我有这样的主要课程:
public class Main extends Activity {
Button edit,save,eraser,clear;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
edit = (Button) findViewById(R.id.edit);
save = (Button) findViewById(R.id.save);
clear = (Button) findViewById(R.id.clear);
eraser = (Button) findViewById(R.id.eraser);
eraser.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
GameBoard aa = new GameBoard(Main.this);
aa.eraser();
aa.invalidate();
}
});
}
}
我的视图类看起来像这样:
public class GameBoard extends View{
public void init() {
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setDither(true);
// mPaint.setColor(Color.BLACK);
mPaint.setColor(0xFFFF0000);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setStrokeWidth(12);
}
public Paint mPaint;
public GameBoard(Context context) {
super(context);
init();
}
private Bitmap mBitmap;
private Canvas mCanvas;
private Path mPath;
private Paint mBitmapPaint;
public GameBoard(Context context, AttributeSet aSet) {
super(context, aSet);
init();
mBitmap = Bitmap.createBitmap(800, 1024, Bitmap.Config.ARGB_8888);
mCanvas = new Canvas(mBitmap);
mPath = new Path();
mBitmapPaint = new Paint(Paint.DITHER_FLAG);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
}
@Override
public void onDraw(Canvas canvas) {
// initialize
// canvas.drawColor(Color.WHITE);
canvas.drawColor(0xFFAAAAAA);
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 eraser() {
// TODO Auto-generated method stub
Toast.makeText(getContext(), "eraser", Toast.LENGTH_LONG).show();
mPaint.setXfermode(null);
mPaint.setAlpha(0xFF);
mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
invalidate();
}
}
这是布局:
<com.authorwjf.GameBoard
android:id="@+id/the_canvas"
android:layout_width="fill_parent"
android:layout_height="fill_parent" />
当我点击某个按钮时,它不会将mPaint
更改为eraser
。
任何人都可以帮助我吗?
答案 0 :(得分:3)
据我所知,你在onClick中创建的GameBoard永远不会附加到任何东西。
该视图是否属于Activity的布局?