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>