问题内容
我创建了一个布局，其中包含一些视图，还包含一个用于绘制图形的 linearlayout
main_page_layout.xml
.... ...
我正在尝试使用名为 graphplotter 的自定义类在其上绘制图形
graphplotter.java
public class graphplotter extends view {
private paint paint = null;
private bitmap bitmap;
private canvas canvas;
public graphplotter(context context) {
super(context);
this.init();
}
/* initiates graph plotter */
private void init()
{
this.paint = new paint();
this.paint.setcolor(color.blue);
this.paint.setstrokewidth(5);
this.paint.setstyle(paint.style.fill_and_stroke);
// create a bitmap and a canvas associated with the bitmap
this.bitmap = bitmap.createbitmap(1000, 1000, bitmap.config.argb_8888);
this.canvas = new canvas(bitmap);
}
public void setcolor(int color) {
this.paint.setcolor(color);
invalidate(); // force a redraw
}
/* draws a line with a custom color */
public void drawline(float starx, float starty, float stopx, float stopy,int color)
{
this.setcolor(color);
this.canvas.drawline(starx, starty, stopx, stopy, this.paint);
}
........
这是我要画的活动
mainpageactivity.java
public class MainPageActivity extends AppCompatActivity {
private ConnectionHelper connectionHelper = null;
private SQLQuery sqlQuery = null;
private Person person = null;
private TextView txtID = null;
private RecyclerView recyclerView = null;
private final ProductAdapter productAdapter = null;
private AsyncTaskRunner asyncTaskRunner = null;
private ViewHolder viewHolder = null;
private Spinner graphicTypeSpinner = null;
private Button menuButton = null;
private ConstraintLayout menuView = null;
private List productList = null;
private GraphPlotter graphPlotter = null;
@Override
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState); // necessary for onCreate function
setContentView(R.layout.main_page_layout); // R = resource , R.layout => layouts directory
init();
LinearLayout graphicView = (LinearLayout) findViewById(R.id.graphicView);
graphPlotter = new GraphPlotter(this);
graphPlotter.drawAxisX(159,159,259, Color.BLUE);
graphicView.addView(graphPlotter);
}
...........
...................
但我看不到任何线或轴。
我想使用画布为产品绘制图形，但看不到任何结果，我的类或代码有什么问题
正确答案
将绘制行为放入 ondraw() 函数中
@Override
protected void onDraw(Canvas canvas) {
drawLine(...);
drawAxisX();
} 
