Android操作栏上带有按钮的调用方法

Question

I have two classes at the moment, MainActivity and DrawView . The DrawView is working fine and creating a canvas that allows me to draw lines. What I have no idea how to do is when I click the button I've placed on the Action Bar it saves whatever is drawn on the canvas as an image.

I don't know how to use the segment of code below from my MainActivity class. Do I need to create a new class with a method in it or can I create the method within the MainActivity class (in relation to the line "//method goes here")? I'm also assuming I have to retrieve the canvas object, from DrawView , and pass it to the method as a parameter. How do I do that when it's in the DrawView object?

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    drawView = new DrawView(this);
    setContentView(drawView);
    drawView.requestFocus();
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle presses on the action bar items
  switch (item.getItemId()) {
    case R.id.action_save:
       //method goes here
       return true;
    default:
       return super.onOptionsItemSelected(item);
  }
}

Answer 1

Create a field called drawView that is private but accessible throughout the class like this:

private DrawView drawView;

Set it in the onCreate method like you already do now:

drawView = new DrawView(this);

Now you can access the drawView variable in your onOptionsItemSelected method. This means that you can access all public variables in that class. If you store your draw path in a public variable you can access it. You can do that by making the canvas a public field in your DrawView class. Just like you made the DrawView a private field in your MainActivity class.

You should be able to access the canvas like this.

Make the field in DrawView:

public Canvas canvas;

And you can access it like this:

drawView.canvas;

Answer 2

Invoke method from your action bar button and write code for save in that method . if method is in other class use static keyword to call that method and define that method static or you can create class object to access it.