Android: how to draw a border to a LinearLayout

Question

I have three files. The XML, the draw function and the main Activity. I have some LinearLayout in my XML file.

<LinearLayout android:orientation="horizontal"
              android:layout_width="fill_parent"
              android:layout_height="fill_parent"
              android:layout_weight="1">
    <LinearLayout android:layout_width="fill_parent"
                  android:layout_height="fill_parent"
                  android:layout_weight="1"
                  android:background="#ef3"
                  android:id="@+id/img01"/>
    <LinearLayout android:layout_width="fill_parent"
                  android:layout_height="fill_parent"
                  android:layout_weight="1"
                  android:background="#E8A2B4"
                  android:id="@+id/img02"/>
</LinearLayout>

This is the draw function:

public class getBorder extends TextView {
    public getBorder(Context context) {
        super(context);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        Paint paint = new Paint();

        paint.setColor(android.graphics.Color.RED);

        canvas.drawLine(0, 0, this.getWidth() - 1, 0, paint);
        canvas.drawLine(0, 0, 0, this.getHeight() - 1, paint);
        canvas.drawLine(this.getWidth() - 1, 0, this.getWidth() - 1,
            this.getHeight() - 1, paint);
        canvas.drawLine(0, this.getHeight() - 1, this.getWidth() - 1,
            this.getHeight() - 1, paint);
    }
}

And this is the main Activity:

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    final getBorder getBorder = new getBorder(this);
    final LinearLayout img01 = (LinearLayout) findViewById(R.id.img01);
    img01.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            getBorder.setWidth(100);
            getBorder.setHeight(100);
            img01.addView(getBorder);
        }
    });       
}

The program could draw border but the size doesn't fit the LinearLayout. And when I click the LinearLayout again, the program crashed.

Also, I want to draw two circles in the center of the LinearLayout, but how could I figure out the center coordinates?

Answer 1

Do you really need to do that programmatically?

Just considering the title: You could use a ShapeDrawable as android:background…

For example, let's define res/drawable/my_custom_background.xml as:

<shape xmlns:android="http://schemas.android.com/apk/res/android"
       android:shape="rectangle">
  <corners
      android:radius="2dp"
      android:topRightRadius="0dp"
      android:bottomRightRadius="0dp"
      android:bottomLeftRadius="0dp" />
  <stroke
      android:width="1dp"
      android:color="@android:color/white" />
</shape>

and define android:background="@drawable/my_custom_background".

I've not tested but it should work.

Update:

I think that's better to leverage the xml shape drawable resource power if that fits your needs. With a "from scratch" project (for android-8), define res/layout/main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@drawable/border"
    android:padding="10dip" >
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Hello World, SOnich"
        />
    [... more TextView ...]
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Hello World, SOnich"
        />
</LinearLayout>

and a res/drawable/border.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
       android:shape="rectangle">
   <stroke
        android:width="5dip"
        android:color="@android:color/white" />
</shape>

Reported to work on a gingerbread device. Note that you'll need to relate android:padding of the LinearLayout to the android:width shape/stroke's value. Please, do not use @android:color/white in your final application but rather a project defined color.

You could apply android:background="@drawable/border" android:padding="10dip" to each of the LinearLayout from your provided sample.

As for your other posts related to display some circles as LinearLayout's background, I'm playing with Inset/Scale/Layer drawable resources (see Drawable Resources for further information) to get something working to display perfect circles in the background of a LinearLayout but failed at the moment…

Your problem resides clearly in the use of getBorder.set{Width,Height}(100);. Why do you do that in an onClick method?

I need further information to not miss the point: why do you do that programmatically? Do you need a dynamic behavior? Your input drawables are png or ShapeDrawable is acceptable? etc.

To be continued (maybe tomorrow and as soon as you provide more precisions on what you want to achieve)…

Answer 2

Extend LinearLayout/RelativeLayout and use it straight on the XML

package com.pkg_name ;
...imports...
public class LinearLayoutOutlined extends LinearLayout {
    Paint paint;    

    public LinearLayoutOutlined(Context context) {
        super(context);
        // TODO Auto-generated constructor stub
        setWillNotDraw(false) ;
        paint = new Paint();
    }
    public LinearLayoutOutlined(Context context, AttributeSet attrs) {
        super(context, attrs);
        // TODO Auto-generated constructor stub
        setWillNotDraw(false) ;
        paint = new Paint();
    }
    @Override
    protected void onDraw(Canvas canvas) {
        /*
        Paint fillPaint = paint;
        fillPaint.setARGB(255, 0, 255, 0);
        fillPaint.setStyle(Paint.Style.FILL);
        canvas.drawPaint(fillPaint) ;
        */

        Paint strokePaint = paint;
        strokePaint.setARGB(255, 255, 0, 0);
        strokePaint.setStyle(Paint.Style.STROKE);
        strokePaint.setStrokeWidth(2);  
        Rect r = canvas.getClipBounds() ;
        Rect outline = new Rect( 1,1,r.right-1, r.bottom-1) ;
        canvas.drawRect(outline, strokePaint) ;
    }

}

---

<?xml version="1.0" encoding="utf-8"?>

<com.pkg_name.LinearLayoutOutlined
   xmlns:android="http://schemas.android.com/apk/res/android"
   android:orientation="vertical"
    android:layout_width=...
    android:layout_height=...
   >
   ... your widgets here ...

</com.pkg_name.LinearLayoutOutlined>