Activity中创建View时将this作为Context参数：

setContentView(new MyContentView(this));

然后在View中可以这么获取Intent参数：

Bundle bundle = ((Activity)getContext()).getIntent().getExtras();

换行问题可以用这个自定义方法修复：

void drawString(Canvas canvas, Paint paint, String str, int x, int y) {
    String[] lines = str.split(System.getProperty("line.separator"));
    int yoff = 0;
    for (int i = 0; i < lines.length; ++i) {
        canvas.drawText(lines[i], x, y + yoff, paint);
        paint.getTextBounds(lines[i], 0, lines[i].length(), bounds);
        yoff += bounds.height();
    }
}
...
drawString(canvas, paint, "这是通过继承和扩展View类来显示的。" + System.getProperty("line.separator") + "abc", 0, 50);