Note about Relative Layout parameters Android 28.08.2016

RelativeLayout give flexbility to position your component base on the relative or sibling component’s position. It’s the most flexible layout, that allow you to position your component to display in anywhere you want.

In RelativeLayout, you can use "above, below, left and right" to arrange the component position, for example, display a button1 below button2, or display button3 on right of the button1.

android_relativelayout.png

Following is my takeaway from RelativeLayout.LayoutParams in short form.

Property Description Value
Relative To Container
android:layout_alignParentBottom If true, makes the bottom edge of this view match the bottom edge of the parent. Accommodates bottom margin. Boolean
android:layout_alignParentLeft If true, makes the left edge of this view match the left edge of the parent. Accommodates left margin. Boolean
android:layout_alignParentRight If true, makes the right edge of this view match the right edge of the parent. Accommodates right margin. Boolean
android:layout_alignParentEnd If true, makes the end edge of this view match the end edge of the parent. Accommodates end margin. Boolean
android:layout_alignParentStart If true, makes the start edge of this view match the start edge of the parent. Accommodates start margin. Boolean
android:layout_alignParentTop If true, makes the top edge of this view match the top edge of the parent. Accommodates top margin. Boolean
android:layout_centerHorizontal If true, centers this child horizontally within its parent. Boolean
android:layout_centerInParent If true, centers this child horizontally and vertically within its parent. Boolean
android:layout_centerVertical If true, centers this child vertically within its parent. Boolean
android:layout_alignWithParentIfMissing If set to true, the parent will be used as the anchor when the anchor cannot be be found for layout_toLeftOf, layout_toRightOf, etc. Boolean
Relative To Siblings
android:layout_above Positions the bottom edge of this view above the given anchor view ID. Accommodates bottom margin of this view and top margin of anchor view. ID
android:layout_below Positions the top edge of this view below the given anchor view ID. Accommodates top margin of this view and bottom margin of anchor view. ID
android:layout_toEndOf Positions the start edge of this view to the end of the given anchor view ID. Accommodates start margin of this view and end margin of anchor view. ID
android:layout_toLeftOf Positions the right edge of this view to the left of the given anchor view ID. Accommodates right margin of this view and left margin of anchor view. ID
android:layout_toRightOf Positions the left edge of this view to the right of the given anchor view ID. Accommodates left margin of this view and right margin of anchor view. ID
android:layout_toStartOf Positions the end edge of this view to the start of the given anchor view ID. Accommodates end margin of this view and start margin of anchor view. ID
Alignment With Other Elements
android:layout_alignBaseline Positions the baseline of this view on the baseline of the given anchor view ID. ID
android:layout_alignBottom Makes the bottom edge of this view match the bottom edge of the given anchor view ID. Accommodates bottom margin. ID
android:layout_alignEnd Makes the end edge of this view match the end edge of the given anchor view ID. Accommodates end margin. ID
android:layout_alignLeft Makes the left edge of this view match the left edge of the given anchor view ID. Accommodates left margin. ID
android:layout_alignRight Makes the right edge of this view match the right edge of the given anchor view ID. Accommodates right margin. ID
android:layout_alignStart Makes the start edge of this view match the start edge of the given anchor view ID. Accommodates start margin. ID
android:layout_alignTop Makes the top edge of this view match the top edge of the given anchor view ID. Accommodates top margin. ID 



Sometimes it's useful to set some parameter programmatically. For example, let's arrange TextView below Button.


RelativeLayout.LayoutParams params = (RelativeLayout.LayoutParams) textView.getLayoutParams();
params.addRule(RelativeLayout.BELOW, R.id.button);




Change width of RelativeLayout


// convert dp to px
float scale = getResources().getDisplayMetrics().density;
int width = (int) (210 * scale + 0.5f);

RelativeLayout rlWrapper = (RelativeLayout) findViewById(R.id.rlWrapper);
ViewGroup.LayoutParams params = rlWrapper.getLayoutParams();
params.height = height;




Also we can crate a entire layout without XML.


public class ProgrammaticLayout extends Activity {
    private int TV_CENTER_ID = 100011;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // here is an alternative to: setContentView(R.layout.main);

        final RelativeLayout relLayout = new RelativeLayout(this);
        relLayout.setLayoutParams(new RelativeLayout.LayoutParams(
            LayoutParams.MATCH_PARENT,
            LayoutParams.MATCH_PARENT));

        TextView tvCenter = new TextView(this);
        tvCenter.setText("Center");
        tvCenter.setTag(TV_CENTER_ID);

        RelativeLayout.LayoutParams lpCenter = new RelativeLayout.LayoutParams(
            LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
        lpCenter.addRule(RelativeLayout.CENTER_IN_PARENT);
        relLayout.addView(tvCenter, lpCenter);

        TextView tvTop = new TextView(this);
        tvTop.setText("Top");
        RelativeLayout.LayoutParams llTop = new RelativeLayout.LayoutParams(
            LayoutParams.WRAP_CONTENT,
            LayoutParams.WRAP_CONTENT);
        llTop.addRule(RelativeLayout.ABOVE, TV_CENTER_ID);
        relLayout.addView(tvTop, llTop);
        setContentView(relLayout);
    }
}




We can programmatically place a view above of another view in a RelativeLayout in Android


LayoutParams lp = (LayoutParams) tvText.getLayoutParams();

// to remove a rule, make it value to zero
lp.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM, 0);
lp.addRule(RelativeLayout.ABOVE, btnSend.getId());
lp.addRule(RelativeLayout.ALIGN_LEFT, btnSend.getId());

tvText.setLayoutParams(lp);






        

        

            
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