如何清除在画布上的Android按钮点击

Question

import android.content.Context; 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
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; 

public class SingleTouchEventView extends View { 
private Paint paint = new Paint(); 
private Path path = new Path(); 
public boolean cc = false; 

public SingleTouchEventView(Context context, AttributeSet attrs) { 
    super(context, attrs); 

    paint.setAntiAlias(true); 
    paint.setStrokeWidth(18f); 
    paint.setColor(Color.LTGRAY); 
    paint.setStyle(Paint.Style.STROKE); 
    paint.setStrokeJoin(Paint.Join.ROUND); 
    paint.setStrokeCap(Paint.Cap.ROUND); 
} 

@Override 
protected void onDraw(Canvas canvas) { 
    if(cc) 
    { 
     Bitmap back = BitmapFactory.decodeResource(getResources(), R.drawable.black_square); 
     Bitmap cb = Bitmap.createScaledBitmap(back, 0, 0, false); 
     canvas.drawBitmap(cb,0,0,null); 
     cc = false; 

    } 
    canvas.drawPath(path, paint); 
} 

public void clearCanvas() 
{ 
    cc =true; 
    invalidate(); 
} 

@Override 
public boolean onTouchEvent(MotionEvent event) { 
    float eventX = event.getX(); 
    float eventY = event.getY(); 

    switch (event.getAction()) { 
    case MotionEvent.ACTION_DOWN: 
    path.moveTo(eventX, eventY); 
    return true; 
    case MotionEvent.ACTION_MOVE: 
    path.lineTo(eventX, eventY); 
    break; 
    case MotionEvent.ACTION_UP: 
    // nothing to do 
    break; 
    default: 
    return false; 
    } 

    // Schedules a repaint. 
    invalidate(); 
    return true; 
    } 
} 

上述文件是我SingleTouchEventView.Java 这是我MainActivity.java

public class MainActivity extends Activity { 

    Button reset;; 
LinearLayout canvasAlphabets; 
    SingleTouchEventView myView; 


    @Override 
protected void onCreate(Bundle savedInstanceState) { 
    // TODO Auto-generated method stub 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main_activity); 


    reset = (Button)findViewById(R.id.reset_canvas); 

    myView = new SingleTouchEventView(this, null); 
    canvasAlphabets = (LinearLayout)findViewById(R.id.canvas_Alphabets); 
    canvasAlphabets.addView(myView); 


      reset.setOnClickListener(new View.OnClickListener() { 


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


     } 
     }); 

     } 

    } 

我的问题是什么样的代码，我应该在复位按钮用于删除画布的所有内容。 请帮我 我试过执行myView.clearCanvas()但这没有帮助。如果我添加此代码重置点击buutons它引起FC

感谢

Answer 1

path = new Path(); 
Paint clearPaint = new Paint(); 
clearPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR)); 
canvas.drawRect(0, 0, 0, 0, clearPaint); 
cc = false; 

我用上面的代码修复了它

Answer 2

您可以在panit一切与透明色，清除一切。

Answer 3

也许我不明白你想画什么，但你尝试过这样的：

protected void onDraw(Canvas canvas) 
{ 
    if (cc) 
    { 
     Bitmap back = BitmapFactory.decodeResource(getResources(), R.drawable.black_square); 
     Bitmap cb = Bitmap.createScaledBitmap(back, 0, 0, false); 
     canvas.drawBitmap(cb,0,0,null); 
     cc = false; 
    } 
    else 
     canvas.drawPath(path, paint); 
    } 
} 

否则，如果你想删除所有，你可以使用这个新的油漆：

Paint transparent = new Paint(); 
transparent.setAlpha(0);