Set margins in a LinearLayout programmatically

问题

I'm trying to use Java (not XML) to create a LinearLayout with buttons that fill the screen, and have margins. Here is code that works without margins:

LinearLayout buttonsView = new LinearLayout(this);
buttonsView.setOrientation(LinearLayout.VERTICAL);
for (int r = 0; r < 6; ++r) {
    Button btn = new Button(this);
    btn.setText("A");

    LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.FILL_PARENT, LinearLayout.LayoutParams.FILL_PARENT); // Verbose!
    lp.weight = 1.0f; // This is critical. Doesn't work without it.
    buttonsView.addView(btn, lp);
}

ViewGroup.LayoutParams lp = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT, ViewGroup.LayoutParams.FILL_PARENT);
setContentView(buttonsView, lp);

So that works fine, but how on earth do you give the buttons margins so there is space between them? I tried using LinearLayout.MarginLayoutParams, but that has no weight member so it's no good. And it doesn't work if you pass it lp in its constructor either.

Is this impossible? Because it sure looks it, and it wouldn't be the first Android layout task you can only do in XML.

回答1:

Here is a little code to accomplish it:

LinearLayout ll = new LinearLayout(this);
ll.setOrientation(LinearLayout.VERTICAL);

LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(
     LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT);

layoutParams.setMargins(30, 20, 30, 0);

Button okButton=new Button(this);
okButton.setText("some text");
ll.addView(okButton, layoutParams);

回答2:

So that works fine, but how on earth do you give the buttons margins so there is space between them?

You call setMargins() on the LinearLayout.LayoutParams object.

I tried using LinearLayout.MarginLayoutParams, but that has no weight member so it's no good.

LinearLayout.LayoutParams is a subclass of LinearLayout.MarginLayoutParams, as indicated in the documentation.

Is this impossible?

No.

it wouldn't be the first Android layout task you can only do in XML

You are welcome to supply proof of this claim.

Personally, I am unaware of anything that can only be accomplished via XML and not through Java methods in the SDK. In fact, by definition, everything has to be doable via Java (though not necessarily via SDK-reachable methods), since XML is not executable code. But, if you're aware of something, point it out, because that's a bug in the SDK that should get fixed someday.

回答3:

To add margins directly to items (some items allow direct editing of margins), you can do:

LayoutParams lp = ((ViewGroup) something).getLayoutParams();
if( lp instanceof MarginLayoutParams )
{
    ((MarginLayoutParams) lp).topMargin = ...;
    ((MarginLayoutParams) lp).leftMargin = ...;
    //... etc
}
else
    Log.e("MyApp", "Attempted to set the margins on a class that doesn't support margins: "+something.getClass().getName() );

...this works without needing to know about / edit the surrounding layout. Note the "instanceof" check in case you try and run this against something that doesn't support margins.

回答4:

Due to variation in device screen pixel densities its good to always use DIP unit to set margin programmatically. Like below_

//get resources
Resources r = getResources();
float pxLeftMargin = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 10, r.getDisplayMetrics());
float pxTopMargin = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 10, r.getDisplayMetrics());
float pxRightMargin = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 10, r.getDisplayMetrics());
float pxBottomMargin = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 20, r.getDisplayMetrics());

//get layout params...
LayoutParams params=new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
params.setMargins(Math.round(pxLeftMargin), Math.round(pxTopMargin), Math.round(pxRightMargin), Math.round(pxBottomMargin));

//set margin...
yourLayoutTOsetMargin.setLayoutParams(params);

Hope this will help.

回答5:

I have set up margins directly using below code

LinearLayout layout = (LinearLayout)findViewById(R.id.yourrelative_layout);
LayoutParams params = new LayoutParams(LayoutParams.MATCH_PARENT,LayoutParams.WRAP_CONTENT);            
params.setMargins(3, 300, 3, 3); 
layout.setLayoutParams(params);

Only thing here is to notice that LayoutParams should be imported for following package android.widget.RelativeLayout.LayoutParams, or else there will be an error.

回答6:

Try this

 LayoutParams params = new LayoutParams(
            LayoutParams.WRAP_CONTENT,      
            LayoutParams.WRAP_CONTENT
    );
    params.setMargins(left, top, right, bottom);
    yourbutton.setLayoutParams(params);

回答7:

 MarginLayoutParams layoutParams = (MarginLayoutParams) getLayoutParams();
 layoutParams.setMargins(leftMargin, topMargin, rightMargin, bottomMargin);

回答8:

Try this:

MarginLayoutParams params = (MarginLayoutParams) view.getLayoutParams();
params.width = 250;
params.leftMargin = 50;
params.topMargin = 50;

回答9:

/*
 * invalid margin
 */
private void invalidMarginBottom() {
    RelativeLayout.LayoutParams lp = (RelativeLayout.LayoutParams) frameLayoutContent.getLayoutParams();
    lp.setMargins(0, 0, 0, 0);
    frameLayoutContent.setLayoutParams(lp);
}

you should be ware of the type of the view's viewGroup.In the code above, for example,I want to change the frameLayout's margin,and the frameLayout's view group is a RelativeLayout，so you need to covert to (RelativeLayout.LayoutParams)

回答10:

Here a single line Solution:

((LinearLayout.LayoutParams) yourLinearLayout.getLayoutParams()).marginToAdd = ((int)(Resources.getSystem().getDisplayMetrics().density * yourDPValue));

来源：https://stackoverflow.com/questions/2481455/set-margins-in-a-linearlayout-programmatically

标签

java

android

layout

view

margin