;
			case MotionEvent.ACTION_UP:
				 cacheCanvas.drawPath(path, brush);//抬起时，才画线
				 //path.reset();//对画布以外的部分有影响
				 break;
		}
		// Force a view to draw again
		//postInvalidate();
		invalidate();
		return true;
	}

	
	@Override 
	 protected void onDraw(Canvas canvas) 
	{
		 canvas.drawBitmap(cachebBitmap, 0, 0, null);
		 canvas.drawPath(path, brush);
	}
	
}

同1.2；

2.3 主Activity

只需要将1.3中bitmap信息，即bm修改为cachbBitmap即可以。