我创建了一个自定义视图，与您的不同。但会运作良好。我已经实施了。
public class SingleTouchView extends View {
private Bitmap mBitmap;
private Canvas mCanvas;
private Path mPath;
private Paint mBitmapPaint;
private Paint mPaint;
public SingleTouchView(Context context, AttributeSet attrs) {
super(context, attrs);
/**
* you need to pass here something width and height if it is predefined,
* otherwise use explicit constructor to use this view.
*
* I have taken 400 * 400 here. You can get screen height and width and
* according to that you can pass it.
*/
mBitmap = Bitmap.createBitmap(400, 400, Bitmap.Config.ARGB_8888);
mCanvas = new Canvas(mBitmap);
mPath = new Path();
mBitmapPaint = new Paint(Paint.DITHER_FLAG);
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(12);
}
/**
* Dynamic View adding with parameters
*
* @param c
* : Context
* @param width
* : Width of View
* @param height
* : Height of View
*/
public SingleTouchView(Context c, int width, int height) {
super(c);
mBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
mCanvas = new Canvas(mBitmap);
mPath = new Path();
mBitmapPaint = new Paint(Paint.DITHER_FLAG);
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(12);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
}
@Override
protected void onDraw(Canvas canvas) {
// canvas.drawColor(0xFFAAAAAA);
canvas.drawColor(0x00FFFFFF);
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);
// commit the path to our offscreen
mCanvas.drawPath(mPath, mPaint);
// kill this so we don't double draw
mPath.reset();
}
@Override
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;
}
public void setErase() {
mPaint.setXfermode(null);
mPaint.setAlpha(0xFF);
mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
}
}
我在setErase()这里设置了方法。您可以像以前一样使用它。您可以根据需要添加其他代码。
要显式初始化视图，请使用以下短代码。
SingleTouchView View = new SingleTouchView(this, 480, 800);
relativeLayout..addView(View);
编辑
使用此视图的 XML 布局
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<Button
android:id="@+id/btnErase"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Erase" />
<com.example.SingleTouchView
android:id="@+id/paintView"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
只需启动一些活动并设置此布局。