How to set margin dynamically in Android?

Just sharing a slightly different approach.

Instead of casting to LinearLayout.LayoutParams, RelativeLayout.LayoutParams, etc, you can just cast to MarginLayoutParams.

Casting to MarginLayoutParams is better because you can later update your layout and you don't need to return to your java code to change from LinearLayout to RelativeLayout or any other Layout type

You can do something like:

MarginLayoutParams layoutParams = (MarginLayoutParams) view.getLayoutParams();

// Set bottom margin
layoutParams.bottomMargin = x;

// Set top margin
layoutParams.topMargin = x;

// Set left margin
// This won't have effect if you set any relative margin (start) previously or in the layout.xml
layoutParams.leftMargin = x;

// Set left margin
// This won't have effect if you set any relative margin (end) previously or in the layout.xml
layoutParams.rightMargin = x;

// Set start margin
layoutParams.setMarginStart(x);

// Set end margin
layoutParams.setMarginStart(x);

// Set all left, top, right, bottom margins at once
// Note that here, left and right margins are set (not start/end).
// So, if you have used start/end margin before (or via layout.xml), 
// setting left/right here won't have any effect.
layoutParams.setMargins(left, top, end, bottom)

// Then re-apply the layout params again to force the view to be re-draw
// This step may not be necessary because depending where you set the margin, 
// view is already scheduled to be drawn
// For any case, to ensure the view will apply the new margin, call:
view.setLayoutParams(layoutParams);

Write below code to set margin, it may help you.

AlertDialog.Builder myDialog = new AlertDialog.Builder(Login.this);
Button button = new Button(Login.this);
EditText editText = new EditText(Login.this);
TextView textView = new TextView(Login.this);
button.setText("Send");
LinearLayout.LayoutParams buttonLayoutParams = new LinearLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
buttonLayoutParams.setMargins(50, 10, 0, 0);
button.setLayoutParams(buttonLayoutParams);
String resetPassword = editText.getText().toString();
LinearLayout layout = new LinearLayout(Login.this);
layout.setOrientation(LinearLayout.VERTICAL);
layout.addView(textView);
layout.addView(editText);
layout.addView(button);
myDialog.setView(layout);
myDialog.show();

Use LinearLayout.LayoutParams or RelativeLayout.LayoutParams according to parent layout of the child view