Question

I´m writing an Android Aplication that is very similar to a binary tree/graph, there are several buttons created dinamically but I can´t figure out how to create lines connecting the buttons.

Here´s an image showing what I need to do:

Here is my XML file:

    <ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/vscroll"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="#000000" >

    <HorizontalScrollView
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/hscroll"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:background="#888888" >

        <RelativeLayout
            xmlns:android="http://schemas.android.com/apk/res/android"
            xmlns:tools="http://schemas.android.com/tools"
            android:id="@+id/relativescroll"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:background="#FFFFFF" >

            <!-- Buttons and lines connecting them -->

        </RelativeLayout>
    </HorizontalScrollView>

</ScrollView>

And here is an example of the activity class:

public class MainActivity extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        RelativeLayout mainLayout = (RelativeLayout) findViewById(R.id.relativescroll);
        RelativeLayout.LayoutParams newParams;

        // Botão 1
        Button btn1 = new Button(this); 
        btn1.setId(1);
        btn1.setText("Botão 1");
        newParams = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, 
                RelativeLayout.LayoutParams.WRAP_CONTENT
                );
        newParams.setMargins(0, 0, 20, 50);
        newParams.addRule(RelativeLayout.CENTER_HORIZONTAL);
        btn1.setLayoutParams(newParams);
        mainLayout.addView(btn1);

        // Botão 2
        Button btn2 = new Button(this);
        btn2.setId(2);
        btn2.setText("Botão 2");
        newParams = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, 
                RelativeLayout.LayoutParams.WRAP_CONTENT
                );
        newParams.setMargins(0, 0, 20, 50);
        newParams.addRule(RelativeLayout.BELOW, 1);
        newParams.addRule(RelativeLayout.ALIGN_PARENT_LEFT);
        btn2.setLayoutParams(newParams);
        mainLayout.addView(btn2); 

        // Botão 3
        Button btn3 = new Button(this);
        btn3.setId(3);
        btn3.setText("Botão 3");
        newParams = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, 
                RelativeLayout.LayoutParams.WRAP_CONTENT
                );
        newParams.setMargins(0, 0, 20, 50);
        newParams.addRule(RelativeLayout.BELOW, 1);
        newParams.addRule(RelativeLayout.RIGHT_OF, 2);
        btn3.setLayoutParams(newParams);
        mainLayout.addView(btn3);

        // Botão 4
        Button btn4 = new Button(this);
        btn4.setId(4);
        btn4.setText("Botão 4");
        newParams = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, 
                RelativeLayout.LayoutParams.WRAP_CONTENT
                );
        newParams.setMargins(0, 0, 20, 50);
        newParams.addRule(RelativeLayout.BELOW, 1);
        newParams.addRule(RelativeLayout.RIGHT_OF, 3);
        btn4.setLayoutParams(newParams);
        mainLayout.addView(btn4);

        // Botão 4
        Button btn5 = new Button(this);
        btn5.setId(5);
        btn5.setText("Botão 5");
        newParams = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, 
                RelativeLayout.LayoutParams.WRAP_CONTENT
                );
        newParams.setMargins(0, 0, 20, 50);
        newParams.addRule(RelativeLayout.BELOW, 1);
        newParams.addRule(RelativeLayout.RIGHT_OF, 4);
        btn5.setLayoutParams(newParams);
        mainLayout.addView(btn5);   

        // DRAW LINK        
        NodeLink link = new NodeLink(this);
        newParams = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, 
                RelativeLayout.LayoutParams.WRAP_CONTENT
                );
        newParams.addRule(RelativeLayout.BELOW, 1);
        newParams.addRule(RelativeLayout.ABOVE, 2);
        newParams.addRule(RelativeLayout.RIGHT_OF, 1);
        newParams.addRule(RelativeLayout.LEFT_OF, 2);
        mainLayout.addView(link);

    }

}

Please, any ideas on how can I do that?

Answer 1

You might want to say what NodeLink is doing – custom view class?

Any case, I’d suggest getting the coordinates of “anchors” on your buttons (top-center points, from your diagram), then creating Paths that link associated buttons’ anchors. Draw/paint these Paths into a Picture, save it as a PictureDrawable, and then you can set that Drawable as the background of your buttons’ parent (the RelativeLayout/mainLayout).