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我正在尝试开发一个应用程序。我现在想清除画布，我编写了清除屏幕的代码。它的工作..但是一个问题背景图像也被清除了。我只想清除图纸。如何只清除图纸？在这里，我动态设置背景图像。

package com.example.graphicsdraw;

import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.EmbossMaskFilter;
import android.graphics.MaskFilter;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.view.Display;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.RelativeLayout;
import android.widget.RelativeLayout.LayoutParams;

public class MainActivity extends Activity {
    private Button Back, Next, Erase,clrScreen;
    int FlagSet = 0, ImageSet = 0;
    static int Flag = 0;
    MyView myview;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        myview = new MyView(this);
        RelativeLayout myLayout = new RelativeLayout(this);        
        myLayout.setLayoutParams(new RelativeLayout.LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT)); 
        Back = new Button(this); 
        Back.setText("Back"); 
        Next = new Button(this);
        Next.setText("Next");
        Erase = new Button(this);
        Erase.setText("Eraser");
        clrScreen = new Button(this);
        clrScreen.setText("Clear");
        myLayout.addView(myview); 
        myLayout.addView(Back); 
        myLayout.addView(Next);
        myLayout.addView(Erase);
        myLayout.addView(clrScreen);
        RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(60, LayoutParams.WRAP_CONTENT); 
        params.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM); 
        params.addRule(RelativeLayout.ALIGN_PARENT_LEFT); 
        RelativeLayout.LayoutParams params2 = new RelativeLayout.LayoutParams(60, LayoutParams.WRAP_CONTENT); 
        params2.addRule(RelativeLayout.ALIGN_PARENT_RIGHT); 
        params2.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM); 
        RelativeLayout.LayoutParams params3 = new RelativeLayout.LayoutParams(65, LayoutParams.WRAP_CONTENT); 
        params3.addRule(RelativeLayout.CENTER_HORIZONTAL); 
        params3.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
        Erase.setLayoutParams(params3); 
        Erase.bringToFront(); 
        Next.setLayoutParams(params2); 
        Next.bringToFront(); 
        Back.setLayoutParams(params); 
        Back.bringToFront(); 
        clrScreen.setLayoutParams(params3); 
        clrScreen.bringToFront(); 
        this.setContentView(myLayout);


        Back.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                Intent i = new Intent(MainActivity.this, MainActivity.class);
                Flag = Flag - 1;
                startActivity(i);
                finish();

            }
        });
        Next.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                Intent i = new Intent(MainActivity.this, MainActivity.class);
                Flag = Flag + 1;
                startActivity(i);
                finish();

            }
        });

        Erase.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                //mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
                /*Intent i = new Intent(MainActivity.this, MainActivity.class);
                Flag = Flag;
                startActivity(i);
                finish();*/
                mPaint = new Paint();
                mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC));
                mPaint.setColor(Color.BLUE);
                mPaint.setAntiAlias(true); 
            }
        });
        clrScreen.setOnClickListener(new OnClickListener() 
        {

            @Override
            public void onClick(View v) 
            {
                // TODO Auto-generated method stub
                myview.Clear_Drawing();

            }


        });

        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setDither(true);
        mPaint.setColor(Color.WHITE);//0xffffffff
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeJoin(Paint.Join.ROUND);
        mPaint.setStrokeCap(Paint.Cap.ROUND);
        mPaint.setStrokeWidth(10);
        mEmboss = new EmbossMaskFilter(new float[] { 1, 1, 1 }, 0.4f, 6, 3.5f);
        mPaint.setMaskFilter(mEmboss);
    }
    private Paint       mPaint;
    private MaskFilter  mEmboss;
    public  class MyView extends View 
    {
        MainActivity ma=new MainActivity();
        Bitmap  mBitmap = null;
        private Canvas  mCanvas;
        Path    mPath = null;
        private Paint   mBitmapPaint;
        Bitmap bmp;
        Display  display = getWindowManager().getDefaultDisplay();
        int width = display.getWidth();
        public MyView(Context c) {
            super(c);
            switch(Flag)
            {
            case 0:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 1:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 2:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 3:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 4:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 5:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 6:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 7:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 8:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 9:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 10:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 11:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 12:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 13:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 14:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 15:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 16:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 17:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 18:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 19:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 20:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 21:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 22:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 23:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 24:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 25:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 26:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 27:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 28:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 29:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 30:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 31:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 32:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 33:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 34:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 35:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 36:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 37:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 38:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 39:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 40:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 41:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 42:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 43:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 44:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            case 45:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                break;
            case 46:
                bmp = BitmapFactory.decodeResource(getResources(), R.drawable.a);
                break;
            default:
                break;
            }
            //Display  display = getWindowManager().getDefaultDisplay();
           // int width = display.getWidth();
            mBitmap = Bitmap.createScaledBitmap(bmp, width, 350, true);
            //mBitmap = Bitmap.createBitmap(width, 350, Bitmap.Config.ARGB_8888);
            mCanvas = new Canvas(mBitmap);
            mPath = new Path();
            mBitmapPaint = new Paint(Paint.DITHER_FLAG);
            mBitmapPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC)) ;                 

        }     
        protected void onDraw(Canvas canvas)
        {
            canvas.drawColor(Color.TRANSPARENT);
            canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
            canvas.drawPath(mPath, mPaint);
        }
        private float mX, mY;
        private static final float TOUCH_TOLERANCE = 4;
        private void touch_start(float x, float y) {
            mPath.reset();
            mPath.moveTo(x, y);
            mX = x;
            mY = y;
        }
        private void touch_move(float x, float y) {
            float dx = Math.abs(x - mX);
            float dy = Math.abs(y - mY);
            if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
                mPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2);
                mX = x;
                mY = y;
            }
        }
        private void touch_up() {
            mPath.lineTo(mX, mY);
            mCanvas.drawPath(mPath, mPaint);
            mPath.reset();
        }
        public void Clear_Drawing()
        {
            //mBitmap = null;
            mPath = null;
            mBitmap = Bitmap.createBitmap(width, 350, Bitmap.Config.ARGB_8888);
            mPath = new Path();
        }
       public boolean onTouchEvent(MotionEvent event) {
            float x = event.getX();
            float y = event.getY();
            switch (event.getAction()) {
                case MotionEvent.ACTION_DOWN:
                    touch_start(x, y);
                    invalidate();
                    break;
                case MotionEvent.ACTION_MOVE:
                    touch_move(x, y);
                    invalidate();
                    break;
                case MotionEvent.ACTION_UP:
                    touch_up();
                    invalidate();
                    break;
            }
            return true;
        }
    }
}
4

3 回答 3

0

这就像重置您的绘图工具并提供一个新的画布来绘制。 

 mBitmap = Bitmap.createBitmap(mv.getWidth(),mv.getHeight() ,Bitmap.Config.ARGB_8888);      
 mCanvas = new Canvas(mBitmap);
 mPaint = new Paint();
 mPaint.setAntiAlias(true);
 mPaint.setDither(true);
 mPaint.setColor(0xFFFF0000);
 mPaint.setStyle(Paint.Style.STROKE);                               
 mPaint.setStrokeJoin(Paint.Join.ROUND);       
 mPaint.setStrokeCap(Paint.Cap.ROUND);
 mPaint.setStrokeWidth(0);
 mv.invalidate();// call invalidate to refresh the view's draw.
于 2013-03-25T09:38:33.360 回答
0

与其直接在背景上绘图，不如将myview.setBackground()其用于背景。继续使用Bitmap.createBitmap(width, 350, Bitmap.Config.ARGB_8888)创建一个空白位图用于绘图。

mBitmap = Bitmap.createScaledBitmap(bmp, width, 350, true);
setBackground(mBitmap);
mBitmap = Bitmap.createBitmap(width, 350, Bitmap.Config.ARGB_8888);
mCanvas = new Canvas(mBitmap);
于 2013-03-25T09:23:38.033 回答
0

它肯定会清除背景图像，因为它是画布的一部分，您应该做的是使用框架布局放置背景作为第一个孩子并在其上创建透明画布并更改框架布局中第一个孩子的背景不要绘制画布上的图像

在透明画布下创建一个布局，当用户更改背景图像时，在下面的布局上更改该图像而不是在画布上，休息就好了

于 2013-03-25T09:24:35.643 回答