你可以用百分比表示宽度。

<style name="Theme.Holo.Dialog.MinWidth">
<item name="android:windowMinWidthMajor">70%</item>

在这个例子中，我使用了Holo Theme。

当我需要使对话片段更宽一点时，我设置minWidth:

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:minWidth="320dp"
    ... />

在我的案例中，唯一有效的是指向这里的解决方案:http://adilatwork.blogspot.mx/2012/11/android-dialogfragment-dialog-sizing.html

来自Adil博客文章的片段:

@Override
public void onStart()
{
  super.onStart();

  // safety check
  if (getDialog() == null)
    return;

  int dialogWidth = ... // specify a value here
  int dialogHeight = ... // specify a value here

  getDialog().getWindow().setLayout(dialogWidth, dialogHeight);

  // ... other stuff you want to do in your onStart() method
}

@Override
public void onStart() {
    super.onStart();
    Dialog dialog = getDialog();
    if (dialog != null)
    {
        dialog.getWindow().setLayout(-1, -2);
        dialog.getWindow().getAttributes().windowAnimations = R.style.DialogAnimation;
        Window window = getDialog().getWindow();
        WindowManager.LayoutParams params = window.getAttributes();
        params.dimAmount = 1.0f;
        window.setAttributes(params);
        window.setBackgroundDrawableResource(android.R.color.transparent);
    }
}

Working on Android 6.0, ran into the same issue. AlertDialog would default to predefined width set in the theme regardless of the actual width set in the custom view's root Layout. I was able to get it to set properly adjusting the width of the loading_message TextView. Without investigating further, it seems that sizing the actual elements and having the root Layout wrap around them makes it work as expected. Below is an XML layout of a loading dialog which sets width of the the dialog correctly. Using the this library for the animation.

<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="@color/custom_color"
    android:padding="@dimen/custom_dimen">
    <com.github.rahatarmanahmed.cpv.CircularProgressView
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:id="@+id/progress_view"
        android:layout_width="40dp"
        android:layout_height="40dp"
        android:layout_centerHorizontal="true"
        app:cpv_color="@color/white"
        app:cpv_animAutostart="true"
        app:cpv_indeterminate="true" />
    <TextView
        android:id="@+id/loading_message"
        android:layout_width="100dp"
        android:layout_height="wrap_content"
        android:layout_below="@+id/progress_view"
        android:layout_centerHorizontal="true"
        android:gravity="center"
        android:textSize="18dp"
        android:layout_marginTop="@dimen/custom_dimen"
        android:textColor="@color/white"
        android:text="@string/custom_string"/>
</RelativeLayout>

public void onResume() {

    Window window = Objects.requireNonNull(getDialog()).getWindow();
    Point size = new Point();
    assert window != null;
    Display display = window.getWindowManager().getDefaultDisplay();
    display.getSize(size);
    window.setLayout( (int)(size.x * 0.9), (int) (size.y * 0.75));
    window.setGravity( Gravity.CENTER );
    super.onResume();
    

}