Question

请问为什么 void 对于变量 onDraw 是无效类型 protected void onDraw（Canvas canvas）代码如下

public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new Myview(this));

}
private class Myview extends View{
public Myview (Context context) {
super(context);
@Override
protected void onDraw (Canvas canvas) {
super.onDraw(canvas);
canvas.drawColor(Color.DKGRAY);
Paint paint = new Paint();
paint.setAntiAlias(true);
paint.setColor(Color.BLACK);
canvas.drawPoint(5,5,paint);

}
}
}

Answer 1

请不要在构造函数里面 定义方法
方法应该定义在 class 级别下
改成这样：
private class Myview extends View{
public Myview (Context context) {
super(context);

}
@Override
protected void onDraw (Canvas canvas) {
super.onDraw(canvas);
canvas.drawColor(Color.DKGRAY);
Paint paint = new Paint();
paint.setAntiAlias(true);
paint.setColor(Color.BLACK);
canvas.drawPoint(5,5,paint);
}

}

Answer 2

void 返回空