Android学习笔记进阶之在图片上涂鸦(能清屏)

HandWritingActivity.java

package xiaosi.handWriting;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class HandWritingActivity extends Activity
{
	/** Called when the activity is first created. */
	private HandWrite handWrite = null;
	private Button clear = null;
	@Override
	public void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		
		handWrite = (HandWrite)findViewById(R.id.handwriteview);
		clear = (Button)findViewById(R.id.clear);
		clear.setOnClickListener(new clearListener());
	}
     
	
	private class clearListener implements OnClickListener{

		public void onClick(View v)
		{
			handWrite.clear();
		}
	}
}

HandWrite.java

public class HandWrite extends View
{
    private Paint paint = null;
    private Bitmap originalBitmap = null;
    private Bitmap new1Bitmap = null;
    private Bitmap new2Bitmap = null;
    private float clickX = 0,clickY = 0;
    private float startX = 0,startY = 0;
    private boolean isMove = true;
    private boolean isClear = false;
    private int color = Color.GREEN;
    private float strokeWidth = 2.0f;
	public HandWrite(Context context, AttributeSet attrs)
	{
		super(context, attrs);
		originalBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.girl_a);
		new1Bitmap = Bitmap.createBitmap(originalBitmap);
	}
	

    public void clear(){
    	isClear = true;
    	new2Bitmap = Bitmap.createBitmap(originalBitmap);
    	invalidate();
    }
    public void setstyle(float strokeWidth){
    	this.strokeWidth = strokeWidth;
    }
	@Override
	protected void onDraw(Canvas canvas)
	{
		super.onDraw(canvas);
		canvas.drawBitmap(HandWriting(new1Bitmap), 0, 0,null);
		
	}

	public Bitmap HandWriting(Bitmap originalBitmap)
	{
		Canvas canvas = null;
		
		if(isClear){
			canvas = new Canvas(new2Bitmap);
		}
		else{
			canvas = new Canvas(originalBitmap);
		}
		paint = new Paint();
		paint.setStyle(Style.STROKE);
		paint.setAntiAlias(true);
		paint.setColor(color);
		paint.setStrokeWidth(strokeWidth);
		if(isMove){
			canvas.drawLine(startX, startY, clickX, clickY, paint);
		}
		
		startX = clickX;
		startY = clickY;
		
		if(isClear){
			return new2Bitmap;
		}
		return originalBitmap;
	}

	@Override
	public boolean onTouchEvent(MotionEvent event)
	{
		clickX = event.getX();
		clickY = event.getY();
		if(event.getAction() == MotionEvent.ACTION_DOWN){
			
			isMove = false;
			invalidate();
			return true;
		}
		else if(event.getAction() == MotionEvent.ACTION_MOVE){
			
			isMove = true;
			invalidate();
			return true;
		}
		
		return super.onTouchEvent(event);
	}
   
}

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <xiaosi.handWriting.HandWrite
        android:id="@+id/handwriteview"
        android:layout_width="fill_parent"
        android:layout_height="380dp" />

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:orientation="horizontal"
        android:gravity="center_horizontal" >

        <Button
            android:id="@+id/clear"
            android:layout_width="200dp"
            android:layout_height="wrap_content"
            android:text="清屏" />
        
        
    </LinearLayout>
</LinearLayout>