Android get full width for custom Dialog

You need to get the current Window and set it's LayoutParams like so:

Dialog d=new Dialog(mContext);
.........
.........
myDialog.show();
Window window = myDialog.getWindow();
window.setLayout(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);

Alternative(if above solution does't works)

In case above code not works well you can use a workaround

styles.xml

<style name="mydialog"></style>

Java

Dialog d=new Dialog(mContext,R.style.mydialog);
.........
.........
myDialog.show();
Window window = myDialog.getWindow();
window.setLayout(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);

Two ways this can be done, first one in style.xml and second in code:

1. Add as below in style.xml, alter the value(currently 90%) to meet your needs.

<style name="Theme_Dialog" parent="android:Theme.Holo.Dialog">
    <item name="android:windowMinWidthMajor">90%</item>
    <item name="android:windowMinWidthMinor">90%</item>
</style>

2. Add setlayout to match_parent

 final Dialog contacts_dialog = new Dialog(ActivityGroup.this,
 R.style.theme_sms_receive_dialog);
 contacts_dialog.setContentView(R.layout.dialog_schedule_date_time);

getWindow().setLayout(ViewGroup.LayoutParams.MATCH_PARENT,ViewGroup.LayoutParams.MATCH_PARENT);

 contacts_dialog.setCancelable(true);
 contacts_dialog.setCanceledOnTouchOutside(true);
 contacts_dialog.show();

For full width dialog you can create custom style for dialog. Code is given below for full width dialog:

<style name="Custom_Dialog" parent="ThemeOverlay.AppCompat.Light" >
    <item name="windowMinWidthMajor">100%</item>
    <item name="windowMinWidthMinor">65%</item>
</style>

To assign this style to the dialog's constructor, add this to onCreate() method right after setContentView():

getWindow()
    .setLayout(
        ViewGroup.LayoutParams.FILL_PARENT,
        ViewGroup.LayoutParams.WRAP_CONTENT
    );

In case anyone is wondering how to do it for a dialog shown using DialogFragment, you can override onCreateDialog to return a Dialog with custom style that has windowMinWidthMajor and minor set to 90%

@NonNull
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
    return new Dialog(getActivity(), R.style.WideDialog);
}

Style:

<style name="WideDialog" parent="Base.Theme.AppCompat.Dialog">
    <item name="android:windowMinWidthMajor">90%</item>
    <item name="android:windowMinWidthMinor">90%</item>
</style>

You don't need to add any style for that just try below one

  Dialog dialog = new Dialog(context);
  dialog.setContentView(R.layout.your_layout_here);
  dialog.getWindow().setLayout(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
  dialog.show();

Note: using empty style is memory time consuming inside the processor. Instead directly use dailog.getWindow().setLayout(width,height).